feat: add comments and cleanup unused imports across codebase

api/anime/handler.go

@@ -28,10 +28,10 @@ func NewHandler(service *Service) *Handler {
 }
 
 type quickSearchResult struct {
-	ID    int    `json:"id"`
+	ID    int    `json:"id"`    // anime mal id
-	Title string `json:"title"`
+	Title string `json:"title"` // display title
-	Type  string `json:"type"`
+	Type  string `json:"type"`  // anime type (tv, movie, etc)
-	Image string `json:"image"`
+	Image string `json:"image"` // cover image url
 }
 
 func (h *Handler) HandleCatalog(w http.ResponseWriter, r *http.Request) {
@@ -63,6 +63,7 @@ func (h *Handler) HandleCatalogContinue(w http.ResponseWriter, r *http.Request)
 	h.renderCatalogSection(w, r, "Continue")
 }
 
+// renderCatalogSection fetches catalog data (airing/popular/continue) and renders as htmx fragment
 func (h *Handler) renderCatalogSection(w http.ResponseWriter, r *http.Request, section string) {
 	user := middleware.GetUser(r.Context())
 	userID := ""
@@ -82,6 +83,7 @@ func (h *Handler) renderCatalogSection(w http.ResponseWriter, r *http.Request, s
 	data["User"] = user
 	data["Section"] = section
 
+	// render section as htmx partial, not full page
 	if err := templates.GetRenderer().ExecuteFragment(r.Context(), w, "index.gohtml", "catalog_section", data); err != nil {
 		log.Printf("fragment render error: %v", err)
 	}
@@ -133,15 +135,17 @@ func (h *Handler) renderDiscoverSection(w http.ResponseWriter, r *http.Request,
 	}
 }
 
+// HandleBrowse handles anime search/browse with filters. supports htmx partial loading.
 func (h *Handler) HandleBrowse(w http.ResponseWriter, r *http.Request) {
 	user := middleware.GetUser(r.Context())
 
+	// parse query params for search/filter
 	q := r.URL.Query().Get("q")
 	animeType := r.URL.Query().Get("type")
 	status := r.URL.Query().Get("status")
 	orderBy := r.URL.Query().Get("order_by")
 	sort := r.URL.Query().Get("sort")
-	sfw := r.URL.Query().Get("sfw") != "false"
+	sfw := r.URL.Query().Get("sfw") != "false" // default to safe
 
 	var genres []int
 	for _, g := range r.URL.Query()["genres"] {
@@ -165,6 +169,7 @@ func (h *Handler) HandleBrowse(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if r.Header.Get("HX-Request") == "true" {
+		// htmx: return just the card scroll fragment with watchlist state
 		watchlistMap := make(map[int]bool)
 		if user != nil {
 			watchlist, _ := h.service.db.GetUserWatchList(ctx, user.ID)
@@ -195,6 +200,7 @@ func (h *Handler) HandleBrowse(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// full page load: fetch genres list and full watchlist
 	genresList, err := h.service.jikanClient.GetAnimeGenres(ctx)
 	if err != nil {
 		if !errors.Is(err, context.Canceled) {
@@ -237,6 +243,7 @@ func (h *Handler) HandleBrowse(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// HandleAnimeDetails renders anime detail page. handles htmx requests for characters/recommendations sections.
 func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 	idStr := strings.TrimPrefix(r.URL.Path, "/anime/")
 	idStr = strings.TrimSuffix(idStr, "/")
@@ -248,7 +255,7 @@ func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 
 	user := middleware.GetUser(r.Context())
 
-	// If it's an HTMX request for a specific section, handle it
+	// htmx: return just the section (characters or recommendations)
 	section := r.URL.Query().Get("section")
 	if section != "" && r.Header.Get("HX-Request") == "true" {
 		h.renderAnimeDetailsSection(w, r, id, section)
@@ -264,10 +271,12 @@ func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 
 	g, gCtx := errgroup.WithContext(r.Context())
 
+	// fetch anime details + episode count if airing
 	g.Go(func() error {
 		var err error
 		anime, err = h.service.jikanClient.GetAnimeByID(gCtx, id)
 		if err == nil && anime.Airing {
+			// get episode count for airing anime (may span multiple pages)
 			eps, err := h.service.jikanClient.GetEpisodes(gCtx, id, 1)
 			if err == nil {
 				if eps.Pagination.LastVisiblePage > 1 {
@@ -288,6 +297,7 @@ func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 	})
 
 	if user != nil {
+		// fetch user's watchlist status for this anime
 		g.Go(func() error {
 			entry, err := h.service.db.GetWatchListEntry(gCtx, db.GetWatchListEntryParams{
 				UserID:  user.ID,
@@ -298,6 +308,7 @@ func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 			}
 			return nil
 		})
+		// fetch all watchlist ids for nav state
 		g.Go(func() error {
 			watchlist, err := h.service.db.GetUserWatchList(gCtx, user.ID)
 			if err == nil {
@@ -329,6 +340,7 @@ func (h *Handler) HandleAnimeDetails(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// renderAnimeDetailsSection fetches and renders htmx partial for character/recommendation sections
 func (h *Handler) renderAnimeDetailsSection(w http.ResponseWriter, r *http.Request, id int, section string) {
 	ctx := r.Context()
 	var data any
@@ -355,6 +367,7 @@ func (h *Handler) renderAnimeDetailsSection(w http.ResponseWriter, r *http.Reque
 		tplName = "anime_recommendations"
 	}
 
+	// render htmx partial for the section
 	if err := templates.GetRenderer().ExecuteFragment(ctx, w, "anime.gohtml", tplName, data); err != nil {
 		log.Printf("fragment render error: %v", err)
 	}

api/anime/service.go

@@ -17,6 +17,7 @@ func NewService(jikanClient *jikan.Client, db db.Querier) *Service {
 	return &Service{jikanClient: jikanClient, db: db}
 }
 
+// GetCatalogSection fetches homepage catalog sections (Airing, Popular, Continue) from jikan and db.
 func (s *Service) GetCatalogSection(ctx context.Context, userID string, section string) (map[string]any, error) {
 	var (
 		res       jikan.TopAnimeResult
@@ -27,6 +28,7 @@ func (s *Service) GetCatalogSection(ctx context.Context, userID string, section
 
 	g, gCtx := errgroup.WithContext(ctx)
 
+	// fetch jikan data (season now or top anime)
 	g.Go(func() error {
 		switch section {
 		case "Airing":
@@ -37,6 +39,7 @@ func (s *Service) GetCatalogSection(ctx context.Context, userID string, section
 		return err
 	})
 
+	// fetch user-specific data if logged in
 	if userID != "" {
 		g.Go(func() error {
 			if section == "Continue" {
@@ -57,6 +60,7 @@ func (s *Service) GetCatalogSection(ctx context.Context, userID string, section
 		return nil, err
 	}
 
+	// limit to 6 items for homepage grid
 	animes := res.Animes
 	if len(animes) > 6 {
 		animes = animes[:6]
@@ -74,6 +78,7 @@ func (s *Service) GetCatalogSection(ctx context.Context, userID string, section
 	}, nil
 }
 
+// GetDiscoverSection fetches discover page sections (Trending, Upcoming, Top) from jikan.
 func (s *Service) GetDiscoverSection(ctx context.Context, userID string, section string) (map[string]any, error) {
 	var (
 		res       jikan.TopAnimeResult
@@ -107,6 +112,7 @@ func (s *Service) GetDiscoverSection(ctx context.Context, userID string, section
 		return nil, err
 	}
 
+	// limit to 8 items for discover grid
 	animes := res.Animes
 	if len(animes) > 8 {
 		animes = animes[:8]
@@ -123,6 +129,7 @@ func (s *Service) GetDiscoverSection(ctx context.Context, userID string, section
 	}, nil
 }
 
+// filterUnique deduplicates anime list by mal id, respecting limit.
 func (s *Service) filterUnique(animes []jikan.Anime, seen map[int]bool, limit int) []jikan.Anime {
 	unique := make([]jikan.Anime, 0)
 	for _, a := range animes {

api/auth/auth.go

@@ -31,6 +31,7 @@ func NewService(db db.Querier) *Service {
 	return &Service{db: db}
 }
 
+// generateToken creates a cryptographically random base64-encoded token
 func generateToken(size int) (string, error) {
 	b := make([]byte, size)
 	if _, err := rand.Read(b); err != nil {
@@ -39,6 +40,7 @@ func generateToken(size int) (string, error) {
 	return base64.URLEncoding.EncodeToString(b), nil
 }
 
+// generateSessionToken creates a 32-byte session token
 func generateSessionToken() (string, error) {
 	return generateToken(32)
 }
@@ -84,7 +86,7 @@ func (s *Service) ValidateSession(ctx context.Context, sessionID string) (*db.Us
 	}
 
 	if time.Now().After(session.ExpiresAt) {
-		_ = s.db.DeleteSession(ctx, sessionID)
+		_ = s.db.DeleteSession(ctx, sessionID) // clean up expired session
 		return nil, ErrNotAuthenticated
 	}
 
@@ -96,6 +98,7 @@ func (s *Service) ValidateSession(ctx context.Context, sessionID string) (*db.Us
 	return &user, nil
 }
 
+// SetSessionCookie sets an http-only, secure session cookie
 func SetSessionCookie(w http.ResponseWriter, sessionID string, expiresAt time.Time) {
 	secure := os.Getenv("ENV") == "production" || os.Getenv("FORCE_SECURE_COOKIES") == "true"
 	http.SetCookie(w, &http.Cookie{
@@ -113,11 +116,12 @@ func (s *Service) Logout(ctx context.Context, sessionID string) error {
 	return s.db.DeleteSession(ctx, sessionID)
 }
 
+// ClearSessionCookie invalidates the session cookie
 func ClearSessionCookie(w http.ResponseWriter) {
 	http.SetCookie(w, &http.Cookie{
 		Name:     "session_id",
 		Value:    "",
-		Expires:  time.Unix(0, 0),
+		Expires:  time.Unix(0, 0), // epoch to expire immediately
 		MaxAge:   -1,
 		HttpOnly: true,
 		Path:     "/",

api/auth/handler.go

@@ -17,6 +17,7 @@ func NewHandler(authService *Service) *Handler {
 	return &Handler{authService: authService}
 }
 
+// rateLimitErrorFromQuery checks for rate limit errors in the query string
 func rateLimitErrorFromQuery(r *http.Request) string {
 	if r.URL.Query().Get("error") == "rate_limited" {
 		return rateLimitFormError
@@ -24,6 +25,7 @@ func rateLimitErrorFromQuery(r *http.Request) string {
 	return ""
 }
 
+// HandleLoginPage renders the login form
 func (h *Handler) HandleLoginPage(w http.ResponseWriter, r *http.Request) {
 	if err := templates.GetRenderer().ExecuteTemplate(r.Context(), w, "login.gohtml", map[string]any{
 		"CurrentPath": r.URL.Path,
@@ -32,6 +34,7 @@ func (h *Handler) HandleLoginPage(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// HandleLogin validates credentials and creates a session on success
 func (h *Handler) HandleLogin(w http.ResponseWriter, r *http.Request) {
 	if err := r.ParseForm(); err != nil {
 		templates.GetRenderer().ExecuteTemplate(r.Context(), w, "login.gohtml", map[string]any{
@@ -69,6 +72,7 @@ func (h *Handler) HandleLogin(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/", http.StatusSeeOther)
 }
 
+// HandleLogout destroys the session and clears the cookie
 func (h *Handler) HandleLogout(w http.ResponseWriter, r *http.Request) {
 	cookie, err := r.Cookie("session_id")
 	if err == nil {

api/playback/allanime_client.go

@@ -215,6 +215,7 @@ func (c *allAnimeClient) graphqlRequestWithHash(ctx context.Context, showID, epi
 	return nil, fmt.Errorf("no usable data in response")
 }
 
+// GetEpisodeSources fetches stream URLs for a given show, episode, and mode (dub/sub).
 func (c *allAnimeClient) GetEpisodeSources(ctx context.Context, showID string, episode string, mode string) ([]StreamSource, error) {
 	episodeQuery := `query($showId: String!, $translationType: VaildTranslationTypeEnumType!, $episodeString: String!) {
 		episode(showId: $showId, translationType: $translationType, episodeString: $episodeString) {
@@ -387,6 +388,7 @@ type sourceReference struct {
 	Name string
 }
 
+// buildSourceReferences orders source URLs by provider priority, deduplicating entries.
 func buildSourceReferences(rawSourceURLs []any) []sourceReference {
 	priorityOrder := []string{"default", "yt-mp4", "s-mp4", "luf-mp4"}
 	prioritySet := map[string]struct{}{"default": {}, "yt-mp4": {}, "s-mp4": {}, "luf-mp4": {}}
@@ -416,6 +418,7 @@ func buildSourceReferences(rawSourceURLs []any) []sourceReference {
 
 		ref := sourceReference{URL: sourceURL, Name: sourceName}
 		normalized := strings.ToLower(sourceName)
+		// separate prioritized providers from fallback
 		if _, prioritizedProvider := prioritySet[normalized]; prioritizedProvider {
 			if _, exists := prioritized[normalized]; !exists {
 				prioritized[normalized] = ref
@@ -426,6 +429,7 @@ func buildSourceReferences(rawSourceURLs []any) []sourceReference {
 		fallback = append(fallback, ref)
 	}
 
+	// output: prioritized in order, then fallback
 	ordered := make([]sourceReference, 0, len(prioritized)+len(fallback))
 	for _, provider := range priorityOrder {
 		if ref, ok := prioritized[provider]; ok {
@@ -489,6 +493,7 @@ func tryDecryptCTR(block cipher.Block, iv []byte, cipherText []byte) ([]byte, er
 	return plainText, nil
 }
 
+// Search queries AllAnime for shows matching the given search term.
 func (c *allAnimeClient) Search(ctx context.Context, query string, mode string) ([]searchResult, error) {
 	graphqlQuery := `query($search: SearchInput, $limit: Int, $page: Int, $translationType: VaildTranslationTypeEnumType, $countryOrigin: VaildCountryOriginEnumType) {
 		shows(search: $search, limit: $limit, page: $page, translationType: $translationType, countryOrigin: $countryOrigin) {
@@ -557,6 +562,7 @@ func (c *allAnimeClient) Search(ctx context.Context, query string, mode string)
 	return out, nil
 }
 
+// GetEpisodes returns the list of available episode strings for a show and mode.
 func (c *allAnimeClient) GetEpisodes(ctx context.Context, showID string, mode string) ([]string, error) {
 	graphqlQuery := `query($showId: String!) {
 		show(_id: $showId) {
@@ -607,6 +613,7 @@ func (c *allAnimeClient) GetEpisodes(ctx context.Context, showID string, mode st
 	return episodes, nil
 }
 
+// GetAvailableEpisodes returns the count of sub/dub/raw episodes available for a show.
 func (c *allAnimeClient) GetAvailableEpisodes(ctx context.Context, showID string) (AvailableEpisodes, error) {
 	graphqlQuery := `query($showId: String!) {
 		show(_id: $showId) {

api/playback/handler.go

@@ -20,13 +20,14 @@ import (
 
 type Handler struct {
 	svc         *Service
-	jikanClient *jikan.Client
+	jikanClient *jikan.Client // client for Jikan API (MyAnimeList)
 }
 
 func NewHandler(svc *Service, jikanClient *jikan.Client) *Handler {
 	return &Handler{svc: svc, jikanClient: jikanClient}
 }
 
+// renderNotFoundPage renders the 404 page.
 func renderNotFoundPage(r *http.Request, w http.ResponseWriter) {
 	w.WriteHeader(http.StatusNotFound)
 	if err := templates.GetRenderer().ExecuteTemplate(r.Context(), w, "not_found.gohtml", map[string]any{
@@ -36,8 +37,9 @@ func renderNotFoundPage(r *http.Request, w http.ResponseWriter) {
 	}
 }
 
+// HandleWatchPage serves the anime watch page.
 func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
-	// Path is like /anime/123/watch
+	// path format: /anime/123/watch
 	parts := strings.Split(r.URL.Path, "/")
 	if len(parts) < 4 {
 		renderNotFoundPage(r, w)
@@ -63,6 +65,7 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 
 	user := middleware.GetUser(r.Context())
 
+	// fetch user's watchlist to highlight episodes and show status
 	var watchlistIDs []int64
 	var watchlistStatus string
 	if user != nil {
@@ -76,7 +79,8 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	currentEpID := r.URL.Query().Get("ep")
+	// resolve current episode: query param > saved progress > first episode
+currentEpID := r.URL.Query().Get("ep")
 	if currentEpID == "" {
 		if user != nil {
 			entry, err := h.svc.db.GetWatchListEntry(r.Context(), db.GetWatchListEntryParams{
@@ -85,7 +89,7 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 			})
 			if err == nil && entry.CurrentEpisode.Valid {
 				currentEpID = strconv.FormatInt(entry.CurrentEpisode.Int64, 10)
-				// Redirect to the correct episode URL to keep state consistent
+				// redirect to include ep param for consistent URLs
 				http.Redirect(w, r, fmt.Sprintf("/anime/%d/watch?ep=%s", id, currentEpID), http.StatusFound)
 				return
 			}
@@ -147,7 +151,7 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 		return allEpisodes[i].MalID < allEpisodes[j].MalID
 	})
 
-	// Fetch seasons/relations
+	// fetch relations to build season/movie list
 	relations, err := h.jikanClient.GetFullRelations(r.Context(), id)
 	if err != nil {
 		log.Printf("failed to fetch relations: %v", err)
@@ -204,6 +208,7 @@ func (h *Handler) HandleWatchPage(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// HandleProxy proxies media requests through the backend to avoid CORS and hide source URLs.
 func (h *Handler) HandleProxy(w http.ResponseWriter, r *http.Request) {
 	token := r.URL.Query().Get("token")
 	if token == "" {
@@ -211,6 +216,7 @@ func (h *Handler) HandleProxy(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// determine proxy scope based on URL suffix
 	scope := proxyScopeStream
 	if strings.HasSuffix(r.URL.Path, "/segment") {
 		scope = proxyScopeSegment
@@ -244,6 +250,7 @@ func (h *Handler) HandleProxy(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// HandleSaveProgress saves playback progress for a user.
 func (h *Handler) HandleSaveProgress(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
@@ -291,6 +298,7 @@ func (h *Handler) HandleSaveProgress(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusOK)
 }
 
+// HandleCompleteAnime marks an anime as completed for a user.
 func (h *Handler) HandleCompleteAnime(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
@@ -337,9 +345,10 @@ func (h *Handler) HandleCompleteAnime(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusOK)
 }
 
+// HandleEpisodeData returns episode streaming data for the player.
 func (h *Handler) HandleEpisodeData(w http.ResponseWriter, r *http.Request) {
+	// path: /api/watch/episode/{animeId}/{episodeId}
 	parts := strings.Split(r.URL.Path, "/")
-	// /api/watch/episode/{animeId}/{episodeId}
 	if len(parts) < 6 {
 		http.Error(w, "invalid path", http.StatusBadRequest)
 		return
@@ -394,9 +403,10 @@ func (h *Handler) HandleEpisodeData(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+// HandleEpisodeThumbnails returns episode list for the thumbnail strip.
 func (h *Handler) HandleEpisodeThumbnails(w http.ResponseWriter, r *http.Request) {
+	// path: /api/watch/thumbnails/{animeId}
 	parts := strings.Split(r.URL.Path, "/")
-	// /api/watch/thumbnails/{animeId}
 	if len(parts) < 5 {
 		http.Error(w, "invalid path", http.StatusBadRequest)
 		return

api/playback/http_utils.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 )
 
+// doProxiedRequest performs an HTTP GET with standard playback headers.
 func doProxiedRequest(ctx context.Context, client *http.Client, url string, referer string) (*http.Response, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
 	if err != nil {

api/playback/progress.go

@@ -12,6 +12,7 @@ import (
 	"mal/internal/db"
 )
 
+// SaveProgress updates watch progress and continue-watching state in a transaction.
 func (s *Service) SaveProgress(ctx context.Context, userID string, animeID int64, episode int, timeSeconds float64, animeSeed *db.UpsertAnimeParams) error {
 	if strings.TrimSpace(userID) == "" || animeID <= 0 || episode <= 0 {
 		return errors.New("invalid save progress input")
@@ -77,6 +78,7 @@ func (s *Service) SaveProgress(ctx context.Context, userID string, animeID int64
 	return nil
 }
 
+// CompleteAnime marks an anime as completed in the watchlist and clears continue-watching.
 func (s *Service) CompleteAnime(ctx context.Context, userID string, animeID int64, episode int, animeSeed *db.UpsertAnimeParams) error {
 	if strings.TrimSpace(userID) == "" || animeID <= 0 || episode <= 0 {
 		return errors.New("invalid complete anime input")

api/playback/provider_extractor.go

@@ -25,6 +25,7 @@ func newProviderExtractor() *providerExtractor {
 	}
 }
 
+// ExtractVideoLinks fetches provider page and returns stream sources.
 func (e *providerExtractor) ExtractVideoLinks(ctx context.Context, providerPath string) ([]StreamSource, error) {
 	endpoint := e.baseURL + providerPath
 
@@ -52,7 +53,7 @@ func (e *providerExtractor) ExtractVideoLinks(ctx context.Context, providerPath
 
 	defer resp.Body.Close()
 
-	body, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024)) // 2MB limit
 	if err != nil {
 		return nil, fmt.Errorf("read provider response: %w", err)
 	}
@@ -60,10 +61,12 @@ func (e *providerExtractor) ExtractVideoLinks(ctx context.Context, providerPath
 	return e.parseProviderResponse(ctx, string(body))
 }
 
+// parseProviderResponse extracts stream sources from provider JSON response.
 func (e *providerExtractor) parseProviderResponse(ctx context.Context, response string) ([]StreamSource, error) {
 	sources := make([]StreamSource, 0)
 	providerReferer := e.referer
 
+	// extract per-source referer if present
 	refererPattern := regexp.MustCompile(`"Referer":"([^"]+)"`)
 	if match := refererPattern.FindStringSubmatch(response); len(match) >= 2 {
 		providerReferer = strings.ReplaceAll(match[1], `\/`, "/")
@@ -72,6 +75,7 @@ func (e *providerExtractor) parseProviderResponse(ctx context.Context, response
 		providerReferer = e.referer
 	}
 
+	// extract direct link sources (mp4/embed)
 	linkPattern := regexp.MustCompile(`"link":"([^"]+)","resolutionStr":"([^"]+)"`)
 	for _, match := range linkPattern.FindAllStringSubmatch(response, -1) {
 		if len(match) < 3 {
@@ -94,6 +98,7 @@ func (e *providerExtractor) parseProviderResponse(ctx context.Context, response
 		})
 	}
 
+	// extract HLS playlist sources
 	hlsPattern := regexp.MustCompile(`"url":"([^"]+)","hardsub_lang":"en-US"`)
 	for _, match := range hlsPattern.FindAllStringSubmatch(response, -1) {
 		if len(match) < 2 {
@@ -118,6 +123,7 @@ func (e *providerExtractor) parseProviderResponse(ctx context.Context, response
 		})
 	}
 
+	// extract subtitles and attach to all sources
 	subtitlePattern := regexp.MustCompile(`"subtitles":\[(.*?)\]`)
 	if subtitleMatch := subtitlePattern.FindStringSubmatch(response); len(subtitleMatch) >= 2 {
 		subtitles := make([]Subtitle, 0)
@@ -143,6 +149,7 @@ func (e *providerExtractor) parseProviderResponse(ctx context.Context, response
 	return sources, nil
 }
 
+// parseM3U8 fetches a master playlist and extracts individual stream URLs with bandwidth-derived quality.
 func (e *providerExtractor) parseM3U8(ctx context.Context, masterURL string, referer string) ([]StreamSource, error) {
 	resp, err := doProxiedRequest(ctx, e.httpClient, masterURL, referer)
 	if err != nil {
@@ -150,7 +157,7 @@ func (e *providerExtractor) parseM3U8(ctx context.Context, masterURL string, ref
 	}
 	defer resp.Body.Close()
 
-	body, err := io.ReadAll(io.LimitReader(resp.Body, 512*1024))
+	body, err := io.ReadAll(io.LimitReader(resp.Body, 512*1024)) // 512KB limit
 	if err != nil {
 		return nil, err
 	}
@@ -178,6 +185,7 @@ func (e *providerExtractor) parseM3U8(ctx context.Context, masterURL string, ref
 			continue
 		}
 
+		// skip empty lines and non-stream lines
 		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
 			continue
 		}

api/playback/proxy_security.go

@@ -63,6 +63,7 @@ func (s *proxyTokenSigner) Sign(payload proxyTokenPayload) (string, error) {
 	mac.Write(body)
 	signature := mac.Sum(nil)
 
+	// format: payload.signature (both base64url encoded)
 	encodedBody := base64.RawURLEncoding.EncodeToString(body)
 	encodedSignature := base64.RawURLEncoding.EncodeToString(signature)
 	return encodedBody + "." + encodedSignature, nil
@@ -87,7 +88,7 @@ func (s *proxyTokenSigner) Verify(token string) (proxyTokenPayload, error) {
 	mac := hmac.New(sha256.New, s.secret)
 	mac.Write(body)
 	expected := mac.Sum(nil)
-	if !hmac.Equal(signature, expected) {
+	if !hmac.Equal(signature, expected) { // constant-time comparison
 		return proxyTokenPayload{}, errors.New("invalid proxy token signature")
 	}
 
@@ -107,6 +108,7 @@ func (s *Service) buildClientModeSources(modeSources map[string]ModeSource) (map
 	clientModeSources := make(map[string]ModeSource, len(modeSources))
 
 	for mode, source := range modeSources {
+		// wrap stream url with proxy token
 		streamToken, err := s.issueProxyToken(source.URL, source.Referer, proxyScopeStream)
 		if err != nil {
 			return nil, err
@@ -162,6 +164,7 @@ func (s *Service) issueProxyToken(targetURL string, referer string, scope proxyS
 	})
 }
 
+// proxyTokenTTLs defines ttl per scope type.
 var proxyTokenTTLs = map[proxyScope]time.Duration{
 	proxyScopeStream:   proxyStreamTokenTTL,
 	proxyScopeSegment:  proxySegmentTokenTTL,
@@ -194,6 +197,7 @@ func (s *Service) resolveProxyToken(ctx context.Context, token string, scope pro
 		return "", "", err
 	}
 
+	// resolve referer only if it passes public target check
 	normalizedReferer := ""
 	if strings.TrimSpace(payload.Referer) != "" {
 		refererURL, refererErr := normalizeProxyURL(payload.Referer)
@@ -207,6 +211,7 @@ func (s *Service) resolveProxyToken(ctx context.Context, token string, scope pro
 	return normalizedTarget, normalizedReferer, nil
 }
 
+// normalizeProxyURL validates and canonicalizes a proxy target URL.
 func normalizeProxyURL(rawURL string) (string, error) {
 	parsed, err := url.Parse(strings.TrimSpace(rawURL))
 	if err != nil {
@@ -222,6 +227,7 @@ func normalizeProxyURL(rawURL string) (string, error) {
 		return "", errors.New("invalid proxy target host")
 	}
 
+	// block localhost and .local TLD
 	if host == "localhost" || strings.HasSuffix(host, ".localhost") || strings.HasSuffix(host, ".local") {
 		return "", errors.New("localhost targets are not allowed")
 	}
@@ -234,6 +240,7 @@ func normalizeProxyURL(rawURL string) (string, error) {
 	return parsed.String(), nil
 }
 
+// isBlockedProxyIP checks for loopback, private, multicast, and unspecified addresses.
 func isBlockedProxyIP(ip net.IP) bool {
 	return ip.IsLoopback() ||
 		ip.IsPrivate() ||
@@ -243,6 +250,8 @@ func isBlockedProxyIP(ip net.IP) bool {
 		ip.IsUnspecified()
 }
 
+// ensurePublicProxyTarget validates that the target host resolves to a public IP.
+// results are cached to avoid repeated DNS lookups.
 func (s *Service) ensurePublicProxyTarget(ctx context.Context, rawURL string) error {
 	parsed, err := url.Parse(rawURL)
 	if err != nil {
@@ -254,6 +263,7 @@ func (s *Service) ensurePublicProxyTarget(ctx context.Context, rawURL string) er
 		return errors.New("invalid proxy target host")
 	}
 
+	// direct IP already checked by normalizeProxyURL
 	if ip := net.ParseIP(host); ip != nil {
 		if isBlockedProxyIP(ip) {
 			return errors.New("private proxy targets are not allowed")
@@ -261,6 +271,7 @@ func (s *Service) ensurePublicProxyTarget(ctx context.Context, rawURL string) er
 		return nil
 	}
 
+	// check cache first
 	cached, ok := s.proxyHostCache.Get(host)
 	if ok {
 		if cached.Allowed {
@@ -269,6 +280,7 @@ func (s *Service) ensurePublicProxyTarget(ctx context.Context, rawURL string) er
 		return errors.New("private proxy targets are not allowed")
 	}
 
+	// DNS resolution for hostname
 	resolvedIPs, err := net.DefaultResolver.LookupIPAddr(ctx, host)
 	if err != nil || len(resolvedIPs) == 0 {
 		return errors.New("proxy target lookup failed")
@@ -293,6 +305,7 @@ func (s *Service) ensurePublicProxyTarget(ctx context.Context, rawURL string) er
 	return nil
 }
 
+// rewritePlaylistWithTokens replaces segment URLs with proxy tokens for HLS playlists.
 func (s *Service) rewritePlaylistWithTokens(ctx context.Context, content string, baseURL string, referer string) (string, error) {
 	base, err := url.Parse(baseURL)
 	if err != nil {
@@ -310,6 +323,7 @@ func (s *Service) rewritePlaylistWithTokens(ctx context.Context, content string,
 
 		line := scanner.Text()
 		trimmed := strings.TrimSpace(line)
+		// preserve comments and empty lines
 		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
 			out.WriteString(line)
 			out.WriteString("\n")

api/playback/service_base.go

@@ -89,6 +89,7 @@ type userPlaybackState struct {
 	StartTimeSeconds float64
 }
 
+// NewService initializes the playback service with db and sql connections.
 func NewService(db db.Querier, sqlDB *sql.DB, cfg Config) (*Service, error) {
 	proxyTokens, err := newProxyTokenSigner(cfg.ProxyTokenSecret)
 	if err != nil {
@@ -120,6 +121,7 @@ func NewService(db db.Querier, sqlDB *sql.DB, cfg Config) (*Service, error) {
 	}, nil
 }
 
+// BuildWatchPageData resolves show metadata and sources for a given MAL ID and episode.
 func (s *Service) BuildWatchPageData(ctx context.Context, malID int, titleCandidates []string, episode string, mode string, userID string) (WatchPageData, error) {
 	if malID <= 0 {
 		return WatchPageData{}, errors.New("invalid mal id")
@@ -283,11 +285,13 @@ func (s *Service) resolveShowCached(ctx context.Context, malID int, titleCandida
 	return showID, resolvedTitle, nil
 }
 
+// fetchPlaybackSourcesAndSegments resolves sources for both dub and sub modes concurrently.
 func (s *Service) fetchPlaybackSourcesAndSegments(ctx context.Context, showID string, malID int, episode string) (map[string]ModeSource, []SkipSegment) {
 	modeCh := make(chan modeSourceResult, 2)
 	probeCache := make(map[string]directProbeResult)
 	probeCacheMu := sync.Mutex{}
 
+	// parallel fetch for both modes
 	for _, mode := range []string{"dub", "sub"} {
 		modeValue := mode
 		go func() {
@@ -321,7 +325,8 @@ func (s *Service) fetchPlaybackSourcesAndSegments(ctx context.Context, showID st
 		segmentsCh <- s.fetchSkipSegments(ctx, malID, episode)
 	}()
 
-	modeSources := make(map[string]ModeSource)
+modeSources := make(map[string]ModeSource)
+		// collect results from both mode goroutines
 		for range 2 {
 		result := <-modeCh
 		if !result.OK {
@@ -344,6 +349,7 @@ func clonePlaybackBaseData(data playbackBaseData) playbackBaseData {
 	}
 }
 
+// GetEpisodeMetadata fetches episode notes and thumbnails from AllAnime.
 func (s *Service) GetEpisodeMetadata(ctx context.Context, malID int, episode string) (map[string]any, error) {
 	showID, _, err := s.resolveShowCached(ctx, malID, nil)
 	if err != nil {

api/playback/service_http.go

@@ -11,6 +11,8 @@ import (
 	"strings"
 )
 
+// fetchSkipSegments queries aniskip API for OP/ED skip times.
+// returns nil if the API is unavailable or has no data.
 func (s *Service) fetchSkipSegments(ctx context.Context, malID int, episode string) []SkipSegment {
 	if malID <= 0 || strings.TrimSpace(episode) == "" {
 		return nil
@@ -49,6 +51,7 @@ func (s *Service) fetchSkipSegments(ctx context.Context, malID int, episode stri
 		return nil
 	}
 
+	// filter to valid OP/ED segments
 	segments := make([]SkipSegment, 0, len(parsed.Result))
 	for _, item := range parsed.Result {
 		if item.Interval.EndTime <= item.Interval.StartTime {

api/playback/service_proxy.go

@@ -11,6 +11,8 @@ import (
 	"time"
 )
 
+// ProxyStream fetches a stream URL and returns the response.
+// retries on failure, rewrites m3u8 playlists to include auth tokens.
 func (s *Service) ProxyStream(ctx context.Context, targetURL string, referer string, rangeHeader string) (int, http.Header, []byte, io.ReadCloser, error) {
 	const maxRetries = 2
 	const retryDelay = 500 * time.Millisecond
@@ -51,8 +53,11 @@ func (s *Service) ProxyStream(ctx context.Context, targetURL string, referer str
 	return 0, nil, nil, nil, fmt.Errorf("upstream request failed after %d retries: %w", maxRetries+1, lastErr)
 }
 
+// handleProxyResponse processes the upstream response.
+// rewrites m3u8 playlists to proxy through our backend.
 func (s *Service) handleProxyResponse(ctx context.Context, resp *http.Response, targetURL string, referer string, rangeHeader string) (int, http.Header, []byte, io.ReadCloser, error) {
 
+	// check if response is an m3u8 playlist that needs rewriting
 	if isM3U8(targetURL, resp.Header.Get("Content-Type")) {
 		defer resp.Body.Close()
 		body, readErr := io.ReadAll(io.LimitReader(resp.Body, 2*1024*1024))
@@ -73,12 +78,13 @@ func (s *Service) handleProxyResponse(ctx context.Context, resp *http.Response,
 		return resp.StatusCode, headers, []byte(rewritten), nil, nil
 	}
 
+	// for binary streams, remove chunked encoding and return body reader
 	headers := cloneHeaders(resp.Header)
-	// Some upstream servers send transfer-encoding chunked, we should let go's http server handle it
 	headers.Del("Transfer-Encoding")
 	return resp.StatusCode, headers, nil, resp.Body, nil
 }
 
+// isM3U8 checks if the response is an m3u8 playlist by URL or content-type.
 func isM3U8(targetURL string, contentType string) bool {
 	if strings.Contains(strings.ToLower(targetURL), ".m3u8") {
 		return true
@@ -97,6 +103,8 @@ var hopHeaders = map[string]struct{}{
 	"upgrade":             {},
 }
 
+// cloneHeaders copies headers, filtering out hop-by-hop headers.
+// hop-by-hop headers are specific to a single transport connection.
 func cloneHeaders(src http.Header) http.Header {
 	dst := make(http.Header)
 	for key, values := range src {

api/playback/service_ranking.go

@@ -49,6 +49,7 @@ func rankSources(sources []StreamSource, quality string) ([]sourceScore, error)
 		})
 	}
 
+	// stable sort to preserve insertion order for equal scores
 	sort.SliceStable(scored, func(i int, j int) bool {
 		return scored[i].total > scored[j].total
 	})
@@ -97,6 +98,7 @@ func lookupPriority(m map[string]int, key string, fallback int) int {
 	return fallback
 }
 
+// sourceQualityPriority scores quality match: exact match gets boost, mismatch gets penalty.
 func sourceQualityPriority(sourceQuality string, targetQuality string) int {
 	qualityValue := parseQualityValue(sourceQuality)
 
@@ -114,6 +116,7 @@ func sourceQualityPriority(sourceQuality string, targetQuality string) int {
 	}
 }
 
+// qualityMatches checks if source matches target by substring or extracted digits.
 func qualityMatches(sourceQuality string, targetQuality string) bool {
 	sourceLower := strings.ToLower(sourceQuality)
 	targetLower := strings.ToLower(targetQuality)
@@ -129,6 +132,7 @@ func qualityMatches(sourceQuality string, targetQuality string) bool {
 	return extractDigits(sourceLower) == extractDigits(targetLower)
 }
 
+// parseQualityValue extracts numeric value from quality string.
 func parseQualityValue(rawQuality string) int {
 	lower := strings.ToLower(rawQuality)
 	if lower == "auto" {
@@ -147,6 +151,7 @@ func parseQualityValue(rawQuality string) int {
 	return value
 }
 
+// extractDigits reads leading digits until a non-digit or break condition.
 func extractDigits(value string) string {
 	var digits []byte
 	for _, char := range value {
@@ -159,6 +164,7 @@ func extractDigits(value string) string {
 	return string(digits)
 }
 
+// normalizeSourceTypeFromProbe overrides source type based on Content-Type header.
 func normalizeSourceTypeFromProbe(source StreamSource, contentType string) StreamSource {
 	lower := strings.ToLower(contentType)
 	switch {
@@ -170,6 +176,7 @@ func normalizeSourceTypeFromProbe(source StreamSource, contentType string) Strea
 	return source
 }
 
+// isLikelyMP4 checks ftyp box header (bytes 4-8 of mp4 files).
 func isLikelyMP4(payload []byte) bool {
 	if len(payload) < 12 {
 		return false
@@ -178,6 +185,7 @@ func isLikelyMP4(payload []byte) bool {
 	return bytes.Equal(payload[4:8], []byte("ftyp"))
 }
 
+// isLikelyM3U8 checks for m3u8 file header.
 func isLikelyM3U8(payload []byte) bool {
 	trimmed := strings.TrimSpace(string(payload))
 	return strings.HasPrefix(trimmed, "#EXTM3U")

api/playback/service_resolution.go

@@ -19,6 +19,7 @@ func (s *Service) resolveShow(ctx context.Context, malID int, titleCandidates []
 
 		for _, mode := range modeCandidates {
 			for _, result := range resultsByMode[mode] {
+				// exact mal id match
 				if strings.TrimSpace(result.MalID) == malText && strings.TrimSpace(result.ID) != "" {
 					return result.ID, result.Name, nil
 				}
@@ -31,6 +32,7 @@ func (s *Service) resolveShow(ctx context.Context, malID int, titleCandidates []
 				continue
 			}
 
+			// fallback to first result if no exact match
 			best := results[0]
 			if strings.TrimSpace(best.ID) != "" {
 				return best.ID, best.Name, nil
@@ -47,7 +49,7 @@ func (s *Service) searchShowResultsByMode(ctx context.Context, query string, mod
 
 	var wg sync.WaitGroup
 	for _, mode := range modeCandidates {
-		modeValue := mode
+		modeValue := mode // capture loop variable
 		wg.Go(func() {
 			results, err := s.allAnimeClient.Search(ctx, query, modeValue)
 			searchCh <- searchModeResult{Mode: modeValue, Results: results, Err: err}
@@ -96,6 +98,7 @@ func buildTitleSearchQueries(titleCandidates []string) []string {
 		add(normalized)
 		add(strings.ReplaceAll(normalized, "+", " "))
 
+		// strip apostrophes to improve match rate
 		withoutApostrophes := strings.NewReplacer("'", "", "’", "", "`", "").Replace(normalized)
 		add(withoutApostrophes)
 		add(strings.ReplaceAll(withoutApostrophes, "+", " "))
@@ -144,6 +147,7 @@ func availableModes(modeSources map[string]ModeSource) []string {
 	return append(ordered, extra...)
 }
 
+// selectInitialMode picks a mode prioritizing: requested mode > dub > sub > first available.
 func selectInitialMode(requestedMode string, modeSources map[string]ModeSource) string {
 	normalizedRequested := normalizeMode(requestedMode)
 	if normalizedRequested != "" {

api/playback/service_sources.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 )
 
+// resolveModeSource fetches sources for a given mode and selects the best one.
 func (s *Service) resolveModeSource(ctx context.Context, showID string, episode string, mode string, quality string) (StreamSource, error) {
 	sources, err := s.allAnimeClient.GetEpisodeSources(ctx, showID, episode, mode)
 	if err != nil {
@@ -28,6 +29,7 @@ func (s *Service) resolveModeSource(ctx context.Context, showID string, episode
 	return selected, nil
 }
 
+// resolveModeSourceWithCache is like resolveModeSource but caches probe results.
 func (s *Service) resolveModeSourceWithCache(
 	ctx context.Context,
 	showID string,
@@ -56,6 +58,8 @@ func (s *Service) resolveModeSourceWithCache(
 	return selected, nil
 }
 
+// choosePlaybackSource selects the best playable source from ranked candidates.
+// priority: direct media > probed media > embed sources > ranked fallback.
 func (s *Service) choosePlaybackSource(
 	ctx context.Context,
 	ranked []sourceScore,
@@ -70,22 +74,25 @@ func (s *Service) choosePlaybackSource(
 		source := candidate.source
 		switch strings.ToLower(source.Type) {
 		case "mp4", "m3u8":
-			return source, "direct-media", nil
+			return source, "direct-media", nil // known playable types
 		case "embed":
-			embedCandidates = append(embedCandidates, source)
+			embedCandidates = append(embedCandidates, source) // need probing
 		default:
+			// probe unknown types
 			if playable, contentType := probeFn(ctx, source); playable {
 				return normalizeSourceTypeFromProbe(source, contentType), "probed-media", nil
 			}
 		}
 	}
 
+	// check embed sources for playability
 	for _, embed := range embedCandidates {
 		if s.probeEmbedSource(ctx, embed) {
 			return embed, "embed-probed", nil
 		}
 	}
 
+	// fallback to first embed or first ranked
 	if len(embedCandidates) > 0 {
 		return embedCandidates[0], "embed-fallback", nil
 	}
@@ -93,6 +100,7 @@ func (s *Service) choosePlaybackSource(
 	return ranked[0].source, "ranked-fallback", nil
 }
 
+// choosePlaybackSourceWithCache wraps choosePlaybackSource with cached probing.
 func (s *Service) choosePlaybackSourceWithCache(
 	ctx context.Context,
 	ranked []sourceScore,
@@ -131,6 +139,8 @@ func (s *Service) probeDirectMediaCached(
 	return playable, contentType
 }
 
+// probeDirectMedia checks if a direct media URL is playable.
+// checks content-type header, reads prefix for magic bytes, falls back to URL extension.
 func (s *Service) probeDirectMedia(ctx context.Context, source StreamSource) (bool, string) {
 	probeCtx, cancel := context.WithTimeout(ctx, providerProbeTimeout)
 	defer cancel()
@@ -144,7 +154,7 @@ func (s *Service) probeDirectMedia(ctx context.Context, source StreamSource) (bo
 		req.Header.Set("Referer", source.Referer)
 	}
 	req.Header.Set("User-Agent", defaultUserAgent)
-	req.Header.Set("Range", "bytes=0-4095")
+	req.Header.Set("Range", "bytes=0-4095") // small range to detect playable content
 
 	resp, err := s.httpClient.Do(req)
 	if err != nil {
@@ -152,11 +162,13 @@ func (s *Service) probeDirectMedia(ctx context.Context, source StreamSource) (bo
 	}
 	defer resp.Body.Close()
 
+	// check content-type header first
 	contentType := strings.ToLower(resp.Header.Get("Content-Type"))
 	if strings.Contains(contentType, "video/") || strings.Contains(contentType, "mpegurl") {
 		return true, contentType
 	}
 
+	// check magic bytes in prefix
 	prefix, err := io.ReadAll(io.LimitReader(resp.Body, 4096))
 	if err == nil {
 		if isLikelyM3U8(prefix) {
@@ -167,6 +179,7 @@ func (s *Service) probeDirectMedia(ctx context.Context, source StreamSource) (bo
 		}
 	}
 
+	// fallback to URL extension
 	finalURL := ""
 	if resp.Request != nil && resp.Request.URL != nil {
 		finalURL = strings.ToLower(resp.Request.URL.String())
@@ -179,6 +192,8 @@ func (s *Service) probeDirectMedia(ctx context.Context, source StreamSource) (bo
 	return false, contentType
 }
 
+// probeEmbedSource checks if an embed page is still available.
+// returns false if the page contains deletion markers.
 func (s *Service) probeEmbedSource(ctx context.Context, source StreamSource) bool {
 	ctx, cancel := context.WithTimeout(ctx, providerProbeTimeout)
 	defer cancel()
@@ -203,6 +218,7 @@ func (s *Service) probeEmbedSource(ctx context.Context, source StreamSource) boo
 		return false
 	}
 
+	// check for common deletion messages
 	body, err := io.ReadAll(io.LimitReader(resp.Body, 512*1024))
 	if err != nil {
 		return false

api/playback/service_utils.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 )
 
+// toSubtitleItems converts raw subtitle entries into client-safe items.
 func toSubtitleItems(source StreamSource) []SubtitleItem {
 	items := make([]SubtitleItem, 0, len(source.Subtitles))
 	for _, subtitle := range source.Subtitles {

api/playback/types.go

@@ -1,10 +1,11 @@
 package playback
 
+// StreamSource represents a video stream from a provider.
 type StreamSource struct {
 	URL                string
 	Quality            string
 	Provider           string
-	Type               string
+	Type               string // m3u8, mp4, embed, unknown
 	Referer            string
 	Subtitles          []Subtitle
 	AvailableQualities []StreamSource
@@ -36,6 +37,7 @@ type SkipSegment struct {
 	End   float64 `json:"end"`
 }
 
+// WatchPageData is the response payload for the watch page frontend.
 type WatchPageData struct {
 	MalID            int
 	Title            string

api/watchlist/handler.go

@@ -19,6 +19,7 @@ func NewHandler(service *Service) *Handler {
 	return &Handler{service: service}
 }
 
+// HandleUpdateWatchlist adds or updates anime in user's watchlist. accepts json {animeId, status}.
 func (h *Handler) HandleUpdateWatchlist(w http.ResponseWriter, r *http.Request) {
 	if r.Method != http.MethodPost {
 		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
@@ -40,6 +41,7 @@ func (h *Handler) HandleUpdateWatchlist(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	// default status if not provided
 	if body.Status == "" {
 		body.Status = "plan_to_watch"
 	}
@@ -53,6 +55,7 @@ func (h *Handler) HandleUpdateWatchlist(w http.ResponseWriter, r *http.Request)
 	w.WriteHeader(http.StatusOK)
 }
 
+// HandleDeleteWatchlist removes anime from user's watchlist. expects /api/watchlist/{animeId}.
 func (h *Handler) HandleDeleteWatchlist(w http.ResponseWriter, r *http.Request) {
 	user := middleware.GetUser(r.Context())
 	if user == nil {
@@ -73,10 +76,12 @@ func (h *Handler) HandleDeleteWatchlist(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	// htmx: redirect to watchlist page after delete
 	w.Header().Set("HX-Redirect", "/watchlist")
 	w.WriteHeader(http.StatusOK)
 }
 
+// HandleDeleteContinueWatching removes entry from user's continue watching. expects /api/continue-watching/{animeId}.
 func (h *Handler) HandleDeleteContinueWatching(w http.ResponseWriter, r *http.Request) {
 	user := middleware.GetUser(r.Context())
 	if user == nil {
@@ -101,6 +106,7 @@ func (h *Handler) HandleDeleteContinueWatching(w http.ResponseWriter, r *http.Re
 	w.WriteHeader(http.StatusOK)
 }
 
+// HandleGetWatchlist renders user's watchlist page, grouped by status.
 func (h *Handler) HandleGetWatchlist(w http.ResponseWriter, r *http.Request) {
 	user := middleware.GetUser(r.Context())
 	if user == nil {
@@ -119,6 +125,7 @@ func (h *Handler) HandleGetWatchlist(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// group entries by status for display
 	watchlistByStatus := make(map[string][]db.GetUserWatchListRow)
 	allEntries := make([]db.GetUserWatchListRow, 0)
 	watchlistIDs := make([]int64, len(entries))
@@ -149,6 +156,7 @@ func (h *Handler) HandleGetWatchlist(w http.ResponseWriter, r *http.Request) {
 		},
 	}
 
+	// use partial template for htmx requests
 	templateName := "watchlist.gohtml"
 	if r.Header.Get("HX-Request") == "true" {
 		templateName = "watchlist_partial.gohtml"

api/watchlist/service.go

@@ -36,12 +36,14 @@ func NewService(db db.Querier, sqlDB *sql.DB, jikanClient *jikan.Client) *Servic
 	return &Service{db: db, sqlDB: sqlDB, jikanClient: jikanClient}
 }
 
+// ensureAnimeExists checks if anime exists in db, fetches from jikan if not, then upserts.
 func (s *Service) ensureAnimeExists(ctx context.Context, animeID int64) error {
 	_, err := s.db.GetAnime(ctx, animeID)
 	if err == nil {
-		return nil
+		return nil // already exists
 	}
 
+	// fetch from jikan and store locally
 	anime, err := s.jikanClient.GetAnimeByID(ctx, int(animeID))
 	if err != nil {
 		return fmt.Errorf("failed to fetch anime from jikan: %w", err)
@@ -72,6 +74,7 @@ type AddRequest struct {
 	Airing        bool
 }
 
+// AddToWatchlist adds or updates an anime entry in user's watchlist.
 func (s *Service) AddToWatchlist(ctx context.Context, userID string, animeID int64, status string) error {
 	if animeID <= 0 {
 		return ErrInvalidAnimeID
@@ -81,6 +84,7 @@ func (s *Service) AddToWatchlist(ctx context.Context, userID string, animeID int
 		return ErrInvalidStatus
 	}
 
+	// ensure anime exists in local db before linking
 	if err := s.ensureAnimeExists(ctx, animeID); err != nil {
 		return err
 	}
@@ -101,6 +105,7 @@ func (s *Service) AddToWatchlist(ctx context.Context, userID string, animeID int
 	return nil
 }
 
+// RemoveEntry deletes a watchlist entry and returns the anime for potential use.
 func (s *Service) RemoveEntry(ctx context.Context, userID string, animeID int64) (db.Anime, error) {
 	if animeID <= 0 {
 		return db.Anime{}, ErrInvalidAnimeID
@@ -122,6 +127,7 @@ func (s *Service) RemoveEntry(ctx context.Context, userID string, animeID int64)
 	return anime, nil
 }
 
+// GetUserWatchlist retrieves all watchlist entries for a user.
 func (s *Service) GetUserWatchlist(ctx context.Context, userID string) ([]db.GetUserWatchListRow, error) {
 	entries, err := s.db.GetUserWatchList(ctx, userID)
 	if err != nil {
@@ -130,6 +136,7 @@ func (s *Service) GetUserWatchlist(ctx context.Context, userID string) ([]db.Get
 	return entries, nil
 }
 
+// GetContinueWatching retrieves entries for continue watching section.
 func (s *Service) GetContinueWatching(ctx context.Context, userID string) ([]db.GetContinueWatchingEntriesRow, error) {
 	if strings.TrimSpace(userID) == "" {
 		return nil, errors.New("invalid user id")
@@ -143,6 +150,8 @@ func (s *Service) GetContinueWatching(ctx context.Context, userID string) ([]db.
 	return entries, nil
 }
 
+// DeleteContinueWatching removes entry and clears associated watch progress.
+// uses transaction when sqlDB is available.
 func (s *Service) DeleteContinueWatching(ctx context.Context, userID string, animeID int64) error {
 	if strings.TrimSpace(userID) == "" {
 		return errors.New("invalid user id")
@@ -164,6 +173,7 @@ func (s *Service) DeleteContinueWatching(ctx context.Context, userID string, ani
 		AnimeID:            animeID,
 	}
 
+	// use transaction when sqlDB available for consistency
 	if s.sqlDB == nil {
 		if err := s.db.DeleteContinueWatchingEntry(ctx, params); err != nil {
 			return fmt.Errorf("failed to delete continue watching entry: %w", err)

integrations/jikan/anime.go

@@ -6,6 +6,7 @@ import (
 	"time"
 )
 
+// GetAnimeCharacters returns character list for an anime with voice actor info.
 func (c *Client) GetAnimeCharacters(ctx context.Context, id int) ([]CharacterEntry, error) {
 	url := fmt.Sprintf("%s/anime/%d/characters", c.baseURL, id)
 	cacheKey := fmt.Sprintf("anime:characters:%d", id)
@@ -18,6 +19,7 @@ func (c *Client) GetAnimeCharacters(ctx context.Context, id int) ([]CharacterEnt
 	return resp.Data, nil
 }
 
+// GetAnimeRecommendations returns user-submitted recommendations for an anime.
 func (c *Client) GetAnimeRecommendations(ctx context.Context, id int) ([]RecommendationEntry, error) {
 	url := fmt.Sprintf("%s/anime/%d/recommendations", c.baseURL, id)
 	cacheKey := fmt.Sprintf("anime:recommendations:%d", id)
@@ -30,6 +32,7 @@ func (c *Client) GetAnimeRecommendations(ctx context.Context, id int) ([]Recomme
 	return resp.Data, nil
 }
 
+// GetAnimeByID returns full anime details; finished series cached 30 days, airing cached 1 day.
 func (c *Client) GetAnimeByID(ctx context.Context, id int) (Anime, error) {
 	cacheKey := fmt.Sprintf("anime:%d", id)
 

integrations/jikan/client.go

@@ -20,9 +20,9 @@ type Client struct {
 	httpClient  *http.Client
 	baseURL     string
 	db          db.Querier
-	retrySignal chan struct{}
+	retrySignal chan struct{} // signals retry worker to process queued retries
 	mu          sync.Mutex
-	lastReqTime time.Time
+	lastReqTime time.Time     // rate limiting: last request timestamp
 }
 
 func NewClient(db db.Querier) *Client {
@@ -51,6 +51,7 @@ func (e *APIError) Error() string {
 	return fmt.Sprintf("jikan api returned status %d", e.StatusCode)
 }
 
+// IsNotFoundError returns true if the error is an APIError with 404 status.
 func IsNotFoundError(err error) bool {
 	var apiErr *APIError
 	if errors.As(err, &apiErr) {
@@ -60,6 +61,7 @@ func IsNotFoundError(err error) bool {
 	return false
 }
 
+// IsRetryableError returns true if the error should trigger a retry.
 func IsRetryableError(err error) bool {
 	if err == nil {
 		return false
@@ -90,6 +92,7 @@ func isRetryableStatus(statusCode int) bool {
 	return statusCode >= 500 && statusCode <= 504
 }
 
+// retryDelay returns exponential backoff delay: 500ms, 1s, 2s, 4s, 8s (capped).
 func retryDelay(attempt int) time.Duration {
 	base := 500 * time.Millisecond
 	delay := base * time.Duration(1<<attempt)
@@ -100,6 +103,7 @@ func retryDelay(attempt int) time.Duration {
 	return delay
 }
 
+// parseRetryAfter parses Retry-After header value (seconds) into duration.
 func parseRetryAfter(value string) (time.Duration, bool) {
 	trimmed := strings.TrimSpace(value)
 	if trimmed == "" {
@@ -138,6 +142,7 @@ func truncateErrorMessage(message string) string {
 	return message[:400]
 }
 
+// notifyRetryWorker signals the retry worker, non-blocking.
 func (c *Client) notifyRetryWorker() {
 	select {
 	case c.retrySignal <- struct{}{}:
@@ -145,10 +150,12 @@ func (c *Client) notifyRetryWorker() {
 	}
 }
 
+// RetrySignal returns channel that signals when retries are enqueued.
 func (c *Client) RetrySignal() <-chan struct{} {
 	return c.retrySignal
 }
 
+// EnqueueAnimeFetchRetry queues a failed anime fetch for later retry if the error is retryable.
 func (c *Client) EnqueueAnimeFetchRetry(parentCtx context.Context, animeID int, cause error) {
 	if animeID <= 0 || !IsRetryableError(cause) {
 		return
@@ -168,6 +175,7 @@ func (c *Client) EnqueueAnimeFetchRetry(parentCtx context.Context, animeID int,
 	c.notifyRetryWorker()
 }
 
+// waitRateLimit enforces Jikan's 3 req/sec rate limit with 400ms spacing.
 func (c *Client) waitRateLimit(ctx context.Context) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -193,6 +201,7 @@ func (c *Client) waitRateLimit(ctx context.Context) error {
 	return nil
 }
 
+// getCache retrieves cached data by key, returns true on cache hit.
 func (c *Client) getCache(parentCtx context.Context, key string, out any) bool {
 	ctx, cancel := context.WithTimeout(parentCtx, 2*time.Second)
 	defer cancel()
@@ -206,6 +215,7 @@ func (c *Client) getCache(parentCtx context.Context, key string, out any) bool {
 	return err == nil
 }
 
+// getStaleCache retrieves expired-but-available cache by key.
 func (c *Client) getStaleCache(parentCtx context.Context, key string, out any) bool {
 	ctx, cancel := context.WithTimeout(parentCtx, 2*time.Second)
 	defer cancel()
@@ -219,6 +229,7 @@ func (c *Client) getStaleCache(parentCtx context.Context, key string, out any) b
 	return err == nil
 }
 
+// setCache stores data in cache with specified TTL.
 func (c *Client) setCache(parentCtx context.Context, key string, data any, ttl time.Duration) {
 	ctx, cancel := context.WithTimeout(parentCtx, 2*time.Second)
 	defer cancel()
@@ -240,6 +251,7 @@ type cacheResult struct {
 	hasStale bool
 }
 
+// isEmptyResult detects if response contains no meaningful data.
 func isEmptyResult(out any) bool {
 	switch v := out.(type) {
 	case *TopAnimeResponse:
@@ -254,6 +266,7 @@ func isEmptyResult(out any) bool {
 	return false
 }
 
+// getWithCache fetches URL with cache-aside pattern: checks cache first, falls back to stale on error.
 func (c *Client) getWithCache(ctx context.Context, cacheKey string, ttl time.Duration, url string, out any) error {
 	if c.getCache(ctx, cacheKey, out) {
 		if !isEmptyResult(out) {
@@ -289,6 +302,7 @@ func (c *Client) getWithCache(ctx context.Context, cacheKey string, ttl time.Dur
 	return nil
 }
 
+// fetchWithRetry makes HTTP request with exponential backoff retry on transient failures.
 func (c *Client) fetchWithRetry(ctx context.Context, urlStr string, out any) error {
 	maxRetries := 5
 	for attempt := range maxRetries {

integrations/jikan/constants.go

@@ -2,5 +2,5 @@ package jikan
 
 import "time"
 
-const shortCacheTTL = time.Hour
+const shortCacheTTL = time.Hour       // 1 hour - for frequently changing data
-const longCacheTTL = time.Hour * 24
+const longCacheTTL = time.Hour * 24   // 24 hours - for stable data like genres

integrations/jikan/episodes.go

@@ -7,6 +7,7 @@ import (
 	"time"
 )
 
+// GetEpisodes returns episode list for a specific page.
 func (c *Client) GetEpisodes(ctx context.Context, animeID int, page int) (EpisodesResponse, error) {
 	if page < 1 {
 		page = 1
@@ -20,6 +21,7 @@ func (c *Client) GetEpisodes(ctx context.Context, animeID int, page int) (Episod
 	return result, err
 }
 
+// GetAllEpisodes fetches all pages of episodes in parallel and flattens results.
 func (c *Client) GetAllEpisodes(ctx context.Context, animeID int) ([]Episode, error) {
 	// First page to get total pages
 	first, err := c.GetEpisodes(ctx, animeID, 1)
@@ -67,6 +69,7 @@ func (c *Client) GetAllEpisodes(ctx context.Context, animeID int) ([]Episode, er
 	return result, nil
 }
 
+// GetEpisodesRange fetches episodes from startPage to endPage sequentially.
 func (c *Client) GetEpisodesRange(ctx context.Context, animeID int, startPage, endPage int) ([]Episode, error) {
 	var all []Episode
 	for page := startPage; page <= endPage; page++ {

integrations/jikan/relations.go

@@ -14,10 +14,12 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
+// chiaki.watchOrderURL is the external watch order tool used for relation ordering.
 const chiakiWatchOrderURL = "https://chiaki.site/?/tools/watch_order/id/%d"
 const watchOrderCacheTTL = time.Hour * 24
-const maxWatchOrderEntries = 120
+const maxWatchOrderEntries = 120 // cap to prevent huge relation chains
 
+// watchOrderTypeLabel normalizes watch order type to display-friendly labels.
 func watchOrderTypeLabel(value string) string {
 	normalized := strings.ToLower(strings.TrimSpace(value))
 	switch normalized {
@@ -30,6 +32,7 @@ func watchOrderTypeLabel(value string) string {
 	}
 }
 
+// isAllowedWatchOrderType returns true only for TV and Movie types (filters out specials, etc).
 func isAllowedWatchOrderType(value string) bool {
 	normalized := strings.ToLower(strings.TrimSpace(value))
 	return normalized == "tv" || normalized == "movie"
@@ -39,6 +42,7 @@ func relationCacheKey(id int) string {
 	return fmt.Sprintf("relations:watch-order:%d", id)
 }
 
+// getWatchOrder fetches watch order from chiaki, caches result for 24h.
 func (c *Client) getWatchOrder(ctx context.Context, id int) (watchorder.WatchOrderResult, error) {
 	cacheKey := relationCacheKey(id)
 
@@ -81,6 +85,7 @@ func (c *Client) getWatchOrder(ctx context.Context, id int) (watchorder.WatchOrd
 	return result, nil
 }
 
+// currentOnlyRelation returns just the current anime when watch order lookup fails.
 func (c *Client) currentOnlyRelation(ctx context.Context, id int) ([]RelationEntry, error) {
 	currentAnime, err := c.GetAnimeByID(ctx, id)
 	if err != nil {
@@ -95,6 +100,7 @@ func (c *Client) currentOnlyRelation(ctx context.Context, id int) ([]RelationEnt
 	}}, nil
 }
 
+// GetFullRelations returns related anime based on watch order, with parallel fetching (3 concurrent).
 func (c *Client) GetFullRelations(ctx context.Context, id int) ([]RelationEntry, error) {
 	result, err := c.getWatchOrder(ctx, id)
 	if err != nil {

integrations/jikan/search.go

@@ -8,10 +8,12 @@ import (
 	"strings"
 )
 
+// Search performs a basic anime search by query string.
 func (c *Client) Search(ctx context.Context, query string, page int) (SearchResult, error) {
 	return c.search(ctx, query, page, 0)
 }
 
+// SearchAdvanced performs a filtered anime search with type, status, ordering, and genre filters.
 func (c *Client) SearchAdvanced(ctx context.Context, query, animeType, status, orderBy, sort string, genres []int, sfw bool, page, limit int) (SearchResult, error) {
 	if page < 1 {
 		page = 1
@@ -122,6 +124,7 @@ func (c *Client) search(ctx context.Context, query string, page int, limit int)
 	}, nil
 }
 
+// GetTopAnime returns the top-rated anime list for a given page.
 func (c *Client) GetTopAnime(ctx context.Context, page int) (TopAnimeResult, error) {
 	if page < 1 {
 		page = 1
@@ -145,6 +148,7 @@ func (c *Client) GetTopAnime(ctx context.Context, page int) (TopAnimeResult, err
 	}, nil
 }
 
+// GetAnimeGenres returns list of all anime genres, cached long-term.
 func (c *Client) GetAnimeGenres(ctx context.Context) ([]Genre, error) {
 	const cacheKey = "anime_genres"
 

integrations/jikan/seasons.go

@@ -8,9 +8,10 @@ import (
 
 type ScheduleResult struct {
 	Animes      []Anime
-	HasNextPage bool
+	HasNextPage bool // whether more pages available
 }
 
+// GetSchedule returns anime airing on a specific day of the week.
 func (c *Client) GetSchedule(ctx context.Context, day string) (ScheduleResult, error) {
 	day = strings.ToLower(day)
 	cacheKey := fmt.Sprintf("schedule_%s", day)
@@ -29,6 +30,7 @@ func (c *Client) GetSchedule(ctx context.Context, day string) (ScheduleResult, e
 	}, nil
 }
 
+// GetFullSchedule returns anime airing schedule for all seven days.
 func (c *Client) GetFullSchedule(ctx context.Context) (map[string][]Anime, error) {
 	days := []string{"monday", "tuesday", "wednesday", "thursday", "friday", "saturday", "sunday"}
 	schedule := make(map[string][]Anime)
@@ -44,6 +46,7 @@ func (c *Client) GetFullSchedule(ctx context.Context) (map[string][]Anime, error
 	return schedule, nil
 }
 
+// GetSeasonsNow returns currently airing anime for the current season.
 func (c *Client) GetSeasonsNow(ctx context.Context, page int) (TopAnimeResult, error) {
 	if page < 1 {
 		page = 1
@@ -64,6 +67,7 @@ func (c *Client) GetSeasonsNow(ctx context.Context, page int) (TopAnimeResult, e
 	}, nil
 }
 
+// GetSeasonsUpcoming returns anime scheduled to air in upcoming seasons.
 func (c *Client) GetSeasonsUpcoming(ctx context.Context, page int) (TopAnimeResult, error) {
 	if page < 1 {
 		page = 1
@@ -84,6 +88,7 @@ func (c *Client) GetSeasonsUpcoming(ctx context.Context, page int) (TopAnimeResu
 	}, nil
 }
 
+// GetRandomAnime returns a random anime from the database.
 func (c *Client) GetRandomAnime(ctx context.Context) (Anime, error) {
 	var result struct {
 		Data Anime `json:"data"`

integrations/jikan/studio.go

@@ -28,6 +28,7 @@ type ProducerResponse struct {
 	} `json:"data"`
 }
 
+// GetAnimeByProducer returns anime list for a producer/studio, includes producer name.
 func (c *Client) GetAnimeByProducer(ctx context.Context, producerID int, page int) (StudioAnimeResult, error) {
 	if page < 1 {
 		page = 1
@@ -75,6 +76,7 @@ func (c *Client) GetAnimeByProducer(ctx context.Context, producerID int, page in
 	return res, nil
 }
 
+// GetProducerByID returns full producer/studio details.
 func (c *Client) GetProducerByID(ctx context.Context, producerID int) (ProducerResponse, error) {
 	cacheKey := fmt.Sprintf("producer:info:%d", producerID)
 

integrations/jikan/types.go

@@ -155,18 +155,22 @@ type RecommendationsResponse struct {
 	Data []RecommendationEntry `json:"data"`
 }
 
+// ScoredByFormatted returns formatted count (e.g. "1 234 567").
 func (a Anime) ScoredByFormatted() string {
 	return formatNumber(a.ScoredBy)
 }
 
+// MembersFormatted returns formatted count (e.g. "1 234 567").
 func (a Anime) MembersFormatted() string {
 	return formatNumber(a.Members)
 }
 
+// FavoritesFormatted returns formatted count (e.g. "1 234 567").
 func (a Anime) FavoritesFormatted() string {
 	return formatNumber(a.Favorites)
 }
 
+// formatNumber adds space separators to a number (1234567 -> "1 234 567").
 func formatNumber(n int) string {
 	if n == 0 {
 		return ""
@@ -180,10 +184,12 @@ func formatNumber(n int) string {
 	return strings.Join(res, " ")
 }
 
+// ImageURL returns the webp large image URL for the anime.
 func (a Anime) ImageURL() string {
 	return a.Images.Webp.LargeImageURL
 }
 
+// ShortRating extracts just the rating code (e.g. "PG-13") from full rating string.
 func (a Anime) ShortRating() string {
 	if a.Rating == "" {
 		return ""
@@ -197,6 +203,7 @@ func (a Anime) ShortRating() string {
 	return a.Rating
 }
 
+// ShortDuration extracts numeric duration in minutes (e.g. "23m" from "23 min per ep").
 func (a Anime) ShortDuration() string {
 	if a.Duration == "" {
 		return ""
@@ -216,6 +223,7 @@ func (a Anime) ShortDuration() string {
 	return a.Duration
 }
 
+// DurationSeconds converts duration string to total seconds (e.g. "1 hr 30 min" -> 5400).
 func (a Anime) DurationSeconds() float64 {
 	if a.Duration == "" {
 		return 0
@@ -256,6 +264,7 @@ func (a Anime) DurationSeconds() float64 {
 	return float64(hours*60+minutes) * 60
 }
 
+// Premiered returns formatted premiere string (e.g. "Winter 2020").
 func (a Anime) Premiered() string {
 	if a.Season != "" && a.Year > 0 {
 		return fmt.Sprintf("%s %d", seasonLabel(a.Season), a.Year)
@@ -263,6 +272,7 @@ func (a Anime) Premiered() string {
 	return ""
 }
 
+// seasonLabel normalizes season string to title case (fall/autumn -> Fall).
 func seasonLabel(season string) string {
 	switch strings.ToLower(season) {
 	case "winter":
@@ -356,6 +366,7 @@ type RelationEntry struct {
 	IsExtra   bool
 }
 
+// DisplayTitle returns English title if available, otherwise Japanese, then default.
 func (a Anime) DisplayTitle() string {
 	if a.TitleEnglish != "" {
 		return a.TitleEnglish

integrations/watchorder/watch_order.go

@@ -15,7 +15,9 @@ import (
 
 const defaultUserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36"
 
+// idPattern extracts the watch order ID from chiaki.site URLs
 var idPattern = regexp.MustCompile(`/id/(\d+)`)
+// malLinkPattern extracts MAL IDs from watch order entries
 var malLinkPattern = regexp.MustCompile(`myanimelist\.net/anime/(\d+)`)
 
 var ErrInvalidWatchOrderURL = errors.New("invalid watch order url")
@@ -46,10 +48,10 @@ func (e *HTTPStatusError) Error() string {
 }
 
 type WatchOrderEntry struct {
-	ID       int    `json:"id"`
+	ID       int    `json:"id"`       // MAL anime ID
-	Type     string `json:"type"`
+	Type     string `json:"type"`      // anime type label (e.g. "TV", "Movie")
-	Title    string `json:"title"`
+	Title    string `json:"title"`     // primary title
-	TitleAlt string `json:"title_alt,omitempty"`
+	TitleAlt string `json:"title_alt,omitempty"` // alternative title
 }
 
 type WatchOrderResult struct {
@@ -106,6 +108,7 @@ func fetchDocument(ctx context.Context, httpClient *http.Client, url string) (*g
 	defer response.Body.Close()
 
 	if response.StatusCode != http.StatusOK {
+		// limit body read for error context; avoid reading large error pages
 		body, _ := io.ReadAll(io.LimitReader(response.Body, 512))
 		return nil, &HTTPStatusError{
 			StatusCode:  response.StatusCode,
@@ -198,6 +201,8 @@ func hasWatchOrderTable(doc *goquery.Document) bool {
 	return doc.Find("#wo_list").Length() > 0
 }
 
+// shouldTryProxy returns true for transient errors where the Jina proxy may help
+// (e.g. Cloudflare blocking, rate limits)
 func shouldTryProxy(err error) bool {
 	var statusError *HTTPStatusError
 	if errors.As(err, &statusError) {
@@ -243,6 +248,8 @@ func fetchProxyText(ctx context.Context, httpClient *http.Client, url string) (s
 	return string(body), nil
 }
 
+// parseJinaEntries parses Jina proxy output, which contains one line per entry
+// in format: "title | type | https://myanimelist.net/anime/ID"
 func parseJinaEntries(text string) []WatchOrderEntry {
 	lines := strings.Split(text, "\n")
 	entries := make([]WatchOrderEntry, 0)
@@ -312,6 +319,8 @@ func isNoiseTitleLine(value string) bool {
 	return false
 }
 
+// titleFromContext looks backward from metaIndex to find the actual title lines.
+// It skips noise lines (URLs, metadata prefixes, etc.) and returns (primary, alt).
 func titleFromContext(lines []string, metaIndex int) (string, string) {
 	collected := make([]string, 0, 2)
 
@@ -340,6 +349,7 @@ func titleFromContext(lines []string, metaIndex int) (string, string) {
 		return collected[0], ""
 	}
 
+	// reversed order: older lines first -> title, newer -> alt
 	return collected[1], collected[0]
 }
 
@@ -357,6 +367,8 @@ func fetchViaProxy(ctx context.Context, httpClient *http.Client, url string, roo
 	return WatchOrderResult{ID: rootID, WatchOrder: entries}, nil
 }
 
+// FetchWatchOrder fetches the watch order from chiaki.site.
+// Falls back to the Jina proxy if the site is blocked or returns an empty table.
 func FetchWatchOrder(ctx context.Context, httpClient *http.Client, url string) (WatchOrderResult, error) {
 	rootID, err := parseRootID(url)
 	if err != nil {
@@ -371,6 +383,7 @@ func FetchWatchOrder(ctx context.Context, httpClient *http.Client, url string) (
 		return WatchOrderResult{}, err
 	}
 
+	// empty table indicates JS-rendered content; need proxy
 	if !hasWatchOrderTable(doc) {
 		return fetchViaProxy(ctx, httpClient, url, rootID)
 	}

internal/context/context.go

@@ -1,5 +1,7 @@
 package context
 
+// UserKey is the context key for storing the authenticated user.
+// It is unexported to prevent collisions.
 type key int
 
 const (

internal/db/helpers.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 )
 
+// NullStringOr returns n.String if valid and non-empty, otherwise fallback
 func NullStringOr(n sql.NullString, fallback string) string {
 	if n.Valid && n.String != "" {
 		return n.String
@@ -14,6 +15,7 @@ func NullStringOr(n sql.NullString, fallback string) string {
 	return fallback
 }
 
+// DisplayTitle returns the English title, falling back to Japanese then original
 func DisplayTitle(titleEnglish, titleJapanese sql.NullString, titleOriginal string) string {
 	return NullStringOr(titleEnglish, NullStringOr(titleJapanese, titleOriginal))
 }
@@ -22,6 +24,7 @@ func (r GetUserWatchListRow) DisplayTitle() string {
 	return DisplayTitle(r.TitleEnglish, r.TitleJapanese, r.TitleOriginal)
 }
 
+// BoolPtr converts a nullable bool to a pointer; nil if not valid
 func BoolPtr(b sql.NullBool) *bool {
 	if !b.Valid {
 		return nil
@@ -29,6 +32,7 @@ func BoolPtr(b sql.NullBool) *bool {
 	return &b.Bool
 }
 
+// BeginTx starts a transaction and returns the Queries wrapper bound to it
 func BeginTx(ctx context.Context, db *sql.DB) (*Queries, *sql.Tx, error) {
 	if db == nil {
 		return nil, nil, errors.New("database unavailable")

internal/db/migrate.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 )
 
+// RunMigrations applies all *.sql files in migrationsDir in sorted order,
+// skipping any already recorded in migration_version.
 func RunMigrations(db *sql.DB, migrationsDir string) error {
 	if migrationsDir == "" {
 		return fmt.Errorf("migrations directory is required")
@@ -44,22 +46,19 @@ func RunMigrations(db *sql.DB, migrationsDir string) error {
 	for _, migrationFile := range migrations {
 		migrationName := filepath.Base(migrationFile)
 		if migrationApplied(appliedNames, migrationName) {
-			// already applied, skipping silently
+			continue // already applied
-			continue
 		}
 
-		// Read and execute migration
 		migrationSQL, err := os.ReadFile(migrationFile)
 		if err != nil {
 			return err
 		}
 
-		// Strict execution: if it fails, it halts.
 		if _, err := db.Exec(string(migrationSQL)); err != nil {
-			return err
+			return err // stop on first failure
 		}
 
-		// Mark as applied
+		// record applied migration
 		_, err = db.Exec("INSERT INTO migration_version (name) VALUES (?)", migrationName)
 		if err != nil {
 			return err
@@ -97,6 +96,8 @@ func loadAppliedMigrationNames(db *sql.DB) (map[string]struct{}, error) {
 	return applied, nil
 }
 
+// migrationApplied checks the applied names map for a match,
+// including legacy paths and case-insensitive basename matches.
 func migrationApplied(appliedNames map[string]struct{}, migrationName string) bool {
 	if _, exists := appliedNames[migrationName]; exists {
 		return true

internal/db/sqlite.go

@@ -9,6 +9,7 @@ import (
 	_ "github.com/mattn/go-sqlite3"
 )
 
+// Open connects to a sqlite3 database with foreign keys enforced
 func Open(dbFile string) (*sql.DB, error) {
 	db, err := sql.Open("sqlite3", fmt.Sprintf("file:%s?_foreign_keys=on", dbFile))
 	if err != nil {
@@ -17,6 +18,7 @@ func Open(dbFile string) (*sql.DB, error) {
 	return db, nil
 }
 
+// GetDBFile returns the database file path, checking DATABASE_FILE env var first
 func GetDBFile() string {
 	if f := os.Getenv("DATABASE_FILE"); f != "" {
 		return f
@@ -24,6 +26,7 @@ func GetDBFile() string {
 	return "mal.db"
 }
 
+// GetMigrationsDir returns the migrations directory, checking MIGRATIONS_DIR env var first
 func GetMigrationsDir() (string, error) {
 	if dir := os.Getenv("MIGRATIONS_DIR"); dir != "" {
 		return dir, nil
@@ -35,6 +38,7 @@ func GetMigrationsDir() (string, error) {
 	return filepath.Join(wd, "migrations"), nil
 }
 
+// Init opens the database, runs migrations, and returns a Queries instance
 func Init(db *sql.DB) (*Queries, error) {
 	migrationsDir, err := GetMigrationsDir()
 	if err != nil {

internal/middleware/access.go

@@ -6,18 +6,18 @@ import (
 )
 
 type AccessPolicy struct {
-	PublicPaths map[string]struct{}
+	PublicPaths map[string]struct{} // exact match paths (e.g. /login)
-	PublicHeads []string
+	PublicHeads []string             // prefix match paths (e.g. /static/)
 }
 
 func NewAccessPolicy() AccessPolicy {
 	return AccessPolicy{
 		PublicPaths: map[string]struct{}{
-			"/login": {},
+			"/login": {}, // login page is public
 		},
 		PublicHeads: []string{
-			"/static/",
+			"/static/", // static assets
-			"/dist/",
+			"/dist/",    // bundled assets
 		},
 	}
 }
@@ -36,6 +36,8 @@ func (p AccessPolicy) IsPublicPath(path string) bool {
 	return false
 }
 
+// RequireGlobalAuthWithPolicy redirects unauthenticated users to /login
+// uses HX-Redirect for HTMX requests, regular redirect otherwise
 func RequireGlobalAuthWithPolicy(policy AccessPolicy) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

internal/middleware/auth.go

@@ -9,18 +9,19 @@ import (
 	"mal/internal/db"
 )
 
+// Auth middleware validates the session cookie and injects the user into context
 func Auth(authService *auth.Service) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			cookie, err := r.Cookie("session_id")
 			if err != nil {
-				next.ServeHTTP(w, r)
+				next.ServeHTTP(w, r) // no cookie, proceed unauthenticated
 				return
 			}
 
 			user, err := authService.ValidateSession(r.Context(), cookie.Value)
 			if err != nil {
-				next.ServeHTTP(w, r)
+				next.ServeHTTP(w, r) // invalid session, proceed unauthenticated
 				return
 			}
 
@@ -30,6 +31,7 @@ func Auth(authService *auth.Service) func(http.Handler) http.Handler {
 	}
 }
 
+// GetUser retrieves the authenticated user from context, or nil if not authenticated
 func GetUser(ctx context.Context) *db.User {
 	user, ok := ctx.Value(ctxpkg.UserKey).(*db.User)
 	if !ok {

internal/server/routes.go

@@ -27,6 +27,7 @@ type Config struct {
 	PlaybackProxySecret string
 }
 
+// withMimeTypes sets Content-Type for common static asset extensions
 func withMimeTypes(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		ext := strings.ToLower(filepath.Ext(r.URL.Path))
@@ -44,6 +45,7 @@ func withMimeTypes(next http.Handler) http.Handler {
 	})
 }
 
+// noCache sends headers to prevent caching of dynamic/static assets
 func noCache(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
@@ -53,6 +55,7 @@ func noCache(next http.Handler) http.Handler {
 	})
 }
 
+// NewAuthLimiter returns a rate limiter for auth endpoints: 5 attempts per minute
 func NewAuthLimiter() *pkgmiddleware.Limiter {
 	return pkgmiddleware.NewLimiter(pkgmiddleware.Config{
 		MaxAttempts: 5,
@@ -60,6 +63,8 @@ func NewAuthLimiter() *pkgmiddleware.Limiter {
 	})
 }
 
+// NewRouter wires up all HTTP handlers and middleware.
+// Auth is enforced globally; public routes must opt-out via middleware policy.
 func NewRouter(cfg Config) http.Handler {
 	mux := http.NewServeMux()
 

internal/worker/relations.go

@@ -26,12 +26,13 @@ func New(db *db.Queries, client *jikan.Client) *Worker {
 
 func (w *Worker) Start(ctx context.Context) {
 	log.Println("Starting relations sync worker...")
+	// ticker: regular sync; retryTicker: check for failed API retries
 	ticker := time.NewTicker(1 * time.Minute)
 	retryTicker := time.NewTicker(30 * time.Second)
 	defer ticker.Stop()
 	defer retryTicker.Stop()
 
-	// Run once immediately
+	// Run once immediately on startup
 	w.runAllTasks(ctx)
 
 	cleanupCounter := 0
@@ -78,6 +79,7 @@ func (w *Worker) runAllTasks(ctx context.Context) {
 	wg.Wait()
 }
 
+// retryBackoff calculates the next retry delay, doubling up to 30 minutes max
 func retryBackoff(attempts int64) string {
 	if attempts < 1 {
 		attempts = 1
@@ -97,6 +99,7 @@ func retryBackoff(attempts int64) string {
 	return fmt.Sprintf("+%d minutes", minutes)
 }
 
+// processAnimeFetchRetries retries failed Jikan API fetches for anime with pending entries
 func (w *Worker) processAnimeFetchRetries(ctx context.Context) {
 	retries, err := w.db.GetDueAnimeFetchRetries(ctx, 20)
 	if err != nil {
@@ -139,6 +142,7 @@ func (w *Worker) cleanupCache(ctx context.Context) {
 	}
 }
 
+// syncRelations fetches relation data for anime that need syncing via a worker pool
 func (w *Worker) syncRelations(ctx context.Context) {
 	animes, err := w.db.GetAnimeNeedingRelationSync(ctx)
 	if err != nil {
@@ -170,6 +174,8 @@ func (w *Worker) syncRelations(ctx context.Context) {
 	wg.Wait()
 }
 
+// syncSingleAnime fetches relations for one anime, inserts them, and marks it synced.
+// For sequels, also ensures the related anime exists in the DB to enable linking.
 func (w *Worker) syncSingleAnime(ctx context.Context, id int64) {
 	animeData, err := w.client.GetAnimeByID(ctx, int(id))
 	if err != nil {

pkg/middleware/csrf.go

@@ -5,6 +5,8 @@ import (
 	"net/url"
 )
 
+// VerifyOrigin validates that the request Origin/Referer matches the host
+// skips validation for safe methods (GET, HEAD, OPTIONS)
 func VerifyOrigin(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method == http.MethodGet || r.Method == http.MethodHead || r.Method == http.MethodOptions {
@@ -36,7 +38,7 @@ func VerifyOrigin(next http.Handler) http.Handler {
 
 		host := r.Host
 		if forwardedHost := r.Header.Get("X-Forwarded-Host"); forwardedHost != "" {
-			host = forwardedHost
+			host = forwardedHost // support reverse proxies
 		}
 
 		expectedHTTP := "http://" + host

pkg/middleware/logging.go

@@ -10,6 +10,8 @@ import (
 	"time"
 )
 
+// statusRecorder wraps ResponseWriter to capture the status code
+// defaults to 200 if WriteHeader is never called before Write
 type statusRecorder struct {
 	http.ResponseWriter
 	statusCode  int
@@ -23,6 +25,7 @@ func newStatusRecorder(w http.ResponseWriter) *statusRecorder {
 	}
 }
 
+// WriteHeader records the status code and proxies to underlying writer
 func (rw *statusRecorder) WriteHeader(code int) {
 	if rw.wroteHeader {
 		return
@@ -32,6 +35,7 @@ func (rw *statusRecorder) WriteHeader(code int) {
 	rw.ResponseWriter.WriteHeader(code)
 }
 
+// Write ensures a status code is set before writing the body
 func (rw *statusRecorder) Write(b []byte) (int, error) {
 	if !rw.wroteHeader {
 		rw.WriteHeader(http.StatusOK)
@@ -39,12 +43,14 @@ func (rw *statusRecorder) Write(b []byte) (int, error) {
 	return rw.ResponseWriter.Write(b)
 }
 
+// Flush proxies the Flusher interface if supported
 func (rw *statusRecorder) Flush() {
 	if flusher, ok := rw.ResponseWriter.(http.Flusher); ok {
 		flusher.Flush()
 	}
 }
 
+// Hijack proxies the Hijacker interface if supported
 func (rw *statusRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	hijacker, ok := rw.ResponseWriter.(http.Hijacker)
 	if !ok {
@@ -53,6 +59,7 @@ func (rw *statusRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	return hijacker.Hijack()
 }
 
+// Push proxies the Pusher interface if supported
 func (rw *statusRecorder) Push(target string, opts *http.PushOptions) error {
 	pusher, ok := rw.ResponseWriter.(http.Pusher)
 	if !ok {
@@ -61,10 +68,13 @@ func (rw *statusRecorder) Push(target string, opts *http.PushOptions) error {
 	return pusher.Push(target, opts)
 }
 
+// Unwrap returns the underlying ResponseWriter for middleware chaining
 func (rw *statusRecorder) Unwrap() http.ResponseWriter {
 	return rw.ResponseWriter
 }
 
+// RequestLogger logs requests that result in 4xx/5xx responses
+// skips static assets, streaming, and common bot paths
 func RequestLogger(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		start := time.Now()

pkg/middleware/ratelimit.go

@@ -8,16 +8,19 @@ import (
 	"time"
 )
 
+// visitor tracks request attempts and last access time per IP
 type visitor struct {
 	attempts int
 	lastSeen time.Time
 }
 
+// Config holds rate limiter settings
 type Config struct {
-	MaxAttempts int
+	MaxAttempts int           // max requests per window
-	Window      time.Duration
+	Window      time.Duration // sliding window duration
 }
 
+// Limiter implements a simple in-memory IP-based rate limiter
 type Limiter struct {
 	mu       sync.Mutex
 	visitors map[string]*visitor
@@ -31,6 +34,7 @@ func NewLimiter(cfg Config) *Limiter {
 	}
 }
 
+// Cleanup removes stale visitor entries older than 3x the window
 func (l *Limiter) Cleanup(now time.Time) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -41,21 +45,23 @@ func (l *Limiter) Cleanup(now time.Time) {
 	}
 }
 
+// getIP extracts the client IP, checking X-Forwarded-For and X-Real-IP headers
 func getIP(r *http.Request) string {
 	if xff := r.Header.Get("X-Forwarded-For"); xff != "" {
 		ips := strings.Split(xff, ",")
-		return strings.TrimSpace(ips[0])
+		return strings.TrimSpace(ips[0]) // first proxy IP
 	}
 	if realIP := r.Header.Get("X-Real-IP"); realIP != "" {
 		return realIP
 	}
 	ip := r.RemoteAddr
 	if colonIdx := strings.LastIndex(ip, ":"); colonIdx != -1 {
-		ip = ip[:colonIdx]
+		ip = ip[:colonIdx] // strip port for IPv4-mapped IPv6
 	}
 	return ip
 }
 
+// Middleware returns 429 for rate-limited API requests
 func (l *Limiter) Middleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if !l.allow(getIP(r)) {
@@ -66,6 +72,8 @@ func (l *Limiter) Middleware(next http.Handler) http.Handler {
 	})
 }
 
+// AuthMiddleware redirects rate-limited form submissions back to the page
+// returns 429 for non-path requests (e.g. API calls)
 func (l *Limiter) AuthMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if !l.allow(getIP(r)) {
@@ -80,6 +88,8 @@ func (l *Limiter) AuthMiddleware(next http.Handler) http.Handler {
 	})
 }
 
+// allow checks and updates the visitor's attempt count; returns true if allowed
+// resets counter if window has expired, otherwise increments and checks limit
 func (l *Limiter) allow(ip string) bool {
 	l.mu.Lock()
 	defer l.mu.Unlock()
@@ -91,7 +101,7 @@ func (l *Limiter) allow(ip string) bool {
 	}
 
 	if time.Since(v.lastSeen) > l.config.Window {
-		v.attempts = 1
+		v.attempts = 1 // reset counter on window expiry
 		v.lastSeen = time.Now()
 		return true
 	}

static/anime.ts

@@ -1,6 +1,7 @@
 import { parseClassList } from './utils';
 
 const setDropdownMenuState = (menu: HTMLElement, isOpen: boolean): void => {
+  // data attributes store the class lists to add/remove
   const openClasses = parseClassList(menu.getAttribute('data-dropdown-open-classes'));
   const closedClasses = parseClassList(menu.getAttribute('data-dropdown-closed-classes'));
 

static/dedupe.ts

@@ -8,18 +8,19 @@ const dedupe = (): void => {
       return;
     }
     if (seen.has(id)) {
-      item.remove();
+      item.remove(); // duplicate, remove it
     } else {
       seen.add(id);
     }
   });
 };
 
+// run on DOM ready or immediately if already loaded
 if (document.readyState === 'loading') {
   document.addEventListener('DOMContentLoaded', dedupe);
 } else {
   dedupe();
 }
 
-window.addEventListener('load', dedupe);
+// also run on load as a fallback (e.g. htmx swaps)
 window.addEventListener('load', dedupe);

static/discover.ts

@@ -6,6 +6,7 @@ const setActiveDiscoverTab = (clickedTab: Element): void => {
     return;
   }
 
+  // reset all tabs in group
   const triggers = group.querySelectorAll('[data-tab-trigger]');
   triggers.forEach(tab => {
     const activeClasses = parseClassList(tab.getAttribute('data-tab-active-classes'));
@@ -14,6 +15,7 @@ const setActiveDiscoverTab = (clickedTab: Element): void => {
     tab.classList.add(...inactiveClasses);
   });
 
+  // mark clicked tab as active
   const activeClasses = parseClassList(clickedTab.getAttribute('data-tab-active-classes'));
   const inactiveClasses = parseClassList(clickedTab.getAttribute('data-tab-inactive-classes'));
   clickedTab.classList.remove(...inactiveClasses);

static/dropdown.ts

@@ -1,7 +1,7 @@
 class UIDropdown extends HTMLElement {
   isOpen: boolean = false;
   contentEl: HTMLElement | null = null;
-  isClosing: boolean = false;
+  isClosing: boolean = false; // debounce flag
 
   constructor() {
     super();
@@ -53,7 +53,7 @@ class UIDropdown extends HTMLElement {
     }
     setTimeout(() => {
       this.isClosing = false;
-    }, 100);
+    }, 100); // delay prevents rapid open/close flicker
   }
 
   handleClickOutside(event: MouseEvent): void {

static/player/controls.ts

@@ -7,6 +7,9 @@ export const formatTime = (seconds: number): string => {
   return `${mins.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
 };
 
+/**
+ * Shows the controls overlay and schedules auto-hide after 2s if playing.
+ */
 export const showControls = (): void => {
   state.container.classList.add('show-controls');
   window.clearTimeout(state.playerControlsTimeout);
@@ -17,6 +20,7 @@ export const showControls = (): void => {
   }, 2000);
 };
 
+// seek relative to current position
 export const seekBy = (delta: number): void => {
   if (state.video.duration <= 0) return;
   state.video.currentTime = Math.max(
@@ -34,6 +38,7 @@ export const togglePlayPause = (): void => {
   }
 };
 
+// toggle mute, restoring previous volume
 export const toggleMute = (): void => {
   if (state.video.muted || state.video.volume === 0) {
     const restored = state.lastKnownVolume > 0 ? state.lastKnownVolume : 1;
@@ -45,6 +50,7 @@ export const toggleMute = (): void => {
   }
 };
 
+// set volume (0-1), auto-unmute
 export const setVolume = (value: number): void => {
   state.video.volume = Math.max(0, Math.min(1, value));
   state.video.muted = value === 0;
@@ -59,8 +65,9 @@ export const toggleFullscreen = (): void => {
   state.container.requestFullscreen?.();
 };
 
+// syncs volume slider, underline, and mute icon
 export const syncVolumeUI = (): void => {
-  const { volumeRange, volumeUnderline, iconVolume, iconMuted } = getControls();
+  const { volumeRange, volumeUnderline } = getControls();
   const value = state.video.muted ? 0 : Math.round(state.video.volume * 100);
   if (volumeRange) {
     volumeRange.value = String(value);
@@ -125,6 +132,10 @@ const updateMuteIcons = (isMuted: boolean): void => {
   iconMuted?.classList.toggle('hidden', !isMuted);
 };
 
+/**
+ * Binds click handlers to player control buttons.
+ * Sets up video event listeners for icon sync.
+ */
 export const setupControls = (): void => {
   const {
     playPause,
@@ -137,6 +148,7 @@ export const setupControls = (): void => {
     skipSegmentBtn,
   } = getControls();
 
+  // play/pause on button and video click
   playPause?.addEventListener('click', () => {
     togglePlayPause();
     showControls();
@@ -151,11 +163,13 @@ export const setupControls = (): void => {
     showControls();
   });
 
+  // volume slider
   volumeRange?.addEventListener('input', () => {
     const value = Number(volumeRange.value) / 100;
     setVolume(value);
     showControls();
   });
+  // dragging class for visual feedback
   volumeRange?.addEventListener('pointerdown', () => volumePanel?.classList.add('is-dragging'));
   window.addEventListener('pointerup', () => volumePanel?.classList.remove('is-dragging'));
 
@@ -167,18 +181,21 @@ export const setupControls = (): void => {
     showControls();
   });
 
+  // skip intro/outro button
   skipSegmentBtn?.addEventListener('click', () => {
     if (!state.activeSkipSegment) return;
     state.video.currentTime = state.activeSkipSegment.end + 0.01;
     showControls();
   });
 
+  // fullscreen change handler
   document.addEventListener('fullscreenchange', () => {
     state.isFullscreen = !!document.fullscreenElement;
     state.container.classList.toggle('fullscreen', state.isFullscreen);
     if (state.isFullscreen) showControls();
   });
 
+  // icon sync on state changes
   state.video.addEventListener('play', () => {
     updatePlayPauseIcons(true);
     showControls();
@@ -189,8 +206,10 @@ export const setupControls = (): void => {
   });
   state.video.addEventListener('volumechange', syncVolumeUI);
 
+  // mouse move in container shows controls
   state.container.addEventListener('mousemove', showControls);
 
+  // initial sync
   updatePlayPauseIcons(false);
   syncVolumeUI();
 };

static/player/episodes/complete.ts

@@ -1,6 +1,11 @@
 import DOMPurify from 'dompurify';
 import { state } from '../state';
 
+/**
+ * Marks anime as completed when final episode finishes.
+ * Calls completion API, updates dropdown UI, adds to watchlist.
+ * Retries up to 2 times on failure.
+ */
 export const completeAnime = async (episodeNumber: number): Promise<void> => {
   if (state.completionSent || !state.malID || !episodeNumber) return;
   state.completionSent = true;
@@ -15,6 +20,7 @@ export const completeAnime = async (episodeNumber: number): Promise<void> => {
 
     if (!res.ok) {
       state.completionSent = false;
+      // retry
       if (state.completionAttempts < 2) {
         state.completionAttempts++;
         setTimeout(() => completeAnime(episodeNumber), 1000);
@@ -22,6 +28,7 @@ export const completeAnime = async (episodeNumber: number): Promise<void> => {
       return;
     }
 
+    // update dropdown trigger text
     const trigger = document.querySelector('[data-dropdown-trigger]') as HTMLButtonElement | null;
     if (trigger) {
       trigger.textContent = 'Completed ';
@@ -31,6 +38,7 @@ export const completeAnime = async (episodeNumber: number): Promise<void> => {
       trigger.appendChild(caret);
     }
 
+    // add to watchlist with 'completed' status
     const dropdown = document.getElementById('watch-status-dropdown');
     if (dropdown) {
       const payload = {
@@ -51,6 +59,7 @@ export const completeAnime = async (episodeNumber: number): Promise<void> => {
       })
         .then(async res => {
           if (!res.ok) return;
+          // replace dropdown with HTMX response
           const html = await res.text();
           const wrapper = document.createElement('span');
           wrapper.id = 'watch-status-dropdown';

static/player/episodes/nav.ts

@@ -1,22 +1,27 @@
 import { state } from '../state';
 import { SkipSegment } from '../types';
-import { displayTimeFromAbsolute } from '../timeline';
 import { resolveActiveSegments, renderSegments } from '../skip/segments';
 import { updateSubtitleOptions } from '../subtitles';
 import { updateQualityOptions } from '../quality';
 import { updateModeButtons } from '../mode';
-import { updateOverlay, isAutoplayEnabled, updateEpisodeHighlight, switchEpisodeRange } from './ui';
+import { updateOverlay, isAutoplayEnabled, switchEpisodeRange } from './ui';
 import { markEpisodeTransition } from '../progress';
 
+/**
+ * Handles video end: either marks complete or loads next episode.
+ * Fetches episode data from API, updates player state and URL.
+ */
 export const goToNextEpisode = async (): Promise<void> => {
   const currentEp = Number.parseInt(state.currentEpisode, 10);
   if (!currentEp) return;
 
+  // final episode: trigger completion flow
   if (state.totalEpisodes > 0 && currentEp >= state.totalEpisodes) {
     import('./complete').then(m => m.completeAnime(currentEp));
     return;
   }
 
+  // skip if autoplay disabled
   if (!isAutoplayEnabled()) return;
 
   const nextEp = currentEp + 1;
@@ -25,6 +30,7 @@ export const goToNextEpisode = async (): Promise<void> => {
   try {
     const res = await fetch(`/api/watch/episode/${state.malID}/${nextEp}`);
     if (!res.ok) {
+      // fallback: full page navigation
       sessionStorage.setItem('mal:autoplay-next', 'true');
       const url = new URL(window.location.href);
       url.searchParams.set('ep', String(nextEp));
@@ -34,6 +40,7 @@ export const goToNextEpisode = async (): Promise<void> => {
 
     const data = await res.json();
 
+    // update state with new episode data
     state.modeSources = data.mode_sources ?? {};
     state.availableModes = data.available_modes ?? [];
 
@@ -46,6 +53,7 @@ export const goToNextEpisode = async (): Promise<void> => {
       return;
     }
 
+    // load new video
     state.video.src = `${state.streamURL}?mode=${encodeURIComponent(fallback)}&token=${encodeURIComponent(state.modeSources[fallback].token)}`;
     state.video.load();
     if (!state.video.paused) state.video.play().catch(() => {});
@@ -56,11 +64,13 @@ export const goToNextEpisode = async (): Promise<void> => {
     state.completionAttempts = 0;
     state.activeSubtitles = [];
 
+    // update UI
     updateSubtitleOptions();
     updateQualityOptions();
     updateModeButtons();
     updateOverlay(state.currentEpisode, data.episode_title ?? '');
 
+    // update skip segments
     if (data.segments?.length) {
       state.parsedSegments = data.segments
         .map((s: SkipSegment) => ({ ...s, start: Number(s.start) || 0, end: Number(s.end) || 0 }))
@@ -69,6 +79,7 @@ export const goToNextEpisode = async (): Promise<void> => {
       renderSegments();
     }
 
+    // highlight new episode in list/grid
     state.episodeList
       ?.querySelectorAll('[data-episode-id]')
       .forEach(el => el.classList.remove('bg-accent/20'));
@@ -84,6 +95,7 @@ export const goToNextEpisode = async (): Promise<void> => {
       newGridEl?.classList.add('bg-accent/20', 'ring-2', 'ring-accent', 'text-accent');
     }
 
+    // update URL without reload
     const url = new URL(window.location.href);
     url.searchParams.set('ep', String(nextEp));
     history.pushState(null, '', url.toString());

static/player/episodes/ui.ts

@@ -1,8 +1,9 @@
 import { state } from '../state';
-import { updateSubtitleOptions } from '../subtitles';
-import { updateQualityOptions } from '../quality';
-import { updateModeButtons } from '../mode';
 
+/**
+ * Syncs autoplay checkbox with localStorage on init.
+ * Default is enabled (not 'false').
+ */
 export const setupAutoplayButton = (): void => {
   const btn = document.querySelector('[data-autoplay]') as HTMLInputElement | null;
   if (!btn) return;
@@ -12,12 +13,16 @@ export const setupAutoplayButton = (): void => {
 export const isAutoplayEnabled = (): boolean =>
   localStorage.getItem('mal:autoplay-enabled') !== 'false';
 
+/**
+ * Updates video overlay text (shown briefly on episode change).
+ */
 export const updateOverlay = (episode: string, title: string): void => {
   if (!state.videoOverlay) return;
   const p = state.videoOverlay.querySelector('p');
   p && (p.textContent = title ? `Episode ${episode}, ${title}` : `Episode ${episode}`);
 };
 
+// helper: get all episode elements from grid and list
 const getEpisodeEls = () => {
   const grid = state.episodeGrid;
   const list = state.episodeList;
@@ -27,19 +32,30 @@ const getEpisodeEls = () => {
   };
 };
 
+/**
+ * Highlights current episode in grid and list.
+ * Scrolls to episode into view.
+ */
 export const updateEpisodeHighlight = (num: number): void => {
   const { gridEls, listEls } = getEpisodeEls();
+  // clear old highlights
   [...gridEls, ...listEls].forEach(el =>
     el.classList.remove('ring-2', 'ring-accent', 'bg-accent/20', 'text-accent')
   );
 
+  // apply new highlight
   const gridEl = state.episodeGrid?.querySelector(`[data-episode-id="${num}"]`);
   const listEl = state.episodeList?.querySelector(`[data-episode-id="${num}"]`);
   gridEl?.classList.add('ring-2', 'ring-accent');
   listEl?.classList.add('ring-2', 'ring-accent');
+  // scroll into view
   (gridEl ?? listEl)?.scrollIntoView({ behavior: 'smooth', block: 'center' });
 };
 
+/**
+ * Switches visible episode range in grid.
+ * Updates dropdown label and hides/shows episode cards.
+ */
 export const switchEpisodeRange = (idx: number): void => {
   const dropdown = state.container.querySelector('[data-episode-dropdown]') as HTMLElement | null;
   if (!dropdown) return;
@@ -50,10 +66,12 @@ export const switchEpisodeRange = (idx: number): void => {
   const start = Number.parseInt(target.dataset.rangeStart ?? '1', 10);
   const end = Number.parseInt(target.dataset.rangeEnd ?? '100', 10);
 
+  // update label (e.g., "01-100")
   const label = dropdown.querySelector('[data-dropdown-label]') as HTMLElement | null;
   if (label)
     label.textContent = `${String(start).padStart(2, '0')}-${String(end).padStart(2, '0')}`;
 
+  // show/hide episodes in range
   state.episodeGrid?.querySelectorAll('[data-episode-id]').forEach(el => {
     const n = Number.parseInt((el as HTMLElement).dataset.episodeId ?? '0', 10);
     el.classList.toggle('hidden', n < start || n > end);

static/player/keyboard.ts

@@ -1,10 +1,5 @@
 import { state } from './state';
-import {
+import { absoluteTimeFromRatio, getBounds } from './timeline';
-  displayTimeFromAbsolute,
-  absoluteTimeFromDisplay,
-  absoluteTimeFromRatio,
-  getBounds,
-} from './timeline';
 import {
   showControls,
   toggleMute,
@@ -12,12 +7,16 @@ import {
   toggleFullscreen,
   seekBy,
   setVolume,
-  formatTime,
 } from './controls';
 
+/**
+ * Sets up keyboard shortcuts for player control.
+ * Ignores input/textarea to allow typing.
+ */
 export const setupKeyboard = (): void => {
   document.addEventListener('keydown', e => {
     const target = e.target as HTMLElement;
+    // ignore when typing in form fields
     if (target.tagName === 'INPUT' || target.tagName === 'TEXTAREA' || target.isContentEditable)
       return;
 
@@ -59,6 +58,7 @@ export const setupKeyboard = (): void => {
         showControls();
         break;
       default:
+        // number keys 0-9: jump to 0%-90% of video
         if (/^\d$/.test(e.key)) {
           const b = getBounds();
           if (b.duration > 0) {

static/player/main.ts

@@ -14,7 +14,7 @@ import { markEpisodeTransition, setupProgress } from './progress';
 import { absoluteTimeFromRatio, getBounds, displayTimeFromAbsolute } from './timeline';
 import { formatTime } from './controls';
 
-let initialized = false;
+let initialized = false; // prevent double init on htmx swaps
 
 const hidePreviewPopover = (): void => {
   state.previewPopover?.classList.remove('block');
@@ -27,6 +27,7 @@ const showPreviewPopover = (): void => {
   state.previewPopover?.classList.add('block');
 };
 
+// updates time preview on progress bar hover
 const updatePreviewUI = (ratio: number): void => {
   const progressWrap = state.container.querySelector('[data-progress-wrap]') as HTMLElement | null;
   if (!progressWrap || !state.previewPopover || !state.previewTime) {
@@ -39,6 +40,7 @@ const updatePreviewUI = (ratio: number): void => {
     return;
   }
 
+  // show time for hovered position
   state.previewTime.textContent = formatTime(Math.max(0, Math.min(b.duration, ratio * b.duration)));
 
   const barWidth = progressWrap.clientWidth;
@@ -48,6 +50,7 @@ const updatePreviewUI = (ratio: number): void => {
   }
 
   showPreviewPopover();
+  // clamp to stay within bar bounds
   const popoverWidth = state.previewPopover.offsetWidth || 72;
   state.previewPopover.style.left = `${Math.max(popoverWidth / 2, Math.min(barWidth - popoverWidth / 2, ratio * barWidth))}px`;
 };
@@ -62,6 +65,7 @@ const initPlayer = (): void => {
   const loading = container.querySelector('[data-loading]') as HTMLElement | null;
   const progressWrap = container.querySelector('[data-progress-wrap]') as HTMLElement | null;
 
+  // build video src from mode, token, and saved quality preference
   const preferredQuality = localStorage.getItem('mal:preferred-quality') || 'best';
   const streamToken = state.modeSources[state.currentMode]?.token;
   if (streamToken) {
@@ -90,10 +94,12 @@ const initPlayer = (): void => {
     resolveActiveSegments();
     renderSegments();
 
+    // resume from saved position
     const startTime = Number(container.dataset.startTimeSeconds ?? '0');
     if (startTime > 0 && state.video.currentTime <= 0.5 && state.video.duration > startTime) {
       state.video.currentTime = startTime;
     }
+    // resume after mode switch
     if (state.pendingSeekTime !== null) {
       state.video.currentTime = state.pendingSeekTime;
       state.pendingSeekTime = null;
@@ -110,10 +116,12 @@ const initPlayer = (): void => {
   state.video.addEventListener('playing', () => {
     loading && (loading.style.display = 'none');
   });
+  // update progress bar during buffering
   state.video.addEventListener('progress', () => {
     updateTimeline(state.video.currentTime);
   });
 
+  // main loop: update progress, subtitles, skip buttons
   state.video.addEventListener('timeupdate', () => {
     updateTimeline(state.video.currentTime);
     updateSubtitleRender(displayTimeFromAbsolute(state.video.currentTime));
@@ -124,6 +132,7 @@ const initPlayer = (): void => {
     goToNextEpisode();
   });
 
+  // click to seek
   progressWrap?.addEventListener('mousedown', e => {
     state.isScrubbing = true;
     const rect = progressWrap.getBoundingClientRect();
@@ -135,6 +144,7 @@ const initPlayer = (): void => {
     showControls();
   });
 
+  // hover to preview time
   progressWrap?.addEventListener('mousemove', e => {
     const rect = progressWrap.getBoundingClientRect();
     updatePreviewUI(Math.max(0, Math.min(1, (e.clientX - rect.left) / rect.width)));
@@ -142,6 +152,7 @@ const initPlayer = (): void => {
 
   progressWrap?.addEventListener('mouseleave', hidePreviewPopover);
 
+  // dragging outside progress bar while scrubbing
   window.addEventListener('mousemove', e => {
     if (!state.isScrubbing || !progressWrap) return;
     const rect = progressWrap.getBoundingClientRect();
@@ -152,6 +163,7 @@ const initPlayer = (): void => {
     updateSkipButton(state.video.currentTime);
   });
 
+  // track episode transitions from external links
   container.addEventListener('click', e => {
     const anchor = (e.target as Node).parentElement?.closest('a[href]');
     if (!(anchor instanceof HTMLAnchorElement)) return;
@@ -170,9 +182,11 @@ const initPlayer = (): void => {
   if (searchInput) {
     searchInput.addEventListener('input', () => {
       clearTimeout(searchDebounce);
+      // debounce to avoid excessive range switches while typing
       searchDebounce = window.setTimeout(() => {
         const val = searchInput.value.replace(/\D/g, '');
         if (!val) {
+          // clear: jump to current episode range
           const cur = Number.parseInt(state.currentEpisode, 10);
           switchEpisodeRange(Math.floor((cur - 1) / 100));
           updateEpisodeHighlight(cur);
@@ -191,6 +205,7 @@ const initPlayer = (): void => {
     });
   }
 
+  // range buttons (100s of episodes)
   if (dropdown) {
     dropdown.querySelectorAll('.episode-range-btn').forEach(btn => {
       btn.addEventListener('click', () => {
@@ -200,6 +215,7 @@ const initPlayer = (): void => {
     });
   }
 
+  // initial range for large episode lists
   if (state.episodeGrid && state.totalEpisodes > 100) {
     switchEpisodeRange(Math.floor((Number.parseInt(state.currentEpisode, 10) - 1) / 100));
   }

static/player/mode.ts

@@ -1,10 +1,10 @@
 import { state } from './state';
-import { displayTimeFromAbsolute, absoluteTimeFromDisplay } from './timeline';
+import { displayTimeFromAbsolute } from './timeline';
 import { showControls } from './controls';
 import { updateSubtitleOptions } from './subtitles';
 import { updateQualityOptions } from './quality';
-import { ModeSource } from './types';
 
+// builds stream URL with mode, token, and optional quality param
 const streamUrlForMode = (mode: string, quality?: string): string => {
   const src = state.modeSources[mode];
   if (!src?.token) return '';
@@ -13,16 +13,21 @@ const streamUrlForMode = (mode: string, quality?: string): string => {
   return url;
 };
 
+// switches video src while preserving playback position
 const loadVideo = (url: string): void => {
   if (!url) return;
   const wasPlaying = !state.video.paused;
   const prevTime = displayTimeFromAbsolute(state.video.currentTime);
   state.video.src = url;
   state.video.load();
-  state.pendingSeekTime = prevTime;
+  state.pendingSeekTime = prevTime; // restored in loadedmetadata handler
   if (wasPlaying) state.video.play().catch(() => {});
 };
 
+/**
+ * Switches between sub/dub mode.
+ * Saves preference to localStorage, reloads video src.
+ */
 export const switchMode = (mode: string): void => {
   if (!state.availableModes.includes(mode) || mode === state.currentMode) return;
   state.currentMode = mode;
@@ -33,6 +38,10 @@ export const switchMode = (mode: string): void => {
   updateModeButtons();
 };
 
+/**
+ * Updates dub/sub button styling based on current mode.
+ * Disables unavailable modes.
+ */
 export const updateModeButtons = (): void => {
   const dub = state.container.querySelector('[data-mode-dub]') as HTMLButtonElement | null;
   const sub = state.container.querySelector('[data-mode-sub]') as HTMLButtonElement | null;
@@ -51,6 +60,9 @@ export const updateModeButtons = (): void => {
   sub && (sub.disabled = !state.availableModes.includes('sub'));
 };
 
+/**
+ * Binds click handlers for mode buttons and autoplay toggle.
+ */
 export const setupMode = (): void => {
   const dub = state.container.querySelector('[data-mode-dub]') as HTMLButtonElement | null;
   const sub = state.container.querySelector('[data-mode-sub]') as HTMLButtonElement | null;

static/player/progress.ts

@@ -1,6 +1,7 @@
 import { state } from './state';
 import { displayTimeFromAbsolute } from './timeline';
 
+// builds JSON payload for progress API
 const buildPayload = (episode: number, seconds: number) =>
   JSON.stringify({
     mal_id: state.malID,
@@ -8,18 +9,24 @@ const buildPayload = (episode: number, seconds: number) =>
     time_seconds: seconds,
   });
 
+// sends progress via beacon (survives page unload)
 const sendBeacon = (payload: string) => {
   if (!navigator.sendBeacon) return false;
   navigator.sendBeacon('/api/watch-progress', new Blob([payload], { type: 'application/json' }));
   return true;
 };
 
+/**
+ * Saves current progress to backend.
+ * Debounced: skips if within 5s of last save for same episode.
+ */
 export const saveProgress = async (): Promise<void> => {
   if (!state.malID || state.video.currentTime < 1) return;
   const episode = Number.parseInt(state.currentEpisode, 10);
   if (!episode) return;
 
   const safeTime = displayTimeFromAbsolute(state.video.currentTime);
+  // skip if recently saved
   if (
     state.lastSavedProgress.episode === state.currentEpisode &&
     Math.abs(state.lastSavedProgress.seconds - safeTime) < 5
@@ -38,6 +45,7 @@ export const saveProgress = async (): Promise<void> => {
   } catch {}
 };
 
+// schedules periodic save every 30s during playback
 const scheduleProgressSave = (): void => {
   if (state.progressSaveTimer !== undefined) return;
   state.progressSaveTimer = window.setTimeout(() => {
@@ -46,6 +54,10 @@ const scheduleProgressSave = (): void => {
   }, 30000);
 };
 
+/**
+ * Records episode transition (clicked external link to next episode).
+ * Uses beacon for reliability on page unload.
+ */
 export const markEpisodeTransition = (episodeNumber: number): void => {
   if (!state.malID || !episodeNumber) return;
   if (state.progressSaveTimer !== undefined) {
@@ -54,6 +66,7 @@ export const markEpisodeTransition = (episodeNumber: number): void => {
   }
   state.transitionEpisode = episodeNumber;
   const payload = buildPayload(episodeNumber, 0);
+  // beacon falls back to fetch with keepalive
   if (!sendBeacon(payload)) {
     fetch('/api/watch-progress', {
       method: 'POST',
@@ -64,22 +77,29 @@ export const markEpisodeTransition = (episodeNumber: number): void => {
   }
 };
 
+/**
+ * Sets up progress save on timeupdate, pause, mouseup (scrub end), and beforeunload.
+ */
 export const setupProgress = (): void => {
+  // periodic save during playback
   state.video.addEventListener('timeupdate', () => {
     scheduleProgressSave();
   });
 
+  // immediate save on pause
   state.video.addEventListener('pause', () => {
     window.clearTimeout(state.progressSaveTimer);
     state.progressSaveTimer = undefined;
     saveProgress();
   });
 
+  // save after scrubbing
   window.addEventListener('mouseup', () => {
     state.isScrubbing = false;
     saveProgress();
   });
 
+  // save on page close
   window.addEventListener('beforeunload', () => {
     if (state.transitionEpisode !== null || state.completionSent || !state.malID) return;
     const episode = Number.parseInt(state.currentEpisode, 10);

static/player/quality.ts

@@ -1,6 +1,7 @@
 import { state } from './state';
-import { displayTimeFromAbsolute, absoluteTimeFromDisplay } from './timeline';
+import { displayTimeFromAbsolute } from './timeline';
 
+// same as mode.ts - could be extracted to shared util
 const streamUrlForMode = (mode: string, quality?: string): string => {
   const src = state.modeSources[mode];
   if (!src?.token) return '';
@@ -19,6 +20,10 @@ const loadVideo = (url: string): void => {
   if (wasPlaying) state.video.play().catch(() => {});
 };
 
+/**
+ * Switches video quality (resolution).
+ * Persists preference to localStorage.
+ */
 export const switchQuality = (quality: string): void => {
   const url = streamUrlForMode(state.currentMode, quality);
   if (!url) return;
@@ -26,6 +31,10 @@ export const switchQuality = (quality: string): void => {
   loadVideo(url);
 };
 
+/**
+ * Rebuilds quality dropdown options from current mode's available qualities.
+ * Shows/hides dropdown based on availability.
+ */
 export const updateQualityOptions = (): void => {
   const select = state.container.querySelector('[data-quality-select]') as HTMLSelectElement | null;
   if (!select) return;
@@ -44,13 +53,18 @@ export const updateQualityOptions = (): void => {
     select.appendChild(opt);
   });
 
+  // restore saved preference
   const preferred = localStorage.getItem('mal:preferred-quality') || 'best';
   select.value = qualities.includes(preferred) ? preferred : 'best';
 
+  // hide if no quality options
   const wrapper = select.parentElement;
   wrapper?.classList.toggle('hidden', qualities.length === 0);
 };
 
+/**
+ * Binds quality select change handler.
+ */
 export const setupQuality = (): void => {
   const select = state.container.querySelector('[data-quality-select]') as HTMLSelectElement | null;
   select?.addEventListener('change', e => {

static/player/state.ts

@@ -79,7 +79,12 @@ export const state: PlayerState = {
   videoOverlay: null,
 };
 
+/**
+ * Initializes player state from DOM data attributes.
+ * Called once on page load or htmx swap.
+ */
 export const initState = (c: HTMLElement): void => {
+  // core elements
   state.container = c;
   state.video = q<HTMLVideoElement>(c, 'video')!;
   state.progress = q<HTMLElement>(c, '[data-progress]');
@@ -91,14 +96,17 @@ export const initState = (c: HTMLElement): void => {
   state.previewTime = q<HTMLElement>(c, '[data-preview-time]');
   state.videoOverlay = q<HTMLElement>(c, '[data-video-overlay]');
 
+  // data attributes from server
   state.malID = Number.parseInt(dataset(c, 'malId'), 10);
   state.currentEpisode = dataset(c, 'currentEpisode') || '1';
   state.totalEpisodes = Number.parseInt(dataset(c, 'totalEpisodes'), 10);
   state.streamURL = dataset(c, 'streamUrl') || '/watch/proxy/stream';
   state.initialStreamToken = dataset(c, 'streamToken') || '';
+  // from session: previous page set this when autoplay triggered
   state.shouldAutoPlay = sessionStorage.getItem('mal:autoplay-next') === 'true';
   sessionStorage.removeItem('mal:autoplay-next');
 
+  // global elements (not inside player container)
   state.episodeGrid = qs<HTMLElement>('[data-episode-grid]');
   state.episodeList = qs<HTMLElement>('[data-episode-list]');
 
@@ -110,9 +118,11 @@ export const initState = (c: HTMLElement): void => {
     }
   };
 
+  // mode sources = { sub: { token, subtitles, qualities }, dub: { ... } }
   state.modeSources = safeJson(dataset(c, 'modeSources'), {} as Record<string, ModeSource>);
   state.availableModes = safeJson(dataset(c, 'availableModes'), [] as string[]);
 
+  // resolve initial mode: localStorage > backend default > first available > 'dub'
   const backendInitialMode = dataset(c, 'initialMode') || 'dub';
   const storedMode = localStorage.getItem('player-audio-mode');
   const initialMode =
@@ -122,6 +132,7 @@ export const initState = (c: HTMLElement): void => {
     ? initialMode
     : (fallbackMode ?? state.availableModes[0] ?? 'dub');
 
+  // parse skip segments from data attribute
   const segments = safeJson(dataset(c, 'segments'), [] as SkipSegment[]);
   state.parsedSegments = segments
     .map(s => ({ ...s, start: Number(s.start) || 0, end: Number(s.end) || 0 }))

static/player/subtitles/index.ts

@@ -2,8 +2,10 @@ import { SubtitleCue, SubtitleTrack } from '../types';
 import { state } from '../state';
 import { parseVtt } from './vtt';
 
+// proxy subtitle URL through backend (avoids CORS)
 const proxyUrl = (token: string) => `/watch/proxy/subtitle?token=${encodeURIComponent(token)}`;
 
+// builds subtitle track list from current mode's source
 const subtitlesForMode = (): SubtitleTrack[] => {
   const src = state.modeSources[state.currentMode];
   if (!src?.subtitles) return [];
@@ -24,6 +26,7 @@ const hideSubtitleText = (): void => {
   el.classList.add('hidden');
 };
 
+// fetches and parses VTT from proxy URL
 const loadSubtitle = async (url: string): Promise<SubtitleCue[]> => {
   try {
     const res = await fetch(url);
@@ -34,6 +37,10 @@ const loadSubtitle = async (url: string): Promise<SubtitleCue[]> => {
   }
 };
 
+/**
+ * Rebuilds subtitle dropdown from current mode's available tracks.
+ * Shows/hides dropdown based on availability.
+ */
 export const updateSubtitleOptions = (): void => {
   const select = state.container.querySelector(
     '[data-subtitle-select]'
@@ -61,6 +68,10 @@ export const updateSubtitleOptions = (): void => {
   hideSubtitleText();
 };
 
+/**
+ * Updates subtitle text display based on current video time.
+ * Finds active cue and shows/hides overlay.
+ */
 export const updateSubtitleRender = (time: number): void => {
   const el = state.container.querySelector('[data-subtitle-text]') as HTMLElement | null;
   if (!el) return;
@@ -69,6 +80,7 @@ export const updateSubtitleRender = (time: number): void => {
     return;
   }
 
+  // find cue containing current time
   const cue = state.activeSubtitles.find(c => time >= c.start && time <= c.end);
   if (!cue) {
     hideSubtitleText();
@@ -79,6 +91,10 @@ export const updateSubtitleRender = (time: number): void => {
   el.classList.remove('hidden');
 };
 
+/**
+ * Binds subtitle select change handler.
+ * Loads and parses selected VTT track.
+ */
 export const setupSubtitles = (): void => {
   const select = state.container.querySelector(
     '[data-subtitle-select]'

static/player/subtitles/vtt.ts

@@ -1,3 +1,4 @@
+// parses VTT timestamp (mm:ss.ms or hh:mm:ss.ms) to seconds
 export const parseVttTime = (raw: string): number => {
   const parts = raw.trim().split(':');
   if (parts.length < 2) return 0;
@@ -7,15 +8,18 @@ export const parseVttTime = (raw: string): number => {
   return Number(hourPart) * 3600 + Number(minPart) * 60 + Number(secPart.replace(',', '.'));
 };
 
+// parses a single VTT cue: timestamp line + text lines
 export const parseVttCue = (line: string, lines: string[], i: number) => {
   if (!line.includes('-->')) return null;
   const [startRaw, endRaw] = line.split('-->');
   const payload: string[] = [];
   let j = i + 1;
+  // collect text until blank line
   while (j < lines.length && lines[j].trim() !== '') {
     payload.push(lines[j]);
     j++;
   }
+  // strip tags, join lines
   const text = payload
     .join('\n')
     .replace(/<[^>]+>/g, '')
@@ -24,17 +28,23 @@ export const parseVttCue = (line: string, lines: string[], i: number) => {
   return { start: parseVttTime(startRaw), end: parseVttTime(endRaw), text };
 };
 
+/**
+ * Parses full VTT file into cue array.
+ * Handles both compact (timestamp on separate line) and standard formats.
+ */
 export const parseVtt = (text: string) => {
   const lines = text.replace(/\r/g, '').split('\n');
   const cues = [];
   for (let i = 0; i < lines.length; i++) {
     const line = lines[i].trim();
     if (!line) continue;
+    // compact: cue id on line i, timestamp on i+1
     if (i + 1 < lines.length && !line.includes('-->') && lines[i + 1].includes('-->')) {
       const cue = parseVttCue(lines[i + 1].trim(), lines, i + 1);
       if (cue) cues.push(cue);
       i++;
     } else if (line.includes('-->')) {
+      // standard: timestamp on same line
       const cue = parseVttCue(line, lines, i);
       if (cue) cues.push(cue);
     }

static/player/timeline.ts

@@ -1,6 +1,7 @@
 import { TimelineBounds } from './types';
 import { state } from './state';
 
+// mm:ss formatter
 const formatTime = (seconds: number): string => {
   if (!Number.isFinite(seconds) || seconds < 0) return '00:00';
   const mins = Math.floor(seconds / 60);
@@ -8,12 +9,18 @@ const formatTime = (seconds: number): string => {
   return `${mins.toString().padStart(2, '0')}:${secs.toString().padStart(2, '0')}`;
 };
 
+// cached to avoid recalc on every timeupdate
 let cachedBounds: TimelineBounds = { start: 0, end: 0, duration: 0 };
 
+/**
+ * Computes timeline bounds from video.
+ * Handles seekable ranges (live streams) and regular duration.
+ */
 export const timelineBounds = (): TimelineBounds => {
   const duration =
     Number.isFinite(state.video.duration) && state.video.duration > 0 ? state.video.duration : 0;
   let start = 0;
+  // check seekable range for live streams
   if (state.video.seekable.length > 0) {
     const seekableStart = state.video.seekable.start(0);
     if (Number.isFinite(seekableStart) && seekableStart > 0) start = seekableStart;
@@ -21,6 +28,7 @@ export const timelineBounds = (): TimelineBounds => {
   if (duration > start) {
     return { start, end: duration, duration: duration - start };
   }
+  // fallback to full seekable range
   if (state.video.seekable.length > 0) {
     const seekableEnd = state.video.seekable.end(state.video.seekable.length - 1);
     if (Number.isFinite(seekableEnd) && seekableEnd > start) {
@@ -36,27 +44,32 @@ export const invalidateBounds = (): void => {
 
 export const getBounds = (): TimelineBounds => cachedBounds;
 
+// converts video.currentTime to timeline-relative time (0-based for UI display)
 export const displayTimeFromAbsolute = (absoluteTime: number): number => {
   const b = getBounds();
   if (!Number.isFinite(absoluteTime) || b.duration <= 0) return 0;
   return Math.max(b.start, Math.min(b.end, absoluteTime)) - b.start;
 };
 
+// converts timeline-relative time back to video time
 export const absoluteTimeFromDisplay = (displayTime: number): number => {
   const b = getBounds();
   if (!Number.isFinite(displayTime) || b.duration <= 0) return 0;
   return b.start + Math.max(0, Math.min(b.duration, displayTime));
 };
 
+// converts 0-1 ratio to absolute video time
 export const absoluteTimeFromRatio = (ratio: number): number => {
   const b = getBounds();
   if (!Number.isFinite(ratio) || b.duration <= 0) return 0;
   return b.start + Math.max(0, Math.min(1, ratio)) * b.duration;
 };
 
+// finds the end of the buffered region containing currentTime
 export const getBufferedEnd = (): number => {
   const currentTime = state.video.currentTime;
   let end = 0;
+  // first: find buffered range that contains current time
   for (let i = 0; i < state.video.buffered.length; i++) {
     if (
       state.video.buffered.start(i) <= currentTime &&
@@ -66,6 +79,7 @@ export const getBufferedEnd = (): number => {
       break;
     }
   }
+  // fallback: next buffered range after current time
   if (end === 0) {
     for (let i = 0; i < state.video.buffered.length; i++) {
       if (state.video.buffered.end(i) > currentTime) {
@@ -76,6 +90,10 @@ export const getBufferedEnd = (): number => {
   return end;
 };
 
+/**
+ * Updates progress bar, scrubber position, and time displays.
+ * Called on timeupdate, progress events, and seek.
+ */
 export const updateTimeline = (currentTime: number): void => {
   const { progress, scrubber, timeDisplay, durationDisplay, buffered } = state;
   const b = getBounds();
@@ -95,6 +113,7 @@ export const updateTimeline = (currentTime: number): void => {
   timeDisplay.textContent = formatTime(displayTimeFromAbsolute(currentTime));
   durationDisplay.textContent = formatTime(b.duration);
 
+  // buffered region
   const bufferedEnd = getBufferedEnd();
   const bufferedPct = (displayTimeFromAbsolute(bufferedEnd) / b.duration) * 100;
   buffered.style.width = `${bufferedPct}%`;

static/player/types.ts

@@ -1,38 +1,45 @@
+// stream source for a single mode (sub/dub)
 export interface ModeSource {
   token: string;
   subtitles: SubtitleItem[];
   qualities?: string[];
 }
 
+// subtitle track from backend
 export interface SubtitleItem {
   lang: string;
   token: string;
 }
 
+// skip segment (intro/outro) from backend data attribute
 export interface SkipSegment {
-  type: string;
+  type: string; // 'op' or 'ed'
   start: number;
   end: number;
 }
 
+// parsed subtitle cue from VTT
 export interface SubtitleCue {
   start: number;
   end: number;
   text: string;
 }
 
+// loaded subtitle track for UI
 export interface SubtitleTrack {
   lang: string;
   label: string;
   url: string;
 }
 
+// validated skip segment within video bounds
 export interface ActiveSegment {
   type: string;
   start: number;
   end: number;
 }
 
+// timeline range (handles seekable ranges in live streams)
 export interface TimelineBounds {
   start: number;
   end: number;

static/q.ts

@@ -1,7 +1,16 @@
+/**
+ * querySelector on a container element, scoped to that element.
+ */
 export const q = <T extends Element>(container: HTMLElement, selector: string): T | null =>
   container.querySelector(selector) as T | null;
 
+/**
+ * querySelector on the document.
+ */
 export const qs = <T extends Element>(selector: string): T | null =>
   document.querySelector(selector) as T | null;
 
+/**
+ * Get a data attribute value from an element, defaults to empty string.
+ */
 export const dataset = (el: HTMLElement, key: string): string => el.dataset[key] ?? '';

static/search.ts

@@ -1,5 +1,3 @@
-export {};
-
 type QuickSearchResult = {
   id?: number;
   image?: string;
@@ -7,6 +5,7 @@ type QuickSearchResult = {
   type?: string;
 };
 
+// singleton flag to prevent double init (e.g. htmx swaps)
 const searchInitializedKey = Symbol('searchInitialized');
 const globalWindow = window as Window & { [searchInitializedKey]?: boolean };
 
@@ -23,6 +22,7 @@ const isSafeImageUrl = (rawUrl?: string): boolean => {
 
   try {
     const parsed = new URL(rawUrl, window.location.origin);
+    // block data: URIs and other potentially dangerous protocols
     return parsed.protocol === 'https:' || parsed.protocol === 'http:';
   } catch {
     return false;
@@ -139,6 +139,7 @@ const onSearchInput = (event: Event): void => {
 };
 
 const onSearchBlur = (): void => {
+  // delay to allow clicking on results before clearing
   window.setTimeout(() => {
     clearSearchResults();
   }, 200);

static/sort_filter.ts

@@ -7,6 +7,7 @@ const initSortFilter = (): void => {
     if (form) form.submit();
   };
 
+  // sync select values to hidden inputs, then submit form
   sortSelect?.addEventListener('change', () => {
     const input = document.getElementById('sort-input') as HTMLInputElement | null;
     if (input) input.value = sortSelect.value;

static/theme.ts

@@ -7,7 +7,7 @@ const getSavedTheme = (): Theme => {
   if (raw === 'light' || raw === 'dark') {
     return raw;
   }
-  return 'dark';
+  return 'dark'; // default to dark
 };
 
 const applyTheme = (theme: Theme): void => {
@@ -25,6 +25,7 @@ const initTheme = (): void => {
   const saved = getSavedTheme();
   applyTheme(saved);
 
+  // delegated click handler on theme buttons
   document.addEventListener('click', e => {
     const target = e.target as HTMLElement;
     const btn = target.closest('#theme-toggle, #footer-theme-toggle') as HTMLButtonElement | null;

static/timezone.ts

@@ -1,5 +1,6 @@
 export {};
 
+// JST offset from UTC in minutes (UTC+9)
 const jstOffsetMinutes = 9 * 60;
 
 type ParsedBroadcast = {
@@ -20,6 +21,7 @@ const parseBroadcastTime = (value: string | null): { hour: number; minute: numbe
 
   const hour = Number.parseInt(match[1], 10);
   const minute = Number.parseInt(match[2], 10);
+  // validate ranges
   if (
     Number.isNaN(hour) ||
     Number.isNaN(minute) ||
@@ -36,7 +38,7 @@ const parseBroadcastTime = (value: string | null): { hour: number; minute: numbe
 
 const isJstTimezone = (timezone: string | null): boolean => {
   if (!timezone) {
-    return true;
+    return true; // treat missing timezone as JST (anime default)
   }
 
   const normalized = timezone.trim().toLowerCase();
@@ -65,6 +67,7 @@ const parseBroadcast = (text: string | null): ParsedBroadcast | null => {
     return null;
   }
 
+  // matches "Monday at 00:00 (JST)" format
   const match = text.match(/^(.*) at (\d{1,2}):(\d{2}) \(JST\)$/i);
   if (!match) {
     return null;
@@ -86,6 +89,7 @@ const parseBroadcast = (text: string | null): ParsedBroadcast | null => {
 };
 
 const normalizeDay = (day: string): number | null => {
+  // strip trailing 's' for plural forms, then lookup
   const key = day.trim().toLowerCase().replace(/s$/, '');
   const days: Record<string, number> = {
     mon: 1,
@@ -116,11 +120,11 @@ const normalizeDay = (day: string): number | null => {
 
 const convertToLocal = (parsed: ParsedBroadcast, localOffsetMinutes: number): string | null => {
   const sourceMinutes = parsed.hour * 60 + parsed.minute;
-  const diff = jstOffsetMinutes - localOffsetMinutes;
+  const diff = jstOffsetMinutes - localOffsetMinutes; // JST ahead of local
   const localTotal = sourceMinutes - diff;
 
   const dayShift = Math.floor(localTotal / 1440);
-  const normalizedMinutes = ((localTotal % 1440) + 1440) % 1440;
+  const normalizedMinutes = ((localTotal % 1440) + 1440) % 1440; // handle negatives
   const localHour = Math.floor(normalizedMinutes / 60);
   const localMinute = normalizedMinutes % 60;
 
@@ -129,7 +133,7 @@ const convertToLocal = (parsed: ParsedBroadcast, localOffsetMinutes: number): st
     return null;
   }
 
-  const localDayIndex = (((sourceDayIndex + dayShift) % 7) + 7) % 7;
+  const localDayIndex = (((sourceDayIndex + dayShift) % 7) + 7) % 7; // proper modulo
   const localDay = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'][
     localDayIndex
   ];
@@ -144,6 +148,7 @@ const nextAiringUTC = (parsed: ParsedBroadcast): Date | null => {
     return null;
   }
 
+  // convert local time to JST to compare against JST now
   const now = new Date();
   const jstNow = new Date(now.getTime() + jstOffsetMinutes * 60 * 1000);
 
@@ -152,6 +157,7 @@ const nextAiringUTC = (parsed: ParsedBroadcast): Date | null => {
   const targetMinuteOfDay = parsed.hour * 60 + parsed.minute;
 
   let dayDelta = (targetDay - currentDay + 7) % 7;
+  // if same day but time has passed, schedule for next week
   if (dayDelta === 0 && targetMinuteOfDay <= currentMinuteOfDay) {
     dayDelta = 7;
   }
@@ -161,11 +167,13 @@ const nextAiringUTC = (parsed: ParsedBroadcast): Date | null => {
 };
 
 const formatRelative = (value: number, unit: Intl.RelativeTimeFormatUnit): string => {
+  // Intl.RelativeTimeFormat not available in all environments
   if (typeof Intl !== 'undefined' && typeof Intl.RelativeTimeFormat === 'function') {
     const formatter = new Intl.RelativeTimeFormat(undefined, { numeric: 'auto' });
     return formatter.format(value, unit);
   }
 
+  // fallback: "in X minutes/hours/days"
   const suffix = value === 1 ? unit : `${unit}s`;
   return `in ${value} ${suffix}`;
 };
@@ -223,6 +231,7 @@ const updateNode = (node: Element, localOffsetMinutes: number): void => {
   const card = node.closest('[data-notification-content]');
   const nextNode = card ? card.querySelector('[data-next-airing]') : null;
 
+  // try structured attrs first, fall back to text parsing
   const structured = parseFromStructuredAttrs(node);
   const source = node.getAttribute('data-jst-text');
   const parsed = structured || parseBroadcast(source);
@@ -252,6 +261,7 @@ const updateAll = (): void => {
 };
 
 const initTimezoneConversion = (): void => {
+  // run on initial load and after htmx swaps (content may change)
   document.addEventListener('DOMContentLoaded', updateAll);
   document.body.addEventListener('htmx:afterSwap', updateAll);
 };

static/toast.ts

@@ -5,6 +5,7 @@ interface ToastOptions {
   duration?: number;
 }
 
+/** Lazily create and return the toast container element. */
 const toastContainer = (): HTMLElement => {
   let container = document.getElementById('toast-container');
   if (!container) {
@@ -16,6 +17,10 @@ const toastContainer = (): HTMLElement => {
   return container;
 };
 
+/**
+ * Show a toast notification with optional auto-dismiss.
+ * Exposed globally via window.showToast.
+ */
 const showToast = ({ message, duration = 3000 }: ToastOptions): void => {
   const container = toastContainer();
   const template = document.getElementById('toast-template') as HTMLTemplateElement | null;
@@ -36,10 +41,12 @@ const showToast = ({ message, duration = 3000 }: ToastOptions): void => {
 
   container.appendChild(toast);
 
+  // trigger entrance animation
   requestAnimationFrame(() => {
     toast.classList.remove('translate-y-2', 'opacity-0');
   });
 
+  // auto-dismiss with exit animation
   setTimeout(() => {
     toast.classList.add('translate-y-2', 'opacity-0');
     setTimeout(() => toast.remove(), 300);

static/utils.ts

@@ -1,3 +1,6 @@
+/**
+ * Parse a space-separated class list string into an array, filtering empty entries.
+ */
 export const parseClassList = (value: string | null): string[] => {
   if (!value) {
     return [];

templates/base.gohtml

@@ -3,6 +3,7 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  {{/* page title injected from child template */}}
   <title>MyAnimeList: {{template "title" .}}</title>
   <link rel="manifest" href="/static/manifest.json">
   <link rel="icon" type="image/svg+xml" href="/static/favicon.svg">
@@ -64,9 +65,10 @@
     });
   </script>
   <script>
-    // Initialize sidebar state immediately to prevent layout shift/transitions
+    // initialize sidebar state immediately to prevent layout shift/transitions
     (function() {
       const isCollapsed = localStorage.getItem('sidebar-collapsed') === 'true';
+      // only apply collapsed state on desktop (lg+)
       if (isCollapsed && window.innerWidth >= 1024) {
         document.documentElement.classList.add('sidebar-collapsed');
       }
@@ -111,9 +113,11 @@
     }
 
     function toggleWatchlist(id, btn) {
+      // determine action based on current watchlist state
       const isInWatchlist = watchlistIds.has(id)
       const url = isInWatchlist ? `/api/watchlist/${id}` : '/api/watchlist'
       const method = isInWatchlist ? 'DELETE' : 'POST'
+      // add to watchlist with default status; remove doesn't need body
       const body = isInWatchlist ? null : JSON.stringify({ animeId: id, status: 'plan_to_watch' })
       fetch(url, {
         method,

templates/renderer.go

@@ -23,6 +23,8 @@ type Renderer struct {
 	templates map[string]*template.Template
 }
 
+// GetRenderer returns the singleton renderer, initializing it on first call.
+// Templates are loaded from ./templates/*.gohtml and ./templates/components/*.gohtml.
 func GetRenderer() *Renderer {
 	once.Do(func() {
 		renderer = &Renderer{
@@ -165,6 +167,7 @@ func GetRenderer() *Renderer {
 	return renderer
 }
 
+// ExecuteTemplate renders a named template into wr, returning early if context is cancelled
 func (r *Renderer) ExecuteTemplate(ctx context.Context, wr io.Writer, name string, data any) error {
 	select {
 	case <-ctx.Done():
@@ -179,6 +182,7 @@ func (r *Renderer) ExecuteTemplate(ctx context.Context, wr io.Writer, name strin
 	return tmpl.ExecuteTemplate(wr, "base.gohtml", data)
 }
 
+// ExecuteFragment renders a specific named block within a template (e.g. a component)
 func (r *Renderer) ExecuteFragment(ctx context.Context, wr io.Writer, name string, block string, data any) error {
 	select {
 	case <-ctx.Done():