refactor: populate watch page data before error return

internal/playback/handler/handler.go

@@ -54,22 +54,32 @@ func (h *PlaybackHandler) HandleWatchPage(c *gin.Context) {
 
 	data, err := h.svc.BuildWatchData(c.Request.Context(), id, []string{}, ep, mode, userID)
 	if err != nil {
+		if data.Anime.MalID == 0 && data.WatchData.MalID == 0 && len(data.Episodes) == 0 {
 			anime, fetchErr := h.animeSvc.GetAnimeByID(c.Request.Context(), id)
 			if fetchErr != nil {
 				fmt.Printf("error fetching anime for error page: %v\n", fetchErr)
 			}
-		c.HTML(http.StatusOK, "watch.gohtml", domain.WatchPageData{
-			Error:       err.Error(),
+			data = domain.WatchPageData{
 				Anime:       anime,
-			Episodes:    []domain.CanonicalEpisode{},
-			CurrentPath: c.Request.URL.Path,
-			User:        user,
 				CurrentEpID: ep,
 				WatchData: domain.WatchData{
+					MalID:          id,
+					Title:          anime.DisplayTitle(),
+					CurrentEpisode: ep,
 					Episodes:       []domain.CanonicalEpisode{},
 					Providers:      []domain.ProviderData{},
+					ModeSources:    map[string]domain.ModeSource{},
+					AvailableModes: []string{},
+					Airing:         anime.Airing,
 				},
-		})
+			}
+		}
+
+		data.Error = err.Error()
+		data.User = user
+		data.CurrentPath = c.Request.URL.Path
+
+		c.HTML(http.StatusOK, "watch.gohtml", data)
 		return
 	}
 

internal/playback/handler/watch_page_test.go

@@ -0,0 +1,126 @@
+package handler
+
+import (
+	"context"
+	"errors"
+	"mal/integrations/jikan"
+	"mal/internal/domain"
+	"mal/templates"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+type watchPagePlaybackService struct {
+	data domain.WatchPageData
+	err  error
+}
+
+func (s *watchPagePlaybackService) BuildWatchData(context.Context, int, []string, string, string, string) (domain.WatchPageData, error) {
+	return s.data, s.err
+}
+
+func (s *watchPagePlaybackService) SaveProgress(context.Context, string, int64, int, float64) error {
+	return nil
+}
+
+func (s *watchPagePlaybackService) CompleteAnime(context.Context, string, int64) error {
+	return nil
+}
+
+func (s *watchPagePlaybackService) SignProxyToken(string, string, string) (string, error) {
+	return "", nil
+}
+
+func (s *watchPagePlaybackService) ResolveProxyToken(string, string) (string, string, error) {
+	return "", "", nil
+}
+
+func (s *watchPagePlaybackService) UpsertSkipSegmentOverride(context.Context, string, int64, int, string, float64, float64) error {
+	return nil
+}
+
+type watchPageAnimeService struct{}
+
+func (watchPageAnimeService) GetAnimeByID(context.Context, int) (domain.Anime, error) {
+	return domain.Anime{}, errors.New("unexpected anime lookup")
+}
+
+func (watchPageAnimeService) GetAllEpisodes(context.Context, int) ([]domain.EpisodeData, error) {
+	return nil, nil
+}
+
+func baseWatchPageData() domain.WatchPageData {
+	return domain.WatchPageData{
+		Anime: domain.Anime{Anime: jikan.Anime{MalID: 123, Title: "Example Anime"}},
+		Episodes: []domain.CanonicalEpisode{
+			{Number: 1, Title: "Episode 1", HasSub: true},
+			{Number: 2, Title: "Episode 2", HasSub: true},
+		},
+		CurrentEpID: "1",
+		WatchData: domain.WatchData{
+			MalID:          123,
+			Title:          "Example Anime",
+			CurrentEpisode: "1",
+			Episodes: []domain.CanonicalEpisode{
+				{Number: 1, Title: "Episode 1", HasSub: true},
+				{Number: 2, Title: "Episode 2", HasSub: true},
+			},
+			ModeSources:    map[string]domain.ModeSource{},
+			AvailableModes: []string{},
+		},
+	}
+}
+
+func newWatchPageRouter(t *testing.T, h *PlaybackHandler) *gin.Engine {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	renderer, err := templates.ProvideRenderer()
+	if err != nil {
+		t.Fatalf("ProvideRenderer() error = %v", err)
+	}
+	router := gin.New()
+	router.HTMLRender = renderer
+	router.GET("/anime/:id/watch", h.HandleWatchPage)
+	return router
+}
+
+func TestHandleWatchPagePreservesPartialDataOnPlaybackFailure(t *testing.T) {
+	t.Parallel()
+
+	router := newWatchPageRouter(t, &PlaybackHandler{
+		svc: &watchPagePlaybackService{
+			data: baseWatchPageData(),
+			err:  errors.New("no streams found"),
+		},
+		animeSvc: watchPageAnimeService{},
+	})
+
+	req := httptest.NewRequestWithContext(context.Background(), http.MethodGet, "/anime/123/watch?ep=1", nil)
+	rec := httptest.NewRecorder()
+	router.ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
+	}
+
+	body := rec.Body.String()
+	if !strings.Contains(body, `data-mal-id="123"`) {
+		t.Fatalf("expected player MAL id in body, got:\n%s", body)
+	}
+	if !strings.Contains(body, `data-episode-id="1"`) {
+		t.Fatalf("expected episode list in body, got:\n%s", body)
+	}
+	if !strings.Contains(body, `data-playback-error="no streams found"`) {
+		t.Fatalf("expected playback error data attribute in body, got:\n%s", body)
+	}
+	if !strings.Contains(body, `/anime/123/watch?ep=2`) {
+		t.Fatalf("expected episode links to keep the anime id, got:\n%s", body)
+	}
+	if strings.Contains(body, "No episodes found") {
+		t.Fatalf("expected partial episode list instead of empty state, got:\n%s", body)
+	}
+}

internal/playback/watch_data.go

@@ -39,15 +39,7 @@ func (s *playbackService) BuildWatchData(ctx context.Context, animeID int, title
 	if resolvedModeSwitchedFrom != "" {
 		modeSwitchedFrom = resolvedModeSwitchedFrom
 	}
-	if len(modeSources) == 0 {
-		return domain.WatchPageData{}, fmt.Errorf("no streams found")
-	}
-	if result == nil {
-		return domain.WatchPageData{}, fmt.Errorf("no streams found for mode %s", mode)
-	}
-
 	startTime, watchlistStatus, watchlistIDs := s.loadWatchProgress(ctx, userID, animeID, anime.Episodes, episode)
-	go s.warmStreamURL(result.URL, result.Referer)
 	seasons := s.loadSeasons(ctx, animeID)
 	segments, err := s.fetchSkipSegments(ctx, userID, animeID, episode)
 	if err != nil {
@@ -57,7 +49,16 @@ func (s *playbackService) BuildWatchData(ctx context.Context, animeID int, title
 		)
 	}
 	watchData := buildWatchDataPayload(animeData, animeID, episode, startTime, canonicalEpisodes.Episodes, modeSources, mode, modeSwitchedFrom, segments)
-	return buildWatchPageData(animeData, canonicalEpisodes.Episodes, episode, watchlistStatus, watchlistIDs, seasons, watchData), nil
+	pageData := buildWatchPageData(animeData, canonicalEpisodes.Episodes, episode, watchlistStatus, watchlistIDs, seasons, watchData)
+	if len(modeSources) == 0 {
+		return pageData, fmt.Errorf("no streams found")
+	}
+	if result == nil {
+		return pageData, fmt.Errorf("no streams found for mode %s", mode)
+	}
+
+	go s.warmStreamURL(result.URL, result.Referer)
+	return pageData, nil
 }
 
 func buildWatchDataPayload(anime domain.Anime, animeID int, episode string, startTime float64, episodes []domain.CanonicalEpisode, modeSources map[string]domain.ModeSource, mode string, modeSwitchedFrom string, segments []domain.SkipSegment) domain.WatchData {