feat: add recommendation scoring and reranking engine
This commit is contained in:
269
internal/anime/recommendations.go
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269
internal/anime/recommendations.go
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@@ -0,0 +1,269 @@
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package anime
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import (
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"mal/integrations/jikan"
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"mal/internal/db"
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"mal/internal/domain"
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"math"
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"slices"
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"strings"
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"time"
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)
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const (
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forYouMaxSeeds = 8
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forYouMaxRecommendations = 8
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forYouCandidateFetchLimit = 36
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forYouResultLimit = 12
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forYouSeedRecencyWindow = 180 * 24 * time.Hour
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forYouFreshReleaseWindow = 540 * 24 * time.Hour
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forYouGenreMatchWeight = 1.8
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forYouThemeMatchWeight = 1.0
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forYouStudioMatchWeight = 0.7
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forYouDemographicMatchWeight = 0.9
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)
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type recommendationSeed struct {
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animeID int
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weight float64
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}
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type recommendationCandidate struct {
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anime jikan.Anime
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score float64
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genreMatches int
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themeMatches int
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studioMatches int
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demographicMatches int
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}
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type userTasteProfile struct {
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genres map[int]float64
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themes map[int]float64
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studios map[int]float64
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demographics map[int]float64
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prefersAiring bool
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prefersRecent bool
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}
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func buildRecommendationSeeds(
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now time.Time,
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watchlist []db.GetUserWatchListRow,
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) []recommendationSeed {
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seeds := make([]recommendationSeed, 0, min(len(watchlist), forYouMaxSeeds))
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for _, entry := range watchlist {
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weight := recommendationEntryWeight(now, entry)
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if weight <= 0 || entry.AnimeID <= 0 {
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continue
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}
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seeds = append(seeds, recommendationSeed{
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animeID: int(entry.AnimeID),
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weight: weight,
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})
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if len(seeds) >= forYouMaxSeeds {
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break
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}
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}
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return seeds
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}
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func recommendationEntryWeight(now time.Time, entry db.GetUserWatchListRow) float64 {
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status := strings.TrimSpace(entry.Status)
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var statusWeight float64
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switch status {
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case "completed":
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statusWeight = 1.0
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case "watching":
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statusWeight = 0.9
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case "plan_to_watch":
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statusWeight = 0.35
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default:
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return 0
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}
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recencyWeight := 1.0
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if !entry.UpdatedAt.IsZero() {
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age := now.Sub(entry.UpdatedAt)
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if age > 0 {
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recencyWeight = math.Max(0.35, 1-(age.Hours()/forYouSeedRecencyWindow.Hours()))
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}
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}
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progressWeight := 0.6
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if entry.CurrentEpisode.Valid && entry.CurrentEpisode.Int64 > 0 {
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progressWeight = min(1.0, 0.6+(0.08*float64(entry.CurrentEpisode.Int64)))
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}
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return statusWeight * recencyWeight * progressWeight
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}
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func buildTasteProfile(seedAnimes []jikan.Anime) userTasteProfile {
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profile := userTasteProfile{
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genres: make(map[int]float64),
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themes: make(map[int]float64),
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studios: make(map[int]float64),
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demographics: make(map[int]float64),
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}
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var airingCount int
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var recentCount int
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for _, anime := range seedAnimes {
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addEntityWeights(profile.genres, anime.Genres, 1.0)
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addEntityWeights(profile.themes, anime.Themes, 0.7)
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addEntityWeights(profile.studios, anime.Studios, 0.5)
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addEntityWeights(profile.demographics, anime.Demographics, 0.7)
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if anime.Airing {
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airingCount++
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}
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if anime.Year > 0 && time.Now().Year()-anime.Year <= 4 {
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recentCount++
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}
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}
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total := len(seedAnimes)
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if total > 0 {
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profile.prefersAiring = float64(airingCount)/float64(total) >= 0.5
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profile.prefersRecent = float64(recentCount)/float64(total) >= 0.5
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}
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return profile
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}
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func addEntityWeights(target map[int]float64, entities []jikan.NamedEntity, weight float64) {
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for _, entity := range entities {
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if entity.MalID <= 0 {
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continue
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}
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target[entity.MalID] += weight
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}
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}
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func scoreRecommendationCandidate(
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now time.Time,
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profile userTasteProfile,
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candidate jikan.Anime,
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collaborativeScore float64,
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) recommendationCandidate {
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genreMatches, genreScore := weightedEntityMatch(profile.genres, candidate.Genres)
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themeMatches, themeScore := weightedEntityMatch(profile.themes, candidate.Themes)
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studioMatches, studioScore := weightedEntityMatch(profile.studios, candidate.Studios)
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demographicMatches, demographicScore := weightedEntityMatch(profile.demographics, candidate.Demographics)
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score := collaborativeScore
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score += genreScore * forYouGenreMatchWeight
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score += themeScore * forYouThemeMatchWeight
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score += studioScore * forYouStudioMatchWeight
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score += demographicScore * forYouDemographicMatchWeight
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if candidate.Score > 0 {
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score += min(candidate.Score/10.0, 1.0)
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}
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if candidate.Popularity > 0 {
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score += 1.0 / math.Log(float64(candidate.Popularity)+8)
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}
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if profile.prefersAiring && candidate.Airing {
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score += 0.5
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}
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if profile.prefersRecent && candidate.Year > 0 && now.Year()-candidate.Year <= 4 {
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score += 0.45
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}
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if candidate.Year > 0 && now.Year()-candidate.Year > 15 {
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score -= 0.2
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}
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if candidate.Status == "Not yet aired" {
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score -= 0.35
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}
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if candidate.Aired.From != "" {
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if airedAt, err := time.Parse(time.RFC3339, candidate.Aired.From); err == nil {
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if now.Sub(airedAt) <= forYouFreshReleaseWindow {
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score += 0.3
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}
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}
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}
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return recommendationCandidate{
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anime: candidate,
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score: score,
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genreMatches: genreMatches,
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themeMatches: themeMatches,
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studioMatches: studioMatches,
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demographicMatches: demographicMatches,
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}
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}
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func weightedEntityMatch(weights map[int]float64, entities []jikan.NamedEntity) (int, float64) {
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var (
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matches int
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score float64
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)
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for _, entity := range entities {
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weight, ok := weights[entity.MalID]
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if !ok {
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continue
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}
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matches++
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score += weight
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}
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return matches, score
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}
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func rerankRecommendationCandidates(candidates []recommendationCandidate, limit int) []domain.Anime {
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selected := make([]domain.Anime, 0, min(limit, len(candidates)))
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seenGenres := make(map[int]int)
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for _, candidate := range candidates {
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if len(selected) >= limit {
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break
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}
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if isGenreOverrepresented(candidate.anime, seenGenres) {
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continue
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}
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selected = append(selected, domain.Anime{Anime: candidate.anime})
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for _, genre := range candidate.anime.Genres {
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seenGenres[genre.MalID]++
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}
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}
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if len(selected) >= limit {
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return selected
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}
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for _, candidate := range candidates {
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if len(selected) >= limit {
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break
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}
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if slices.ContainsFunc(selected, func(anime domain.Anime) bool {
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return anime.MalID == candidate.anime.MalID
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}) {
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continue
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}
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selected = append(selected, domain.Anime{Anime: candidate.anime})
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}
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return selected
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}
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func isGenreOverrepresented(anime jikan.Anime, seenGenres map[int]int) bool {
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if len(anime.Genres) == 0 {
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return false
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}
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matchedGenres := 0
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for _, genre := range anime.Genres {
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if seenGenres[genre.MalID] >= 3 {
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matchedGenres++
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}
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}
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return matchedGenres == len(anime.Genres)
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}
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73
internal/anime/recommendations_test.go
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73
internal/anime/recommendations_test.go
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@@ -0,0 +1,73 @@
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package anime
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import (
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"database/sql"
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"mal/integrations/jikan"
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"mal/internal/db"
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"testing"
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"time"
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)
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func TestRecommendationEntryWeightPrioritizesCommittedRecentHistory(t *testing.T) {
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now := time.Date(2026, time.June, 4, 12, 0, 0, 0, time.UTC)
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completed := recommendationEntryWeight(now, db.GetUserWatchListRow{
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Status: "completed",
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UpdatedAt: now.Add(-24 * time.Hour),
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CurrentEpisode: sql.NullInt64{Int64: 12, Valid: true},
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})
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planned := recommendationEntryWeight(now, db.GetUserWatchListRow{
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Status: "plan_to_watch",
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UpdatedAt: now.Add(-24 * time.Hour),
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})
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if completed <= planned {
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t.Fatalf("expected completed history to outrank planned history, got completed=%f planned=%f", completed, planned)
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}
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}
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func TestBuildRecommendationSeedsFiltersUnsupportedStatuses(t *testing.T) {
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now := time.Date(2026, time.June, 4, 12, 0, 0, 0, time.UTC)
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seeds := buildRecommendationSeeds(now, []db.GetUserWatchListRow{
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{AnimeID: 1, Status: "dropped", UpdatedAt: now},
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{AnimeID: 2, Status: "watching", UpdatedAt: now},
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{AnimeID: 3, Status: "completed", UpdatedAt: now},
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})
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if len(seeds) != 2 {
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t.Fatalf("expected 2 valid seeds, got %d", len(seeds))
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}
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if seeds[0].animeID != 2 || seeds[1].animeID != 3 {
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t.Fatalf("unexpected seed ordering: %+v", seeds)
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}
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}
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func TestScoreRecommendationCandidateRewardsProfileOverlap(t *testing.T) {
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now := time.Date(2026, time.June, 4, 12, 0, 0, 0, time.UTC)
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profile := userTasteProfile{
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genres: map[int]float64{
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1: 2.0,
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},
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themes: map[int]float64{},
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studios: map[int]float64{},
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demographics: map[int]float64{},
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}
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matching := scoreRecommendationCandidate(now, profile, jikan.Anime{
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MalID: 10,
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Genres: []jikan.NamedEntity{{MalID: 1, Name: "Action"}},
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Popularity: 100,
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Score: 8.0,
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}, 5.0)
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nonMatching := scoreRecommendationCandidate(now, profile, jikan.Anime{
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MalID: 11,
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Genres: []jikan.NamedEntity{{MalID: 2, Name: "Drama"}},
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Popularity: 100,
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Score: 8.0,
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}, 5.0)
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if matching.score <= nonMatching.score {
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t.Fatalf("expected matching candidate to score higher, got matching=%f nonMatching=%f", matching.score, nonMatching.score)
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}
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}
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