feat: estimate released episode count for airing anime

internal/anime/details_handler.go

@@ -20,6 +20,23 @@ const (
 	audioLookupTimeout  = 8 * time.Second
 )
 
+func releasedEpisodeCount(anime domain.Anime, now time.Time) int {
+	if !anime.Airing || anime.Aired.From == "" {
+		return 0
+	}
+
+	firstAired, err := time.Parse(time.RFC3339, anime.Aired.From)
+	if err != nil || now.Before(firstAired) {
+		return 0
+	}
+
+	count := int(now.Sub(firstAired)/(7*24*time.Hour)) + 1
+	if anime.Episodes > 0 && count > anime.Episodes {
+		return anime.Episodes
+	}
+	return count
+}
+
 func animeAudioAvailabilityLabel(episodes []domain.CanonicalEpisode) string {
 	hasKnownSub := false
 	for _, episode := range episodes {
@@ -105,6 +122,7 @@ func (h *AnimeHandler) HandleAnimeDetails(c *gin.Context) {
 	}
 
 	audioAvailability := h.animeAudioAvailability(c.Request.Context(), anime)
+	episodesCount := releasedEpisodeCount(anime, time.Now())
 
 	c.HTML(http.StatusOK, "anime.gohtml", gin.H{
 		"Anime":                anime,
@@ -115,6 +133,7 @@ func (h *AnimeHandler) HandleAnimeDetails(c *gin.Context) {
 		"WatchlistIDs":         watchlistIDs,
 		"ContinueWatchingEp":   ep,
 		"ContinueWatchingTime": cwSeconds,
+		"EpisodesCount":        episodesCount,
 	})
 }
 

internal/anime/handler_test.go

@@ -6,6 +6,7 @@ import (
 	"mal/integrations/jikan"
 	"mal/internal/domain"
 	"testing"
+	"time"
 )
 
 type stubEpisodeService struct {
@@ -26,6 +27,92 @@ func (s *stubEpisodeService) RefreshTrackedDue(ctx context.Context, limit int) e
 	return nil
 }
 
+type releasedCountTest struct {
+	name  string
+	anime domain.Anime
+	now   time.Time
+	want  int
+}
+
+var releasedCountTests = []releasedCountTest{
+	{
+		name: "weekly airing count",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing:   true,
+			Episodes: 24,
+			Aired:    jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.June, 13, 15, 0, 0, 0, time.UTC),
+		want: 11,
+	},
+	{
+		name: "before first release",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing: true,
+			Aired:  jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.April, 4, 14, 59, 0, 0, time.UTC),
+		want: 0,
+	},
+	{
+		name: "first release counts as one",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing: true,
+			Aired:  jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.April, 4, 15, 0, 0, 0, time.UTC),
+		want: 1,
+	},
+	{
+		name: "caps at total episode count",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing:   true,
+			Episodes: 12,
+			Aired:    jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.December, 1, 15, 0, 0, 0, time.UTC),
+		want: 12,
+	},
+	{
+		name: "unknown total still estimates current count",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing: true,
+			Aired:  jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.April, 18, 15, 0, 0, 0, time.UTC),
+		want: 3,
+	},
+	{
+		name: "non airing anime is not estimated",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing: false,
+			Aired:  jikan.Aired{From: "2026-04-04T15:00:00+00:00"},
+		}},
+		now:  time.Date(2026, time.April, 18, 15, 0, 0, 0, time.UTC),
+		want: 0,
+	},
+	{
+		name: "invalid aired date is ignored",
+		anime: domain.Anime{Anime: jikan.Anime{
+			Airing: true,
+			Aired:  jikan.Aired{From: "not-a-date"},
+		}},
+		now:  time.Date(2026, time.April, 18, 15, 0, 0, 0, time.UTC),
+		want: 0,
+	},
+}
+
+func TestReleasedEpisodeCount(t *testing.T) {
+	for _, tt := range releasedCountTests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := releasedEpisodeCount(tt.anime, tt.now)
+			if got != tt.want {
+				t.Fatalf("releasedEpisodeCount() = %d, want %d", got, tt.want)
+			}
+		})
+	}
+}
+
 func TestAnimeAudioAvailabilityLabel(t *testing.T) {
 	tests := []struct {
 		name     string