refactor: decompose anime handler and parallelize for-you fetches

internal/anime/schedule.go

@@ -0,0 +1,95 @@
+package anime
+
+import (
+	"context"
+	"fmt"
+	"mal/integrations/animeschedule"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+type cachedWeekSchedule struct {
+	fetchedAt time.Time
+	value     animeschedule.WeekSchedule
+}
+
+func parseYearWeek(c *gin.Context) (int, int) {
+	year, _ := strconv.Atoi(c.Query("year"))
+	week, _ := strconv.Atoi(c.Query("week"))
+	if year <= 0 || week <= 0 {
+		now := time.Now()
+		y, w := now.ISOWeek()
+		if year <= 0 {
+			year = y
+		}
+		if week <= 0 {
+			week = w
+		}
+	}
+	return year, week
+}
+
+func (h *AnimeHandler) getCachedAnimeScheduleWeek(ctx context.Context, year int, week int) (animeschedule.WeekSchedule, error) {
+	cacheKey := fmt.Sprintf("%d-%02d", year, week)
+	const ttl = 10 * time.Minute
+
+	h.scheduleCacheMu.Lock()
+	cached, ok := h.scheduleCache[cacheKey]
+	h.scheduleCacheMu.Unlock()
+
+	if ok && time.Since(cached.fetchedAt) < ttl {
+		return cached.value, nil
+	}
+
+	value, err := animeschedule.FetchWeek(ctx, nil, year, week)
+	if err != nil {
+		return animeschedule.WeekSchedule{}, err
+	}
+
+	h.scheduleCacheMu.Lock()
+	h.scheduleCache[cacheKey] = cachedWeekSchedule{fetchedAt: time.Now(), value: value}
+	h.scheduleCacheMu.Unlock()
+
+	return value, nil
+}
+
+type scheduleDayView struct {
+	DateLabel    string
+	WeekdayLabel string
+	Entries      []animeschedule.Entry
+}
+
+func buildScheduleDays(schedule animeschedule.WeekSchedule, year int, week int) []scheduleDayView {
+	start := isoWeekStartMonday(year, week)
+	order := []time.Weekday{time.Monday, time.Tuesday, time.Wednesday, time.Thursday, time.Friday, time.Saturday, time.Sunday}
+	out := make([]scheduleDayView, 0, 7)
+	for i, wd := range order {
+		date := start.AddDate(0, 0, i)
+		out = append(out, scheduleDayView{
+			DateLabel:    strings.ToUpper(date.Format("02 Jan")),
+			WeekdayLabel: wd.String(),
+			Entries:      schedule.Days[wd],
+		})
+	}
+	return out
+}
+
+func isoWeekStartMonday(year int, week int) time.Time {
+	// ISO week 1 is the week with the year's first Thursday in it.
+	jan4 := time.Date(year, 1, 4, 12, 0, 0, 0, time.Local)
+	// Move back to Monday
+	offset := int(time.Monday - jan4.Weekday())
+	if offset > 0 {
+		offset -= 7
+	}
+	week1Monday := jan4.AddDate(0, 0, offset)
+	return week1Monday.AddDate(0, 0, (week-1)*7)
+}
+
+func adjacentISOWeek(year int, week int, deltaWeeks int) (int, int) {
+	target := isoWeekStartMonday(year, week).AddDate(0, 0, deltaWeeks*7)
+	return target.ISOWeek()
+}