refactor: split modules and harden scraping workflows

internal/service/discover_artwork.go

@@ -0,0 +1,101 @@
+package service
+
+import (
+	"context"
+	"strings"
+	"sync"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+const (
+	discoverArtworkPrefetchLimit       = 48
+	discoverArtworkPrefetchConcurrency = 4
+	discoverArtworkPrefetchTimeout     = 45 * time.Second
+)
+
+func (d *DiscoverService) SetImageProxy(images *ImageProxy) *DiscoverService {
+	if d != nil {
+		d.images = images
+	}
+	return d
+}
+
+func (d *DiscoverService) WarmMatchArtwork(items []Match) int {
+	urls := make([]string, 0, len(items)*2)
+	for _, item := range items {
+		urls = append(urls, item.PosterURL, item.BackdropURL)
+	}
+	return d.warmArtworkURLs(urls)
+}
+
+func (d *DiscoverService) WarmExternalArtwork(items []ExternalMediaResult) int {
+	urls := make([]string, 0, len(items)*2)
+	for _, item := range items {
+		urls = append(urls, item.PosterURL, item.BackdropURL)
+	}
+	return d.warmArtworkURLs(urls)
+}
+
+func (d *DiscoverService) warmArtworkURLs(urls []string) int {
+	if d == nil || d.images == nil || len(urls) == 0 {
+		return 0
+	}
+	pending := uniqueDiscoverArtworkURLs(urls, discoverArtworkPrefetchLimit)
+	if len(pending) == 0 {
+		return 0
+	}
+	if d.log != nil {
+		d.log.Debug("discover artwork prefetch scheduled", zap.Int("count", len(pending)))
+	}
+	go d.prefetchArtworkURLs(pending)
+	return len(pending)
+}
+
+func uniqueDiscoverArtworkURLs(urls []string, limit int) []string {
+	if limit <= 0 {
+		return nil
+	}
+	seen := map[string]struct{}{}
+	out := make([]string, 0, min(len(urls), limit))
+	for _, raw := range urls {
+		raw = strings.TrimSpace(raw)
+		if raw == "" || !isHTTPish(raw) {
+			continue
+		}
+		if _, ok := seen[raw]; ok {
+			continue
+		}
+		seen[raw] = struct{}{}
+		out = append(out, raw)
+		if len(out) >= limit {
+			break
+		}
+	}
+	return out
+}
+
+func (d *DiscoverService) prefetchArtworkURLs(urls []string) {
+	ctx, cancel := context.WithTimeout(context.Background(), discoverArtworkPrefetchTimeout)
+	defer cancel()
+
+	sem := make(chan struct{}, discoverArtworkPrefetchConcurrency)
+	var wg sync.WaitGroup
+	for _, raw := range urls {
+		select {
+		case <-ctx.Done():
+			return
+		case sem <- struct{}{}:
+		}
+		wg.Add(1)
+		go func(raw string) {
+			defer wg.Done()
+			defer func() { <-sem }()
+			if err := d.images.PrefetchRemote(ctx, raw); err != nil && d.log != nil {
+				d.log.Debug("discover artwork prefetch failed", zap.String("url", raw), zap.Error(err))
+			}
+		}(raw)
+	}
+	wg.Wait()
+}