Fix tests and clean up code a bit

core/artwork/cache_warmer.go

@@ -0,0 +1,63 @@
+package artwork
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/model"
+	"github.com/navidrome/navidrome/utils/pl"
+)
+
+type CacheWarmer interface {
+	PreCache(artID model.ArtworkID)
+}
+
+func NewCacheWarmer(artwork Artwork) CacheWarmer {
+	// If image cache is disabled, return a NOOP implementation
+	if conf.Server.ImageCacheSize == "0" {
+		return &noopCacheWarmer{}
+	}
+
+	a := &cacheWarmer{
+		artwork: artwork,
+		input:   make(chan string),
+	}
+	go a.run(context.TODO())
+	return a
+}
+
+type cacheWarmer struct {
+	artwork Artwork
+	input   chan string
+}
+
+func (a *cacheWarmer) PreCache(artID model.ArtworkID) {
+	a.input <- artID.String()
+}
+
+func (a *cacheWarmer) run(ctx context.Context) {
+	errs := pl.Sink(ctx, 2, a.input, a.doCacheImage)
+	for err := range errs {
+		log.Warn(ctx, "Error warming cache", err)
+	}
+}
+
+func (a *cacheWarmer) doCacheImage(ctx context.Context, id string) error {
+	r, _, err := a.artwork.Get(ctx, id, 0)
+	if err != nil {
+		return fmt.Errorf("error cacheing id='%s': %w", id, err)
+	}
+	defer r.Close()
+	_, err = io.Copy(io.Discard, r)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+type noopCacheWarmer struct{}
+
+func (a *noopCacheWarmer) PreCache(id model.ArtworkID) {}