From 1465479f2aeccefde2ec97ce11a92fd8e9079d78 Mon Sep 17 00:00:00 2001
From: Drew Weymouth <dweymouth@gmail.com>
Date: Tue, 18 Jul 2023 18:31:20 -0700
Subject: [PATCH] add expiry to cached full size cover art

---
 backend/imagecache.go   |  9 +++++++++
 backend/imagemanager.go | 21 ++++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/backend/imagecache.go b/backend/imagecache.go
index 299ede6..10257fd 100644
--- a/backend/imagecache.go
+++ b/backend/imagecache.go
@@ -29,6 +29,12 @@ type ImageCache struct {
 	MaxSize    int
 	DefaultTTL time.Duration
 
+	// Sets a callback that is invoked whenever the periodic
+	// eviction has been run. Allows for "tacking on" extra
+	// cleanup tasks outside of the ImageCache's jurisdiction
+	// that are run on the same schedule.
+	OnEvictTaskRan func()
+
 	mu    sync.RWMutex
 	cache map[string]CacheItem
 }
@@ -157,6 +163,9 @@ func (i *ImageCache) periodicallyEvict(ctx context.Context, interval time.Durati
 			return
 		case <-t.C:
 			i.EvictExpired()
+			if i.OnEvictTaskRan != nil {
+				i.OnEvictTaskRan()
+			}
 		}
 	}
 }
diff --git a/backend/imagemanager.go b/backend/imagemanager.go
index b5d4721..d65c07e 100644
--- a/backend/imagemanager.go
+++ b/backend/imagemanager.go
@@ -20,15 +20,19 @@ import (
 
 const CachedImageValidTime = 24 * time.Hour
 
-const coverArtThumbnailSize = 300
+const (
+	coverArtThumbnailSize = 300
+	fullSizeCoverExpires  = 5 * time.Minute
+)
 
 type ImageManager struct {
 	s              *ServerManager
 	baseCacheDir   string
 	thumbnailCache ImageCache
 
-	cachedFullSizeCover   image.Image
-	cachedFullSizeCoverID string
+	cachedFullSizeCover           image.Image
+	cachedFullSizeCoverID         string
+	cachedFullSizeCoverAccessedAt int64 // unixMillis
 }
 
 func NewImageManager(ctx context.Context, s *ServerManager, baseCacheDir string) *ImageManager {
@@ -45,6 +49,7 @@ func NewImageManager(ctx context.Context, s *ServerManager, baseCacheDir string)
 			DefaultTTL: 1 * time.Minute,
 		},
 	}
+	i.thumbnailCache.OnEvictTaskRan = i.clearExpiredFullSizeCover
 	i.thumbnailCache.Init(ctx, 2*time.Minute)
 	return i
 }
@@ -74,6 +79,7 @@ func (i *ImageManager) GetCoverThumbnailWithTTL(coverID string, ttl time.Duratio
 
 func (i *ImageManager) GetFullSizeCoverArt(coverID string) (image.Image, error) {
 	if i.cachedFullSizeCoverID == coverID {
+		i.cachedFullSizeCoverAccessedAt = time.Now().UnixMilli()
 		return i.cachedFullSizeCover, nil
 	}
 	if i.s.Server == nil {
@@ -85,6 +91,7 @@ func (i *ImageManager) GetFullSizeCoverArt(coverID string) (image.Image, error)
 	}
 	i.cachedFullSizeCover = im
 	i.cachedFullSizeCoverID = coverID
+	i.cachedFullSizeCoverAccessedAt = time.Now().UnixMilli()
 	return im, nil
 }
 
@@ -215,3 +222,11 @@ func (i *ImageManager) loadLocalImage(path string) (image.Image, bool) {
 	}
 	return nil, false
 }
+
+func (i *ImageManager) clearExpiredFullSizeCover() {
+	now := time.Now().UnixMilli()
+	if now-i.cachedFullSizeCoverAccessedAt > fullSizeCoverExpires.Milliseconds() {
+		i.cachedFullSizeCoverID = ""
+		i.cachedFullSizeCover = nil
+	}
+}