优化缩略图

internal/service/image_resize_derive_test.go

@@ -0,0 +1,184 @@
+package service
+
+import (
+	"bytes"
+	"image"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+func TestParseResizeVariantSuffixRoundTrip(t *testing.T) {
+	opts := imageResizeOptions{MaxWidth: 480, MaxHeight: 600, Quality: 80}
+	name := "abc123." + opts.resizeVariantSuffix() + ".img"
+
+	width, height, ok := parseResizeVariantSuffix(name, "abc123")
+	if !ok {
+		t.Fatalf("expected %q to parse", name)
+	}
+	if width != 480 || height != 600 {
+		t.Fatalf("parsed %dx%d, want 480x600", width, height)
+	}
+
+	for _, bad := range []string{"abc123.img", "abc124.480x600q80.img", "abc123.480x600.img", "abc123.axbq80.img"} {
+		if _, _, ok := parseResizeVariantSuffix(bad, "abc123"); ok {
+			t.Fatalf("expected %q to be rejected", bad)
+		}
+	}
+}
+
+func TestLargerCachedVariantPicksSmallestCoveringVariant(t *testing.T) {
+	proxy := &ImageProxy{cacheDir: filepath.Join(t.TempDir(), "cache"), log: zap.NewNop()}
+	dir := filepath.Join(proxy.cacheDir, imageResizeCacheSubdir)
+	if err := os.MkdirAll(dir, 0o750); err != nil {
+		t.Fatal(err)
+	}
+
+	key := "deadbeef"
+	writeVariant := func(o imageResizeOptions) string {
+		path := proxy.resizeCachePath(key, o)
+		if err := os.WriteFile(path, []byte("x"), 0o600); err != nil {
+			t.Fatal(err)
+		}
+		return path
+	}
+	// 更小的档位不能用于派生（会放大），更大的档位里要挑最小的那个。
+	writeVariant(imageResizeOptions{MaxWidth: 96, Quality: 60})
+	large := writeVariant(imageResizeOptions{MaxWidth: 1920, MaxHeight: 1080, Quality: 80})
+	card := writeVariant(imageResizeOptions{MaxWidth: 480, MaxHeight: 600, Quality: 80})
+
+	got := proxy.largerCachedVariant(key, imageResizeOptions{MaxWidth: 160, Quality: 60})
+	if got != card {
+		t.Fatalf("largerCachedVariant = %q, want the card variant %q", got, card)
+	}
+
+	// 目标尺寸已与大档位相同（甚至更大）时没有可用来源。
+	if got := proxy.largerCachedVariant(key, imageResizeOptions{MaxWidth: 1920, MaxHeight: 1080, Quality: 80}); got != "" {
+		t.Fatalf("expected no derivable source when the target equals the only covering variant, got %q", got)
+	}
+	if got := proxy.largerCachedVariant(key, imageResizeOptions{MaxWidth: 2400, Quality: 80}); got != "" {
+		t.Fatalf("expected no derivable source for oversize targets, got %q", got)
+	}
+	if large == "" {
+		t.Fatal("large variant should have been written")
+	}
+}
+
+// TestServeResizedDerivesSmallVariantFromCachedCard 小尺寸档位必须能从已缓存
+// 的大尺寸档位派生，而不是每次都重新解码原图。
+//
+// 验证方式：生成卡片档位后，把原图内容替换成同长度、同 mtime 的非图片数据
+// （缓存键不变，但原图已无法解码）。若小图请求仍能返回正确的缩略图，就说明它
+// 是从缓存档位派生的；否则只能退回原图直出（此处会失败，因为原图已不是图片）。
+func TestServeResizedDerivesSmallVariantFromCachedCard(t *testing.T) {
+	dir := t.TempDir()
+	source := filepath.Join(dir, "poster.png")
+	original := encodeTestPNG(t, 1200, 1800, 255)
+	if err := os.WriteFile(source, original, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	// 固定 mtime 并读回平台量化后的值，保证替换内容后缓存键不变。
+	fixed := time.Now().Add(-time.Hour).Truncate(time.Second)
+	if err := os.Chtimes(source, fixed, fixed); err != nil {
+		t.Fatal(err)
+	}
+	srcStat, err := os.Stat(source)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxy := &ImageProxy{cacheDir: filepath.Join(dir, "cache"), log: zap.NewNop()}
+
+	card := imageResizeOptions{MaxWidth: 480, MaxHeight: 600, Quality: 80}
+	cardRec := httptest.NewRecorder()
+	if !proxy.serveResizedFromFile(cardRec, httptest.NewRequest("GET", "/x?maxWidth=480", nil), source, card) {
+		t.Fatal("expected the card variant request to be handled")
+	}
+	cardCfg, _, err := image.DecodeConfig(bytes.NewReader(cardRec.Body.Bytes()))
+	if err != nil {
+		t.Fatalf("decode card variant: %v", err)
+	}
+	if cardCfg.Width != 400 || cardCfg.Height != 600 {
+		t.Fatalf("card variant = %dx%d, want 400x600", cardCfg.Width, cardCfg.Height)
+	}
+
+	// 把原图换成同样长度的非图片数据，并恢复完全相同的 mtime，保持缓存键不变。
+	garbage := bytes.Repeat([]byte{0x11}, len(original))
+	if err := os.WriteFile(source, garbage, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chtimes(source, srcStat.ModTime(), srcStat.ModTime()); err != nil {
+		t.Fatal(err)
+	}
+
+	tiny := imageResizeOptions{MaxWidth: 160, Quality: 60}
+	tinyRec := httptest.NewRecorder()
+	if !proxy.serveResizedFromFile(tinyRec, httptest.NewRequest("GET", "/x?maxWidth=160", nil), source, tiny) {
+		t.Fatal("expected the tiny variant request to be handled")
+	}
+	tinyCfg, _, err := image.DecodeConfig(bytes.NewReader(tinyRec.Body.Bytes()))
+	if err != nil {
+		t.Fatalf("decode tiny variant: %v (the request fell back to the placeholder instead of deriving from the cached card)", err)
+	}
+	if tinyCfg.Width != 160 || tinyCfg.Height != 240 {
+		t.Fatalf("tiny variant = %dx%d, want 160x240", tinyCfg.Width, tinyCfg.Height)
+	}
+}
+
+// TestPrefetchCardVariantWarmsResizeCache 刮削预取要顺带生成卡片档位，
+// 首个海报墙请求即可命中缩放缓存。
+func TestPrefetchCardVariantWarmsResizeCache(t *testing.T) {
+	payload := encodeTestPNG(t, 1200, 1800, 255)
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "image/png")
+		_, _ = w.Write(payload)
+	}))
+	defer upstream.Close()
+
+	proxy := newStreamImageProxy(t, upstream.URL)
+	raw := upstream.URL + "/poster.png"
+
+	if err := proxy.PrefetchCardVariant(t.Context(), raw); err != nil {
+		t.Fatalf("PrefetchCardVariant failed: %v", err)
+	}
+
+	_, cachePath, _ := proxy.remoteImageCachePathsForValidated(raw)
+	stat, err := os.Stat(cachePath)
+	if err != nil {
+		t.Fatalf("expected the original to be cached: %v", err)
+	}
+	variantPath := proxy.resizeCachePath(prefetchCardResizeOptions.resizeSourceKey(cachePath, stat), prefetchCardResizeOptions)
+	if _, err := os.Stat(variantPath); err != nil {
+		t.Fatalf("expected the card variant to be pre-generated at %s: %v", variantPath, err)
+	}
+
+	// 预取失败时仍要返回错误（刮削据此保留旧图）。
+	bad := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadGateway)
+	}))
+	defer bad.Close()
+	failing := newStreamImageProxy(t, bad.URL)
+	if err := failing.PrefetchCardVariant(t.Context(), bad.URL+"/poster.png"); err == nil {
+		t.Fatal("expected an error for an unreachable candidate image")
+	}
+}
+
+// TestPrefetchCardVariantSurvivesUnresizableImage 上游返回的图无法缩放时，
+// 预取仍视为成功（图片可达即可），不能因此让刮削回退到旧图。
+func TestPrefetchCardVariantSurvivesUnresizableImage(t *testing.T) {
+	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "image/jpeg")
+		_, _ = w.Write(testJPEG)
+	}))
+	defer upstream.Close()
+
+	proxy := newStreamImageProxy(t, upstream.URL)
+	if err := proxy.PrefetchCardVariant(t.Context(), upstream.URL+"/cover.jpg"); err != nil {
+		t.Fatalf("PrefetchCardVariant failed: %v", err)
+	}
+}