Optimize backend search and evaluation pipeline

backend/services/gemini.go

@@ -14,6 +14,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -23,6 +24,14 @@ type GeminiService struct {
 	GenerateEndpoint  string
 	TranslateEndpoint string
 	Debug             func(message string, data any)
+	cacheMu           sync.Mutex
+	visualCache       map[string]cachedVisualData
+}
+
+type cachedVisualData struct {
+	data      string
+	mimeType  string
+	expiresAt time.Time
 }
 
 type AIRecommendation struct {
@@ -46,6 +55,7 @@ func NewGeminiService(apiKey string) *GeminiService {
 		Client:            &http.Client{Timeout: 40 * time.Second},
 		GenerateEndpoint:  "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent",
 		TranslateEndpoint: "https://translate.googleapis.com/translate_a/single",
+		visualCache:       map[string]cachedVisualData{},
 	}
 }
 
@@ -187,7 +197,7 @@ User query: ` + query,
 	maxImages := min(len(candidates), 10)
 	visualCount := 0
 	for idx := 0; idx < maxImages; idx++ {
-		img, mimeType, err := fetchCandidateVisualInlineData(g.Client, candidates[idx])
+		img, mimeType, err := g.fetchCandidateVisualInlineData(candidates[idx])
 		if err != nil {
 			g.debug("gemini:vision_candidate_visual_error", map[string]any{
 				"index":  idx,
@@ -330,6 +340,32 @@ func fetchImageAsInlineData(client *http.Client, imageURL, referer string) (stri
 	return base64.StdEncoding.EncodeToString(data), mimeType, nil
 }
 
+func (g *GeminiService) getCachedVisual(key string) (string, string, bool) {
+	g.cacheMu.Lock()
+	defer g.cacheMu.Unlock()
+
+	entry, ok := g.visualCache[key]
+	if !ok {
+		return "", "", false
+	}
+	if time.Now().After(entry.expiresAt) {
+		delete(g.visualCache, key)
+		return "", "", false
+	}
+	return entry.data, entry.mimeType, true
+}
+
+func (g *GeminiService) setCachedVisual(key, data, mimeType string, ttl time.Duration) {
+	g.cacheMu.Lock()
+	defer g.cacheMu.Unlock()
+
+	g.visualCache[key] = cachedVisualData{
+		data:      data,
+		mimeType:  mimeType,
+		expiresAt: time.Now().Add(ttl),
+	}
+}
+
 func newBrowserStyleImageRequest(imageURL, referer string) (*http.Request, error) {
 	req, err := http.NewRequest(http.MethodGet, imageURL, nil)
 	if err != nil {
@@ -344,21 +380,40 @@ func newBrowserStyleImageRequest(imageURL, referer string) (*http.Request, error
 	return req, nil
 }
 
-func fetchCandidateVisualInlineData(client *http.Client, candidate SearchResult) (string, string, error) {
+func (g *GeminiService) fetchCandidateVisualInlineData(candidate SearchResult) (string, string, error) {
 	if candidate.PreviewVideoURL != "" && (candidate.Source == "Envato" || candidate.Source == "Artgrid") {
+		cacheKey := "frame\n" + candidate.PreviewVideoURL
+		if data, mimeType, ok := g.getCachedVisual(cacheKey); ok {
+			return data, mimeType, nil
+		}
 		data, mimeType, err := extractFrameFromVideo(candidate.PreviewVideoURL)
 		if err == nil {
+			g.setCachedVisual(cacheKey, data, mimeType, 10*time.Minute)
 			return data, mimeType, nil
 		}
 	}
 	if candidate.ThumbnailURL != "" {
-		data, mimeType, err := fetchImageAsInlineData(client, candidate.ThumbnailURL, candidate.Link)
+		cacheKey := "image\n" + candidate.ThumbnailURL
+		if data, mimeType, ok := g.getCachedVisual(cacheKey); ok {
+			return data, mimeType, nil
+		}
+		data, mimeType, err := fetchImageAsInlineData(g.Client, candidate.ThumbnailURL, candidate.Link)
 		if err == nil {
+			g.setCachedVisual(cacheKey, data, mimeType, 10*time.Minute)
 			return data, mimeType, nil
 		}
 	}
 	if candidate.PreviewVideoURL != "" {
-		return extractFrameFromVideo(candidate.PreviewVideoURL)
+		cacheKey := "frame\n" + candidate.PreviewVideoURL
+		if data, mimeType, ok := g.getCachedVisual(cacheKey); ok {
+			return data, mimeType, nil
+		}
+		data, mimeType, err := extractFrameFromVideo(candidate.PreviewVideoURL)
+		if err != nil {
+			return "", "", err
+		}
+		g.setCachedVisual(cacheKey, data, mimeType, 10*time.Minute)
+		return data, mimeType, nil
 	}
 	return "", "", fmt.Errorf("candidate has no thumbnail or preview video")
 }