Add GIPHY image search feature

backend/services/gemini.go

@@ -20,6 +20,7 @@ import (
 
 type GeminiService struct {
 	APIKey            string
+	Model             string
 	Client            *http.Client
 	GenerateEndpoint  string
 	TranslateEndpoint string
@@ -69,11 +70,15 @@ type QueryExpansion struct {
 	Querywords []string `json:"querywords"`
 }
 
-func NewGeminiService(apiKey string) *GeminiService {
+func NewGeminiService(apiKey, model string) *GeminiService {
+	if strings.TrimSpace(model) == "" {
+		model = "gemini-2.5-flash"
+	}
 	return &GeminiService{
 		APIKey:            apiKey,
+		Model:             model,
 		Client:            &http.Client{Timeout: 40 * time.Second},
-		GenerateEndpoint:  "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent",
+		GenerateEndpoint:  "https://generativelanguage.googleapis.com/v1beta/models/" + model + ":generateContent",
 		TranslateEndpoint: "https://translate.googleapis.com/translate_a/single",
 		visualCache:       map[string]cachedVisualData{},
 		translationCache:  map[string]cachedStringValue{},
@@ -99,6 +104,75 @@ func (g *GeminiService) ExpandQuery(query string) ([]string, error) {
 	return expanded, nil
 }
 
+func (g *GeminiService) ExpandImageQueries(query string) ([]string, error) {
+	trimmed := strings.TrimSpace(query)
+	if trimmed == "" {
+		return nil, fmt.Errorf("query is empty")
+	}
+	cacheKey := "image-expansion\n" + trimmed
+	if cached, ok := g.getCachedExpansion(cacheKey); ok {
+		g.debug("gemini:image_expand_cache_hit", map[string]any{"query": trimmed, "expanded": cached})
+		return cached, nil
+	}
+
+	fallback := buildFallbackImageQueries(trimmed, g.TranslateQuery(trimmed))
+	if g.APIKey == "" {
+		g.setCachedExpansion(cacheKey, fallback, 15*time.Minute)
+		return fallback, fmt.Errorf("gemini api key is not configured")
+	}
+
+	body := map[string]any{
+		"systemInstruction": map[string]any{
+			"parts": []map[string]string{{
+				"text": "Return exactly 5 concise English search queries for GIPHY image or GIF search. Respond with JSON only in this shape: {\"queries\":[\"...\",\"...\",\"...\",\"...\",\"...\"]}. Keep the queries meaning-preserving, practical, deduplicated, and concise.",
+			}},
+		},
+		"contents": []map[string]any{{
+			"parts": []map[string]string{{
+				"text": "User query: " + trimmed + "\nGenerate exactly 5 English search queries for GIPHY image or GIF search. Include a direct translation, a common phrasing, and only relevant related variants.",
+			}},
+		}},
+		"generationConfig": map[string]any{
+			"responseMimeType": "application/json",
+			"temperature":      0.2,
+			"maxOutputTokens":  160,
+		},
+	}
+
+	rawText, err := g.generateText(body)
+	if err != nil {
+		g.debug("gemini:image_expand_error", map[string]any{"query": trimmed, "error": err.Error()})
+		g.setCachedExpansion(cacheKey, fallback, 15*time.Minute)
+		return fallback, err
+	}
+	jsonText, err := extractJSONObject(rawText)
+	if err != nil {
+		g.debug("gemini:image_expand_parse_error", map[string]any{"query": trimmed, "error": err.Error()})
+		g.setCachedExpansion(cacheKey, fallback, 15*time.Minute)
+		return fallback, err
+	}
+
+	var payload struct {
+		Queries []string `json:"queries"`
+	}
+	if err := json.Unmarshal([]byte(jsonText), &payload); err != nil {
+		g.debug("gemini:image_expand_json_error", map[string]any{"query": trimmed, "error": err.Error(), "raw": truncateForError(rawText, 200)})
+		g.setCachedExpansion(cacheKey, fallback, 15*time.Minute)
+		return fallback, err
+	}
+	queries := normalizeImageExpansionQueries(payload.Queries)
+	if len(queries) != 5 {
+		err := fmt.Errorf("gemini image expansion returned %d queries", len(queries))
+		g.debug("gemini:image_expand_invalid_count", map[string]any{"query": trimmed, "queries": queries, "error": err.Error()})
+		g.setCachedExpansion(cacheKey, fallback, 15*time.Minute)
+		return fallback, err
+	}
+
+	g.setCachedExpansion(cacheKey, queries, 15*time.Minute)
+	g.debug("gemini:image_expand_success", map[string]any{"query": trimmed, "queries": queries})
+	return queries, nil
+}
+
 func (g *GeminiService) TranslateSummaryToKorean(text string) (string, error) {
 	trimmed := strings.TrimSpace(text)
 	if trimmed == "" {