Tighten Gemini expansion and unify crop slider

backend/services/gemini.go

@@ -65,43 +65,48 @@ User query: ` + query,
 		},
 	}
 
-	rawBody, _ := json.Marshal(body)
-	endpoint := "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent?key=" + g.APIKey
-	resp, err := g.Client.Post(endpoint, "application/json", bytes.NewReader(rawBody))
+	rawText, err := g.generateText(body)
 	if err != nil {
-		return []string{query}, fmt.Errorf("gemini query expansion request failed: %w", err)
-	}
-	defer resp.Body.Close()
-
-	if resp.StatusCode >= 300 {
-		data, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
-		return []string{query}, fmt.Errorf("gemini query expansion returned status %d: %s", resp.StatusCode, strings.TrimSpace(string(data)))
+		return []string{query}, err
 	}
 
-	var payload struct {
-		Candidates []struct {
-			Content struct {
-				Parts []struct {
-					Text string `json:"text"`
-				} `json:"parts"`
-			} `json:"content"`
-		} `json:"candidates"`
-	}
-	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
-		return []string{query}, fmt.Errorf("gemini query expansion response decode failed: %w", err)
-	}
-	if len(payload.Candidates) == 0 || len(payload.Candidates[0].Content.Parts) == 0 {
-		return []string{query}, fmt.Errorf("gemini query expansion returned no candidates")
-	}
-
-	jsonText, err := extractJSONObject(payload.Candidates[0].Content.Parts[0].Text)
+	jsonText, err := extractJSONObject(rawText)
 	if err != nil {
-		return []string{query}, fmt.Errorf("gemini query expansion JSON extraction failed: %w", err)
+		strictBody := map[string]any{
+			"contents": []map[string]any{
+				{
+					"parts": []map[string]string{
+						{
+							"text": `STRICT JSON ONLY.
+Output must start with { and end with }.
+Do not add prose, explanations, markdown, code fences, or labels.
+Return exactly this shape: {"querywords":["..."]}.
+Generate up to 10 search queries for media discovery across Google Video, Envato, and Artgrid.
+If the original query is Korean, include strong English stock-footage search phrases.
+User query: ` + query,
+						},
+					},
+				},
+			},
+			"generationConfig": map[string]any{
+				"responseMimeType": "application/json",
+				"temperature":      0.1,
+				"maxOutputTokens":  220,
+			},
+		}
+		rawText, retryErr := g.generateText(strictBody)
+		if retryErr != nil {
+			return []string{query}, retryErr
+		}
+		jsonText, err = extractJSONObject(rawText)
+		if err != nil {
+			return []string{query}, fmt.Errorf("gemini query expansion JSON extraction failed after strict retry: %w", err)
+		}
 	}
 
 	var parsed QueryExpansion
 	if err := json.Unmarshal([]byte(jsonText), &parsed); err != nil {
-		return []string{query}, fmt.Errorf("gemini query expansion JSON parse failed: %w; raw=%q", err, truncateForError(payload.Candidates[0].Content.Parts[0].Text, 200))
+		return []string{query}, fmt.Errorf("gemini query expansion JSON parse failed: %w; raw=%q", err, truncateForError(rawText, 200))
 	}
 
 	queries := []string{query}
@@ -121,6 +126,38 @@ User query: ` + query,
 	return queries, nil
 }
 
+func (g *GeminiService) generateText(body map[string]any) (string, error) {
+	rawBody, _ := json.Marshal(body)
+	endpoint := "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash:generateContent?key=" + g.APIKey
+	resp, err := g.Client.Post(endpoint, "application/json", bytes.NewReader(rawBody))
+	if err != nil {
+		return "", fmt.Errorf("gemini request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 300 {
+		data, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
+		return "", fmt.Errorf("gemini returned status %d: %s", resp.StatusCode, strings.TrimSpace(string(data)))
+	}
+
+	var payload struct {
+		Candidates []struct {
+			Content struct {
+				Parts []struct {
+					Text string `json:"text"`
+				} `json:"parts"`
+			} `json:"content"`
+		} `json:"candidates"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return "", fmt.Errorf("gemini response decode failed: %w", err)
+	}
+	if len(payload.Candidates) == 0 || len(payload.Candidates[0].Content.Parts) == 0 {
+		return "", fmt.Errorf("gemini returned no candidates")
+	}
+	return payload.Candidates[0].Content.Parts[0].Text, nil
+}
+
 func (g *GeminiService) Recommend(query string, candidates []SearchResult) ([]AIRecommendation, error) {
 	if g.APIKey == "" {
 		return nil, fmt.Errorf("gemini api key is not configured")