Fallback query expansion and bust frontend cache

backend/services/gemini.go

@@ -39,7 +39,7 @@ func NewGeminiService(apiKey string) *GeminiService {
 
 func (g *GeminiService) ExpandQuery(query string) ([]string, error) {
 	if g.APIKey == "" {
-		return []string{query}, nil
+		return fallbackQueryExpansion(query), nil
 	}
 
 	body := map[string]any{
@@ -79,7 +79,7 @@ User query: ` + query,
 
 	rawText, err := g.generateText(body)
 	if err != nil {
-		return []string{query}, err
+		return fallbackQueryExpansion(query), nil
 	}
 
 	jsonText, err := extractJSONObject(rawText)
@@ -120,21 +120,24 @@ User query: ` + query,
 		}
 		rawText, retryErr := g.generateText(strictBody)
 		if retryErr != nil {
-			return []string{query}, retryErr
+			return fallbackQueryExpansion(query), nil
 		}
 		jsonText, err = extractJSONObject(rawText)
 		if err != nil {
-			return []string{query}, fmt.Errorf("gemini query expansion JSON extraction failed after strict retry: %w", err)
+			return fallbackQueryExpansion(query), nil
 		}
 	}
 
 	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(rawText, 200))
+		return fallbackQueryExpansion(query), nil
 	}
 
-	queries := []string{query}
-	seen := map[string]bool{strings.ToLower(strings.TrimSpace(query)): true}
+	queries := fallbackQueryExpansion(query)
+	seen := map[string]bool{}
+	for _, existing := range queries {
+		seen[strings.ToLower(strings.TrimSpace(existing))] = true
+	}
 	for _, item := range parsed.Querywords {
 		trimmed := strings.TrimSpace(item)
 		if trimmed == "" {
@@ -384,3 +387,35 @@ func truncateForError(text string, limit int) string {
 	}
 	return trimmed[:limit] + "..."
 }
+
+func fallbackQueryExpansion(query string) []string {
+	base := strings.TrimSpace(query)
+	candidates := []string{
+		base,
+		base + " b-roll",
+		base + " stock footage",
+		base + " cinematic footage",
+		base + " establishing shot",
+		base + " editorial footage",
+		base + " urban scene",
+		base + " ambient footage",
+		base + " 4k footage",
+		base + " cinematic b-roll",
+	}
+
+	seen := map[string]bool{}
+	queries := make([]string, 0, len(candidates))
+	for _, item := range candidates {
+		trimmed := strings.TrimSpace(item)
+		if trimmed == "" {
+			continue
+		}
+		key := strings.ToLower(trimmed)
+		if seen[key] {
+			continue
+		}
+		seen[key] = true
+		queries = append(queries, trimmed)
+	}
+	return queries
+}