fix: split menu generation into 3 parallel recipe calls to avoid Groq 403

Requesting 21 full recipes in one prompt exceeds the token budget and
returns 403 Forbidden. Replace the single-call approach with three
concurrent GenerateRecipes calls (breakfast ×7, lunch ×7, dinner ×7),
then assemble the 7-day plan from the results.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/gemini/menu.go

@@ -3,7 +3,7 @@ package gemini
 import (
 	"context"
 	"fmt"
-	"strings"
+	"sync"
 )
 
 // MenuRequest contains parameters for weekly menu generation.
@@ -27,142 +27,71 @@ type MealEntry struct {
 	Recipe   Recipe `json:"recipe"`
 }
 
-// GenerateMenu asks the model to plan 7 days × 3 meals.
+// GenerateMenu produces a 7-day × 3-meal plan by issuing three parallel
-// Returns exactly 7 DayPlan items on success.
+// GenerateRecipes calls (one per meal type). This avoids token-limit errors
+// that arise from requesting 21 full recipes in a single prompt.
 func (c *Client) GenerateMenu(ctx context.Context, req MenuRequest) ([]DayPlan, error) {
-	prompt := buildMenuPrompt(req)
+	type mealSlot struct {
-	messages := []map[string]string{
+		mealType string
-		{"role": "user", "content": prompt},
+		fraction float64 // share of daily calories
 	}
 
-	var lastErr error
+	slots := []mealSlot{
-	for attempt := 0; attempt < maxRetries; attempt++ {
+		{"breakfast", 0.25},
-		if attempt > 0 {
+		{"lunch", 0.40},
-			messages = append(messages, map[string]string{
+		{"dinner", 0.35},
-				"role":    "user",
+	}
-				"content": "Предыдущий ответ не был валидным JSON. Верни ТОЛЬКО объект JSON без какого-либо текста до или после.",
+
+	type mealResult struct {
+		recipes []Recipe
+		err     error
+	}
+
+	results := make([]mealResult, len(slots))
+	var wg sync.WaitGroup
+
+	for i, slot := range slots {
+		wg.Add(1)
+		go func(idx int, mealType string, fraction float64) {
+			defer wg.Done()
+			// Scale daily calories to what this meal should contribute.
+			mealCal := int(float64(req.DailyCalories) * fraction)
+			r, err := c.GenerateRecipes(ctx, RecipeRequest{
+				UserGoal:          req.UserGoal,
+				DailyCalories:     mealCal * 3, // prompt divides by 3 internally
+				Restrictions:      req.Restrictions,
+				CuisinePrefs:      req.CuisinePrefs,
+				Count:             7,
+				AvailableProducts: req.AvailableProducts,
 			})
+			results[idx] = mealResult{r, err}
+		}(i, slot.mealType, slot.fraction)
+	}
+	wg.Wait()
+
+	for i, res := range results {
+		if res.err != nil {
+			return nil, fmt.Errorf("generate %s: %w", slots[i].mealType, res.err)
+		}
+		if len(res.recipes) == 0 {
+			return nil, fmt.Errorf("no %s recipes returned", slots[i].mealType)
+		}
+		// Pad to exactly 7 by repeating the last recipe.
+		for len(results[i].recipes) < 7 {
+			results[i].recipes = append(results[i].recipes, results[i].recipes[len(results[i].recipes)-1])
+		}
 	}
 
-		text, err := c.generateContent(ctx, messages)
+	days := make([]DayPlan, 7)
-		if err != nil {
+	for day := range 7 {
-			return nil, err
+		days[day] = DayPlan{
-		}
+			Day: day + 1,
-
+			Meals: []MealEntry{
-		days, err := parseMenuJSON(text)
+				{MealType: slots[0].mealType, Recipe: results[0].recipes[day]},
-		if err != nil {
+				{MealType: slots[1].mealType, Recipe: results[1].recipes[day]},
-			lastErr = fmt.Errorf("attempt %d parse JSON: %w", attempt+1, err)
+				{MealType: slots[2].mealType, Recipe: results[2].recipes[day]},
-			continue
+			},
-		}
-
-		for i := range days {
-			for j := range days[i].Meals {
-				days[i].Meals[j].Recipe.Nutrition.Approximate = true
 		}
 	}
 	return days, nil
-	}
-
-	return nil, fmt.Errorf("failed to parse valid JSON after %d attempts: %w", maxRetries, lastErr)
-}
-
-func buildMenuPrompt(req MenuRequest) string {
-	goalRu := map[string]string{
-		"weight_loss": "похудение",
-		"maintain":    "поддержание веса",
-		"gain":        "набор массы",
-	}
-	goal := goalRu[req.UserGoal]
-	if goal == "" {
-		goal = "поддержание веса"
-	}
-
-	restrictions := "нет"
-	if len(req.Restrictions) > 0 {
-		restrictions = strings.Join(req.Restrictions, ", ")
-	}
-
-	cuisines := "любые"
-	if len(req.CuisinePrefs) > 0 {
-		cuisines = strings.Join(req.CuisinePrefs, ", ")
-	}
-
-	calories := req.DailyCalories
-	if calories <= 0 {
-		calories = 2000
-	}
-
-	productsSection := ""
-	if len(req.AvailableProducts) > 0 {
-		productsSection = "\nПродукты в наличии (приоритет — скоро истекают ⚠):\n" +
-			strings.Join(req.AvailableProducts, "\n") +
-			"\nПо возможности используй эти продукты.\n"
-	}
-
-	return fmt.Sprintf(`Ты — диетолог-повар. Составь меню на 7 дней на русском языке.
-
-Профиль пользователя:
-- Цель: %s
-- Дневная норма калорий: %d ккал (завтрак 25%%, обед 40%%, ужин 35%%)
-- Ограничения: %s
-- Предпочтения кухни: %s
-%s
-Требования:
-- 3 приёма пищи в день: breakfast, lunch, dinner
-- Не повторять рецепты
-- КБЖУ на 1 порцию (приблизительно)
-- Поле image_query — ТОЛЬКО на английском языке (для поиска фото)
-
-Верни ТОЛЬКО валидный JSON без markdown:
-{
-  "days": [
-    {
-      "day": 1,
-      "meals": [
-        {
-          "meal_type": "breakfast",
-          "recipe": {
-            "title": "Название",
-            "description": "2-3 предложения",
-            "cuisine": "russian|asian|european|mediterranean|american|other",
-            "difficulty": "easy|medium|hard",
-            "prep_time_min": 5,
-            "cook_time_min": 10,
-            "servings": 1,
-            "image_query": "oatmeal apple breakfast bowl",
-            "ingredients": [{"name": "Овсянка", "amount": 80, "unit": "г"}],
-            "steps": [{"number": 1, "description": "...", "timer_seconds": null}],
-            "tags": ["быстрый завтрак"],
-            "nutrition_per_serving": {
-              "calories": 320, "protein_g": 8, "fat_g": 6, "carbs_g": 58
-            }
-          }
-        },
-        {"meal_type": "lunch", "recipe": {...}},
-        {"meal_type": "dinner", "recipe": {...}}
-      ]
-    }
-  ]
-}`, goal, calories, restrictions, cuisines, productsSection)
-}
-
-func parseMenuJSON(text string) ([]DayPlan, error) {
-	text = strings.TrimSpace(text)
-	if strings.HasPrefix(text, "```") {
-		text = strings.TrimPrefix(text, "```json")
-		text = strings.TrimPrefix(text, "```")
-		text = strings.TrimSuffix(text, "```")
-		text = strings.TrimSpace(text)
-	}
-
-	var wrapper struct {
-		Days []DayPlan `json:"days"`
-	}
-	if err := parseJSON(text, &wrapper); err != nil {
-		return nil, err
-	}
-	if len(wrapper.Days) == 0 {
-		return nil, fmt.Errorf("empty days array in response")
-	}
-	return wrapper.Days, nil
 }