food-ai/backend/internal/adapters/openai/recipe.go

package openai

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"

	"github.com/food-ai/backend/internal/adapters/ai"
)

// goalNames maps internal goal codes to English descriptions used in the prompt.
var goalNames = map[string]string{
	"lose":     "weight loss",
	"maintain": "weight maintenance",
	"gain":     "muscle gain",
}

// GenerateRecipes generates recipes using the OpenAI API.
// Retries up to maxRetries times only when the response is not valid JSON.
// API-level errors (rate limits, auth, etc.) are returned immediately.
func (c *Client) GenerateRecipes(ctx context.Context, req ai.RecipeRequest) ([]ai.Recipe, error) {
	prompt := buildRecipePrompt(req)

	messages := []map[string]string{
		{"role": "user", "content": prompt},
	}

	var lastErr error
	for attempt := range maxRetries {
		if attempt > 0 {
			messages = []map[string]string{
				{"role": "user", "content": prompt},
				{"role": "user", "content": "Previous response was not valid JSON. Return ONLY a JSON array with no text before or after."},
			}
		}

		text, err := c.generateContent(ctx, messages)
		if err != nil {
			return nil, err
		}

		recipes, err := parseRecipesJSON(text)
		if err != nil {
			lastErr = fmt.Errorf("attempt %d parse JSON: %w", attempt+1, err)
			continue
		}

		for i := range recipes {
			recipes[i].Nutrition.Approximate = true
		}
		return recipes, nil
	}

	return nil, fmt.Errorf("failed to parse valid JSON after %d attempts: %w", maxRetries, lastErr)
}

func buildRecipePrompt(req ai.RecipeRequest) string {
	goal := goalNames[req.UserGoal]
	if goal == "" {
		goal = "weight maintenance"
	}

	restrictions := "none"
	if len(req.Restrictions) > 0 {
		restrictions = strings.Join(req.Restrictions, ", ")
	}

	cuisines := "any"
	if len(req.CuisinePrefs) > 0 {
		cuisines = strings.Join(req.CuisinePrefs, ", ")
	}

	count := req.Count
	if count <= 0 {
		count = 5
	}

	perMealCalories := req.DailyCalories / 3
	if perMealCalories <= 0 {
		perMealCalories = 600
	}

	productsSection := ""
	if len(req.AvailableProducts) > 0 {
		productsSection = "\nAvailable products (⚠ = expiring soon, prioritise these):\n" +
			strings.Join(req.AvailableProducts, "\n") + "\n"
	}

	return fmt.Sprintf(`You are a chef and nutritionist. Generate %d recipes in English.

User profile:
- Goal: %s
- Daily calories: %d kcal
- Dietary restrictions: %s
- Cuisine preferences: %s
%s
Requirements for each recipe:
- Max %d kcal per serving
- Total cooking time: max 60 minutes
- Include approximate macros per serving

IMPORTANT:
- All text fields (title, description, ingredient names, units, step descriptions, tags) MUST be in English.
- The "image_query" field MUST always be in English (it is used for stock-photo search).

Return ONLY a valid JSON array without markdown or extra text:
[{
  "title": "...",
  "description": "2-3 sentences",
  "cuisine": "russian|asian|european|mediterranean|american|other",
  "difficulty": "easy|medium|hard",
  "prep_time_min": 10,
  "cook_time_min": 20,
  "servings": 2,
  "image_query": "short English photo-search query",
  "ingredients": [{"name": "...", "amount": 300, "unit": "..."}],
  "steps": [{"number": 1, "description": "...", "timer_seconds": null}],
  "tags": ["..."],
  "nutrition_per_serving": {"calories": 420, "protein_g": 48, "fat_g": 12, "carbs_g": 18}
}]`, count, goal, req.DailyCalories, restrictions, cuisines, productsSection, perMealCalories)
}

func parseRecipesJSON(text string) ([]ai.Recipe, 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 recipes []ai.Recipe
	if err := json.Unmarshal([]byte(text), &recipes); err != nil {
		return nil, err
	}
	return recipes, nil
}