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

package openai

import (
	"context"
	"fmt"
	"sync"
)

// MenuRequest contains parameters for weekly menu generation.
type MenuRequest struct {
	UserGoal          string
	DailyCalories     int
	Restrictions      []string
	CuisinePrefs      []string
	AvailableProducts []string
	Lang              string // ISO 639-1 target language code, e.g. "en", "ru"
}

// DayPlan is the AI-generated plan for a single day.
type DayPlan struct {
	Day   int         `json:"day"`
	Meals []MealEntry `json:"meals"`
}

// MealEntry is a single meal within a day plan.
type MealEntry struct {
	MealType string `json:"meal_type"` // breakfast | lunch | dinner
	Recipe   Recipe `json:"recipe"`
}

// GenerateMenu produces a 7-day × 3-meal plan by issuing three parallel
// 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) {
	type mealSlot struct {
		mealType string
		fraction float64 // share of daily calories
	}

	slots := []mealSlot{
		{"breakfast", 0.25},
		{"lunch", 0.40},
		{"dinner", 0.35},
	}

	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,
				Lang:              req.Lang,
			})
			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])
		}
	}

	days := make([]DayPlan, 7)
	for day := range 7 {
		days[day] = DayPlan{
			Day: day + 1,
			Meals: []MealEntry{
				{MealType: slots[0].mealType, Recipe: results[0].recipes[day]},
				{MealType: slots[1].mealType, Recipe: results[1].recipes[day]},
				{MealType: slots[2].mealType, Recipe: results[2].recipes[day]},
			},
		}
	}
	return days, nil
}