package menu

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/food-ai/backend/internal/infra/locale"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// ErrNotFound is returned when a menu item is not found for the user.
var ErrNotFound = errors.New("menu item not found")

// Repository handles persistence for menu plans, items, and shopping lists.
type Repository struct {
	pool *pgxpool.Pool
}

// NewRepository creates a new Repository.
func NewRepository(pool *pgxpool.Pool) *Repository {
	return &Repository{pool: pool}
}

// GetByWeek loads the full menu plan for the user and given Monday date (YYYY-MM-DD).
// Returns nil, nil when no plan exists for that week.
func (r *Repository) GetByWeek(ctx context.Context, userID, weekStart string) (*MenuPlan, error) {
	lang := locale.FromContext(ctx)

	const q = `
		SELECT mp.id, mp.week_start::text,
		       mi.id, mi.day_of_week, mi.meal_type,
		       rec.id,
		       COALESCE(dt.name, d.name),
		       COALESCE(d.image_url, ''),
		       rec.calories_per_serving,
		       rec.protein_per_serving,
		       rec.fat_per_serving,
		       rec.carbs_per_serving
		FROM menu_plans mp
		LEFT JOIN menu_items mi ON mi.menu_plan_id = mp.id
		LEFT JOIN recipes rec ON rec.id = mi.recipe_id
		LEFT JOIN dishes d ON d.id = rec.dish_id
		LEFT JOIN dish_translations dt ON dt.dish_id = d.id AND dt.lang = $3
		WHERE mp.user_id = $1 AND mp.week_start::text = $2
		ORDER BY mi.day_of_week,
		         CASE mi.meal_type WHEN 'breakfast' THEN 1 WHEN 'lunch' THEN 2 ELSE 3 END`

	rows, err := r.pool.Query(ctx, q, userID, weekStart, lang)
	if err != nil {
		return nil, fmt.Errorf("get menu by week: %w", err)
	}
	defer rows.Close()

	var plan *MenuPlan
	dayMap := map[int]*MenuDay{}

	for rows.Next() {
		var (
			planID, planWeekStart          string
			itemID, mealType               *string
			dow                            *int
			recipeID, title, imageURL      *string
			calPer, protPer, fatPer, carbPer *float64
		)
		if err := rows.Scan(
			&planID, &planWeekStart,
			&itemID, &dow, &mealType,
			&recipeID, &title, &imageURL,
			&calPer, &protPer, &fatPer, &carbPer,
		); err != nil {
			return nil, fmt.Errorf("scan menu row: %w", err)
		}

		if plan == nil {
			plan = &MenuPlan{ID: planID, WeekStart: planWeekStart}
		}

		if itemID == nil || dow == nil || mealType == nil {
			continue
		}

		day, ok := dayMap[*dow]
		if !ok {
			day = &MenuDay{Day: *dow, Date: dayDate(planWeekStart, *dow)}
			dayMap[*dow] = day
		}

		slot := MealSlot{ID: *itemID, MealType: *mealType}
		if recipeID != nil && title != nil {
			nutrition := NutritionInfo{
				Calories: derefFloat(calPer),
				ProteinG: derefFloat(protPer),
				FatG:     derefFloat(fatPer),
				CarbsG:   derefFloat(carbPer),
			}
			slot.Recipe = &MenuRecipe{
				ID:        *recipeID,
				Title:     *title,
				ImageURL:  derefStr(imageURL),
				Nutrition: nutrition,
			}
			day.TotalCalories += nutrition.Calories
		}
		day.Meals = append(day.Meals, slot)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	if plan == nil {
		return nil, nil
	}

	// Assemble days in order.
	for dow := 1; dow <= 7; dow++ {
		if d, ok := dayMap[dow]; ok {
			plan.Days = append(plan.Days, *d)
		}
	}
	return plan, nil
}

// SaveMenuInTx upserts a menu_plan row, wipes previous menu_items, and inserts
// the new ones — all in a single transaction.
func (r *Repository) SaveMenuInTx(ctx context.Context, userID, weekStart string, items []PlanItem) (string, error) {
	tx, err := r.pool.BeginTx(ctx, pgx.TxOptions{})
	if err != nil {
		return "", fmt.Errorf("begin tx: %w", err)
	}
	defer tx.Rollback(ctx) //nolint:errcheck

	var planID string
	err = tx.QueryRow(ctx, `
		INSERT INTO menu_plans (user_id, week_start)
		VALUES ($1, $2::date)
		ON CONFLICT (user_id, week_start) DO UPDATE SET created_at = now()
		RETURNING id`, userID, weekStart).Scan(&planID)
	if err != nil {
		return "", fmt.Errorf("upsert menu_plan: %w", err)
	}

	if _, err = tx.Exec(ctx, `DELETE FROM menu_items WHERE menu_plan_id = $1`, planID); err != nil {
		return "", fmt.Errorf("delete old menu items: %w", err)
	}

	for _, item := range items {
		if _, err = tx.Exec(ctx, `
			INSERT INTO menu_items (menu_plan_id, day_of_week, meal_type, recipe_id)
			VALUES ($1, $2, $3, $4)`,
			planID, item.DayOfWeek, item.MealType, item.RecipeID,
		); err != nil {
			return "", fmt.Errorf("insert menu item: %w", err)
		}
	}

	if err = tx.Commit(ctx); err != nil {
		return "", fmt.Errorf("commit tx: %w", err)
	}
	return planID, nil
}

// UpdateItem replaces the recipe in a menu slot.
func (r *Repository) UpdateItem(ctx context.Context, itemID, userID, recipeID string) error {
	tag, err := r.pool.Exec(ctx, `
		UPDATE menu_items mi
		SET recipe_id = $3
		FROM menu_plans mp
		WHERE mi.id = $1 AND mp.id = mi.menu_plan_id AND mp.user_id = $2`,
		itemID, userID, recipeID,
	)
	if err != nil {
		return fmt.Errorf("update menu item: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// DeleteItem removes a menu slot.
func (r *Repository) DeleteItem(ctx context.Context, itemID, userID string) error {
	tag, err := r.pool.Exec(ctx, `
		DELETE FROM menu_items mi
		USING menu_plans mp
		WHERE mi.id = $1 AND mp.id = mi.menu_plan_id AND mp.user_id = $2`,
		itemID, userID,
	)
	if err != nil {
		return fmt.Errorf("delete menu item: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// UpsertShoppingList stores the shopping list for a menu plan.
func (r *Repository) UpsertShoppingList(ctx context.Context, userID, planID string, items []ShoppingItem) error {
	raw, err := json.Marshal(items)
	if err != nil {
		return fmt.Errorf("marshal shopping items: %w", err)
	}
	_, err = r.pool.Exec(ctx, `
		INSERT INTO shopping_lists (user_id, menu_plan_id, items)
		VALUES ($1, $2, $3::jsonb)
		ON CONFLICT (user_id, menu_plan_id) DO UPDATE
		SET items = EXCLUDED.items, generated_at = now()`,
		userID, planID, string(raw),
	)
	return err
}

// GetShoppingList returns the shopping list for the user's plan.
func (r *Repository) GetShoppingList(ctx context.Context, userID, planID string) ([]ShoppingItem, error) {
	var raw []byte
	err := r.pool.QueryRow(ctx, `
		SELECT items FROM shopping_lists
		WHERE user_id = $1 AND menu_plan_id = $2`,
		userID, planID,
	).Scan(&raw)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("get shopping list: %w", err)
	}
	var items []ShoppingItem
	if err := json.Unmarshal(raw, &items); err != nil {
		return nil, fmt.Errorf("unmarshal shopping items: %w", err)
	}
	return items, nil
}

// ToggleShoppingItem flips the checked flag for the item at the given index.
func (r *Repository) ToggleShoppingItem(ctx context.Context, userID, planID string, index int, checked bool) error {
	tag, err := r.pool.Exec(ctx, `
		UPDATE shopping_lists
		SET items = jsonb_set(items, ARRAY[$1::text, 'checked'], to_jsonb($2::boolean))
		WHERE user_id = $3 AND menu_plan_id = $4`,
		fmt.Sprintf("%d", index), checked, userID, planID,
	)
	if err != nil {
		return fmt.Errorf("toggle shopping item: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrNotFound
	}
	return nil
}

// GetPlanIDByWeek returns the menu_plan id for the user and given Monday date.
func (r *Repository) GetPlanIDByWeek(ctx context.Context, userID, weekStart string) (string, error) {
	var id string
	err := r.pool.QueryRow(ctx, `
		SELECT id FROM menu_plans WHERE user_id = $1 AND week_start::text = $2`,
		userID, weekStart,
	).Scan(&id)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", ErrNotFound
	}
	if err != nil {
		return "", fmt.Errorf("get plan id: %w", err)
	}
	return id, nil
}

// GetIngredientsByPlan returns all ingredients from all recipes in the plan.
func (r *Repository) GetIngredientsByPlan(ctx context.Context, planID string) ([]ingredientRow, error) {
	rows, err := r.pool.Query(ctx, `
		SELECT ri.name, ri.amount, ri.unit_code, mi.meal_type
		FROM menu_items mi
		JOIN recipes rec ON rec.id = mi.recipe_id
		JOIN recipe_ingredients ri ON ri.recipe_id = rec.id
		WHERE mi.menu_plan_id = $1
		ORDER BY ri.sort_order`, planID)
	if err != nil {
		return nil, fmt.Errorf("get ingredients by plan: %w", err)
	}
	defer rows.Close()

	var result []ingredientRow
	for rows.Next() {
		var row ingredientRow
		if err := rows.Scan(&row.Name, &row.Amount, &row.UnitCode, &row.MealType); err != nil {
			return nil, err
		}
		result = append(result, row)
	}
	return result, rows.Err()
}

type ingredientRow struct {
	Name     string
	Amount   float64
	UnitCode *string
	MealType string
}

// --- helpers ---

func dayDate(weekStart string, dow int) string {
	t, err := time.Parse("2006-01-02", weekStart)
	if err != nil {
		return weekStart
	}
	return t.AddDate(0, 0, dow-1).Format("2006-01-02")
}

func derefStr(s *string) string {
	if s == nil {
		return ""
	}
	return *s
}

func derefFloat(f *float64) float64 {
	if f == nil {
		return 0
	}
	return *f
}