package repository

import (
	"context"
	"database/sql"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"shop/internal/models"
)

type CartRepository struct {
	pool *pgxpool.Pool
}

func NewCartRepository(pool *pgxpool.Pool) *CartRepository {
	return &CartRepository{pool: pool}
}

func (r *CartRepository) GetOrCreate(ctx context.Context, sessionKey string, userID *int) (int, error) {
	if userID != nil {
		var cartID int
		err := r.pool.QueryRow(ctx, `SELECT id FROM carts WHERE user_id = $1`, *userID).Scan(&cartID)
		if err == nil {
			return cartID, nil
		}
		if err != pgx.ErrNoRows {
			return 0, err
		}
		err = r.pool.QueryRow(ctx, `
			INSERT INTO carts (user_id, session_key) VALUES ($1, $2) RETURNING id
		`, *userID, sessionKey).Scan(&cartID)
		return cartID, err
	}

	var cartID int
	err := r.pool.QueryRow(ctx, `
		SELECT id FROM carts WHERE session_key = $1 AND user_id IS NULL
	`, sessionKey).Scan(&cartID)
	if err == nil {
		return cartID, nil
	}
	if err != pgx.ErrNoRows {
		return 0, err
	}
	err = r.pool.QueryRow(ctx, `
		INSERT INTO carts (session_key) VALUES ($1) RETURNING id
	`, sessionKey).Scan(&cartID)
	return cartID, err
}

func (r *CartRepository) MergeToUser(ctx context.Context, sessionKey string, userID int) error {
	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)

	var guestCartID int
	err = tx.QueryRow(ctx, `
		SELECT id FROM carts WHERE session_key = $1 AND user_id IS NULL
	`, sessionKey).Scan(&guestCartID)
	if err == pgx.ErrNoRows {
		return tx.Commit(ctx)
	}
	if err != nil {
		return err
	}

	var userCartID int
	err = tx.QueryRow(ctx, `SELECT id FROM carts WHERE user_id = $1`, userID).Scan(&userCartID)
	if err == pgx.ErrNoRows {
		_, err = tx.Exec(ctx, `UPDATE carts SET user_id = $1 WHERE id = $2`, userID, guestCartID)
		if err != nil {
			return err
		}
		return tx.Commit(ctx)
	}
	if err != nil {
		return err
	}

	_, err = tx.Exec(ctx, `
		INSERT INTO cart_items (cart_id, product_id, quantity)
		SELECT $1, product_id, quantity FROM cart_items WHERE cart_id = $2
		ON CONFLICT (cart_id, product_id) DO UPDATE
		SET quantity = cart_items.quantity + EXCLUDED.quantity
	`, userCartID, guestCartID)
	if err != nil {
		return err
	}
	_, err = tx.Exec(ctx, `DELETE FROM carts WHERE id = $1`, guestCartID)
	if err != nil {
		return err
	}
	return tx.Commit(ctx)
}

func (r *CartRepository) AddItem(ctx context.Context, cartID, productID, qty int) error {
	_, err := r.pool.Exec(ctx, `
		INSERT INTO cart_items (cart_id, product_id, quantity)
		VALUES ($1, $2, $3)
		ON CONFLICT (cart_id, product_id) DO UPDATE
		SET quantity = cart_items.quantity + EXCLUDED.quantity
	`, cartID, productID, qty)
	return err
}

func (r *CartRepository) UpdateItem(ctx context.Context, cartID, productID, qty int) error {
	if qty <= 0 {
		_, err := r.pool.Exec(ctx, `DELETE FROM cart_items WHERE cart_id = $1 AND product_id = $2`, cartID, productID)
		return err
	}
	_, err := r.pool.Exec(ctx, `
		UPDATE cart_items SET quantity = $3 WHERE cart_id = $1 AND product_id = $2
	`, cartID, productID, qty)
	return err
}

func (r *CartRepository) RemoveItem(ctx context.Context, cartID, productID int) error {
	_, err := r.pool.Exec(ctx, `DELETE FROM cart_items WHERE cart_id = $1 AND product_id = $2`, cartID, productID)
	return err
}

func (r *CartRepository) Clear(ctx context.Context, cartID int) error {
	_, err := r.pool.Exec(ctx, `DELETE FROM cart_items WHERE cart_id = $1`, cartID)
	return err
}

func (r *CartRepository) ItemCount(ctx context.Context, cartID int) (int, error) {
	var count int
	err := r.pool.QueryRow(ctx, `
		SELECT COALESCE(SUM(quantity), 0) FROM cart_items WHERE cart_id = $1
	`, cartID).Scan(&count)
	return count, err
}

func (r *CartRepository) Items(ctx context.Context, cartID int) ([]models.CartItem, error) {
	rows, err := r.pool.Query(ctx, `
		SELECT ci.id, ci.cart_id, ci.product_id, ci.quantity,
		       p.id, p.name, p.description, p.details, p.price, COALESCE(p.sale_price, 0),
		       p.image_url, COALESCE(c.name, p.category, 'Разное'), p.category_id,
		       COALESCE(c.slug, ''), p.is_active, p.created_at, p.updated_at
		FROM cart_items ci
		JOIN products p ON p.id = ci.product_id
		LEFT JOIN categories c ON c.id = p.category_id
		WHERE ci.cart_id = $1 AND p.is_active = true
		ORDER BY ci.id
	`, cartID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var items []models.CartItem
	for rows.Next() {
		var ci models.CartItem
		var p models.Product
		var catID sql.NullInt64
		if err := rows.Scan(
			&ci.ID, &ci.CartID, &ci.ProductID, &ci.Quantity,
			&p.ID, &p.Name, &p.Description, &p.Details, &p.Price, &p.SalePrice,
			&p.ImageURL, &p.Category, &catID, &p.CategorySlug, &p.IsActive, &p.CreatedAt, &p.UpdatedAt,
		); err != nil {
			return nil, err
		}
		if catID.Valid {
			id := int(catID.Int64)
			p.CategoryID = &id
		}
		ci.Product = p
		items = append(items, ci)
	}
	return items, rows.Err()
}

func (r *CartRepository) Total(ctx context.Context, cartID int) (float64, error) {
	var total float64
	err := r.pool.QueryRow(ctx, `
		SELECT COALESCE(SUM(ci.quantity * CASE
			WHEN p.sale_price > 0 AND p.sale_price < p.price THEN p.sale_price
			ELSE p.price END), 0)
		FROM cart_items ci JOIN products p ON p.id = ci.product_id
		WHERE ci.cart_id = $1
	`, cartID).Scan(&total)
	return total, err
}