<?php
declare(strict_types=1);
@ini_set('display_errors', '1');
@error_reporting(E_ALL);
@date_default_timezone_set('UTC');

header('Content-Type: application/json');

require_once 'db/config.php';

$response = [];

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $sale_data = json_decode(file_get_contents('php://input'), true);
    $cart_data = $sale_data['cart'];
    $customer_id = !empty($sale_data['customer_id']) ? (int)$sale_data['customer_id'] : null;

    if (empty($cart_data)) {
        $response = ['success' => false, 'message' => 'Cart is empty.'];
        echo json_encode($response);
        exit;
    }

    $pdo = db();
    $pdo->beginTransaction();

    try {
        // 1. Calculate total amount
        $total_amount = 0;
        foreach ($cart_data as $item) {
            $total_amount += $item['sale_price'] * $item['quantity'];
        }

        // 2. Insert into sales table
        $sql = "INSERT INTO sales (customer_id, total_amount, payable_amount) VALUES (?, ?, ?)";
        $stmt = $pdo->prepare($sql);
        $stmt->execute([$customer_id, $total_amount, $total_amount]);
        $sale_id = $pdo->lastInsertId();

        // 3. Insert into sale_items and update stock
        $sql_item = "INSERT INTO sale_items (sale_id, product_id, quantity, price_per_unit, total_price) VALUES (?, ?, ?, ?, ?)";
        $stmt_item = $pdo->prepare($sql_item);

        $sql_stock = "UPDATE products SET stock_quantity = stock_quantity - ? WHERE id = ?";
        $stmt_stock = $pdo->prepare($sql_stock);

        foreach ($cart_data as $item) {
            $item_total = $item['sale_price'] * $item['quantity'];
            $stmt_item->execute([$sale_id, $item['id'], $item['quantity'], $item['sale_price'], $item_total]);
            $stmt_stock->execute([$item['quantity'], $item['id']]);
        }

        $pdo->commit();
        $response = ['success' => true, 'message' => 'Sale processed successfully!', 'sale_id' => $sale_id];

    } catch (PDOException $e) {
        $pdo->rollBack();
        $response = ['success' => false, 'message' => 'Error processing sale: ' . $e->getMessage()];
    }

} else {
    $response = ['success' => false, 'message' => 'Invalid request method.'];
}

echo json_encode($response);