<?php
require_once '../db/config.php';

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

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method Not Allowed']);
    exit;
}

$data = json_decode(file_get_contents('php://input'), true);

$customer_id = $data['customer_id'] ?? null;
$items = $data['items'] ?? [];
$tax_ids = $data['tax_ids'] ?? [];

if (empty($items)) {
    http_response_code(400);
    echo json_encode(['error' => 'Sale must have at least one item']);
    exit;
}

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

    // 1. Calculate subtotal and check stock
    $subtotal = 0;
    foreach ($items as $item) {
        $product_id = $item['product_id'] ?? null;
        $quantity = $item['quantity'] ?? null;

        if (!$product_id || !$quantity || $quantity <= 0) {
            throw new Exception('Invalid item data');
        }

        $stmt = $pdo->prepare("SELECT price, quantity FROM products WHERE id = ? FOR UPDATE");
        $stmt->execute([$product_id]);
        $product = $stmt->fetch(PDO::FETCH_ASSOC);

        if (!$product) {
            throw new Exception("Product with ID $product_id not found");
        }
        if ($product['quantity'] < $quantity) {
            throw new Exception("Not enough stock for product ID $product_id");
        }

        $subtotal += $product['price'] * $quantity;
    }

    // 2. Calculate taxes
    $tax_total = 0;
    $taxes_to_apply = [];
    if (!empty($tax_ids)) {
        $sql = "SELECT id, rate FROM taxes WHERE id IN (" . implode(',', array_fill(0, count($tax_ids), '?')) . ")";
        $stmt = $pdo->prepare($sql);
        $stmt->execute($tax_ids);
        $taxes = $stmt->fetchAll(PDO::FETCH_ASSOC);

        foreach ($taxes as $tax) {
            $tax_amount = ($subtotal * $tax['rate']) / 100;
            $tax_total += $tax_amount;
            $taxes_to_apply[] = ['id' => $tax['id'], 'amount' => $tax_amount];
        }
    }

    $total_amount = $subtotal + $tax_total;

    // 3. Update product quantities
    foreach ($items as $item) {
        $stmt = $pdo->prepare("UPDATE products SET quantity = quantity - ? WHERE id = ?");
        $stmt->execute([$item['quantity'], $item['product_id']]);
    }

    // 4. Insert into sales table
    $stmt = $pdo->prepare("INSERT INTO sales (customer_id, subtotal, tax_total, total_amount) VALUES (?, ?, ?, ?)");
    $stmt->execute([$customer_id, $subtotal, $tax_total, $total_amount]);
    $sale_id = $pdo->lastInsertId();

    // 5. Insert into sale_items
    $stmt = $pdo->prepare("INSERT INTO sale_items (sale_id, product_id, quantity, price) VALUES (?, ?, ?, (SELECT price FROM products WHERE id = ?))");
    foreach ($items as $item) {
        $stmt->execute([$sale_id, $item['product_id'], $item['quantity'], $item['product_id']]);
    }

    // 6. Insert into sale_taxes
    if (!empty($taxes_to_apply)) {
        $stmt = $pdo->prepare("INSERT INTO sale_taxes (sale_id, tax_id, tax_amount) VALUES (?, ?, ?)");
        foreach ($taxes_to_apply as $tax) {
            $stmt->execute([$sale_id, $tax['id'], $tax['amount']]);
        }
    }

    $pdo->commit();

    http_response_code(201);
    echo json_encode(['success' => 'Sale created successfully', 'sale_id' => $sale_id, 'total_amount' => $total_amount]);

} catch (Exception $e) {
    if ($pdo->inTransaction()) {
        $pdo->rollBack();
    }
    http_response_code(400);
    echo json_encode(['error' => $e->getMessage()]);
}