<?php
include '../config.php';
include 'auth.php';

// Check if ID is set
if (!isset($_GET['id']) || empty($_GET['id'])) {
    $_SESSION['error_message'] = 'ไม่พบรหัสลูกค้าที่ต้องการลบ';
    header("Location: customer-list.php");
    exit;
}

$id = mysqli_real_escape_string($conn, $_GET['id']);

// Check if customer exists
$check_query = "SELECT * FROM customers WHERE id = $id";
$check_result = mysqli_query($conn, $check_query);

if (mysqli_num_rows($check_result) == 0) {
    $_SESSION['error_message'] = 'ไม่พบข้อมูลลูกค้า';
    header("Location: customer-list.php");
    exit;
}

// Check if customer is used in invoices
$invoice_query = "SELECT COUNT(*) as count FROM invoices WHERE customer_id = $id";
$invoice_result = mysqli_query($conn, $invoice_query);
$invoice_row = mysqli_fetch_assoc($invoice_result);

if ($invoice_row['count'] > 0) {
    $_SESSION['error_message'] = 'ไม่สามารถลบข้อมูลลูกค้าได้ เนื่องจากมีการใช้งานในใบกำกับภาษี';
    header("Location: customer-list.php");
    exit;
}

// Delete customer
$query = "DELETE FROM customers WHERE id = $id";

if (mysqli_query($conn, $query)) {
    $_SESSION['success_message'] = 'ลบข้อมูลลูกค้าเรียบร้อยแล้ว';
} else {
    $_SESSION['error_message'] = 'เกิดข้อผิดพลาด: ' . mysqli_error($conn);
}

header("Location: customer-list.php");
exit;
?>