<?php
require_once 'includes/auth.php';
require_login();

require_once 'db/config.php';

$pdo = db();

// Filter logic
$start_date = $_GET['start_date'] ?? '';
$end_date = $_GET['end_date'] ?? '';
$payment_method = $_GET['payment_method'] ?? '';

$sql = "SELECT s.id, s.sale_date, s.total_amount, s.payment_method, GROUP_CONCAT(CONCAT(p.name, ' (', si.quantity, ' x $', si.price, ')')) AS items
        FROM sales s
        JOIN sale_items si ON s.id = si.sale_id
        JOIN products p ON si.product_id = p.id";

$conditions = [];
$params = [];

if ($start_date) {
    $conditions[] = "s.sale_date >= ?";
    $params[] = $start_date . ' 00:00:00';
}
if ($end_date) {
    $conditions[] = "s.sale_date <= ?";
    $params[] = $end_date . ' 23:59:59';
}
if ($payment_method) {
    $conditions[] = "s.payment_method = ?";
    $params[] = $payment_method;
}

if (count($conditions) > 0) {
    $sql .= " WHERE " . implode(' AND ', $conditions);
}

$sql .= " GROUP BY s.id ORDER BY s.sale_date DESC";

$stmt = $pdo->prepare($sql);
$stmt->execute($params);
$sales = $stmt->fetchAll(PDO::FETCH_ASSOC);

// CSV generation
$filename = "sales_report_" . date('Y-m-d') . ".csv";

header('Content-Type: text/csv');
header('Content-Disposition: attachment; filename="' . $filename . '"');

$output = fopen('php://output', 'w');

// Add BOM to support UTF-8 in Excel
fputs($output, "\xEF\xBB\xBF");

// Header row
fputcsv($output, ['Sale ID', 'Date', 'Total Amount', 'Payment Method', 'Items']);

// Data rows
foreach ($sales as $sale) {
    fputcsv($output, [
        $sale['id'],
        $sale['sale_date'],
        number_format($sale['total_amount'], 2),
        $sale['payment_method'],
        $sale['items']
    ]);
}

fclose($output);
exit;