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

if (!isset($_SESSION['user_id'])) {
    header('Location: login.php');
    exit;
}

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $invoice_id = $_POST['invoice_id'];
    $amount = $_POST['amount'];
    $payment_method = $_POST['payment_method'];
    $payment_date = date('Y-m-d');

    try {
        $pdo = db();
        
        // Insert payment
        $sql = "INSERT INTO payments (invoice_id, payment_date, amount, payment_method) VALUES (?, ?, ?, ?)";
        $stmt = $pdo->prepare($sql);
        $stmt->execute([$invoice_id, $payment_date, $amount, $payment_method]);

        // Update invoice status if fully paid
        $sql = "SELECT i.total_amount, SUM(p.amount) as total_paid FROM invoices i LEFT JOIN payments p ON i.id = p.invoice_id WHERE i.id = ? GROUP BY i.id";
        $stmt = $pdo->prepare($sql);
        $stmt->execute([$invoice_id]);
        $invoice_data = $stmt->fetch();

        if ($invoice_data['total_paid'] >= $invoice_data['total_amount']) {
            $sql = "UPDATE invoices SET status = 'paid' WHERE id = ?";
            $stmt = $pdo->prepare($sql);
            $stmt->execute([$invoice_id]);
        }

        header('Location: invoice_details.php?id=' . $invoice_id);
        exit;

    } catch (PDOException $e) {
        die("Database error: " . $e->getMessage());
    }
} else {
    header('Location: invoices.php');
    exit;
}
?>