itflow/guest/guest_ajax.php

<?php

/*
 * guest_ajax.php
 * Similar to post.php/ajax.php, but for unauthenticated requests using Asynchronous JavaScript
 * Always returns data in JSON format, unless otherwise specified
 */

require_once "../config.php";

// Set Timezone
require_once "../includes/inc_set_timezone.php";
require_once "../functions.php";


/*
 * Creates & Returns a Stripe Payment Intent for a particular invoice ID
 */

if (isset($_GET['stripe_create_pi'])) {

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

    // Params from POST (guest_pay_invoice_stripe.js)
    $jsonStr = file_get_contents('php://input');
    $jsonObj = json_decode($jsonStr, true);
    $invoice_id = intval($jsonObj['invoice_id']);
    $url_key = escapeSql($jsonObj['url_key']);

    // Query invoice details
    $invoice_sql = mysqli_query(
        $mysqli,
        "SELECT client_id, client_name, invoice_amount, invoice_currency_code, invoice_number,
            invoice_prefix FROM invoices
        LEFT JOIN clients ON invoice_client_id = client_id
        WHERE invoice_id = $invoice_id
        AND invoice_url_key = '$url_key'
        AND invoice_status NOT IN ('Draft','Paid','Cancelled')
        LIMIT 1"
    );
    if (!$invoice_sql || mysqli_num_rows($invoice_sql) !== 1) {
        exit("Invalid Invoice ID/SQL query");
    }

    $row = mysqli_fetch_assoc($invoice_sql);
    $invoice_prefix = escapeHtml($row['invoice_prefix']);
    $invoice_number = intval($row['invoice_number']);
    $invoice_amount = floatval($row['invoice_amount']);
    $invoice_currency_code = escapeHtml($row['invoice_currency_code']);
    $client_id = intval($row['client_id']);
    $client_name = escapeHtml($row['client_name']);

    // Add up all the payments for the invoice and get the total amount paid to the invoice
    $sql_amount_paid = mysqli_query($mysqli, "SELECT SUM(payment_amount) AS amount_paid FROM payments WHERE payment_invoice_id = $invoice_id");
    $row_amt = mysqli_fetch_assoc($sql_amount_paid);
    $amount_paid = floatval($row_amt['amount_paid']);
    $balance_to_pay = $invoice_amount - $amount_paid;

    $balance_to_pay = round($balance_to_pay, 2);

    if (intval($balance_to_pay) == 0) {
        exit("No balance outstanding");
    }

    // Setup Stripe from payment_providers
    $stripe_provider = mysqli_fetch_assoc(mysqli_query($mysqli, "SELECT payment_provider_id, payment_provider_private_key FROM payment_providers WHERE payment_provider_name = 'Stripe' AND payment_provider_active = 1 LIMIT 1"));
    if (!$stripe_provider) {
        exit("Stripe not enabled / configured");
    }
    $stripe_provider_id = intval($stripe_provider['payment_provider_id']);
    $stripe_secret_key = $stripe_provider['payment_provider_private_key'];

    require_once '../includes/stripe_init.php';

    // Get client's Stripe customer ID
    $stripe_customer_query = mysqli_query($mysqli, "
        SELECT payment_provider_client FROM client_payment_provider
        WHERE client_id = $client_id AND payment_provider_id = $stripe_provider_id
        LIMIT 1
    ");
    $stripe_customer = mysqli_fetch_assoc($stripe_customer_query);
    $stripe_customer_id = $stripe_customer ? escapeSql($stripe_customer['payment_provider_client']) : null;

    // The card fee, when the client pays it - as guest_pay_invoice_stripe.php showed it, and booked from itflow_fees on the way back
    $balance_cents = (int) round($balance_to_pay * 100);
    $fee_cents = billingCardFeeCents($balance_cents, billingCardFeeFor($client_id));
    $pi_metadata = [
        'itflow_client_id' => $client_id,
        'itflow_client_name' => $client_name,
        'itflow_invoice_number' => $invoice_prefix . $invoice_number,
        'itflow_invoice_id' => $invoice_id,
    ];
    if ($fee_cents > 0) {
        $pi_metadata['itflow_fees'] = "$invoice_id:$fee_cents";
    }

    $pi_description = "ITFlow: $client_name payment of $invoice_currency_code " . number_format(($balance_cents + $fee_cents) / 100, 2, '.', '')
        . ($fee_cents > 0 ? ' (with a ' . number_format($fee_cents / 100, 2, '.', '') . ' card fee)' : '') . " for $invoice_prefix$invoice_number";

    try {
        \Stripe\Stripe::setApiKey($stripe_secret_key);

        $paymentIntent = \Stripe\PaymentIntent::create([
            'amount' => $balance_cents + $fee_cents, // Stripe expects cents
            'currency' => $invoice_currency_code,
            'description' => $pi_description,
            'metadata' => $pi_metadata,
            'payment_method_types' => ['card'],
            'customer' => $stripe_customer_id,
        ]);

        $output = [
            'clientSecret' => $paymentIntent->client_secret,
        ];

        echo json_encode($output);

    } catch (\Throwable $e) {
        http_response_code(500);
        error_log("Stripe PI create failed (invoice $invoice_id): " . $e->getMessage());
        echo json_encode(['error' => $e->getMessage()]);
    }

    exit;
}