<?php
/**
 * PayPal Webhook Handler
 * ──────────────────────
 * Setup (do once):
 *  1. Deploy this file and note its public URL, e.g. https://app.hotlunches.net/sm/webhook.php
 *  2. In PayPal Developer Dashboard → Your App → Webhooks → Add Webhook
 *     Paste the URL and subscribe to:
 *       • MERCHANT.PARTNER-CONSENT.REVOKED
 *       • CUSTOMER.MERCHANT-INTEGRATION.PRODUCT-SUBSCRIPTION-UPDATED
 *  3. Copy the Webhook ID that PayPal generates and set 'webhook_id' in config.php
 *
 * PayPal retries on any non-200 response, so we always respond 200 — errors are logged.
 */

// Read raw body immediately before any output can corrupt it
$rawBody = file_get_contents('php://input');

// Pull in app logging if available
ob_start();
if (file_exists('../include/logging-functions.php')) {
    require_once '../include/logging-functions.php';
    startLog('webhook');
}
ob_end_clean();

// Always respond 200 to stop PayPal from retrying
http_response_code(200);
header('Content-Type: application/json');

$config = require __DIR__ . '/config.php';
require_once __DIR__ . '/lib/PayPalClient.php';

// ── Header helper (works on Apache + Nginx + PHP-FPM) ────────────────────────
function ppWebhookHeader(string $name): string
{
    if (function_exists('getallheaders')) {
        foreach (getallheaders() as $k => $v) {
            if (strcasecmp($k, $name) === 0) return $v;
        }
    }
    $serverKey = 'HTTP_' . strtoupper(str_replace('-', '_', $name));
    return $_SERVER[$serverKey] ?? '';
}

// ── Guard: webhook_id must be configured ────────────────────────────────────
$webhookId = $config['webhook_id'] ?? '';
if ($webhookId === '') {
    if (function_exists('writeLog')) {
        writeLog('webhook: webhook_id is not set in config.php — skipping signature check');
    }
    echo json_encode(['status' => 'webhook_id_not_configured']);
    exit();
}

// ── Collect PayPal signature headers ─────────────────────────────────────────
$transmissionId   = ppWebhookHeader('PAYPAL-TRANSMISSION-ID');
$transmissionTime = ppWebhookHeader('PAYPAL-TRANSMISSION-TIME');
$transmissionSig  = ppWebhookHeader('PAYPAL-TRANSMISSION-SIG');
$certUrl          = ppWebhookHeader('PAYPAL-CERT-URL');
$authAlgo         = ppWebhookHeader('PAYPAL-AUTH-ALGO');

if (!$transmissionId || !$transmissionSig || !$certUrl) {
    if (function_exists('writeLog')) {
        writeLog('webhook: missing PayPal signature headers — request ignored');
    }
    echo json_encode(['status' => 'missing_signature_headers']);
    exit();
}

// ── Verify signature via PayPal API ──────────────────────────────────────────
// This is the simplest and most reliable verification method.
// PayPal docs: /v1/notifications/verify-webhook-signature
try {
    $client = new PayPalClient($config);

    $verifyResp = $client->api('POST', '/v1/notifications/verify-webhook-signature', [
        'auth_algo'         => $authAlgo,
        'cert_url'          => $certUrl,
        'transmission_id'   => $transmissionId,
        'transmission_sig'  => $transmissionSig,
        'transmission_time' => $transmissionTime,
        'webhook_id'        => $webhookId,
        'webhook_event'     => json_decode($rawBody, true) ?: [],
    ]);

    $verificationStatus = $verifyResp['body']['verification_status'] ?? 'FAILURE';

    if ($verificationStatus !== 'SUCCESS') {
        if (function_exists('writeLog')) {
            writeLog('webhook: signature FAILED verification_status=' . $verificationStatus
                . ' debug_id=' . ($verifyResp['debug_id'] ?? 'n/a'));
        }
        echo json_encode(['status' => 'signature_verification_failed']);
        exit();
    }
} catch (Throwable $e) {
    if (function_exists('writeLog')) {
        writeLog('webhook: signature verification threw — ' . $e->getMessage());
    }
    echo json_encode(['status' => 'verification_error']);
    exit();
}

// ── Parse event ───────────────────────────────────────────────────────────────
$event     = json_decode($rawBody, true) ?: [];
$eventType = $event['event_type'] ?? '';
$resource  = $event['resource']   ?? [];

if (function_exists('writeLog')) {
    writeLog('webhook: verified event_type=' . $eventType . ' event_id=' . ($event['id'] ?? '?'));
}

$dataDir       = __DIR__ . '/data';
$merchantsFile = $dataDir . '/school_merchants.json';

// ── Helper: persist merchants JSON ───────────────────────────────────────────
function ppSaveMerchants(string $file, array $merchants): void
{
    file_put_contents($file, json_encode($merchants, JSON_PRETTY_PRINT));
}

// ── Helper: find school name by merchant_id ───────────────────────────────────
function ppFindSchoolByMerchant(array $merchants, string $merchantId): ?string
{
    foreach ($merchants as $school => $data) {
        if (($data['merchant_id'] ?? '') === $merchantId) {
            return $school;
        }
    }
    return null;
}

// ════════════════════════════════════════════════════════════════════════════
// EVENT: MERCHANT.PARTNER-CONSENT.REVOKED
// The seller has revoked your API permissions from their PayPal account.
// Action: immediately disable PayPal for this school.
// ════════════════════════════════════════════════════════════════════════════
if ($eventType === 'MERCHANT.PARTNER-CONSENT.REVOKED') {
    $merchantId = $resource['merchant_id']
               ?? $resource['payer_id']
               ?? null;

    if (!$merchantId) {
        if (function_exists('writeLog')) {
            writeLog('webhook: CONSENT.REVOKED — no merchant_id in resource, skipping');
        }
        echo json_encode(['status' => 'ok']);
        exit();
    }

    if (function_exists('writeLog')) {
        writeLog('webhook: CONSENT.REVOKED merchant_id=' . $merchantId);
    }

    // ── Update JSON ───────────────────────────────────────────────────────
    if (file_exists($merchantsFile)) {
        $merchants  = json_decode(file_get_contents($merchantsFile), true) ?: [];
        $schoolName = ppFindSchoolByMerchant($merchants, $merchantId);

        if ($schoolName) {
            $merchants[$schoolName]['paypal_ready']        = false;
            $merchants[$schoolName]['consent_revoked']     = true;
            $merchants[$schoolName]['consent_revoked_at']  = time();
            $merchants[$schoolName]['status_issues']       = [
                'MERCHANT.PARTNER-CONSENT.REVOKED — the seller has revoked API permissions.'
                . ' They must reconnect their PayPal account before payments can resume.',
            ];
            ppSaveMerchants($merchantsFile, $merchants);

            if (function_exists('writeLog')) {
                writeLog('webhook: CONSENT.REVOKED — disabled PayPal for school=' . $schoolName);
            }
        } else {
            if (function_exists('writeLog')) {
                writeLog('webhook: CONSENT.REVOKED — merchant_id=' . $merchantId . ' not found in school_merchants.json');
            }
        }
    }

    // ── Update DB ─────────────────────────────────────────────────────────
    // We keep the paypal_merchant_id so re-onboarding can match the school,
    // but a NULL signals "not ready" in any direct DB check.
    try {
        $dbConfig = require __DIR__ . '/db_config.php';
        $conn = new mysqli($dbConfig['host'], $dbConfig['username'], $dbConfig['password'], $dbConfig['database']);
        if (!$conn->connect_error) {
            $conn->set_charset($dbConfig['charset'] ?? 'utf8mb4');
            // If your schema has a paypal_consent_revoked column, set it here.
            // Otherwise, null out paypal_merchant_id to block payments at the DB level.
            $stmt = $conn->prepare(
                "UPDATE schools SET paypal_merchant_id = NULL WHERE paypal_merchant_id = ?"
            );
            $stmt->bind_param('s', $merchantId);
            $stmt->execute();
            $affected = $stmt->affected_rows;
            $stmt->close();
            $conn->close();
            if (function_exists('writeLog')) {
                writeLog('webhook: CONSENT.REVOKED — nulled paypal_merchant_id for ' . $affected . ' row(s)');
            }
        }
    } catch (Throwable $e) {
        if (function_exists('writeLog')) {
            writeLog('webhook: CONSENT.REVOKED — DB update failed: ' . $e->getMessage());
        }
    }

    echo json_encode(['status' => 'ok']);
    exit();
}

// ════════════════════════════════════════════════════════════════════════════
// EVENT: CUSTOMER.MERCHANT-INTEGRATION.PRODUCT-SUBSCRIPTION-UPDATED
// A product subscription (e.g. PPCP_CUSTOM vetting) has changed.
// Action: re-check seller status to pick up new ACDC / Apple Pay / Google Pay readiness.
// ════════════════════════════════════════════════════════════════════════════
if ($eventType === 'CUSTOMER.MERCHANT-INTEGRATION.PRODUCT-SUBSCRIPTION-UPDATED') {
    $merchantId = $resource['merchant_id'] ?? null;

    if (!$merchantId) {
        if (function_exists('writeLog')) {
            writeLog('webhook: PRODUCT-SUBSCRIPTION-UPDATED — no merchant_id in resource, skipping');
        }
        echo json_encode(['status' => 'ok']);
        exit();
    }

    if (function_exists('writeLog')) {
        writeLog('webhook: PRODUCT-SUBSCRIPTION-UPDATED merchant_id=' . $merchantId);
    }

    if (file_exists($merchantsFile)) {
        $merchants  = json_decode(file_get_contents($merchantsFile), true) ?: [];
        $schoolName = ppFindSchoolByMerchant($merchants, $merchantId);

        if ($schoolName) {
            try {
                $sellerStatus = $client->getSellerStatus($config['partner_merchant_id'], $merchantId);

                $merchants[$schoolName] = array_merge($merchants[$schoolName], [
                    'paypal_ready'         => $sellerStatus['paypal_ready'],
                    'email_confirmed'      => $sellerStatus['email_confirmed'],
                    'payments_receivable'  => $sellerStatus['payments_receivable'],
                    'oauth_ok'             => $sellerStatus['oauth_ok'],
                    'seller_email'         => $sellerStatus['seller_email'],
                    'status_issues'        => $sellerStatus['issues'],
                    'status_checked_at'    => time(),
                    // ACDC fields — updated whenever subscription status changes
                    'acdc_ready'           => $sellerStatus['acdc_ready'],
                    'acdc_vetting_status'  => $sellerStatus['acdc_vetting_status'],
                    'acdc_denied'          => $sellerStatus['acdc_denied'],
                    'acdc_pending'         => $sellerStatus['acdc_pending'],
                ]);
                ppSaveMerchants($merchantsFile, $merchants);

                if (function_exists('writeLog')) {
                    writeLog('webhook: PRODUCT-SUBSCRIPTION-UPDATED — re-checked school=' . $schoolName
                        . ' paypal_ready=' . ($sellerStatus['paypal_ready'] ? 'true' : 'false'));
                }
            } catch (Throwable $e) {
                if (function_exists('writeLog')) {
                    writeLog('webhook: PRODUCT-SUBSCRIPTION-UPDATED — getSellerStatus failed: ' . $e->getMessage());
                }
            }
        } else {
            if (function_exists('writeLog')) {
                writeLog('webhook: PRODUCT-SUBSCRIPTION-UPDATED — merchant_id=' . $merchantId . ' not found');
            }
        }
    }

    echo json_encode(['status' => 'ok']);
    exit();
}

// ── Unhandled event — still 200 so PayPal stops retrying ─────────────────────
if (function_exists('writeLog')) {
    writeLog('webhook: unhandled event_type=' . $eventType . ' — no action taken');
}
echo json_encode(['status' => 'ok', 'note' => 'event_type not handled by this integration']);