<?php

function stripeRequest(string $method, string $path, array $fields = []): array {
    $secret = trim((string)getConfigVal('stripe.secret_key', ''));
    if ($secret === '') throw new RuntimeException('Stripe is not configured');
    if (!function_exists('curl_init')) throw new RuntimeException('PHP cURL extension is required');
    $url = 'https://api.stripe.com/v1/' . ltrim($path, '/');
    if ($method === 'GET' && $fields) $url .= '?' . http_build_query($fields);
    $curl = curl_init($url);
    $options = [
        CURLOPT_USERPWD => $secret . ':',
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_TIMEOUT => 25,
        CURLOPT_CUSTOMREQUEST => $method,
        CURLOPT_HTTPHEADER => ['Content-Type: application/x-www-form-urlencoded'],
    ];
    if ($method !== 'GET' && $fields) $options[CURLOPT_POSTFIELDS] = http_build_query($fields);
    curl_setopt_array($curl, $options);
    $body = curl_exec($curl);
    $status = (int)curl_getinfo($curl, CURLINFO_RESPONSE_CODE);
    $error = curl_error($curl);
    curl_close($curl);
    $decoded = json_decode((string)$body, true);
    if ($body === false || $status < 200 || $status >= 300) {
        $message = $decoded['error']['message'] ?? $error ?: ('Stripe HTTP ' . $status);
        throw new RuntimeException($message);
    }
    return is_array($decoded) ? $decoded : [];
}

function stripeReturnUrl(string $configKey, string $fallback): string {
    $configured = trim((string)getConfigVal($configKey, ''));
    return $configured !== '' ? $configured : $fallback;
}

function createStripeCheckout(array $user, array $plan): string {
    if (empty($user['email_verified_at']) || empty($user['email'])) {
        throw new RuntimeException('A verified email is required before checkout');
    }
    if (empty($plan['stripe_price_id'])) throw new RuntimeException('This plan does not have a Stripe price ID');
    $base = appBaseUrl();
    $fields = [
        'mode' => 'subscription',
        'line_items[0][price]' => $plan['stripe_price_id'],
        'line_items[0][quantity]' => 1,
        'success_url' => stripeReturnUrl('stripe.success_url', $base . '/index.html?billing=success'),
        'cancel_url' => stripeReturnUrl('stripe.cancel_url', $base . '/index.html?billing=cancelled'),
        'client_reference_id' => (string)$user['id'],
        'metadata[user_id]' => (string)$user['id'],
        'metadata[plan_id]' => (string)$plan['id'],
        'subscription_data[metadata][user_id]' => (string)$user['id'],
        'subscription_data[metadata][plan_id]' => (string)$plan['id'],
        'allow_promotion_codes' => 'true',
    ];
    if (!empty($user['stripe_customer_id'])) $fields['customer'] = $user['stripe_customer_id'];
    else $fields['customer_email'] = $user['email'];
    $session = stripeRequest('POST', 'checkout/sessions', $fields);
    if (empty($session['url'])) throw new RuntimeException('Stripe did not return a checkout URL');
    return $session['url'];
}

function createStripePortal(array $user): string {
    if (empty($user['stripe_customer_id'])) throw new RuntimeException('No Stripe customer is connected');
    $session = stripeRequest('POST', 'billing_portal/sessions', [
        'customer' => $user['stripe_customer_id'],
        'return_url' => stripeReturnUrl('stripe.portal_return_url', appBaseUrl() . '/index.html?view=account'),
    ]);
    if (empty($session['url'])) throw new RuntimeException('Stripe did not return a portal URL');
    return $session['url'];
}

function verifyStripeSignature(string $payload, string $header): bool {
    $secret = trim((string)getConfigVal('stripe.webhook_secret', ''));
    if ($secret === '' || $header === '') return false;
    $timestamp = null;
    $signatures = [];
    foreach (explode(',', $header) as $part) {
        [$key, $value] = array_pad(explode('=', trim($part), 2), 2, '');
        if ($key === 't') $timestamp = $value;
        if ($key === 'v1') $signatures[] = $value;
    }
    if (!$timestamp || abs(time() - (int)$timestamp) > 300) return false;
    $expected = hash_hmac('sha256', $timestamp . '.' . $payload, $secret);
    foreach ($signatures as $signature) if (hash_equals($expected, $signature)) return true;
    return false;
}

function planIdFromStripeObject(array $object): ?int {
    $metadataPlan = (int)($object['metadata']['plan_id'] ?? 0);
    if ($metadataPlan > 0 && planById($metadataPlan)) return $metadataPlan;
    $priceId = $object['items']['data'][0]['price']['id'] ?? '';
    if ($priceId !== '') {
        $stmt = getDB()->prepare("SELECT id FROM plans WHERE stripe_price_id=?");
        $stmt->execute([$priceId]);
        $id = (int)$stmt->fetchColumn();
        if ($id > 0) return $id;
    }
    return null;
}

function syncSubscriptionFromStripe(array $object): void {
    $db = getDB();
    $subscriptionId = (string)($object['id'] ?? '');
    $customerId = (string)($object['customer'] ?? '');
    $userId = (int)($object['metadata']['user_id'] ?? 0);
    if ($userId < 1 && $subscriptionId !== '') {
        $stmt = $db->prepare("SELECT user_id FROM subscriptions WHERE stripe_subscription_id=?");
        $stmt->execute([$subscriptionId]);
        $userId = (int)$stmt->fetchColumn();
    }
    if ($userId < 1 && $customerId !== '') {
        $stmt = $db->prepare("SELECT id FROM users WHERE stripe_customer_id=?");
        $stmt->execute([$customerId]);
        $userId = (int)$stmt->fetchColumn();
    }
    if ($userId < 1) return;

    $status = (string)($object['status'] ?? 'active');
    $paidStatuses = ['active', 'trialing', 'past_due'];
    $planId = planIdFromStripeObject($object);
    if (!in_array($status, $paidStatuses, true)) {
        $planId = (int)$db->query("SELECT id FROM plans WHERE slug='free'")->fetchColumn();
    }
    if (!$planId) return;
    $periodEnd = (int)($object['current_period_end'] ?? 0) ?: null;
    $cancel = !empty($object['cancel_at_period_end']) ? 1 : 0;

    $db->beginTransaction();
    $db->prepare("INSERT INTO subscriptions
        (user_id,plan_id,stripe_customer_id,stripe_subscription_id,status,current_period_end,cancel_at_period_end,updated_at)
        VALUES (?,?,?,?,?,?,?,?)
        ON CONFLICT(user_id) DO UPDATE SET plan_id=excluded.plan_id,stripe_customer_id=excluded.stripe_customer_id,
        stripe_subscription_id=excluded.stripe_subscription_id,status=excluded.status,
        current_period_end=excluded.current_period_end,cancel_at_period_end=excluded.cancel_at_period_end,updated_at=excluded.updated_at")
        ->execute([$userId, $planId, $customerId, $subscriptionId, $status, $periodEnd, $cancel, time()]);
    $db->prepare("UPDATE users SET plan_id=?,stripe_customer_id=?,stripe_subscription_id=?,
        subscription_status=?,subscription_period_end=?,cancel_at_period_end=? WHERE id=?")
        ->execute([$planId, $customerId, $subscriptionId, $status, $periodEnd, $cancel, $userId]);
    $db->commit();
}