<?php

function faceai_env($key, $default = null)
{
    $value = getenv($key);
    return $value === false ? $default : $value;
}

function faceai_env_flag($key, $default = false)
{
    $value = strtolower(trim((string) faceai_env($key, $default ? '1' : '0')));
    return in_array($value, array('1', 'true', 'yes', 'on'), true);
}

function faceai_request_host()
{
    if (empty($_SERVER['HTTP_HOST'])) {
        return '';
    }

    return strtolower(trim((string) $_SERVER['HTTP_HOST']));
}

function faceai_is_local_host($host)
{
    $normalized = strtolower(trim((string) $host));
    if ($normalized === '') {
        return false;
    }

    $withoutPort = preg_replace('/:\d+$/', '', $normalized);
    return in_array($withoutPort, array('localhost', '127.0.0.1', '::1'), true);
}

function faceai_request_targets_local_frontend()
{
    if (faceai_is_local_host(faceai_request_host())) {
        return true;
    }

    $returnUrl = faceai_request_value('returnUrl');
    if ($returnUrl === '') {
        return false;
    }

    $host = parse_url($returnUrl, PHP_URL_HOST);
    if (!is_string($host) || $host === '') {
        return false;
    }

    return faceai_is_local_host($host);
}

function faceai_default_frontend_url()
{
    if (faceai_request_targets_local_frontend()) {
        return 'http://localhost:3001';
    }

    return 'https://ai.regalamiunsorriso.it';
}

function faceai_default_backend_internal_url()
{
    if (faceai_is_local_host(faceai_request_host())) {
        return 'http://localhost:3001';
    }

    return 'https://ai.regalamiunsorriso.it';
}

function faceai_config()
{
    static $config = null;

    if ($config !== null) {
        return $config;
    }

    $config = array(
        'feature_enabled' => faceai_env_flag('FACEAI_FEATURE_ENABLED', true),
        'frontend_url' => rtrim(faceai_env('FACEAI_FRONTEND_URL', faceai_default_frontend_url()), '/'),
        'backend_internal_url' => rtrim(faceai_env('FACEAI_BACKEND_INTERNAL_URL', faceai_default_backend_internal_url()), '/'),
        'shared_secret' => (string) faceai_env('FACEAI_SHARED_SECRET', 'disagio-spaghetti-science-lol-boh'),
        'allow_dev_handoff' => faceai_env_flag('FACEAI_ALLOW_DEV_HANDOFF', true),
        'identity_cookie' => (string) faceai_env('FACEAI_IDENTITY_COOKIE', 'rus_faceai_identity'),
        'return_forward_url' => rtrim((string) faceai_env('FACEAI_RETURN_FORWARD_URL', ''), '/')
    );

    return $config;
}

function faceai_base64url_encode($value)
{
    return rtrim(strtr(base64_encode($value), '+/', '-_'), '=');
}

function faceai_base64url_decode($value)
{
    $padding = strlen($value) % 4;
    if ($padding > 0) {
        $value .= str_repeat('=', 4 - $padding);
    }

    return base64_decode(strtr($value, '-_', '+/'));
}

function faceai_sign_payload(array $payload, $secret)
{
    $body = faceai_base64url_encode(json_encode($payload));
    $signature = hash_hmac('sha256', $body, $secret, true);
    return $body . '.' . faceai_base64url_encode($signature);
}

function faceai_verify_payload($token, $secret)
{
    if (!is_string($token) || strpos($token, '.') === false) {
        throw new RuntimeException('Invalid token format.');
    }

    list($body, $signature) = explode('.', $token, 2);
    $expected = faceai_base64url_encode(hash_hmac('sha256', $body, $secret, true));

    if (!hash_equals($expected, $signature)) {
        throw new RuntimeException('Invalid token signature.');
    }

    $decoded = faceai_base64url_decode($body);
    $payload = json_decode($decoded, true);

    if (!is_array($payload)) {
        throw new RuntimeException('Invalid token payload.');
    }

    if (isset($payload['expiresAt']) && (int) $payload['expiresAt'] < (int) round(microtime(true) * 1000)) {
        throw new RuntimeException('Token expired.');
    }

    return $payload;
}

function faceai_build_url($baseUrl, array $params)
{
    return $baseUrl . (strpos($baseUrl, '?') === false ? '?' : '&') . http_build_query($params);
}

function faceai_redirect_with_error($returnUrl, $message, $title = 'Face ID non disponibile')
{
    if (is_string($returnUrl) && trim($returnUrl) !== '') {
        header('Cache-Control: no-store, no-cache, must-revalidate, max-age=0');
        header('Pragma: no-cache');
        header('Location: ' . faceai_build_url($returnUrl, array(
            'faceaiError' => '1',
            'faceaiErrorTitle' => $title,
            'faceaiErrorMessage' => $message
        )), true, 302);
        exit;
    }

    faceai_render_message_page($title, $message, array(), 503);
}

function faceai_request_value($key, $default = '')
{
    if (!isset($_GET[$key])) {
        return $default;
    }

    if (is_array($_GET[$key])) {
        return $default;
    }

    return trim((string) $_GET[$key]);
}

function faceai_html($value)
{
    return htmlspecialchars((string) $value, ENT_QUOTES, 'UTF-8');
}

function faceai_resolve_identity(array $config)
{
    if (!empty($_COOKIE[$config['identity_cookie']])) {
        $payload = faceai_verify_payload($_COOKIE[$config['identity_cookie']], $config['shared_secret']);
        if (($payload['type'] ?? '') !== 'legacy-identity') {
            throw new RuntimeException('Unexpected identity cookie payload.');
        }

        return array(
            'id' => (string) ($payload['userId'] ?? ''),
            'displayName' => (string) ($payload['displayName'] ?? ''),
            'email' => (string) ($payload['email'] ?? ''),
            'membershipStatus' => (string) ($payload['membershipStatus'] ?? 'inactive')
        );
    }

    if ($config['allow_dev_handoff']) {
        $userId = faceai_request_value('devUserId');
        if ($userId !== '') {
            return array(
                'id' => $userId,
                'displayName' => faceai_request_value('devDisplayName', 'Local Test User'),
                'email' => faceai_request_value('devEmail', 'local.test@example.invalid'),
                'membershipStatus' => faceai_request_value('devMembershipStatus', 'active')
            );
        }
    }

    return null;
}

function faceai_render_message_page($title, $message, array $details = array(), $statusCode = 400)
{
    http_response_code($statusCode);
    header('Content-Type: text/html; charset=UTF-8');

    echo '<!doctype html><html lang="it"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1">';
    echo '<title>' . faceai_html($title) . '</title>';
    echo '<style>body{font-family:Georgia,serif;background:#f7f1e8;color:#2a231b;margin:0;padding:32px}main{max-width:900px;margin:0 auto;background:#fff;border:1px solid #ddcbb5;padding:24px}h1{margin-top:0}code{background:#f2ece2;padding:2px 5px}ul{padding-left:20px}li{margin:8px 0}</style>';
    echo '</head><body><main>';
    echo '<h1>' . faceai_html($title) . '</h1>';
    echo '<p>' . faceai_html($message) . '</p>';

    if (!empty($details)) {
        echo '<ul>';
        foreach ($details as $detail) {
            echo '<li>' . faceai_html($detail) . '</li>';
        }
        echo '</ul>';
    }

    echo '</main></body></html>';
    exit;
}

function faceai_fetch_json($url)
{
    $context = stream_context_create(array(
        'http' => array(
            'ignore_errors' => true,
            'timeout' => 10
        )
    ));

    $response = @file_get_contents($url, false, $context);
    if ($response === false) {
        throw new RuntimeException('Unable to fetch remote FaceAI data.');
    }

    $statusCode = 0;
    if (!empty($http_response_header[0]) && preg_match('/\s(\d{3})\s/', $http_response_header[0], $matches)) {
        $statusCode = (int) $matches[1];
    }

    $payload = json_decode($response, true);
    if (!is_array($payload)) {
        throw new RuntimeException('FaceAI returned invalid JSON.');
    }

    if ($statusCode >= 400) {
        throw new RuntimeException($payload['error'] ?? ('FaceAI bridge request failed with status ' . $statusCode . '.'));
    }

    return $payload;
}