<?php

declare(strict_types=1);

if (session_status() !== PHP_SESSION_ACTIVE) {
    session_start();
}

require_once dirname(__DIR__, 2) . '/vendor/autoload.php';
require_once dirname(__DIR__, 2) . '/bootstrap.php';
require_once dirname(__DIR__, 2) . '/config/config.php';

if (!function_exists('env')) {
    function env(string $key, ?string $default = null): ?string
    {
        if (array_key_exists($key, $_ENV) && $_ENV[$key] !== '') {
            return (string)$_ENV[$key];
        }
        $v = getenv($key);
        if ($v !== false && $v !== '') {
            return (string)$v;
        }
        return $default;
    }
}

$debug = (env('APP_DEBUG', '0') === '1');

$OIDC_ISSUER        = rtrim((string)(env('OIDC_ISSUER') ?? ''), '/');
$OIDC_CLIENT_ID     = (string)(env('OIDC_CLIENT_ID') ?? '');
$OIDC_CLIENT_SECRET = (string)(env('OIDC_CLIENT_SECRET') ?? '');
$OIDC_REDIRECT_URI  = (string)(env('OIDC_REDIRECT_URI') ?: url('oidc/callback.php'));

if (!$OIDC_ISSUER || !$OIDC_CLIENT_ID || !$OIDC_REDIRECT_URI) {
    http_response_code(500);
    echo $debug ? 'OIDC config manquante.' : 'Erreur.';
    exit;
}

$tokenEndpoint    = $OIDC_ISSUER . '/protocol/openid-connect/token';
$userInfoEndpoint = $OIDC_ISSUER . '/protocol/openid-connect/userinfo';

if (!isset($_GET['state'], $_SESSION['oidc_state']) || !hash_equals((string)$_SESSION['oidc_state'], (string)$_GET['state'])) {
    http_response_code(400);
    echo $debug ? 'State invalide.' : 'Requête invalide.';
    exit;
}
unset($_SESSION['oidc_state']);

if (empty($_GET['code'])) {
    http_response_code(400);
    echo $debug ? 'Code manquant.' : 'Requête invalide.';
    exit;
}
$code = (string)$_GET['code'];

$codeVerifier = $_SESSION['oidc_code_verifier'] ?? null;
unset($_SESSION['oidc_code_verifier'], $_SESSION['oidc_nonce']);

if (!$codeVerifier) {
    http_response_code(400);
    echo $debug ? 'PKCE code_verifier manquant.' : 'Requête invalide.';
    exit;
}

// Échange code → tokens
$post = [
    'grant_type'    => 'authorization_code',
    'code'          => $code,
    'redirect_uri'  => $OIDC_REDIRECT_URI,
    'client_id'     => $OIDC_CLIENT_ID,
    'code_verifier' => $codeVerifier,
];
if ($OIDC_CLIENT_SECRET !== '') {
    $post['client_secret'] = $OIDC_CLIENT_SECRET;
}

$ch = curl_init($tokenEndpoint);
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_POST           => true,
    CURLOPT_POSTFIELDS     => http_build_query($post, '', '&', PHP_QUERY_RFC3986),
    CURLOPT_TIMEOUT        => 15,
    CURLOPT_SSL_VERIFYPEER => true,
    CURLOPT_SSL_VERIFYHOST => 2,
]);
$tokenResponse = curl_exec($ch);
$httpCode      = curl_getinfo($ch, CURLINFO_HTTP_CODE);
$curlErr       = curl_error($ch);
curl_close($ch);

if ($tokenResponse === false || $httpCode !== 200) {
    http_response_code(500);
    echo $debug ? 'Échec échange token : ' . htmlspecialchars($curlErr ?: (string)$tokenResponse) : 'Erreur d\'authentification.';
    exit;
}

$tokens      = json_decode((string)$tokenResponse, true) ?: [];
$accessToken = $tokens['access_token'] ?? null;
$idToken     = $tokens['id_token']     ?? null;

if (!$accessToken) {
    http_response_code(500);
    echo $debug ? 'Access token manquant.' : 'Erreur d\'authentification.';
    exit;
}

// UserInfo
$ch = curl_init($userInfoEndpoint);
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER     => ['Authorization: Bearer ' . $accessToken],
    CURLOPT_TIMEOUT        => 10,
    CURLOPT_SSL_VERIFYPEER => true,
    CURLOPT_SSL_VERIFYHOST => 2,
]);
$userInfoResponse = curl_exec($ch);
$httpCode         = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);

if ($userInfoResponse === false || $httpCode !== 200) {
    http_response_code(500);
    echo $debug ? 'Échec UserInfo.' : 'Erreur d\'authentification.';
    exit;
}

$claims = json_decode((string)$userInfoResponse, true) ?: [];
$email  = $claims['email'] ?? null;

// Fallback : lire l'email depuis le payload du id_token
if (!$email && $idToken && substr_count($idToken, '.') === 2) {
    [, $p, ] = explode('.', $idToken, 3);
    $payload = json_decode((string)base64_decode(strtr($p, '-_', '+/'), true), true);
    if (is_array($payload) && !empty($payload['email'])) {
        $email = $payload['email'];
    }
}

if (!$email) {
    http_response_code(400);
    echo $debug ? 'Email non fourni par l\'IdP.' : 'Impossible de récupérer votre email.';
    exit;
}

// Ouvre la session authentifiée
session_regenerate_id(true);
$_SESSION['user_email'] = strtolower(trim($email));
$_SESSION['oidc'] = [
    'issuer'       => $OIDC_ISSUER,
    'sub'          => $claims['sub'] ?? null,
    'access_token' => $accessToken,
    'id_token'     => $idToken,
    'expires_at'   => time() + (int)($tokens['expires_in'] ?? 3600),
];

$target = $_SESSION['oidc_return_to'] ?? '/';
unset($_SESSION['oidc_return_to'], $_SESSION['oidc_flow']);
if (!is_string($target) || $target === '' || $target[0] !== '/') {
    $target = '/';
}
header('Location: ' . $target, true, 303);
exit;