<?php

/**
 * MCP endpoint (Streamable HTTP), OAuth-protected by Authelia. See issue #111.
 *
 * Serves /mcp and the RFC 9728 Protected Resource Metadata paths (nginx routes
 * all of them here). This is the ONLY file allowed to load vendor/autoload.php.
 *
 * Identity comes exclusively from the validated access token. Never read
 * Remote-User / Remote-* headers or $_SESSION for identity here: this location
 * is exempt from Authelia forward-auth at the proxy, so those headers are
 * client-controlled on this path.
 */

require_once dirname(__DIR__) . '/middleware/RateLimitMiddleware.php';
RateLimitMiddleware::apply('api', false);

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

use Laminas\HttpHandlerRunner\Emitter\SapiEmitter;
use Mcp\Server;
use Mcp\Server\Session\FileSessionStore;
use Mcp\Server\Transport\Http\Middleware\AuthorizationMiddleware;
use Mcp\Server\Transport\Http\Middleware\CorsMiddleware;
use Mcp\Server\Transport\Http\Middleware\DnsRebindingProtectionMiddleware;
use Mcp\Server\Transport\Http\Middleware\OAuthRequestMetaMiddleware;
use Mcp\Server\Transport\Http\Middleware\ProtectedResourceMetadataMiddleware;
use Mcp\Server\Transport\Http\OAuth\JwksProvider;
use Mcp\Server\Transport\Http\OAuth\JwtTokenValidator;
use Mcp\Server\Transport\Http\OAuth\OidcDiscovery;
use Mcp\Server\Transport\Http\OAuth\ProtectedResourceMetadata;
use Mcp\Server\Transport\StreamableHttpTransport;
use Nyholm\Psr7\Factory\Psr17Factory;
use Nyholm\Psr7Server\ServerRequestCreator;
use Symfony\Component\Cache\Adapter\FilesystemAdapter;
use Symfony\Component\Cache\Psr16Cache;

$resourceUrl = $GLOBALS['config']['MCP_RESOURCE_URL'] ?? null;
$issuer      = $GLOBALS['config']['MCP_OAUTH_ISSUER'] ?? null;
if (empty($resourceUrl) || empty($issuer)) {
    http_response_code(503);
    header('Content-Type: application/json');
    echo json_encode(['error' => 'MCP endpoint is not configured (MCP_RESOURCE_URL / MCP_OAUTH_ISSUER)']);
    exit;
}

$psr17 = new Psr17Factory();
$request = (new ServerRequestCreator($psr17, $psr17, $psr17, $psr17))->fromGlobals();

// ServerRequestCreator adds Host both from the URI and from the request
// headers, so getHeaderLine('Host') comes back as "h, h" under PHP-FPM, which
// the DNS-rebinding check below then rejects. Collapse to the single value the
// client actually sent.
$clientHost = $request->getHeader('Host')[0] ?? '';
if ($clientHost !== '') {
    $request = $request->withHeader('Host', $clientHost);
}

// TLS terminates at the reverse proxy, so PHP sees plain http and a Host header
// the client controls. The SDK derives the resource_metadata URL in its 401
// challenge from the request URI, so pin scheme/host/port to the configured
// canonical URL instead of anything the request claims. preserveHost keeps
// the client's real Host header for the DNS-rebinding check below; without
// it withUri() would overwrite Host and make that check a no-op.
$canonical = parse_url($resourceUrl);
$request = $request->withUri(
    $request->getUri()
        ->withScheme($canonical['scheme'])
        ->withHost($canonical['host'])
        ->withPort($canonical['port'] ?? null),
    true
);

// Cache OIDC discovery + JWKS so every MCP call isn't two extra round trips to
// Authelia. Outside the webroot on purpose.
$cache = new Psr16Cache(new FilesystemAdapter('tinker_mcp', 3600, sys_get_temp_dir() . '/tinker_mcp_cache'));

$validator = new JwtTokenValidator(
    issuer: $issuer,
    audience: $resourceUrl,
    jwksProvider: new JwksProvider(new OidcDiscovery(cache: $cache), cache: $cache),
    // Authelia puts scopes in an `scp` array, not the standard `scope` string
    // (verified in #111 phase 1). With the default, every scope check fails.
    scopeClaim: 'scp',
);

$resourcePath = $canonical['path'] ?? '';
$metadata = new ProtectedResourceMetadata(
    authorizationServers: [$issuer],
    scopesSupported: ['tickets:read', 'tickets:write'],
    resource: $resourceUrl,
    resourceName: 'Tinker Tickets',
    // RFC 9728 path-suffixed form first (used in the WWW-Authenticate
    // challenge), plus the root form some clients probe.
    metadataPaths: array_values(array_unique([
        '/.well-known/oauth-protected-resource' . $resourcePath,
        '/.well-known/oauth-protected-resource',
    ])),
);

$server = Server::builder()
    ->setServerInfo('Tinker Tickets', '1.0.0')
    // Handshake-era clients (pre-2026-07-28) still use protocol sessions.
    ->setSession(new FileSessionStore(sys_get_temp_dir() . '/tinker_mcp_sessions'))
    ->build();

$transport = new StreamableHttpTransport(
    $request,
    middleware: [
        // CORS: SDK default (no Access-Control-Allow-Origin, so cross-origin
        // browser calls are refused). Host allowlist: only the canonical
        // hostname, which also refuses direct-by-IP access.
        new CorsMiddleware(),
        new DnsRebindingProtectionMiddleware([$canonical['host']]),
        new ProtectedResourceMetadataMiddleware($metadata),
        new AuthorizationMiddleware($validator, $metadata),
        new OAuthRequestMetaMiddleware(),
    ],
);

try {
    $response = $server->run($transport);
} catch (\Throwable $e) {
    error_log('mcp/server.php: ' . $e::class . ': ' . $e->getMessage());
    $response = $psr17->createResponse(500)
        ->withHeader('Content-Type', 'application/json')
        ->withBody($psr17->createStream(json_encode([
            'jsonrpc' => '2.0',
            'id' => null,
            'error' => ['code' => -32603, 'message' => 'Internal error'],
        ])));
}

(new SapiEmitter())->emit($response);