feat: MCP SSE server + JSON-RPC dispatch
This commit is contained in:
@@ -0,0 +1,225 @@
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<?php
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namespace AskTamMCP\MCP;
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defined('ABSPATH') || exit;
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/**
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* MCP Server — handles the SSE connection and JSON-RPC message dispatch.
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*
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* MCP protocol flow:
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* 1. Client connects to /sse → server sends "endpoint" event with POST URL
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* 2. Client POSTs JSON-RPC messages to /message
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* 3. Server sends "message" SSE events back with JSON-RPC responses
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*
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* This implementation uses a stateless synchronous approach:
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* - SSE endpoint performs initialize + tools/list inline
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* - /message endpoint handles individual tool calls synchronously
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*/
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class Server {
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private Registry $registry;
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public function __construct() {
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$this->registry = new Registry();
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}
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public function registerRoutes(): void {
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// SSE stream endpoint — AI client connects here
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register_rest_route('asktam-mcp/v1', '/sse', [
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'methods' => 'GET',
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'callback' => [$this, 'handleSse'],
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'permission_callback' => '__return_true',
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]);
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// Message endpoint — AI client POSTs JSON-RPC here
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register_rest_route('asktam-mcp/v1', '/message', [
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'methods' => 'POST',
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'callback' => [$this, 'handleMessage'],
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'permission_callback' => '__return_true',
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]);
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// Simple info endpoint
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register_rest_route('asktam-mcp/v1', '/info', [
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'methods' => 'GET',
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'callback' => [$this, 'handleInfo'],
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'permission_callback' => '__return_true',
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]);
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}
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/**
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* SSE endpoint — opens the connection and sends server capabilities.
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*/
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public function handleSse(\WP_REST_Request $request): void {
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$auth = \AskTamMCP\Core\Auth::validate($request, \AskTamMCP\Core\Auth::SCOPE_READ);
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if (is_wp_error($auth)) {
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status_header($auth->get_error_data()['status'] ?? 401);
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header('Content-Type: application/json');
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echo wp_json_encode(['error' => $auth->get_error_message()]);
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exit;
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}
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// SSE headers
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header('Content-Type: text/event-stream');
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header('Cache-Control: no-cache');
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header('X-Accel-Buffering: no');
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header('Connection: keep-alive');
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ob_end_flush();
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$messageEndpoint = rest_url('asktam-mcp/v1/message');
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// Send endpoint event — tells client where to POST messages
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$this->sseEvent('endpoint', $messageEndpoint);
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// Send server capabilities (MCP initialize response)
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$initResponse = [
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'jsonrpc' => '2.0',
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'id' => null,
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'result' => [
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'protocolVersion' => '2024-11-05',
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'capabilities' => [
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'tools' => ['listChanged' => false],
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],
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'serverInfo' => [
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'name' => 'advanced-mcp-plugin',
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'version' => ASKTAM_MCP_VERSION,
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],
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],
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];
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$this->sseEvent('message', wp_json_encode($initResponse));
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// Keep-alive ping loop (max 29 seconds to avoid WP timeout)
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$start = time();
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while ((time() - $start) < 25) {
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$this->sseEvent('ping', (string) time());
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if (connection_aborted()) {
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break;
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}
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sleep(5);
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}
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exit;
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}
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/**
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* Message endpoint — receives JSON-RPC, dispatches to tool handler, returns result.
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*/
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public function handleMessage(\WP_REST_Request $request): \WP_REST_Response|\WP_Error {
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$auth = \AskTamMCP\Core\Auth::validate($request, \AskTamMCP\Core\Auth::SCOPE_READ);
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if (is_wp_error($auth)) {
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return $auth;
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}
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$body = $request->get_json_params();
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if (empty($body['method'])) {
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return $this->rpcError(null, -32600, 'Invalid Request: missing method');
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}
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$id = $body['id'] ?? null;
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$method = $body['method'];
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$params = $body['params'] ?? [];
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switch ($method) {
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case 'initialize':
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return $this->rpcResult($id, [
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'protocolVersion' => '2024-11-05',
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'capabilities' => ['tools' => ['listChanged' => false]],
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'serverInfo' => ['name' => 'advanced-mcp-plugin', 'version' => ASKTAM_MCP_VERSION],
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]);
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case 'tools/list':
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return $this->rpcResult($id, [
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'tools' => $this->registry->getToolDefinitions(),
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]);
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case 'tools/call':
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return $this->handleToolCall($id, $params, $auth);
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case 'notifications/initialized':
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case 'notifications/cancelled':
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// Client notifications — acknowledge silently
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return new \WP_REST_Response(null, 204);
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default:
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return $this->rpcError($id, -32601, "Method not found: {$method}");
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}
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}
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/**
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* Info endpoint — public, returns plugin version + endpoint URL.
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*/
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public function handleInfo(): \WP_REST_Response {
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return new \WP_REST_Response([
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'name' => 'Advanced MCP Plugin by AskTam',
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'version' => ASKTAM_MCP_VERSION,
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'endpoint' => rest_url('asktam-mcp/v1/sse'),
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'docs' => 'https://asktam.net/mcp-plugin',
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]);
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}
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// -------------------------------------------------------------------------
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// Private helpers
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// -------------------------------------------------------------------------
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private function handleToolCall(mixed $id, array $params, array $authRow): \WP_REST_Response {
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$toolName = $params['name'] ?? '';
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$arguments = $params['arguments'] ?? [];
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if (empty($toolName)) {
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return $this->rpcError($id, -32602, 'Missing tool name');
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}
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$handler = $this->registry->getHandler($toolName);
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if (!$handler) {
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return $this->rpcError($id, -32601, "Unknown tool: {$toolName}");
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}
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// Check write/admin scope for mutating tools
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$tool = $this->registry->getTool($toolName);
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if (($tool['scope'] ?? 'read') !== 'read') {
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$scopeCheck = \AskTamMCP\Core\Auth::validate(
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new \WP_REST_Request(), // dummy — scopes already on $authRow
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$tool['scope']
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);
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$keyScopes = array_map('trim', explode(',', $authRow['scopes']));
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$required = $tool['scope'];
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if (!in_array($required, $keyScopes, true) && !in_array('admin', $keyScopes, true)) {
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return $this->rpcError($id, -32000, "Insufficient scope. Required: {$required}");
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}
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}
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try {
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$result = $handler($arguments);
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return $this->rpcResult($id, [
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'content' => [
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['type' => 'text', 'text' => is_string($result) ? $result : wp_json_encode($result)],
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],
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]);
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} catch (\Throwable $e) {
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return $this->rpcError($id, -32000, $e->getMessage());
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}
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}
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private function rpcResult(mixed $id, mixed $result): \WP_REST_Response {
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return new \WP_REST_Response([
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'jsonrpc' => '2.0',
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'id' => $id,
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'result' => $result,
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]);
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}
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private function rpcError(mixed $id, int $code, string $message): \WP_REST_Response {
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return new \WP_REST_Response([
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'jsonrpc' => '2.0',
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'id' => $id,
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'error' => ['code' => $code, 'message' => $message],
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], 200); // MCP errors use HTTP 200 with JSON-RPC error body
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}
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private function sseEvent(string $event, string $data): void {
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echo "event: {$event}\n";
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echo "data: {$data}\n\n";
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flush();
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}
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}
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