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<?php |
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/** |
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* MCP server — the per-site JSON-RPC endpoint. |
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* |
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* The plugin speaks the MCP protocol directly at this site's own URL |
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* (https://thissite.com/thinkrank/mcp), so there is NO hosted broker in the |
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* path. MCP's Streamable-HTTP transport is JSON-RPC 2.0 over HTTP POST. We |
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* implement the small server surface an AI client needs: |
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* - initialize → capabilities + serverInfo |
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* - notifications/* → acknowledged (no response body) |
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* - ping → {} |
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* - tools/list → Mcp_Tools::list() |
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* - tools/call → Mcp_Tools::invoke() wrapped as MCP content |
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* |
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* Auth: either the static pairing token (Mcp_Pairing) or an OAuth 2.1 access |
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* token (Mcp_OAuth), both presented as a Bearer token. On success the request |
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* runs AS the admin who granted the credential (wp_set_current_user), so |
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* every ability's own capability check still applies. A single |
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* unauthenticated call gets a JSON-RPC 401 + RFC 9728 WWW-Authenticate |
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* challenge that points OAuth-capable clients at the discovery metadata. |
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* |
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* @package ThinkRank\Mcp |
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*/ |
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|
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declare(strict_types=1); |
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|
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namespace ThinkRank\Mcp; |
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|
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if ( ! defined( 'ABSPATH' ) ) { |
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exit; // Exit if accessed directly. |
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} |
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|
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/** |
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* JSON-RPC 2.0 handler for the ThinkRank MCP endpoint. |
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*/ |
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final class Mcp_Server { |
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|
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/** |
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* MCP protocol version this server implements. |
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*/ |
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public const PROTOCOL_VERSION = '2025-06-18'; |
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|
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/** |
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* JSON-RPC standard error codes. |
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*/ |
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private const PARSE_ERROR = -32700; |
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private const INVALID_REQUEST = -32600; |
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private const METHOD_NOT_FOUND = -32601; |
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private const INVALID_PARAMS = -32602; |
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private const UNAUTHORIZED = -32001; |
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|
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/** |
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* Handle a raw MCP HTTP request. Reads the JSON-RPC message from the |
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* request body, dispatches it, and returns a WP_REST_Response (or a |
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* 202 with empty body for notifications). |
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* |
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* @param \WP_REST_Request $request Incoming request (raw body). |
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* @return \WP_REST_Response |
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*/ |
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public static function handle( \WP_REST_Request $request ): \WP_REST_Response { |
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// Diagnostic tap: define THINKRANK_MCP_DEBUG in wp-config.php to log |
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// every inbound MCP request (pre-auth) to the PHP error log. Bodies |
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// are truncated; credentials are never logged. |
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if ( defined( 'THINKRANK_MCP_DEBUG' ) && THINKRANK_MCP_DEBUG ) { |
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error_log( sprintf( // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log -- opt-in debug tap. |
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'[TR-MCP] in method=%s auth=%s accept=%s body=%s', |
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isset( $_SERVER['REQUEST_METHOD'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_METHOD'] ) ) : '?', |
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$request->get_header( 'authorization' ) ? 'yes' : 'no', |
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(string) $request->get_header( 'accept' ), |
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substr( (string) $request->get_body(), 0, 300 ) |
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) ); |
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} |
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|
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// The admin toggle is the master switch: off = no MCP surface at all. |
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if ( ! Mcp_Manager::is_enabled() ) { |
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return self::error_response( null, self::UNAUTHORIZED, 'MCP is disabled on this site. Enable it under ThinkRank → MCP.', 403 ); |
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} |
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|
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// A request carrying NO credential is the normal opening move of the |
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// OAuth flow — the client is asking for the RFC 9728 challenge, not |
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// guessing a token. Only a credential that was PRESENTED and rejected |
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// counts against the limiter, and only such a request can be locked |
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// out; otherwise every OAuth-capable client walls itself off after |
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// DEFAULT_MAX_FAILS discovery probes. |
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$presented = self::extract_token( $request ); |
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|
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// Lockout check first: a rate-limited IP never reaches the compare. |
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if ( '' !== $presented && Mcp_Rate_Limiter::is_locked() ) { |
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$response = self::error_response( null, self::UNAUTHORIZED, 'Too many failed attempts. Try again later.', 429 ); |
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// Keep the challenge on the 429 too: a client that only ever sees |
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// a bare 429 concludes the server has no OAuth at all. |
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$response->header( 'WWW-Authenticate', self::challenge_header() ); |
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$response->header( 'Retry-After', (string) Mcp_Rate_Limiter::retry_after() ); |
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return $response; |
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} |
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|
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// Authenticate: static pairing token OR an OAuth 2.1 access token |
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// (both Bearer). Either satisfies the gate. |
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if ( true !== self::authorize( $request ) ) { |
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if ( '' !== $presented ) { |
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Mcp_Rate_Limiter::record_failure(); |
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} |
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$response = self::error_response( null, self::UNAUTHORIZED, 'Unauthorized: invalid or missing connection token.', 401 ); |
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// RFC 9728 challenge: point OAuth-capable clients at the |
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// protected-resource metadata so they can start the auth flow. |
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$response->header( 'WWW-Authenticate', self::challenge_header() ); |
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return $response; |
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} |
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Mcp_Rate_Limiter::clear(); |
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|
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$raw = $request->get_body(); |
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$msg = json_decode( $raw, true ); |
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|
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if ( null === $msg && JSON_ERROR_NONE !== json_last_error() ) { |
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return self::error_response( null, self::PARSE_ERROR, 'Parse error: body is not valid JSON.', 400 ); |
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} |
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|
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// Batched requests: an array of messages. Handle each; drop |
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// notification (id-less) responses per JSON-RPC. |
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// |
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// KEPT DELIBERATELY, not left behind by accident. The revision we |
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// advertise in PROTOCOL_VERSION (2025-06-18) removed JSON-RPC |
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// batching, so this is more than the spec requires — but accepting a |
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// batch harms nobody, while refusing one would break any client still |
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// on an older SDK that sends them. Please don't delete this as a spec |
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// violation; that trade is the reason it is here (#488). |
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if ( is_array( $msg ) && array_key_exists( 0, $msg ) ) { |
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$responses = []; |
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foreach ( $msg as $one ) { |
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$r = self::dispatch( is_array( $one ) ? $one : [] ); |
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if ( null !== $r ) { |
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$responses[] = $r; |
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} |
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} |
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if ( empty( $responses ) ) { |
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return new \WP_REST_Response( null, 202 ); |
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} |
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return new \WP_REST_Response( $responses, 200 ); |
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} |
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|
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if ( ! is_array( $msg ) ) { |
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return self::error_response( null, self::INVALID_REQUEST, 'Invalid request.', 400 ); |
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} |
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|
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$response = self::dispatch( $msg ); |
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if ( null === $response ) { |
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// Notification — no response body, 202 Accepted. |
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return new \WP_REST_Response( null, 202 ); |
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} |
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return new \WP_REST_Response( $response, 200 ); |
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} |
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|
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/** |
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* Dispatch a single JSON-RPC message. Returns the response array, or |
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* null for notifications (messages with no `id`). |
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* |
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* @param array $msg Decoded JSON-RPC message. |
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* @return array|null |
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*/ |
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private static function dispatch( array $msg ): ?array { |
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$method = isset( $msg['method'] ) ? (string) $msg['method'] : ''; |
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$id = $msg['id'] ?? null; |
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$params = isset( $msg['params'] ) && is_array( $msg['params'] ) ? $msg['params'] : []; |
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|
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// Notifications (no id) get acknowledged with no response. |
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$is_notification = ! array_key_exists( 'id', $msg ); |
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|
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$response = self::handle_method( $method, $id, $params, $is_notification ); |
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|
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// JSON-RPC 2.0: a message with no `id` is a notification and MUST NOT |
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// be answered. Only the default branch below used to consult this, so |
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// initialize, ping, tools/list and tools/call sent without an id all |
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// fell through to self::result( null, ... ) and were answered with a |
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// 200 carrying "id": null instead of the 202 with no body a |
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// notification should get (#488). The message is still PROCESSED — |
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// only the reply is suppressed, which is what the spec asks for. |
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return $is_notification ? null : $response; |
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} |
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|
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/** |
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* Run one JSON-RPC method. Whether the caller wanted an answer is |
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* dispatch()'s business, not this method's. |
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* |
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* @param string $method Method name. |
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* @param mixed $id JSON-RPC id (null for a notification). |
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* @param array $params Method params. |
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* @param bool $is_notification Whether the message carried no id. |
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* @return array|null |
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*/ |
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private static function handle_method( string $method, $id, array $params, bool $is_notification ): ?array { |
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switch ( $method ) { |
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case 'initialize': |
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return self::result( |
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$id, |
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[ |
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'protocolVersion' => self::PROTOCOL_VERSION, |
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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' => 'thinkrank', |
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'version' => defined( 'THINKRANK_VERSION' ) ? THINKRANK_VERSION : '1.0.0', |
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], |
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] |
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); |
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|
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case 'ping': |
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return self::result( $id, (object) [] ); |
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|
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case 'tools/list': |
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$tools = Mcp_Tools::list(); |
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// An empty list while MCP is enabled means the Abilities |
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// runtime never loaded (broken package) — the client sees a |
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// clean, useless connection. Leave a trail for whoever debugs |
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// it; the admin notice and self-test carry the loud version. |
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if ( empty( $tools ) && defined( 'WP_DEBUG' ) && WP_DEBUG ) { |
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error_log( '[TR-MCP] tools/list returned 0 tools. ' . \ThinkRank\Abilities\Abilities_Registrar::summary() ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log -- WP_DEBUG-gated diagnostic. |
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} |
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return self::result( $id, [ 'tools' => $tools ] ); |
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|
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case 'tools/call': |
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return self::call_tool( $id, $params ); |
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|
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default: |
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// notifications/initialized, notifications/cancelled, etc. |
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if ( $is_notification || 0 === strpos( $method, 'notifications/' ) ) { |
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return null; |
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} |
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return self::error( $id, self::METHOD_NOT_FOUND, 'Method not found: ' . $method ); |
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} |
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} |
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|
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/** |
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* Execute a tools/call request and wrap the result in MCP content. |
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* |
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* @param mixed $id JSON-RPC id. |
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* @param array $params { name:string, arguments:array }. |
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* @return array |
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*/ |
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private static function call_tool( $id, array $params ): array { |
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$name = isset( $params['name'] ) ? (string) $params['name'] : ''; |
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$args = isset( $params['arguments'] ) && is_array( $params['arguments'] ) ? $params['arguments'] : []; |
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|
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if ( '' === $name ) { |
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return self::error( $id, self::INVALID_PARAMS, 'Missing tool name.' ); |
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} |
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|
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$result = Mcp_Tools::invoke( $name, $args ); |
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|
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if ( is_wp_error( $result ) ) { |
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// Tool-level failure is reported as a successful JSON-RPC |
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// response with isError=true (per MCP), so the model can read |
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// the message rather than the transport swallowing it. |
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return self::result( |
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$id, |
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[ |
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'content' => [ |
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[ |
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'type' => 'text', |
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'text' => $result->get_error_message(), |
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], |
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], |
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'isError' => true, |
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] |
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); |
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} |
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|
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return self::result( |
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$id, |
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[ |
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'content' => [ |
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[ |
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'type' => 'text', |
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'text' => wp_json_encode( $result, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES ), |
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], |
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], |
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'isError' => false, |
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] |
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); |
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} |
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|
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// -- Auth -- |
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|
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/** |
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* Validate the Bearer credential — pairing token or OAuth access token. |
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* On success, switch the request to the granting admin's user so every |
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* ability's own permission callback (current_user_can) still applies. |
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* |
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* @param \WP_REST_Request $request Incoming request. |
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* @return bool |
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*/ |
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private static function authorize( \WP_REST_Request $request ): bool { |
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$presented = self::extract_token( $request ); |
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if ( '' === $presented ) { |
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return false; |
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} |
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|
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// Path 1: the static per-site pairing token. Leave the tool scope |
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// override cleared so Mcp_Tools defers to the pairing token's scope. |
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// |
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// Compared through Mcp_Pairing::verify_token(), which checks the stored |
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// hash rather than a plaintext copy — the token is encrypted at rest and |
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// only its hash is used to authenticate (#396). |
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if ( Mcp_Pairing::verify_token( $presented ) ) { |
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Mcp_Tools::set_read_only_override( null ); |
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if ( self::impersonate( Mcp_Pairing::user_id() ) ) { |
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// Record activity for the "Static token connections" row. |
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Mcp_Pairing::touch_last_used(); |
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return true; |
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} |
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return false; |
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} |
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|
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// Path 2: an OAuth 2.1 access token minted by Mcp_OAuth. Its own |
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// granted scope decides read-only, independent of the pairing token. |
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$grant = Mcp_OAuth::validate_token( $presented ); |
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if ( null !== $grant ) { |
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Mcp_Tools::set_read_only_override( Mcp_OAuth::scope_is_read_only( $grant['scope'] ) ); |
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return self::impersonate( $grant['user_id'] ); |
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} |
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|
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return false; |
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} |
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|
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/** |
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* Run the request as the admin who granted the credential. Refuses when |
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* the stored user no longer exists or lost manage_options — a demoted or |
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* deleted admin's grants die with them. |
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* |
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* @param int $user_id Granting user id. |
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* @return bool |
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*/ |
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private static function impersonate( int $user_id ): bool { |
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if ( $user_id <= 0 ) { |
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return false; |
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} |
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$user = get_user_by( 'id', $user_id ); |
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if ( ! $user || ! user_can( $user, 'manage_options' ) ) { |
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return false; |
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} |
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wp_set_current_user( $user_id ); |
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return true; |
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} |
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|
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/** |
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* The RFC 9728 WWW-Authenticate challenge value. Points the client at |
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* this site's protected-resource metadata so an OAuth-capable client |
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* can discover the authorization server and begin the flow. |
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* |
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* @return string |
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*/ |
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private static function challenge_header(): string { |
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// REST-served, not the /.well-known/ path-insert form: some hosts |
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// (SiteGround) intercept root /.well-known/ at their Nginx edge and |
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// 404 it before WordPress runs, killing the flow on the client's very |
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// first fetch. See Mcp_OAuth::resource_metadata_url() for the full |
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// reasoning and the override filter. |
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return sprintf( 'Bearer resource_metadata="%s"', Mcp_OAuth::resource_metadata_url() ); |
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} |
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|
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/** |
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* Pull the token from the Authorization: Bearer header. |
| 363 |
* |
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* @param \WP_REST_Request $request Incoming request. |
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* @return string |
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*/ |
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private static function extract_token( \WP_REST_Request $request ): string { |
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$auth = $request->get_header( 'authorization' ); |
| 369 |
if ( is_string( $auth ) && preg_match( '/^Bearer\s+(.+)$/i', trim( $auth ), $m ) ) { |
| 370 |
return trim( $m[1] ); |
| 371 |
} |
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return ''; |
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} |
| 374 |
|
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// -- JSON-RPC envelope helpers -- |
| 376 |
|
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/** |
| 378 |
* Build a JSON-RPC success envelope. |
| 379 |
* |
| 380 |
* @param mixed $id JSON-RPC id. |
| 381 |
* @param mixed $result Result payload. |
| 382 |
* @return array |
| 383 |
*/ |
| 384 |
private static function result( $id, $result ): array { |
| 385 |
return [ |
| 386 |
'jsonrpc' => '2.0', |
| 387 |
'id' => $id, |
| 388 |
'result' => $result, |
| 389 |
]; |
| 390 |
} |
| 391 |
|
| 392 |
/** |
| 393 |
* Build a JSON-RPC error envelope (for a single message). |
| 394 |
* |
| 395 |
* @param mixed $id JSON-RPC id. |
| 396 |
* @param int $code JSON-RPC error code. |
| 397 |
* @param string $message Error message. |
| 398 |
* @return array |
| 399 |
*/ |
| 400 |
private static function error( $id, int $code, string $message ): array { |
| 401 |
return [ |
| 402 |
'jsonrpc' => '2.0', |
| 403 |
'id' => $id, |
| 404 |
'error' => [ |
| 405 |
'code' => $code, |
| 406 |
'message' => $message, |
| 407 |
], |
| 408 |
]; |
| 409 |
} |
| 410 |
|
| 411 |
/** |
| 412 |
* Build a top-level error WP_REST_Response with an HTTP status. |
| 413 |
* |
| 414 |
* @param mixed $id JSON-RPC id. |
| 415 |
* @param int $code JSON-RPC error code. |
| 416 |
* @param string $message Error message. |
| 417 |
* @param int $http HTTP status. |
| 418 |
* @return \WP_REST_Response |
| 419 |
*/ |
| 420 |
private static function error_response( $id, int $code, string $message, int $http ): \WP_REST_Response { |
| 421 |
return new \WP_REST_Response( self::error( $id, $code, $message ), $http ); |
| 422 |
} |
| 423 |
} |
| 424 |
|
