92 lines
2.9 KiB
TypeScript
92 lines
2.9 KiB
TypeScript
import process from 'node:process';
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import { Readable, Writable } from 'node:stream';
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import { ReadBuffer, serializeMessage } from '../shared/stdio.js';
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import { JSONRPCMessage } from '../types.js';
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import { Transport } from '../shared/transport.js';
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/**
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* Server transport for stdio: this communicates with an MCP client by reading from the current process' stdin and writing to stdout.
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*
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* This transport is only available in Node.js environments.
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*/
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export class StdioServerTransport implements Transport {
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private _readBuffer: ReadBuffer = new ReadBuffer();
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private _started = false;
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constructor(
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private _stdin: Readable = process.stdin,
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private _stdout: Writable = process.stdout
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) {}
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onclose?: () => void;
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onerror?: (error: Error) => void;
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onmessage?: (message: JSONRPCMessage) => void;
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// Arrow functions to bind `this` properly, while maintaining function identity.
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_ondata = (chunk: Buffer) => {
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this._readBuffer.append(chunk);
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this.processReadBuffer();
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};
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_onerror = (error: Error) => {
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this.onerror?.(error);
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};
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/**
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* Starts listening for messages on stdin.
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*/
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async start(): Promise<void> {
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if (this._started) {
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throw new Error(
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'StdioServerTransport already started! If using Server class, note that connect() calls start() automatically.'
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);
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}
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this._started = true;
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this._stdin.on('data', this._ondata);
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this._stdin.on('error', this._onerror);
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}
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private processReadBuffer() {
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while (true) {
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try {
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const message = this._readBuffer.readMessage();
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if (message === null) {
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break;
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}
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this.onmessage?.(message);
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} catch (error) {
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this.onerror?.(error as Error);
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}
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}
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}
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async close(): Promise<void> {
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// Remove our event listeners first
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this._stdin.off('data', this._ondata);
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this._stdin.off('error', this._onerror);
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// Check if we were the only data listener
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const remainingDataListeners = this._stdin.listenerCount('data');
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if (remainingDataListeners === 0) {
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// Only pause stdin if we were the only listener
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// This prevents interfering with other parts of the application that might be using stdin
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this._stdin.pause();
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}
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// Clear the buffer and notify closure
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this._readBuffer.clear();
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this.onclose?.();
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}
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send(message: JSONRPCMessage): Promise<void> {
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return new Promise(resolve => {
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const json = serializeMessage(message);
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if (this._stdout.write(json)) {
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resolve();
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} else {
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this._stdout.once('drain', resolve);
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}
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});
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}
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}
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