#!/usr/bin/env node
import { spawn } from "child_process";
import { parseFlags } from "./lib/parseFlags";
import { parseNdjsonChunk } from "./lib/ndjson";
export function run(
args: string[],
stdin: NodeJS.ReadableStream = process.stdin,
stdout: NodeJS.WritableStream = process.stdout,
) {
// Extract proxy flags
const knownFlags = { visible_tools: "" };
const { flags, filteredArgs } = parseFlags(args, knownFlags);
const allowedTools = flags.visible_tools;
const realCommand = filteredArgs[0];
const realArgs = filteredArgs.slice(1);
if (!realCommand) {
console.error("Usage: mcpwrapped --visible_tools=a,b realCmd realArgs...");
process.exit(1);
}
// Start wrapped server
const child = spawn(realCommand, realArgs, {
stdio: ["pipe", "pipe", "inherit"],
env: process.env,
});
if (require.main === module) {
// When run directly from the CLI, exit the process when the child exits.
child.on("exit", (code) => process.exit(code ?? 0));
} else {
// When this module is required (e.g. in tests), do not call process.exit to avoid
// terminating the hosting process.
child.on("exit", () => {});
}
// RAW FORWARD: client → server
stdin.on("data", (chunk) => {
child.stdin?.write(chunk);
});
// BUFFERING FOR SERVER OUTPUT: server → client
let buffer = "";
/**
* Parse incoming stdout chunks as NDJSON while preserving trailing buffer.
* parseNdjsonChunk returns the updated buffer and an array of records:
* { line, msg } where msg is the parsed JSON object or undefined for non-JSON/blank lines.
*/
child.stdout?.on("data", (chunk) => {
const result = parseNdjsonChunk(buffer, chunk);
buffer = result.buffer;
for (const { line, msg } of result.records) {
// Non-JSON or blank lines — pass through unchanged (blank lines are skipped)
if (msg === undefined) {
if (line.trim()) stdout.write(line + "\n");
continue;
}
// === FILTER TOOL ===
if (allowedTools && msg?.result) {
const allowed = allowedTools.split(",").map((t) => t.trim());
if (msg.result.capabilities?.tools) {
const filtered: Record<string, any> = {};
for (const [name, def] of Object.entries(
msg.result.capabilities.tools,
)) {
if (allowed.includes(name)) {
filtered[name] = def;
}
}
msg.result.capabilities.tools = filtered;
}
// Legacy array form
if (Array.isArray(msg.result.tools)) {
msg.result.tools = msg.result.tools.filter((t: { name: string }) =>
allowed.includes(t.name),
);
}
stdout.write(JSON.stringify(msg) + "\n");
continue;
}
// Forward everything else
stdout.write(line + "\n");
}
});
return child;
}
if (require.main === module) {
run(process.argv.slice(2));
}
