next.js 16 + Rust MCP Server example

page.tsx

"use client";
// app/page.tsx
import Image from "next/image";

export default function Home() {

  const testCreate = async function() {
    try{
      const res = await fetch("/api/test/create", {
        method: 'POST',
        headers: {'Content-Type': 'application/json'}, 
        /* @ts-ignore */     
        body: JSON.stringify({name: "tea", price: 140})
      });
      const json = await res.json()
      console.log(json)
      return json;
    }catch(e){console.error(e)}
  }

  const testList = async function() {
    try{
      const res = await fetch("/api/test/list", {
        method: 'POST',
        headers: {'Content-Type': 'application/json'},  
        /* @ts-ignore */    
        body: {}
      });
      const json = await res.json()
      console.log(json)
      const out = [];
      let rowData = null;
      const jsonData = JSON.parse(json.data)
      jsonData.forEach((item=>{
        rowData = JSON.parse(item.data)
        item.data = rowData;
        out.push(item)
      }));      
      console.log(out)
      return out;
    }catch(e){console.error(e)}
  }

  return (
    <div className="bg-zinc-50 font-sans dark:bg-black">
      <main className="max-w-3xl flex-col items-center justify-between py-4 px-16 bg-white dark:bg-black sm:items-start">
        <h1 className="text-3xl font-bold my-6">hello</h1>
        <hr className="border border-gray-200" />
        <button onClick={()=>testCreate()}>[ Add ]</button>
        <hr className="border border-gray-200" />
        <button onClick={()=>testList()}>[ List ]</button>
        <hr className="border border-gray-200" />
      </main>
    </div>
  );
}

route.ts

// app/api/test/create/route.ts
import { NextResponse } from "next/server";
import RpcClient from '../../../lib/RpcClient'
const __dirname = process.cwd();
const CMD_PATH = __dirname + "/dist/rust_mcp_server_4"
console.log("CMD_PATH=", CMD_PATH)

export async function POST(req: Request) {
  const retObj = {ret: 500, data: null}
  try{  
    const reqJson = await req.json();
    console.log(reqJson);
    const client = new RpcClient(CMD_PATH);

    const resp = await client.call(
      "tools/call", 
      { 
        name: "purchase", 
        arguments: {name: reqJson.name, price: reqJson.price }, 
      },
    );
    client.close();  

    retObj.ret = 200;
    return NextResponse.json(retObj);
  } catch (error) {
    console.error(error);
    return NextResponse.json(retObj);
  }
}

RpcClient.ts

// app/lib/RpcClient.ts
import { spawn } from "child_process";

class RpcClient {
  constructor(command: any) {
    /* @ts-ignore */
    this.proc = spawn(command);
    /* @ts-ignore */
    this.idCounter = 1;
    /* @ts-ignore */
    this.pending = new Map();

    /* @ts-ignore */
    this.proc.stdout.setEncoding("utf8");
    /* @ts-ignore */
    this.proc.stdout.on("data", (data) => this._handleData(data));
    /* @ts-ignore */
    this.proc.stderr.on("data", (err) => console.error("Rust stderr:", err.toString()));
    /* @ts-ignore */
    this.proc.on("exit", (code) => console.log(`Rust server exited (${code})`));
  }

  _handleData(data: any) {
    // 複数行対応
    /* @ts-ignore */
    data.split("\n").forEach((line) => {
      if (!line.trim()) return;
      try {
        const msg = JSON.parse(line);
       /* @ts-ignore */
        if (msg.id && this.pending.has(msg.id)) {
          /* @ts-ignore */
          const { resolve } = this.pending.get(msg.id);
          /* @ts-ignore */
          this.pending.delete(msg.id);
          resolve(msg.result);
        }
      } catch (e) {
        //console.error("JSON parse error:", e, line);
      }
    });
  }

  call(method: any, params = {}) {
    /* @ts-ignore */
    const id = this.idCounter++;
    const payload = {
      jsonrpc: "2.0",
      id,
      method,
      params,
    };

    return new Promise((resolve, reject) => {
      /* @ts-ignore */
      this.pending.set(id, { resolve, reject });
      /* @ts-ignore */
      this.proc.stdin.write(JSON.stringify(payload) + "\n");
    });
  }

  close() {
    /* @ts-ignore */
    this.proc.kill();
  }
}
export default RpcClient;

test_list_route.ts

// app/api/test/list/route.ts
import { NextResponse } from "next/server";
import RpcClient from '../../../lib/RpcClient'
const __dirname = process.cwd();
const CMD_PATH = __dirname + "/dist/rust_mcp_server_4"
console.log("CMD_PATH=", CMD_PATH)

export async function POST(req: Request) {
  const retObj = {ret: 500, data: null}
  try{  
    //const reqJson = await req.json();
    const client = new RpcClient(CMD_PATH);
    const resp = await client.call(
      "tools/call", 
      { 
        name: "purchase_list", 
        arguments: null, 
      },
    );
    client.close();  
    console.log("resp=", resp);
    /* @ts-ignore */
    if(resp.content[0]){
      retObj.ret = 200;
      /* @ts-ignore */
      retObj.data = resp.content[0].text;
      return NextResponse.json(retObj);
/*
      const json = JSON.parse(resp.content[0].text)
      console.log(json)
      let rowData = null;
      const out = [];
      json.forEach((item=>{
        console.log(item.id)
        rowData = JSON.parse(item.data)
        console.log(rowData)
        item.data = rowData;
        out.push(item)
      }));
      console.log(out)
*/
    }
    return NextResponse.json(retObj);
  } catch (error) {
    console.error(error);
    return NextResponse.json(retObj);
  }
}