MCP Payment Proxy

import "dotenv/config"
import express from "express"
import { payer } from "@faremeter/rides"
import { getLogger } from "@faremeter/logs"

const logger = await getLogger(["mcp-proxy"])

await payer.addLocalWallet(process.env.PAYER_KEYPAIR_PATH)

const app = express()
app.use(express.json())

const MCP_SERVER_URL = process.env.MCP_SERVER_URL ?? "https://your-mcp-server.com/mcp"

// ── Free path ────────────────────────────────────────────────
// Protocol-level methods: forwarded with plain fetch (no payment)
const FREE_METHODS = ["initialize", "tools/list", "prompts/list", "resources/list"]

// ── Paid path ────────────────────────────────────────────────
// Everything else (tools/call, prompts/get, resources/read, …)
// goes through payer.fetch, which handles the 402 → pay → retry flow

app.all("/mcp", async (req, res) => {
  const method = req.body?.method
  const shouldPay = !FREE_METHODS.includes(method)

  logger.info(`${method} → ${shouldPay ? "paying" : "free"}`)

  // Free methods use plain fetch; paid methods use payer.fetch
  const fetchFn = shouldPay ? payer.fetch : fetch
  const response = await fetchFn(MCP_SERVER_URL, {
    method: req.method,
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(req.body),
  })

  const data = await response.text()
  res.status(response.status).send(data)
})

app.listen(8402, () => {
  logger.info("MCP proxy running on http://localhost:8402/mcp")
})