import express from "express";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { requirePayment } from "@blockchain0x/mcp";
import { webhooks } from "@blockchain0x/node";

const server = new McpServer({ name: "docs-search", version: "1.0.0" });

// You decide who counts as paid. Back this with Redis/Postgres in production.
const paid = new Set<string>();

server.tool(
  "search_docs",
  "Semantic search across our docs",
  { query: { type: "string" }, payer: { type: "string" } },
  async ({ query, payer }) => {
    if (!paid.has(`search_docs:${payer}`)) {
      // Not paid yet: build an x402-compatible 402 challenge and return its
      // body as a tool error. requirePayment is a challenge builder - it does
      // not gate the call for you; this check is yours.
      const { body } = requirePayment({
        amountUsdc: "0.02",
        payTo: "0xYourMcpAgentAddress",
        hostedUrl: "https://pay.blockchain0x.com/checkout/docs-search",
        description: "docs search",
      });
      return { content: [{ type: "text", text: JSON.stringify(body) }], isError: true };
    }
    const results = await runVectorSearch(query);
    return { content: [{ type: "text", text: JSON.stringify(results) }] };
  },
);

// Your webhook endpoint marks a payer as paid once the checkout settles.
const app = express();
app.post("/webhooks/blockchain0x", express.raw({ type: "*/*" }), (req, res) => {
  const r = webhooks.verify({ headers: req.headers, rawBody: req.body, secret: process.env.BLOCKCHAIN0X_WEBHOOK_SECRET! });
  if (!r.ok) return res.status(400).json({ code: r.code });
  if (r.eventType === "payment.received") {
    // Resolve (tool, payer) from the reference you encoded in hostedUrl, then:
    paid.add("search_docs:0xPayer");
  }
  res.json({ received: true });
});