src/a2a-http.ts

import { serve } from '@hono/node-server';
import { Hono } from 'hono';
import { rateLimit } from 'express-rate-limit';
import { readFileSync } from 'node:fs';
import { join } from 'node:path';
import { executeBackendAgentAction, BackendAgentAction } from './runtime.js';

export function runHttpServer() {
  const app = new Hono();
  const PORT = Number(process.env.PORT) || 8080;

  const rateLimiter = rateLimit({
    windowMs: 60 * 1000,
    max: 100,
    message: 'Too many requests, please try again later.',
  });

  app.use('*', async (c, next) => {
    return new Promise<void>((resolve) => {
      const env = (c as any).env as any;
      rateLimiter(env?.req as any, env?.res as any, () => {
        next().then(resolve);
      });
    });
  });

  app.get('/health', (c) => c.json({ status: 'ok', agent: 'sin-backend' }));

  app.get('/.well-known/agent-card.json', (c) => {
    try {
      const card = readFileSync(join(process.cwd(), '.well-known', 'agent-card.json'), 'utf8');
      return c.json(JSON.parse(card));
    } catch {
      return c.json({ error: 'Agent card not found' }, 404);
    }
  });

  app.get('/.well-known/agent.json', (c) => {
    try {
      const spec = readFileSync(join(process.cwd(), '.well-known', 'agent.json'), 'utf8');
      return c.json(JSON.parse(spec));
    } catch {
      return c.json({ error: 'Agent spec not found' }, 404);
    }
  });

  app.post('/a2a/v1', async (c) => {
    try {
      const body = await c.req.json();
      
      const rpcMethod = body.method;
      let action: BackendAgentAction;

      if (rpcMethod === 'sin.backend.health') {
        action = { action: 'sin.backend.health' };
      } else if (rpcMethod === 'sin.backend.code.generate') {
        action = { action: 'sin.backend.code.generate', prompt: body.params?.prompt, contextDir: body.params?.contextDir };
      } else if (rpcMethod === 'sin.backend.code.review') {
        action = { action: 'sin.backend.code.review', targetDir: body.params?.targetDir };
      } else if (rpcMethod === 'agent.help' || body.action === 'agent.help') {
        action = { action: 'agent.help' };
      } else {
        return c.json({ error: { code: -32601, message: 'Method not found' } }, 400);
      }

      const result = await executeBackendAgentAction(action);
      return c.json({ jsonrpc: '2.0', id: body.id || null, result });
    } catch (e: any) {
      return c.json({ error: { code: -32000, message: e.message } }, 500);
    }
  });

  serve({ fetch: app.fetch, port: PORT }, (info) => {
    console.log(`SIN-Backend HTTP A2A server running at http://localhost:${info.port}`);
  });
}