import { createServer } from 'node:http';
import { readFileSync } from 'node:fs';
import { resolve } from 'node:path';
import { isIP } from 'node:net';
import { BusReadError, busStatus, subjectOk } from './bus.mjs';

export const DEFAULT_BOARD = 'http://127.0.0.1:7331';
export function isLoopback(host) {
  return host === 'localhost' || host === '::1' || (isIP(host) === 4 && host.startsWith('127.'));
}
export function boardURL(value) {
  const url = new URL(value);
  if (url.protocol !== 'http:' || !isLoopback(url.hostname.replace(/^\[|\]$/g, '')) || url.username || url.password || url.search || url.hash || url.pathname !== '/') {
    throw new Error('board must be an HTTP loopback origin without credentials, path, query or fragment');
  }
  // Avoid hostname resolution for localhost.
  if (url.hostname === 'localhost') url.hostname = '127.0.0.1';
  return url.origin;
}
const root = resolve(import.meta.dirname, 'public');
const files = new Map([
  ['/', ['index.html', 'text/html; charset=utf-8']],
  ...['app.js', 'brand.js', 'bus.js'].map(f => ['/' + f, [f, 'text/javascript; charset=utf-8']]),
  ...['shared/app.css', 'console.css', 'live.css', 'bus.css'].map(f => ['/' + f, [f, 'text/css; charset=utf-8']]),
  ...[400, 500, 600, 700].map(w => [`/assets/fonts/manrope-${w}.woff2`, [`assets/fonts/manrope-${w}.woff2`, 'font/woff2']]),
]);
function json(res, status, body) {
  res.writeHead(status, { 'content-type': 'application/json', 'cache-control': 'no-store' });
  res.end(JSON.stringify(body));
}
async function body(req) {
  if ((req.headers['content-type'] || '').split(';')[0].trim().toLowerCase() !== 'application/json') throw new Error('Content-Type must be application/json');
  const chunks = [];
  let size = 0;
  for await (const chunk of req) {
    size += chunk.length;
    if (size > 4096) throw new Error('body larger than 4096 bytes');
    chunks.push(chunk);
  }
  const bytes = Buffer.concat(chunks);
  const value = JSON.parse(bytes.toString('utf8'));
  if (!value || typeof value !== 'object' || Array.isArray(value)) throw new Error('body must be a JSON object');
  return bytes;
}
// Slice 1 S5 (#1522): GET only, the four Q1 verbs, nothing else (lead decision 56, Q4).
const BUS_VERBS = ['inbox', 'tasks', 'agents', 'trail'];
async function busRead(res, bus, verb, search) {
  let subject;
  if (verb === 'trail') {
    subject = new URLSearchParams(search).get('subject');
    if (!subjectOk(subject)) return json(res, 400, { error: 'invalid-request', message: 'subject must be a decision id, message id or task ref' });
  }
  if (!bus) return json(res, 503, { error: 'not-configured', message: 'the Console has no bus configured' });
  try {
    const rows = await bus[verb](subject);
    if (!Array.isArray(rows)) throw new BusReadError('invalid-response');
    return json(res, 200, { rows, at: new Date().toISOString() });
  } catch (err) {
    const code = err instanceof BusReadError ? err.code : 'invalid-response';
    return json(res, busStatus(code), { error: code, message: err instanceof BusReadError ? err.message : code });
  }
}
export async function startServer({ host = '127.0.0.1', port = 7330, board = DEFAULT_BOARD, timeout = 20000, bus = null } = {}) {
  if (!isLoopback(host)) throw new Error('refusing to bind to non-loopback host');
  if (host === 'localhost') host = '127.0.0.1';
  const upstream = boardURL(board);
  const server = createServer(async (req, res) => {
    res.setHeader('x-content-type-options', 'nosniff');
    res.setHeader('referrer-policy', 'no-referrer');
    res.setHeader('content-security-policy', "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; connect-src 'self'; font-src 'self'; object-src 'none'; base-uri 'none'; frame-ancestors 'none'; form-action 'self'");
    let path, search;
    try {
      const authority = new URL(`http://${req.headers.host}`);
      if (!isLoopback(authority.hostname.replace(/^\[|\]$/g, '')) || Number(authority.port || 80) !== server.address().port) return json(res, 403, { error: 'non-local Host refused' });
      ({ pathname: path, search } = new URL(req.url, 'http://localhost'));
    } catch { return json(res, 400, { error: 'invalid URL' }); }
    // No CORS. JSON content type and same-origin checks keep browser forms out.
    if (req.headers.origin && req.headers.origin !== `http://${req.headers.host}`) return json(res, 403, { error: 'cross-origin request refused' });
    // The conversation routes (#1507, CHAT-02) keep their query; the board validates it.
    const conversation = path === '/api/conversations' || path === '/api/conversation';
    const allowed = path === '/api/board' || conversation ? 'GET' : ['/api/seen', '/api/reply'].includes(path) ? 'POST' : null;
    if (allowed) {
      if (req.method !== allowed) return json(res, 405, { error: 'method not allowed' });
      let bytes;
      if (allowed === 'POST') {
        try { bytes = await body(req); } catch (err) { return json(res, 400, { error: err.message }); }
      }
      try {
        const response = await fetch(upstream + path + (conversation ? search : ''), {
          method: allowed, headers: bytes ? { 'content-type': 'application/json' } : {}, body: bytes,
          redirect: 'error', signal: AbortSignal.timeout(timeout),
        });
        const text = await response.text();
        JSON.parse(text); // Never serve upstream HTML or scripts as API data.
        res.writeHead(response.status, { 'content-type': 'application/json', 'cache-control': 'no-store' });
        return res.end(text);
      } catch {
        return json(res, 502, { error: `Board unreachable or invalid response at ${upstream}. Check the board server. No automatic action retry.`, board: upstream });
      }
    }
    if (path.startsWith('/api/bus/')) {
      const verb = path.slice('/api/bus/'.length);
      if (!BUS_VERBS.includes(verb)) return json(res, 404, { error: 'not found' });
      if (req.method !== 'GET') return json(res, 405, { error: 'method not allowed' });
      return busRead(res, bus, verb, search);
    }
    if (req.method !== 'GET' && req.method !== 'HEAD') return json(res, 405, { error: 'method not allowed' });
    if (path === '/api/config') return json(res, 200, { board: upstream });
    if (path === '/healthz') return json(res, 200, { ok: true });
    if (path === '/favicon.ico') { res.writeHead(204); return res.end(); }
    const file = files.get(path);
    if (!file) return json(res, 404, { error: 'not found' });
    try {
      const content = readFileSync(resolve(root, file[0]));
      res.writeHead(200, { 'content-type': file[1], 'cache-control': 'no-store' });
      res.end(req.method === 'HEAD' ? undefined : content);
    } catch { json(res, 500, { error: 'WebUI asset unavailable' }); }
  });
  return new Promise((resolvePromise, reject) => {
    server.once('error', reject);
    server.listen(port, host, () => { server.off('error', reject); resolvePromise(server); });
  });
}