import http from 'node:http';
import crypto from 'node:crypto';
import { readFileSync } from 'node:fs';
import { validateJob, isValidSub, isValidRunId } from './validate.js';

const MAX_BODY = 256 * 1024;

export function readMemAvailable(path = '/proc/meminfo') {
  const m = /^MemAvailable:\s+(\d+)\s+kB/m.exec(readFileSync(path, 'utf8'));
  return m ? Number(m[1]) * 1024 : 0;
}

function tokenOk(header, token) {
  if (!token) return false;
  const m = /^Bearer (.+)$/.exec(header || '');
  if (!m) return false;
  const a = crypto.createHash('sha256').update(m[1]).digest();
  const b = crypto.createHash('sha256').update(token).digest();
  return crypto.timingSafeEqual(a, b);
}

function send(res, status, obj) {
  const body = JSON.stringify(obj);
  res.writeHead(status, { 'Content-Type': 'application/json', 'Content-Length': Buffer.byteLength(body) });
  res.end(body);
}

function readJson(req) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    let size = 0;
    let tooBig = false;
    req.on('data', (c) => {
      if (tooBig) return; // Rest verwerfen, damit die Antwort noch ausgeliefert wird
      size += c.length;
      if (size > MAX_BODY) { tooBig = true; chunks.length = 0; return; }
      chunks.push(c);
    });
    req.on('end', () => {
      if (tooBig) return reject(Object.assign(new Error('Anfrage zu groß'), { status: 413 }));
      const raw = Buffer.concat(chunks).toString('utf8');
      if (!raw) return resolve({});
      try { resolve(JSON.parse(raw)); } catch { reject(Object.assign(new Error('Ungültiges JSON'), { status: 400 })); }
    });
    req.on('error', reject);
  });
}

export function createApiServer({ config, jobs, dev, mem = readMemAvailable }) {
  return http.createServer(async (req, res) => {
    try {
      if (!tokenOk(req.headers.authorization, config.token)) return send(res, 401, { error: 'Nicht autorisiert' });
      const url = new URL(req.url, 'http://x');
      const parts = url.pathname.split('/').filter(Boolean);
      const method = req.method;

      if (method === 'GET' && url.pathname === '/status') {
        return send(res, 200, { dev: dev.list(), queue: jobs.queueLength(), memAvailable: mem() });
      }
      if (method === 'POST' && url.pathname === '/jobs/build') {
        const v = validateJob(await readJson(req));
        if (!v.ok) return send(res, 400, { error: v.error });
        return send(res, 200, jobs.submit(v.job));
      }
      if (method === 'GET' && parts[0] === 'jobs' && parts.length === 2) {
        if (!isValidRunId(parts[1])) return send(res, 400, { error: 'Ungültige Lauf-ID' });
        const run = jobs.get(parts[1]);
        return run ? send(res, 200, run) : send(res, 404, { error: 'Lauf nicht gefunden' });
      }
      if (method === 'PUT' && parts[0] === 'dev' && parts.length === 2) {
        const sub = parts[1];
        if (!isValidSub(sub)) return send(res, 400, { error: 'Ungültige Subdomain' });
        const v = validateJob(await readJson(req));
        if (!v.ok) return send(res, 400, { error: v.error });
        if (v.job.sub !== sub) return send(res, 400, { error: 'Subdomain stimmt nicht überein' });
        return send(res, 200, { state: (await dev.register(sub, v.job)).state });
      }
      if (method === 'POST' && parts[0] === 'dev' && parts.length === 3 && ['start', 'stop'].includes(parts[2])) {
        const sub = parts[1];
        if (!isValidSub(sub)) return send(res, 400, { error: 'Ungültige Subdomain' });
        if (parts[2] === 'stop') {
          await dev.stop(sub);
          return send(res, 200, { ok: true });
        }
        const v = validateJob(await readJson(req));
        if (!v.ok) return send(res, 400, { error: v.error });
        if (v.job.sub !== sub) return send(res, 400, { error: 'Subdomain stimmt nicht überein' });
        return send(res, 200, await dev.ensure(sub, v.job));
      }
      return send(res, 404, { error: 'Nicht gefunden' });
    } catch (e) {
      const status = e.status || 500;
      if (status >= 500) console.error('Runner-Fehler:', e);
      if (!res.headersSent) send(res, status, { error: status === 500 ? 'Interner Fehler' : e.message });
    }
  });
}