const http = require('http');
const fs = require('fs');
const path = require('path');
const url = require('url');

const ROOT = __dirname;
const CONFIG_PATH = path.join(ROOT, 'project.config.json');
const TEMPLATE_HTML = path.join(ROOT, '飞书审批配置文件_V1.0.html');
const ADDRESS_REGIONS_JS = path.join(ROOT, 'address-regions.js');

function loadProjectConfig() {
  try {
    if (fs.existsSync(CONFIG_PATH)) return JSON.parse(fs.readFileSync(CONFIG_PATH, 'utf8'));
  } catch (e) {}
  return { projectId: 'approval_of_design', port: 8080, host: '0.0.0.0', label: '飞书审批配置服务' };
}

const PROJECT = loadProjectConfig();
const PORT = Number(process.env.PORT) || PROJECT.port || 8080;
const HOST = process.env.HOST || PROJECT.host || '0.0.0.0';

const NODE_MAJOR = parseInt(String(process.versions.node).split('.')[0], 10);
if (NODE_MAJOR < 16) {
  console.error('[ERROR] Node.js 16.x or later is required. Current: ' + process.version);
  process.exit(1);
}

let templateCache = null;

function readTemplate() {
  if (!templateCache) {
    templateCache = fs.readFileSync(TEMPLATE_HTML, 'utf8');
  }
  return templateCache;
}

function reloadTemplate() {
  templateCache = null;
  return readTemplate();
}

function safeJsonForScript(value) {
  return JSON.stringify(value).replace(/<\//g, '\\u003c/');
}

function renderBootScript(config, mode) {
  const project = {
    id: PROJECT.projectId || 'approval_of_design',
    label: PROJECT.label || '飞书审批配置服务'
  };
  return [
    '<script id="app-boot">',
    'window.APP_PROJECT = ' + safeJsonForScript(project) + ';',
    "window.APP_MODE = '" + mode + "';",
    'window.__INITIAL_CONFIG__ = ' + safeJsonForScript(config) + ';',
    '</script>'
  ].join('\n');
}

function injectBoot(html, config, mode) {
  return html.replace(/<script id="app-boot">[\s\S]*?<\/script>/, renderBootScript(config, mode));
}

function inlineAddressRegions(html) {
  if (!fs.existsSync(ADDRESS_REGIONS_JS)) return html;
  const js = fs.readFileSync(ADDRESS_REGIONS_JS, 'utf8');
  return html.replace(
    /<script src="address-regions\.js"><\/script>/,
    '<script>\n' + js + '\n</script>'
  );
}

function prepareHtml(config, mode) {
  return inlineAddressRegions(injectBoot(readTemplate(), config, mode));
}

function sanitizeFilename(name) {
  return String(name || '审批配置')
    .replace(/[<>:"/\\|?*\x00-\x1f]/g, '_')
    .replace(/\s+/g, '_')
    .slice(0, 80) || '审批配置';
}

function sendJson(res, status, data) {
  res.writeHead(status, { 'Content-Type': 'application/json; charset=utf-8' });
  res.end(JSON.stringify(data));
}

function readBody(req, limit) {
  const maxBytes = limit || 20 * 1024 * 1024;
  return new Promise(function (resolve, reject) {
    var body = '';
    var size = 0;
    req.on('data', function (chunk) {
      size += chunk.length;
      if (size > maxBytes) {
        reject(new Error('request body too large'));
        req.destroy();
        return;
      }
      body += chunk;
    });
    req.on('end', function () { resolve(body); });
    req.on('error', reject);
  });
}

function parseInitialConfigFromHtml(html) {
  const match = html.match(/window\.__INITIAL_CONFIG__\s*=\s*([\s\S]*?);\s*(?:\n|<\/script>)/);
  if (!match) return null;
  try {
    return JSON.parse(match[1]);
  } catch (e) {
    return null;
  }
}

const server = http.createServer(async (req, res) => {
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type');

  if (req.method === 'OPTIONS') {
    res.writeHead(204);
    res.end();
    return;
  }

  const parsed = url.parse(req.url, true);
  const pathname = parsed.pathname;

  try {
    if (req.method === 'GET' && (pathname === '/' || pathname === '/editor')) {
      const initial = parsed.query.config ? JSON.parse(parsed.query.config) : null;
      const html = prepareHtml(initial, 'server');
      res.writeHead(200, { 'Content-Type': 'text/html; charset=utf-8', 'Cache-Control': 'no-store' });
      res.end(html);
      return;
    }

    if (req.method === 'GET' && pathname === '/address-regions.js') {
      if (!fs.existsSync(ADDRESS_REGIONS_JS)) {
        res.writeHead(404, { 'Content-Type': 'text/plain; charset=utf-8' });
        res.end('address-regions.js not found');
        return;
      }
      res.writeHead(200, { 'Content-Type': 'application/javascript; charset=utf-8', 'Cache-Control': 'no-store' });
      res.end(fs.readFileSync(ADDRESS_REGIONS_JS, 'utf8'));
      return;
    }

    if (req.method === 'GET' && pathname === '/api/health') {
      sendJson(res, 200, { ok: true, service: PROJECT.label, projectId: PROJECT.projectId });
      return;
    }

    if (req.method === 'POST' && pathname === '/api/export') {
      const body = await readBody(req);
      const config = JSON.parse(body);
      config.exportedAt = new Date().toISOString();
      config.projectId = PROJECT.projectId;
      const html = prepareHtml(config, 'standalone');
      const filename = sanitizeFilename(config.approvalName) + '.html';
      res.writeHead(200, {
        'Content-Type': 'text/html; charset=utf-8',
        'Content-Disposition': 'attachment; filename="' + encodeURIComponent(filename) + '"',
        'Cache-Control': 'no-store'
      });
      res.end(html);
      return;
    }

    if (req.method === 'POST' && pathname === '/api/import') {
      const body = await readBody(req);
      const payload = JSON.parse(body);
      let config = null;
      if (payload.config) {
        config = payload.config;
      } else if (payload.html) {
        config = parseInitialConfigFromHtml(payload.html);
      }
      if (!config) {
        sendJson(res, 400, { ok: false, error: 'invalid import payload' });
        return;
      }
      sendJson(res, 200, { ok: true, config });
      return;
    }

    if (req.method === 'POST' && pathname === '/api/reload-template') {
      reloadTemplate();
      sendJson(res, 200, { ok: true });
      return;
    }

    res.writeHead(404, { 'Content-Type': 'text/plain; charset=utf-8' });
    res.end('Not Found');
  } catch (err) {
    sendJson(res, 500, { ok: false, error: err.message || 'server error' });
  }
});

server.listen(PORT, HOST, () => {
  console.log('[' + (PROJECT.label || 'approval') + '] http://' + HOST + ':' + PORT);
});