const http = require('http');
const fs = require('fs');
const path = require('path');
const { URL } = require('url');

const HOST = process.env.HOST || '127.0.0.1';
const PORT = Number(process.env.PORT) || 8000;
const ROOT = __dirname;
const DATA_TXT_PATH = path.join(ROOT, 'data.txt');
const DATA_JSON_PATH = path.join(ROOT, 'data.json');

const MIME_TYPES = {
  '.css': 'text/css; charset=utf-8',
  '.html': 'text/html; charset=utf-8',
  '.js': 'application/javascript; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.txt': 'text/plain; charset=utf-8'
};

function sendJson(res, statusCode, payload) {
  res.writeHead(statusCode, {
    'Content-Type': 'application/json; charset=utf-8',
    'Cache-Control': 'no-store'
  });
  res.end(JSON.stringify(payload, null, 2));
}

function sendText(res, statusCode, text, contentType = 'text/plain; charset=utf-8') {
  res.writeHead(statusCode, {
    'Content-Type': contentType,
    'Cache-Control': 'no-store'
  });
  res.end(text);
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    let body = '';
    req.on('data', chunk => {
      body += chunk;
      if (body.length > 1_000_000) {
        reject(new Error('Request body too large.'));
        req.destroy();
      }
    });
    req.on('end', () => resolve(body));
    req.on('error', reject);
  });
}

function normalizeItem(item, fallbackId) {
  return {
    id: String(item.id || fallbackId || Date.now()),
    level: String(item.level || 'new').trim() || 'new',
    position: String(item.position || '').trim(),
    title: String(item.title || '').trim(),
    url: String(item.url || '').trim()
  };
}

function parseTxtData(txt) {
  return txt
    .split(/\r?\n/)
    .map(line => line.trim())
    .filter(Boolean)
    .map((line, index) => {
      const parts = line.split('|').map(part => part.trim());
      return normalizeItem({
        level: parts[0],
        position: parts[1],
        title: parts[2],
        url: parts[3]
      }, `legacy-${index + 1}`);
    });
}

function serializeTxtData(items) {
  return items
    .map(item => [item.level, item.position, item.title, item.url].join('|'))
    .join('\n') + '\n';
}

function loadItems() {
  if (fs.existsSync(DATA_JSON_PATH)) {
    const raw = fs.readFileSync(DATA_JSON_PATH, 'utf8');
    const parsed = JSON.parse(raw);
    if (!Array.isArray(parsed)) return [];
    return parsed.map((item, index) => normalizeItem(item, `json-${index + 1}`));
  }

  if (!fs.existsSync(DATA_TXT_PATH)) return [];
  const txt = fs.readFileSync(DATA_TXT_PATH, 'utf8');
  const items = parseTxtData(txt);
  saveItems(items);
  return items;
}

function saveItems(items) {
  const normalized = items.map((item, index) => normalizeItem(item, `item-${index + 1}`));
  fs.writeFileSync(DATA_JSON_PATH, `${JSON.stringify(normalized, null, 2)}\n`, 'utf8');
  fs.writeFileSync(DATA_TXT_PATH, serializeTxtData(normalized), 'utf8');
  return normalized;
}

function validateItem(item) {
  if (!item.title) return 'Title is required.';
  if (!item.position) return 'Position is required.';
  if (!/^\d+$/.test(String(item.position))) return 'Position must be numeric.';
  return null;
}

function getStaticPath(requestPath) {
  const cleanPath = requestPath === '/' ? '/index.html' : requestPath;
  const safePath = path.normalize(cleanPath).replace(/^(\.\.[/\\])+/, '').replace(/^[/\\]+/, '');
  return path.join(ROOT, safePath);
}

function serveStatic(reqPath, res) {
  const filePath = getStaticPath(reqPath);
  if (!filePath.startsWith(ROOT)) {
    sendText(res, 403, 'Forbidden');
    return;
  }

  fs.readFile(filePath, (err, content) => {
    if (err) {
      const fallback404 = path.join(ROOT, '404.html');
      fs.readFile(fallback404, (fallbackErr, fallbackContent) => {
        if (fallbackErr) {
          sendText(res, 404, 'Not Found');
          return;
        }
        sendText(res, 404, fallbackContent, 'text/html; charset=utf-8');
      });
      return;
    }

    const ext = path.extname(filePath).toLowerCase();
    sendText(res, 200, content, MIME_TYPES[ext] || 'application/octet-stream');
  });
}

function sortItems(items) {
  return [...items].sort((a, b) => Number(a.position) - Number(b.position));
}

loadItems();

const server = http.createServer(async (req, res) => {
  const url = new URL(req.url, `http://${req.headers.host || 'localhost'}`);
  const pathname = url.pathname;

  if (pathname === '/api/levels' && req.method === 'GET') {
    return sendJson(res, 200, { items: sortItems(loadItems()) });
  }

  if (pathname === '/api/levels' && req.method === 'POST') {
    try {
      const body = await readBody(req);
      const payload = normalizeItem(JSON.parse(body), `item-${Date.now()}`);
      const error = validateItem(payload);
      if (error) return sendJson(res, 400, { error });
      const items = loadItems();
      items.push(payload);
      return sendJson(res, 201, { item: payload, items: sortItems(saveItems(items)) });
    } catch (error) {
      return sendJson(res, 400, { error: 'Invalid JSON request body.' });
    }
  }

  if (pathname.startsWith('/api/levels/') && (req.method === 'PUT' || req.method === 'DELETE')) {
    const id = decodeURIComponent(pathname.slice('/api/levels/'.length));
    const items = loadItems();
    const index = items.findIndex(item => item.id === id);

    if (index === -1) {
      return sendJson(res, 404, { error: 'Level not found.' });
    }

    if (req.method === 'DELETE') {
      items.splice(index, 1);
      return sendJson(res, 200, { items: sortItems(saveItems(items)) });
    }

    try {
      const body = await readBody(req);
      const payload = normalizeItem({ ...items[index], ...JSON.parse(body), id }, id);
      const error = validateItem(payload);
      if (error) return sendJson(res, 400, { error });
      items[index] = payload;
      return sendJson(res, 200, { item: payload, items: sortItems(saveItems(items)) });
    } catch (error) {
      return sendJson(res, 400, { error: 'Invalid JSON request body.' });
    }
  }

  if (pathname === '/api/health') {
    return sendJson(res, 200, { ok: true });
  }

  return serveStatic(pathname, res);
});

server.listen(PORT, HOST, () => {
  console.log(`GD FEDL server running at http://localhost:${PORT}`);
});