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

const PORT = 4000;
const CONFIG_FILE = path.join(__dirname, 'config.json');

const DATA_FILES = {
  blog:     path.join(__dirname, 'posts.json'),
  notes:    path.join(__dirname, 'notes.json'),
  projects: path.join(__dirname, 'projects.json'),
  links:    path.join(__dirname, 'links.json'),
};

const sessions = new Map();

function loadConfig() {
  if (!fs.existsSync(CONFIG_FILE)) {
    const config = { username: 'admin', passwordHash: crypto.createHash('sha256').update('admin').digest('hex') };
    fs.writeFileSync(CONFIG_FILE, JSON.stringify(config, null, 2));
    return config;
  }
  return JSON.parse(fs.readFileSync(CONFIG_FILE, 'utf8'));
}

function loadData(type) {
  const file = DATA_FILES[type];
  if (!fs.existsSync(file)) return [];
  return JSON.parse(fs.readFileSync(file, 'utf8'));
}

function saveData(type, items) {
  fs.writeFileSync(DATA_FILES[type], JSON.stringify(items, null, 2));
}

function generateToken() {
  return crypto.randomBytes(32).toString('hex');
}

function isAuthenticated(req) {
  const auth = req.headers['authorization'] || '';
  const token = auth.replace('Bearer ', '').trim();
  if (!token) return false;
  const expiry = sessions.get(token);
  if (!expiry || Date.now() > expiry) {
    sessions.delete(token);
    return false;
  }
  return true;
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    let body = '';
    req.on('data', chunk => { body += chunk; });
    req.on('end', () => resolve(body));
    req.on('error', reject);
  });
}

function slugify(title) {
  return title.toLowerCase()
    .replace(/æ/g, 'ae').replace(/ø/g, 'oe').replace(/å/g, 'aa')
    .replace(/[^a-z0-9]+/g, '-')
    .replace(/^-|-$/g, '');
}

function uniqueSlug(base, items) {
  if (!items.find(p => p.slug === base)) return base;
  let i = 2;
  while (items.find(p => p.slug === `${base}-${i}`)) i++;
  return `${base}-${i}`;
}

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

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

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

  // POST /api/auth/login
  if (req.method === 'POST' && pathname === '/api/auth/login') {
    try {
      const body = await readBody(req);
      const { username, password } = JSON.parse(body);
      const config = loadConfig();
      const hash = crypto.createHash('sha256').update(password || '').digest('hex');
      if (username === config.username && hash === config.passwordHash) {
        const token = generateToken();
        sessions.set(token, Date.now() + 24 * 60 * 60 * 1000);
        res.writeHead(200);
        res.end(JSON.stringify({ token }));
      } else {
        res.writeHead(401);
        res.end(JSON.stringify({ error: 'Forkert brugernavn eller adgangskode' }));
      }
    } catch {
      res.writeHead(400);
      res.end(JSON.stringify({ error: 'Bad request' }));
    }
    return;
  }

  // POST /api/auth/logout
  if (req.method === 'POST' && pathname === '/api/auth/logout') {
    const auth = req.headers['authorization'] || '';
    const token = auth.replace('Bearer ', '').trim();
    sessions.delete(token);
    res.writeHead(200);
    res.end(JSON.stringify({ ok: true }));
    return;
  }

  const listMatch = pathname.match(/^\/api\/(blog|notes|projects|links)$/);
  const itemMatch = pathname.match(/^\/api\/(blog|notes|projects|links)\/([^/]+)$/);

  // GET list
  if (req.method === 'GET' && listMatch) {
    const type = listMatch[1];
    const items = loadData(type);
    if (type === 'blog') {
      res.writeHead(200);
      res.end(JSON.stringify(items.map(({ slug, title, date }) => ({ slug, title, date }))));
    } else {
      res.writeHead(200);
      res.end(JSON.stringify(items));
    }
    return;
  }

  // GET single item
  if (req.method === 'GET' && itemMatch) {
    const [, type, slug] = itemMatch;
    const item = loadData(type).find(p => p.slug === slug);
    if (!item) { res.writeHead(404); res.end(JSON.stringify({ error: 'Not found' })); return; }
    res.writeHead(200);
    res.end(JSON.stringify(item));
    return;
  }

  // POST create
  if (req.method === 'POST' && listMatch) {
    const type = listMatch[1];
    if (!isAuthenticated(req)) { res.writeHead(401); res.end(JSON.stringify({ error: 'Unauthorized' })); return; }
    try {
      const body = await readBody(req);
      const data = JSON.parse(body);
      const items = loadData(type);
      const today = new Date().toISOString().split('T')[0];
      let item;

      if (type === 'blog' || type === 'notes') {
        const { title, content } = data;
        if (!title || !content) { res.writeHead(400); res.end(JSON.stringify({ error: 'Titel og indhold er påkrævet' })); return; }
        const slug = uniqueSlug(slugify(title), items);
        item = { slug, title, content, date: today };
      } else if (type === 'projects') {
        const { title, description, url: projectUrl, tags } = data;
        if (!title) { res.writeHead(400); res.end(JSON.stringify({ error: 'Titel er påkrævet' })); return; }
        const slug = uniqueSlug(slugify(title), items);
        item = { slug, title, description: description || '', url: projectUrl || '', tags: tags || '', date: today };
      } else if (type === 'links') {
        const { title, url: linkUrl, description, category } = data;
        if (!title || !linkUrl) { res.writeHead(400); res.end(JSON.stringify({ error: 'Titel og URL er påkrævet' })); return; }
        const slug = uniqueSlug(slugify(title), items);
        item = { slug, title, url: linkUrl, description: description || '', category: category || '', date: today };
      }

      items.unshift(item);
      saveData(type, items);
      res.writeHead(201);
      res.end(JSON.stringify(item));
    } catch {
      res.writeHead(400);
      res.end(JSON.stringify({ error: 'Bad request' }));
    }
    return;
  }

  // PUT update
  if (req.method === 'PUT' && itemMatch) {
    const [, type, slug] = itemMatch;
    if (!isAuthenticated(req)) { res.writeHead(401); res.end(JSON.stringify({ error: 'Unauthorized' })); return; }
    try {
      const body = await readBody(req);
      const data = JSON.parse(body);
      const items = loadData(type);
      const idx = items.findIndex(p => p.slug === slug);
      if (idx === -1) { res.writeHead(404); res.end(JSON.stringify({ error: 'Not found' })); return; }

      if (type === 'blog' || type === 'notes') {
        if (data.title !== undefined) items[idx].title = data.title;
        if (data.content !== undefined) items[idx].content = data.content;
      } else if (type === 'projects') {
        if (data.title !== undefined) items[idx].title = data.title;
        if (data.description !== undefined) items[idx].description = data.description;
        if (data.url !== undefined) items[idx].url = data.url;
        if (data.tags !== undefined) items[idx].tags = data.tags;
      } else if (type === 'links') {
        if (data.title !== undefined) items[idx].title = data.title;
        if (data.url !== undefined) items[idx].url = data.url;
        if (data.description !== undefined) items[idx].description = data.description;
        if (data.category !== undefined) items[idx].category = data.category;
      }

      saveData(type, items);
      res.writeHead(200);
      res.end(JSON.stringify(items[idx]));
    } catch {
      res.writeHead(400);
      res.end(JSON.stringify({ error: 'Bad request' }));
    }
    return;
  }

  // DELETE
  if (req.method === 'DELETE' && itemMatch) {
    const [, type, slug] = itemMatch;
    if (!isAuthenticated(req)) { res.writeHead(401); res.end(JSON.stringify({ error: 'Unauthorized' })); return; }
    const items = loadData(type);
    const idx = items.findIndex(p => p.slug === slug);
    if (idx === -1) { res.writeHead(404); res.end(JSON.stringify({ error: 'Not found' })); return; }
    items.splice(idx, 1);
    saveData(type, items);
    res.writeHead(200);
    res.end(JSON.stringify({ ok: true }));
    return;
  }

  res.writeHead(404);
  res.end(JSON.stringify({ error: 'Not found' }));
});

server.listen(PORT, '127.0.0.1', () => {
  console.log(`API listening on port ${PORT}`);
});