import http from 'node:http';
import crypto from 'node:crypto';
import fs from 'node:fs/promises';
import { URL } from 'node:url';
import { parseMultipartUpload } from './src/multipart.js';
import { sendFile, sendHtml, sendJson, sendText, withSecurityHeaders } from './src/http.js';
import { createStore } from './src/store.js';
import { validateImage } from './src/image.js';
import { normalizeToWebp } from './src/normalize.js';
import { seedDemoMemes } from './src/seed.js';
import { moderateImage } from './src/moderation.js';
import { createUploadLimiter } from './src/uploadLimits.js';
import { feedJson, llmsTxt, manifest, noIndex, publicBaseUrl, renderIndex, robotsTxt, sitemapXml } from './src/seo.js';

const PORT = Number.parseInt(process.env.PORT || '8080', 10);
const HOST = process.env.HOST || '0.0.0.0';
const DATA_DIR = process.env.DATA_DIR || './data';
const PAGE_SIZE_MAX = 48;
const UPLOAD_MAX_BYTES = 5 * 1024 * 1024;
const REQUEST_MAX_BYTES = 6 * 1024 * 1024;
const events = new Set();
const ADMIN_TOKEN = process.env.ADMIN_TOKEN || crypto.randomBytes(24).toString('hex');
const indexTemplate = await fs.readFile('./public/index.html', 'utf8');

const store = await createStore({ dataDir: DATA_DIR });
const uploadLimiter = await createUploadLimiter({ dataDir: DATA_DIR });
if (process.env.SEED_DEMO_MEMES !== 'false') {
  await seedDemoMemes(store);
}
if (!process.env.ADMIN_TOKEN) {
  console.log(`Admin review URL: /admin/${ADMIN_TOKEN}`);
}

const server = http.createServer(async (req, res) => {
  withSecurityHeaders(res);

  try {
    const url = new URL(req.url || '/', `http://${req.headers.host || 'localhost'}`);
    const baseUrl = publicBaseUrl(req);

    if (req.method === 'GET' && url.pathname === '/') {
      const nonce = crypto.randomBytes(16).toString('base64');
      withSecurityHeaders(res, { scriptNonce: nonce });
      return sendHtml(res, 200, renderIndex({
        template: indexTemplate,
        baseUrl,
        nonce,
        approvedCount: store.count('approved')
      }));
    }

    if (req.method === 'GET' && url.pathname === '/robots.txt') {
      return sendText(res, 200, robotsTxt(baseUrl));
    }

    if (req.method === 'GET' && url.pathname === '/llms.txt') {
      return sendText(res, 200, llmsTxt(baseUrl));
    }

    if (req.method === 'GET' && url.pathname === '/site.webmanifest') {
      return sendJson(res, 200, manifest(baseUrl));
    }

    if (req.method === 'GET' && url.pathname === '/feed.json') {
      return sendJson(res, 200, feedJson(baseUrl, store.listForReview({ status: 'approved' }).memes));
    }

    if (req.method === 'GET' && url.pathname === '/sitemap.xml') {
      const body = sitemapXml(baseUrl, store.listForReview({ status: 'approved' }).memes);
      res.writeHead(200, {
        'Content-Type': 'application/xml; charset=utf-8',
        'Content-Length': String(Buffer.byteLength(body))
      });
      return res.end(body);
    }

    const adminPageMatch = url.pathname.match(/^\/admin\/([A-Za-z0-9_-]{24,128})$/);
    if (req.method === 'GET' && adminPageMatch) {
      if (!isAdminToken(adminPageMatch[1])) return sendText(res, 404, 'Not found');
      noIndex(res);
      return sendFile(res, './public/admin.html');
    }

    if (req.method === 'GET' && url.pathname.startsWith('/assets/')) {
      return sendFile(res, `./public${url.pathname}`);
    }

    if (req.method === 'GET' && url.pathname === '/api/memes') {
      noIndex(res);
      const page = positiveInt(url.searchParams.get('page'), 1);
      const pageSize = Math.min(positiveInt(url.searchParams.get('pageSize'), 12), PAGE_SIZE_MAX);
      return sendJson(res, 200, store.list({ page, pageSize }));
    }

    if (req.method === 'GET' && url.pathname === '/api/status') {
      noIndex(res);
      return sendJson(res, 200, {
        ok: true,
        memeCount: store.count('approved'),
        liveClients: events.size,
        uptimeSeconds: Math.floor(process.uptime())
      });
    }

    if (req.method === 'GET' && url.pathname === '/api/admin/pending') {
      noIndex(res);
      if (!isAdminRequest(req)) return sendJson(res, 404, { error: 'Not found' });
      return sendJson(res, 200, store.listForReview({ status: 'pending' }));
    }

    if (req.method === 'POST' && url.pathname === '/api/admin/approve') {
      noIndex(res);
      if (!isAdminRequest(req)) return sendJson(res, 404, { error: 'Not found' });
      const body = await readJsonBody(req, 64 * 1024);
      const approved = await store.approve(safeIds(body.ids));
      return sendJson(res, 200, { approved });
    }

    if (req.method === 'POST' && url.pathname === '/api/admin/delete') {
      noIndex(res);
      if (!isAdminRequest(req)) return sendJson(res, 404, { error: 'Not found' });
      const body = await readJsonBody(req, 64 * 1024);
      const deleted = await store.delete(safeIds(body.ids));
      return sendJson(res, 200, { deleted });
    }

    if (req.method === 'GET' && url.pathname === '/api/events') {
      noIndex(res);
      res.writeHead(200, {
        'Content-Type': 'text/event-stream; charset=utf-8',
        'Cache-Control': 'no-cache, no-transform',
        Connection: 'keep-alive'
      });
      res.write('event: ready\ndata: {}\n\n');
      events.add(res);
      req.on('close', () => events.delete(res));
      return;
    }

    if (req.method === 'POST' && url.pathname === '/api/memes') {
      noIndex(res);
      const contentLength = Number.parseInt(req.headers['content-length'] || '0', 10);
      if (!Number.isFinite(contentLength) || contentLength <= 0) {
        return sendJson(res, 411, { error: 'Missing upload size.' });
      }
      if (contentLength > REQUEST_MAX_BYTES) {
        return sendJson(res, 413, { error: 'Upload request is too large.' });
      }
      const quota = await uploadLimiter.checkAndConsume(clientIp(req));

      const upload = await parseMultipartUpload(req, {
        maxRequestBytes: REQUEST_MAX_BYTES,
        maxFileBytes: UPLOAD_MAX_BYTES,
        fieldName: 'meme'
      });
      const image = validateImage(upload.buffer, {
        maxBytes: UPLOAD_MAX_BYTES,
        maxWidth: 6000,
        maxHeight: 6000,
        maxPixels: 20_000_000,
        requireSquare: true
      });
      const normalized = await normalizeToWebp(upload.buffer);
      const moderation = await moderateImage({ buffer: normalized.buffer, mime: normalized.image.mime });
      if (moderation.status === 'rejected') {
        return sendJson(res, 422, {
          error: `Upload rejected: ${moderation.reason}`,
          moderationScore: moderation.score
        });
      }
      const meme = await store.save({
        buffer: normalized.buffer,
        image: normalized.image,
        originalName: upload.filename,
        originalMime: image.mime,
        status: moderation.status,
        moderationScore: moderation.score,
        moderationReason: moderation.reason
      });
      return sendJson(res, meme.status === 'approved' ? 201 : 202, {
        meme,
        quota,
        message: meme.status === 'approved' ? 'Upload approved.' : 'Upload queued for admin review.'
      });
    }

    const viewMatch = url.pathname.match(/^\/api\/memes\/([a-f0-9]{64})\/view$/);
    if (req.method === 'POST' && viewMatch) {
      if (store.get(viewMatch[1])?.status !== 'approved') return sendText(res, 404, 'Not found');
      const meme = await store.incrementMetric(viewMatch[1], 'viewCount');
      if (!meme) return sendText(res, 404, 'Not found');
      broadcastMetric(meme);
      return sendJson(res, 200, { meme });
    }

    const mediaMatch = url.pathname.match(/^\/media\/([a-f0-9]{64})$/);
    if (req.method === 'GET' && mediaMatch) {
      const meme = store.get(mediaMatch[1]);
      if (!meme || meme.status !== 'approved') return sendText(res, 404, 'Not found');
      res.setHeader('Content-Type', meme.mime);
      res.setHeader('Content-Length', String(meme.byteSize));
      res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
      res.setHeader('X-Content-Type-Options', 'nosniff');
      return sendFile(res, store.absolutePath(meme.storageKey), { absolute: true });
    }

    const adminMediaMatch = url.pathname.match(/^\/admin-media\/([A-Za-z0-9_-]{24,128})\/([a-f0-9]{64})$/);
    if (req.method === 'GET' && adminMediaMatch) {
      noIndex(res);
      if (!isAdminToken(adminMediaMatch[1])) return sendText(res, 404, 'Not found');
      const meme = store.get(adminMediaMatch[2]);
      if (!meme) return sendText(res, 404, 'Not found');
      res.setHeader('Content-Type', meme.mime);
      res.setHeader('Content-Length', String(meme.byteSize));
      res.setHeader('Cache-Control', 'no-store');
      res.setHeader('X-Content-Type-Options', 'nosniff');
      return sendFile(res, store.absolutePath(meme.storageKey), { absolute: true });
    }

    const downloadMatch = url.pathname.match(/^\/download\/([a-f0-9]{64})$/);
    if (req.method === 'GET' && downloadMatch) {
      noIndex(res);
      if (store.get(downloadMatch[1])?.status !== 'approved') return sendText(res, 404, 'Not found');
      const updated = await store.incrementMetric(downloadMatch[1], 'downloadCount');
      const meme = store.get(downloadMatch[1]);
      if (!meme) return sendText(res, 404, 'Not found');
      broadcastMetric(updated);
      res.setHeader('Content-Type', meme.mime);
      res.setHeader('Content-Disposition', `attachment; filename="${downloadName(meme)}"`);
      res.setHeader('X-Content-Type-Options', 'nosniff');
      return sendFile(res, store.absolutePath(meme.storageKey), { absolute: true });
    }

    if (req.method === 'GET' && url.pathname === '/healthz') {
      noIndex(res);
      return sendJson(res, 200, { ok: true });
    }

    return sendText(res, 404, 'Not found');
  } catch (error) {
    const status = error.statusCode || 500;
    const message = status === 500 ? 'Internal server error.' : error.message;
    return sendJson(res, status, { error: message });
  }
});

server.listen(PORT, HOST, () => {
  console.log(`The Meme Protocol listening on http://${HOST}:${PORT}`);
});

function positiveInt(value, fallback) {
  const parsed = Number.parseInt(value || '', 10);
  return Number.isFinite(parsed) && parsed > 0 ? parsed : fallback;
}

function downloadName(meme) {
  return `meme-protocol-${meme.id.slice(0, 12)}.${meme.ext}`;
}

function broadcastMetric(meme) {
  const payload = JSON.stringify({
    id: meme.id,
    viewCount: meme.viewCount,
    downloadCount: meme.downloadCount
  });
  for (const res of events) {
    res.write(`event: metric\ndata: ${payload}\n\n`);
  }
}

function isAdminRequest(req) {
  return isAdminToken(req.headers['x-admin-token'] || '');
}

function isAdminToken(value) {
  const received = Buffer.from(String(value));
  const expected = Buffer.from(ADMIN_TOKEN);
  return received.length === expected.length && crypto.timingSafeEqual(received, expected);
}

async function readJsonBody(req, maxBytes) {
  const chunks = [];
  let total = 0;
  for await (const chunk of req) {
    total += chunk.length;
    if (total > maxBytes) {
      const error = new Error('Request body is too large.');
      error.statusCode = 413;
      throw error;
    }
    chunks.push(chunk);
  }
  if (total === 0) return {};
  return JSON.parse(Buffer.concat(chunks, total).toString('utf8'));
}

function safeIds(ids) {
  if (!Array.isArray(ids)) return [];
  return ids.filter((id) => typeof id === 'string' && /^[a-f0-9]{64}$/.test(id));
}

function clientIp(req) {
  if (process.env.TRUST_PROXY === 'true') {
    const forwarded = String(req.headers['x-forwarded-for'] || '').split(',')[0].trim();
    if (forwarded) return forwarded;
  }
  return req.socket.remoteAddress || 'unknown';
}