'use strict';

const http = require('node:http');
const fs = require('node:fs');
const path = require('node:path');

const store = require('./lib/store');
const { toCsv } = require('./lib/csv');

const PUBLIC_DIR = path.join(__dirname, 'public');
const DAY_MS = 24 * 60 * 60 * 1000;

const MIME = {
  '.html': 'text/html; charset=utf-8',
  '.css': 'text/css; charset=utf-8',
  '.js': 'text/javascript; charset=utf-8',
  '.svg': 'image/svg+xml',
  '.ico': 'image/x-icon',
};

/* ------------------------------------------------------------------ replies */

function sendJson(res, status, value) {
  const body = JSON.stringify(value);
  res.writeHead(status, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
    'Cache-Control': 'no-store',
  });
  res.end(body);
}

function sendPage(res, file, status = 200) {
  fs.readFile(path.join(PUBLIC_DIR, file), (err, body) => {
    if (err) return sendText(res, 500, 'Could not read page.');
    res.writeHead(status, {
      'Content-Type': MIME['.html'],
      'Content-Length': body.length,
      'Cache-Control': 'no-store',
    });
    res.end(body);
  });
}

function sendText(res, status, message) {
  const body = `${message}\n`;
  res.writeHead(status, {
    'Content-Type': 'text/plain; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
  });
  res.end(body);
}

function sendCsv(res, filename, csv) {
  const body = Buffer.from(csv, 'utf8');
  res.writeHead(200, {
    'Content-Type': 'text/csv; charset=utf-8',
    'Content-Length': body.length,
    'Content-Disposition': `attachment; filename="${filename}"`,
    'Cache-Control': 'no-store',
  });
  res.end(body);
}

function sendStatic(res, name) {
  const file = path.join(PUBLIC_DIR, name);
  // Never let a crafted path climb out of public/.
  if (!file.startsWith(PUBLIC_DIR + path.sep)) return sendText(res, 403, 'Forbidden');

  fs.readFile(file, (err, body) => {
    if (err) return sendText(res, 404, 'Not found');
    res.writeHead(200, {
      'Content-Type': MIME[path.extname(file)] || 'application/octet-stream',
      'Content-Length': body.length,
      'Cache-Control': 'no-cache',
    });
    res.end(body);
  });
}

function readBody(req) {
  return new Promise((resolve, reject) => {
    let raw = '';
    req.on('data', (chunk) => {
      raw += chunk;
      // Nothing here should ever be large; refuse rather than buffer forever.
      if (raw.length > 256 * 1024) reject(new Error('Request too large.'));
    });
    req.on('error', reject);
    req.on('end', () => {
      if (!raw) return resolve({});
      try {
        resolve(JSON.parse(raw));
      } catch {
        reject(new Error('Expected JSON.'));
      }
    });
  });
}

/* ------------------------------------------------------------------- router */

// Resolve a slug to an event, replying for the caller if it is gone.
function requireEvent(res, slug, asJson) {
  const event = store.loadEvent(slug);
  if (event) return event;

  if (store.isExpired(slug)) {
    if (asJson) sendJson(res, 410, { error: 'This event has expired and its data has been deleted.' });
    else sendPage(res, 'expired.html', 410);
  } else if (asJson) {
    sendJson(res, 404, { error: 'No such event.' });
  } else {
    sendPage(res, 'notfound.html', 404);
  }
  return null;
}

async function route(req, res) {
  const url = new URL(req.url, 'http://localhost');
  const parts = url.pathname.split('/').filter(Boolean).map(decodeURIComponent);
  const method = req.method;

  /* pages and assets */
  if (method === 'GET' && parts.length === 0) return sendPage(res, 'index.html');
  if (method === 'GET' && parts.length === 1 && parts[0] === 'new') return sendPage(res, 'new.html');
  if (method === 'GET' && parts[0] === 'static' && parts.length === 2) return sendStatic(res, parts[1]);

  /* all-events CSV */
  if (method === 'GET' && parts.length === 1 && parts[0] === 'export.csv') {
    return sendCsv(res, 'repair-cafe-all-events.csv', toCsv(store.listEvents()));
  }

  /* api */
  if (parts[0] === 'api') {
    if (method === 'GET' && parts[1] === 'config' && parts.length === 2) {
      const { categories, houseRules, retentionDays } = store.getConfig();
      return sendJson(res, 200, { categories, houseRules, retentionDays });
    }

    if (method === 'POST' && parts[1] === 'events' && parts.length === 2) {
      const body = await readBody(req);
      const event = store.createEvent(body.name, body.randomize === true);
      return sendJson(res, 201, { slug: event.slug, name: event.name });
    }

    if (parts[1] === 'events' && parts.length >= 3) {
      const slug = parts[2];

      if (method === 'GET' && parts.length === 3) {
        const event = requireEvent(res, slug, true);
        if (!event) return;
        return sendJson(res, 200, { ...event, expiresAt: store.expiresAt(event) });
      }

      if (method === 'POST' && parts[3] === 'repairs' && parts.length === 4) {
        const event = requireEvent(res, slug, true);
        if (!event) return;
        return sendJson(res, 201, store.addRepair(event, await readBody(req)));
      }

      if (method === 'PATCH' && parts[3] === 'repairs' && parts.length === 5) {
        const event = requireEvent(res, slug, true);
        if (!event) return;
        const repair = store.updateRepair(event, parts[4], await readBody(req));
        if (!repair) return sendJson(res, 404, { error: 'No such repair.' });
        return sendJson(res, 200, repair);
      }
    }

    return sendJson(res, 404, { error: 'No such endpoint.' });
  }

  /* event pages */
  if (method === 'GET' && parts.length >= 1 && parts.length <= 2) {
    const slug = parts[0];
    if (slug !== store.slugify(slug)) return sendPage(res, 'notfound.html', 404);

    if (parts.length === 1) {
      if (!requireEvent(res, slug, false)) return;
      return sendPage(res, 'intake.html');
    }
    if (parts[1] === 'dashboard') {
      if (!requireEvent(res, slug, false)) return;
      return sendPage(res, 'dashboard.html');
    }
    if (parts[1] === 'export.csv') {
      const event = requireEvent(res, slug, false);
      if (!event) return;
      return sendCsv(res, `${slug}.csv`, toCsv([event]));
    }
  }

  return sendPage(res, 'notfound.html', 404);
}

/* ------------------------------------------------------------------- server */

const server = http.createServer((req, res) => {
  route(req, res).catch((err) => {
    // Validation failures from the store are the user's to fix; anything else
    // is ours, so log it.
    const isValidation = err instanceof Error && !!err.message && err.message.length < 300;
    if (!isValidation) console.error(err);
    if (res.headersSent) return res.end();
    if (req.url.startsWith('/api/')) sendJson(res, 400, { error: err.message || 'Something went wrong.' });
    else sendText(res, 400, err.message || 'Something went wrong.');
  });
});

function start() {
  const config = store.loadConfig();

  const pruned = store.pruneExpired();
  if (pruned.length) console.log(`Deleted ${pruned.length} expired event(s): ${pruned.join(', ')}`);

  // Re-check daily for long-running servers. unref() so this timer alone never
  // keeps the process alive.
  setInterval(() => {
    const gone = store.pruneExpired();
    if (gone.length) console.log(`Deleted ${gone.length} expired event(s): ${gone.join(', ')}`);
  }, DAY_MS).unref();

  const port = Number(process.env.PORT) || config.port || 8080;
  const host = process.env.HOST || '0.0.0.0';
  server.listen(port, host, () => {
    console.log(`Repair Cafe Kanban listening on http://localhost:${port}`);
    console.log(
      config.retentionDays > 0
        ? `Events are deleted ${config.retentionDays} days after they are created.`
        : 'Event retention is off — nothing is deleted automatically.'
    );
  });
}

if (require.main === module) start();

module.exports = { server, start };