'use strict';

const http = require('node:http');
const fs = require('node:fs');
const path = require('node:path');
const { URL } = require('node:url');
const { gregorianToRepublican } = require('./src/republicanCalendar');

const PORT = process.env.PORT || 3000;
const PUBLIC_DIR = path.join(__dirname, 'public');
const LOCALES_DIR = path.join(__dirname, 'locales');

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

function sendJson(res, statusCode, payload) {
  const body = JSON.stringify(payload);
  res.writeHead(statusCode, {
    'Content-Type': 'application/json; charset=utf-8',
    'Content-Length': Buffer.byteLength(body),
  });
  res.end(body);
}

function nowUtc() {
  const now = new Date();
  return {
    year: now.getUTCFullYear(),
    month: now.getUTCMonth() + 1,
    day: now.getUTCDate(),
  };
}

function convertAndRespond(res, gregorianDate) {
  try {
    const republicanDate = gregorianToRepublican(gregorianDate);
    sendJson(res, 200, { ok: true, republicanDate });
  } catch (error) {
    if (error.message === 'BEFORE_EPOCH') {
      sendJson(res, 400, {
        ok: false,
        error: 'BEFORE_EPOCH',
        message: 'The Republican calendar begins on 22 September 1792.',
      });
      return;
    }
    sendJson(res, 400, {
      ok: false,
      error: 'INVALID_DATE',
      message: 'The given date does not exist in the Gregorian calendar.',
    });
  }
}

/** Serves a file from rootDir, rejecting any path that escapes it. */
function serveStatic(res, rootDir, requestPath) {
  const decodedPath = decodeURIComponent(requestPath.split('?')[0]);
  const safeSuffix = path.normalize(decodedPath).replace(/^([.][.][/\\])+/, '');
  const filePath = path.resolve(rootDir, `.${path.sep}${safeSuffix}`);

  if (filePath !== rootDir && !filePath.startsWith(rootDir + path.sep)) {
    res.writeHead(403, { 'Content-Type': 'text/plain; charset=utf-8' });
    res.end('Forbidden');
    return;
  }

  fs.readFile(filePath, (readErr, content) => {
    if (readErr) {
      res.writeHead(404, { 'Content-Type': 'text/plain; charset=utf-8' });
      res.end('Not found');
      return;
    }
    const ext = path.extname(filePath).toLowerCase();
    res.writeHead(200, { 'Content-Type': MIME_TYPES[ext] || 'application/octet-stream' });
    res.end(content);
  });
}

const server = http.createServer((req, res) => {
  if (req.method !== 'GET') {
    res.writeHead(405, { 'Content-Type': 'text/plain; charset=utf-8' });
    res.end('Method not allowed');
    return;
  }

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

  if (pathname === '/api/today') {
    convertAndRespond(res, nowUtc());
    return;
  }

  if (pathname === '/api/convert') {
    const year = Number.parseInt(requestUrl.searchParams.get('year'), 10);
    const month = Number.parseInt(requestUrl.searchParams.get('month'), 10);
    const day = Number.parseInt(requestUrl.searchParams.get('day'), 10);

    if (!Number.isInteger(year) || !Number.isInteger(month) || !Number.isInteger(day)) {
      sendJson(res, 400, {
        ok: false,
        error: 'INVALID_DATE',
        message: 'year, month and day query parameters are required integers.',
      });
      return;
    }

    convertAndRespond(res, { year, month, day });
    return;
  }

  if (pathname.startsWith('/locales/')) {
    serveStatic(res, LOCALES_DIR, pathname.slice('/locales'.length));
    return;
  }

  serveStatic(res, PUBLIC_DIR, pathname === '/' ? '/index.html' : pathname);
});

server.listen(PORT, () => {
  console.log(`Calendrier republicain server listening on port ${PORT}`);
});