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

const PORT = Number(process.env.PORT || 3001)
const API_UPSTREAM = process.env.API_UPSTREAM || 'http://127.0.0.1:6000'
const DIST_DIR = path.join(__dirname, 'dist')

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

function send(res, status, body, headers = {}) {
  res.writeHead(status, headers)
  res.end(body)
}

function proxyRequest(req, res) {
  const target = new URL(req.url, API_UPSTREAM)
  const proxy = http.request(
    target,
    {
      method: req.method,
      headers: {
        ...req.headers,
        host: target.host,
      },
    },
    (proxyRes) => {
      res.writeHead(proxyRes.statusCode || 502, proxyRes.headers)
      proxyRes.pipe(res)
    },
  )

  proxy.on('error', (error) => {
    send(
      res,
      502,
      JSON.stringify({ error: 'API proxy failed', detail: error.message }),
      { 'content-type': 'application/json; charset=utf-8' },
    )
  })

  req.pipe(proxy)
}

function serveStatic(req, res) {
  const requestPath = decodeURIComponent(new URL(req.url, `http://localhost:${PORT}`).pathname)
  const relativePath = requestPath === '/' ? '/index.html' : requestPath
  const filePath = path.normalize(path.join(DIST_DIR, relativePath))

  if (!filePath.startsWith(DIST_DIR)) {
    return send(res, 403, 'Forbidden', { 'content-type': 'text/plain; charset=utf-8' })
  }

  fs.readFile(filePath, (error, data) => {
    if (error) {
      fs.readFile(path.join(DIST_DIR, 'index.html'), (indexError, indexData) => {
        if (indexError) {
          return send(res, 404, 'Build not found. Run npm run build first.', {
            'content-type': 'text/plain; charset=utf-8',
          })
        }

        send(res, 200, indexData, { 'content-type': mimeTypes['.html'] })
      })
      return
    }

    const ext = path.extname(filePath)
    send(res, 200, data, {
      'content-type': mimeTypes[ext] || 'application/octet-stream',
      'cache-control': ext === '.html' ? 'no-cache' : 'public, max-age=31536000, immutable',
    })
  })
}

http
  .createServer((req, res) => {
    if (req.url === '/health' || req.url.startsWith('/api/')) {
      proxyRequest(req, res)
      return
    }

    serveStatic(req, res)
  })
  .listen(PORT, '0.0.0.0', () => {
    console.log(`tssbot-web serving http://localhost:${PORT}`)
    console.log(`proxying API requests to ${API_UPSTREAM}`)
  })