import { createReadStream } from 'node:fs'
import { stat } from 'node:fs/promises'
import { createServer } from 'node:http'
import { extname, join, normalize, resolve } from 'node:path'
import { fileURLToPath } from 'node:url'

const __dirname = fileURLToPath(new URL('.', import.meta.url))
const distDir = resolve(__dirname, 'dist')
const port = Number(process.env.PORT || 7860)
const host = process.env.HOST || '0.0.0.0'

const mimeTypes = new Map([
  ['.html', 'text/html; charset=utf-8'],
  ['.js', 'text/javascript; charset=utf-8'],
  ['.css', 'text/css; charset=utf-8'],
  ['.json', 'application/json; charset=utf-8'],
  ['.png', 'image/png'],
  ['.jpg', 'image/jpeg'],
  ['.jpeg', 'image/jpeg'],
  ['.ico', 'image/x-icon'],
  ['.svg', 'image/svg+xml'],
  ['.webp', 'image/webp'],
  ['.woff', 'font/woff'],
  ['.woff2', 'font/woff2']
])

const hopByHopHeaders = new Set([
  'accept-encoding',
  'connection',
  'content-length',
  'content-encoding',
  'content-md5',
  'host',
  'keep-alive',
  'proxy-authenticate',
  'proxy-authorization',
  'te',
  'trailer',
  'transfer-encoding',
  'upgrade'
])

const server = createServer(async (request, response) => {
  try {
    const requestUrl = new URL(request.url || '/', `http://${request.headers.host || 'localhost'}`)
    if (requestUrl.pathname === '/api/proxy') {
      await proxyApiRequest(request, response, requestUrl)
      return
    }
    await serveStatic(requestUrl.pathname, response)
  } catch (error) {
    console.error(error)
    sendJson(response, 500, { error: 'Internal server error.' })
  }
})

server.listen(port, host, () => {
  console.log(`PixAI web server listening on http://${host}:${port}`)
})

async function proxyApiRequest(request, response, requestUrl) {
  const targetValue = requestUrl.searchParams.get('target')
  if (!targetValue) {
    sendJson(response, 400, { error: 'Missing target URL.' })
    return
  }

  let targetUrl
  try {
    targetUrl = new URL(targetValue)
  } catch {
    sendJson(response, 400, { error: 'Invalid target URL.' })
    return
  }

  if (!['https:', 'http:'].includes(targetUrl.protocol)) {
    sendJson(response, 400, { error: 'Unsupported target protocol.' })
    return
  }

  const headers = new Headers()
  for (const [key, value] of Object.entries(request.headers)) {
    if (hopByHopHeaders.has(key.toLowerCase())) continue
    if (Array.isArray(value)) headers.set(key, value.join(', '))
    else if (value != null) headers.set(key, value)
  }
  headers.set('accept-encoding', 'identity')

  const upstream = await fetch(targetUrl, {
    method: request.method,
    headers,
    body: request.method === 'GET' || request.method === 'HEAD' ? undefined : request,
    duplex: 'half'
  })

  response.statusCode = upstream.status
  for (const [key, value] of upstream.headers) {
    if (hopByHopHeaders.has(key.toLowerCase())) continue
    response.setHeader(key, value)
  }

  if (!upstream.body) {
    response.end()
    return
  }

  await upstream.body.pipeTo(new WritableStream({
    write(chunk) {
      response.write(Buffer.from(chunk))
    },
    close() {
      response.end()
    },
    abort(reason) {
      response.destroy(reason)
    }
  }))
}

async function serveStatic(pathname, response) {
  const decodedPath = decodeURIComponent(pathname)
  const safePath = normalize(decodedPath).replace(/^(\.\.[/\\])+/, '')
  const requestedPath = resolve(join(distDir, safePath))
  const requestedStat = requestedPath.startsWith(distDir) ? await stat(requestedPath).catch(() => null) : null
  const filePath = requestedStat?.isFile()
    ? requestedPath
    : join(distDir, 'index.html')

  const fileStat = await stat(filePath).catch(() => null)
  if (!fileStat?.isFile()) {
    sendJson(response, 404, { error: 'Build output not found. Run pnpm build first.' })
    return
  }

  response.statusCode = 200
  response.setHeader('Content-Type', mimeTypes.get(extname(filePath)) || 'application/octet-stream')
  response.setHeader('Cache-Control', filePath.endsWith('index.html') ? 'no-cache' : 'public, max-age=31536000, immutable')
  createReadStream(filePath).pipe(response)
}

function sendJson(response, status, payload) {
  response.statusCode = status
  response.setHeader('Content-Type', 'application/json; charset=utf-8')
  response.end(JSON.stringify(payload))
}