const http = require('http')
const fs = require('fs')
const path = require('path')
const { WebSocketServer } = require('ws')

const HOST = '0.0.0.0'
const PORT = 17865
const WS_PATH = '/mock-gps'
const PROXY_PATH = '/proxy'
const PUBLIC_DIR = path.join(__dirname, 'public')

function getContentType(filePath) {
  const ext = path.extname(filePath).toLowerCase()
  if (ext === '.html') {
    return 'text/html; charset=utf-8'
  }
  if (ext === '.css') {
    return 'text/css; charset=utf-8'
  }
  if (ext === '.js') {
    return 'application/javascript; charset=utf-8'
  }
  if (ext === '.json') {
    return 'application/json; charset=utf-8'
  }
  if (ext === '.svg') {
    return 'image/svg+xml'
  }
  return 'text/plain; charset=utf-8'
}

function serveStatic(requestPath, response) {
  const safePath = requestPath === '/' ? '/index.html' : requestPath
  const resolvedPath = path.normalize(path.join(PUBLIC_DIR, safePath))
  if (!resolvedPath.startsWith(PUBLIC_DIR)) {
    response.writeHead(403)
    response.end('Forbidden')
    return
  }

  fs.readFile(resolvedPath, (error, content) => {
    if (error) {
      response.writeHead(404)
      response.end('Not Found')
      return
    }

    response.writeHead(200, {
      'Content-Type': getContentType(resolvedPath),
      'Cache-Control': 'no-store',
    })
    response.end(content)
  })
}

function isMockGpsPayload(payload) {
  return payload
    && payload.type === 'mock_gps'
    && Number.isFinite(payload.lat)
    && Number.isFinite(payload.lon)
}

async function handleProxyRequest(request, response) {
  const requestUrl = new URL(request.url || '/', `http://127.0.0.1:${PORT}`)
  const targetUrl = requestUrl.searchParams.get('url')
  if (!targetUrl) {
    response.writeHead(400, {
      'Content-Type': 'text/plain; charset=utf-8',
      'Access-Control-Allow-Origin': '*',
    })
    response.end('Missing url')
    return
  }

  try {
    const upstream = await fetch(targetUrl)
    const body = Buffer.from(await upstream.arrayBuffer())
    response.writeHead(upstream.status, {
      'Content-Type': upstream.headers.get('content-type') || 'application/octet-stream',
      'Cache-Control': 'no-store',
      'Access-Control-Allow-Origin': '*',
    })
    response.end(body)
  } catch (error) {
    response.writeHead(502, {
      'Content-Type': 'text/plain; charset=utf-8',
      'Access-Control-Allow-Origin': '*',
    })
    response.end(error && error.message ? error.message : 'Proxy request failed')
  }
}

const server = http.createServer((request, response) => {
  if ((request.url || '').startsWith(PROXY_PATH)) {
    handleProxyRequest(request, response)
    return
  }

  serveStatic(request.url || '/', response)
})

const wss = new WebSocketServer({ noServer: true })

wss.on('connection', (socket) => {
  socket.on('message', (rawMessage) => {
    const text = String(rawMessage)
    let parsed
    try {
      parsed = JSON.parse(text)
    } catch (_error) {
      return
    }

    if (!isMockGpsPayload(parsed)) {
      return
    }

    const serialized = JSON.stringify({
      type: 'mock_gps',
      timestamp: Number.isFinite(parsed.timestamp) ? parsed.timestamp : Date.now(),
      lat: Number(parsed.lat),
      lon: Number(parsed.lon),
      accuracyMeters: Number.isFinite(parsed.accuracyMeters) ? Number(parsed.accuracyMeters) : 6,
      speedMps: Number.isFinite(parsed.speedMps) ? Number(parsed.speedMps) : 0,
      headingDeg: Number.isFinite(parsed.headingDeg) ? Number(parsed.headingDeg) : 0,
    })

    wss.clients.forEach((client) => {
      if (client.readyState === client.OPEN) {
        client.send(serialized)
      }
    })
  })
})

server.on('upgrade', (request, socket, head) => {
  if (!request.url || !request.url.startsWith(WS_PATH)) {
    socket.destroy()
    return
  }

  wss.handleUpgrade(request, socket, head, (ws) => {
    wss.emit('connection', ws, request)
  })
})

server.listen(PORT, HOST, () => {
  console.log(`Mock GPS simulator running:`)
  console.log(`  UI: http://127.0.0.1:${PORT}/`)
  console.log(`  WS: ws://127.0.0.1:${PORT}${WS_PATH}`)
  console.log(`  Proxy: http://127.0.0.1:${PORT}${PROXY_PATH}?url=<remote-url>`)
})