import express, { Request, Response } from 'express'
import cors from 'cors'
import rateLimit from 'express-rate-limit'
import ipaddr from 'ipaddr.js'

const app = express()
const PORT = process.env.PORT || 3000
const GLOBALPING_API = 'https://api.globalping.io/v1'

app.use(express.json())
app.use(cors({ origin: 'http://localhost:5173' }))
app.use(rateLimit({
  windowMs: 60 * 1000,
  limit: 10,
  message: { error: 'Rate limit exceeded' }
}))

interface GlobalPingLocation {
  country: string
  city?: string
}

const NODE_LOCATIONS: Record<string, GlobalPingLocation> = {
  'us-west': { country: 'US', city: 'San Francisco' },
  'us-east': { country: 'US', city: 'New York' },
  'europe': { country: 'DE', city: 'Frankfurt' },
  'asia': { country: 'JP', city: 'Tokyo' },
  'south-america': { country: 'BR', city: 'Sao Paulo' },
  'africa': { country: 'ZA', city: 'Cape Town' },
  'oceania': { country: 'AU', city: 'Sydney' }
}

function extractClientIp(req: Request): string | null {
  const forwarded = req.headers['x-forwarded-for']
  const raw = typeof forwarded === 'string' ? forwarded.split(',')[0].trim() : req.socket.remoteAddress
  if (!raw) return null
  const normalized = raw.replace(/^::ffff:/, '')
  if (ipaddr.isValid(normalized)) return normalized
  return null
}

function isPublicIp(ip: string): boolean {
  if (!ipaddr.isValid(ip)) return false
  const parsed = ipaddr.parse(ip)
  return parsed.range() === 'unicast'
}

interface MeasurementResponse {
  id: string
  probesCount: number
}

interface MeasurementResult {
  id: string
  type: string
  status: 'in-progress' | 'finished'
  results?: Array<{
    probe: {
      continent: string
      country: string
      city: string
      asn: number
      network: string
    }
    result: {
      status: string
      rawOutput: string
      stats?: {
        min: number
        max: number
        avg: number
        total: number
        loss: number
      }
    }
  }>
}

async function createMeasurement(target: string, location: GlobalPingLocation): Promise<string> {
  const res = await fetch(`${GLOBALPING_API}/measurements`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Accept-Encoding': 'gzip',
      'User-Agent': 'LatencyTest/1.0.0'
    },
    body: JSON.stringify({
      type: 'ping',
      target,
      locations: [location],
      measurementOptions: {
        packets: 3
      }
    })
  })

  if (!res.ok) {
    const error = await res.json().catch(() => ({})) as { error?: { message?: string } }
    throw new Error(error.error?.message || `GlobalPing API error: ${res.status}`)
  }

  const data = await res.json() as MeasurementResponse
  return data.id
}

async function getMeasurementResult(id: string, timeout = 30000): Promise<{ latency: number | null; success: boolean }> {
  const startTime = Date.now()

  while (Date.now() - startTime < timeout) {
    await new Promise(r => setTimeout(r, 500))

    const res = await fetch(`${GLOBALPING_API}/measurements/${id}`, {
      headers: {
        'Accept-Encoding': 'gzip',
        'User-Agent': 'LatencyTest/1.0.0'
      }
    })

    if (!res.ok) {
      throw new Error(`Failed to get measurement: ${res.status}`)
    }

    const data = await res.json() as MeasurementResult

    if (data.status !== 'in-progress') {
      const result = data.results?.[0]?.result
      if (result?.status === 'finished' && result.stats?.avg != null) {
        return { latency: Math.round(result.stats.avg), success: true }
      }
      return { latency: null, success: false }
    }
  }

  return { latency: null, success: false }
}

app.get('/api/ip', (req: Request, res: Response) => {
  const ip = extractClientIp(req)
  if (!ip) {
    return res.status(500).json({ error: 'Unable to determine IP' })
  }
  res.json({ ip })
})

app.post('/api/latency', async (req: Request, res: Response) => {
  const { targetIp, nodeId } = req.body

  if (!targetIp || typeof targetIp !== 'string') {
    return res.status(400).json({ error: 'targetIp is required' })
  }

  if (!nodeId || !NODE_LOCATIONS[nodeId]) {
    return res.status(400).json({ error: `Invalid nodeId. Available: ${Object.keys(NODE_LOCATIONS).join(', ')}` })
  }

  if (!isPublicIp(targetIp)) {
    return res.status(400).json({ error: 'Invalid or private IP address' })
  }

  try {
    const measurementId = await createMeasurement(targetIp, NODE_LOCATIONS[nodeId])
    const { latency, success } = await getMeasurementResult(measurementId)
    res.json({ nodeId, latency, success })
  } catch (error) {
    console.error('Latency test error:', error)
    res.status(500).json({ nodeId, latency: null, success: false })
  }
})

app.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`)
})