import { EventEmitter } from 'events'
import * as dgram from 'dgram'
import ms from 'ms'
import { debug as createDebugLogger } from 'debug'
import LRUCache = require('lru-cache')
import { encode, decode } from './message'
import { keccak256, pk2id, createDeferred, formatLogId } from '../util'
import { DPT } from './dpt'
import { Socket as DgramSocket, RemoteInfo } from 'dgram'
import { PeerInfo } from './message'

const debug = createDebugLogger('devp2p:dpt:server')
const verbose = createDebugLogger('verbose').enabled

const VERSION = 0x04

export interface DptServerOptions {
  timeout?: number
  endpoint?: PeerInfo
  createSocket?: Function
}

export class Server extends EventEmitter {
  _dpt: DPT
  _privateKey: Buffer
  _timeout: number
  _endpoint: PeerInfo
  _requests: Map<string, any>
  _parityRequestMap: Map<string, string>
  _requestsCache: LRUCache<string, Promise<any>>
  _socket: DgramSocket | null

  constructor(dpt: DPT, privateKey: Buffer, options: DptServerOptions) {
    super()

    this._dpt = dpt
    this._privateKey = privateKey

    this._timeout = options.timeout || ms('10s')
    this._endpoint = options.endpoint || { address: '0.0.0.0', udpPort: null, tcpPort: null }
    this._requests = new Map()
    this._parityRequestMap = new Map()
    this._requestsCache = new LRUCache({ max: 1000, maxAge: ms('1s'), stale: false })

    const createSocket = options.createSocket || dgram.createSocket.bind(null, { type: 'udp4' })
    this._socket = createSocket()
    if (this._socket) {
      this._socket.once('listening', () => this.emit('listening'))
      this._socket.once('close', () => this.emit('close'))
      this._socket.on('error', err => this.emit('error', err))
      this._socket.on('message', (msg: Buffer, rinfo: RemoteInfo) => {
        try {
          this._handler(msg, rinfo)
        } catch (err) {
          this.emit('error', err)
        }
      })
    }
  }

  bind(...args: any[]) {
    this._isAliveCheck()
    debug('call .bind')

    if (this._socket) this._socket.bind(...args)
  }

  destroy(...args: any[]) {
    this._isAliveCheck()
    debug('call .destroy')

    if (this._socket) {
      this._socket.close(...args)
      this._socket = null
    }
  }

  async ping(peer: PeerInfo): Promise<any> {
    this._isAliveCheck()

    const rckey = `${peer.address}:${peer.udpPort}`
    const promise = this._requestsCache.get(rckey)
    if (promise !== undefined) return promise

    const hash = this._send(peer, 'ping', {
      version: VERSION,
      from: this._endpoint,
      to: peer
    })

    const deferred = createDeferred()
    const rkey = hash.toString('hex')
    this._requests.set(rkey, {
      peer,
      deferred,
      timeoutId: setTimeout(() => {
        if (this._requests.get(rkey) !== undefined) {
          debug(
            `ping timeout: ${peer.address}:${peer.udpPort} ${
              peer.id ? formatLogId(peer.id.toString('hex'), verbose) : '-'
            }`
          )
          this._requests.delete(rkey)
          deferred.reject(new Error(`Timeout error: ping ${peer.address}:${peer.udpPort}`))
        } else {
          return deferred.promise
        }
      }, this._timeout)
    })
    this._requestsCache.set(rckey, deferred.promise)
    return deferred.promise
  }

  findneighbours(peer: PeerInfo, id: Buffer) {
    this._isAliveCheck()
    this._send(peer, 'findneighbours', { id })
  }

  _isAliveCheck() {
    if (this._socket === null) throw new Error('Server already destroyed')
  }

  _send(peer: PeerInfo, typename: string, data: any) {
    debug(
      `send ${typename} to ${peer.address}:${peer.udpPort} (peerId: ${
        peer.id ? formatLogId(peer.id.toString('hex'), verbose) : '-'
      })`
    )

    const msg = encode(typename, data, this._privateKey)
    // Parity hack
    // There is a bug in Parity up to at lease 1.8.10 not echoing the hash from
    // discovery spec (hash: sha3(signature || packet-type || packet-data))
    // but just hashing the RLP-encoded packet data (see discovery.rs, on_ping())
    // 2018-02-28
    if (typename === 'ping') {
      const rkeyParity = keccak256(msg.slice(98)).toString('hex')
      this._parityRequestMap.set(rkeyParity, msg.slice(0, 32).toString('hex'))
      setTimeout(() => {
        if (this._parityRequestMap.get(rkeyParity) !== undefined) {
          this._parityRequestMap.delete(rkeyParity)
        }
      }, this._timeout)
    }
    if (this._socket && peer.udpPort)
      this._socket.send(msg, 0, msg.length, peer.udpPort, peer.address)
    return msg.slice(0, 32) // message id
  }

  _handler(msg: Buffer, rinfo: RemoteInfo) {
    const info = decode(msg)
    const peerId = pk2id(info.publicKey)
    debug(
      `received ${info.typename} from ${rinfo.address}:${rinfo.port} (peerId: ${formatLogId(
        peerId.toString('hex'),
        verbose
      )})`
    )

    // add peer if not in our table
    const peer = this._dpt.getPeer(peerId)
    if (peer === null && info.typename === 'ping' && info.data.from.udpPort !== null) {
      setTimeout(() => this.emit('peers', [info.data.from]), ms('100ms'))
    }

    switch (info.typename) {
      case 'ping': {
        const remote: PeerInfo = {
          id: peerId,
          udpPort: rinfo.port,
          address: rinfo.address
        }
        this._send(remote, 'pong', {
          to: {
            address: rinfo.address,
            udpPort: rinfo.port,
            tcpPort: info.data.from.tcpPort
          },
          hash: msg.slice(0, 32)
        })
        break
      }

      case 'pong': {
        let rkey = info.data.hash.toString('hex')
        const rkeyParity = this._parityRequestMap.get(rkey)
        if (rkeyParity) {
          rkey = rkeyParity
          this._parityRequestMap.delete(rkeyParity)
        }
        const request = this._requests.get(rkey)
        if (request) {
          this._requests.delete(rkey)
          request.deferred.resolve({
            id: peerId,
            address: request.peer.address,
            udpPort: request.peer.udpPort,
            tcpPort: request.peer.tcpPort
          })
        }
        break
      }
      case 'findneighbours': {
        const remote: PeerInfo = {
          id: peerId,
          udpPort: rinfo.port,
          address: rinfo.address
        }
        this._send(remote, 'neighbours', {
          peers: this._dpt.getClosestPeers(info.data.id)
        })
        break
      }

      case 'neighbours': {
        this.emit(
          'peers',
          info.data.peers.map((peer: any) => peer.endpoint)
        )
        break
      }
    }
  }
}