import { EventEmitter } from 'node:events'
import WebSocket, { RawData } from 'ws'

import type { TapeTrade } from '../../core/types.js'

interface KrakenTradeData {
  symbol: string
  side: 'buy' | 'sell'
  price: number
  qty: number
  trade_id: number
  timestamp: string
}

interface KrakenMessage {
  channel?: string
  type?: string
  data?: KrakenTradeData[]
  success?: boolean
  result?: {
    channel?: string
    symbol?: string
  }
}

const KRAKEN_URL = 'wss://ws.kraken.com/v2'

export class KrakenTradeStreamer extends EventEmitter {
  readonly name = 'kraken'

  private socket?: WebSocket
  private reconnectTimer?: NodeJS.Timeout
  private stopped = false

  start(): void {
    this.stopped = false
    const socket = new WebSocket(KRAKEN_URL)
    this.socket = socket

    socket.on('open', () => {
      socket.send(
        JSON.stringify({
          method: 'subscribe',
          params: {
            channel: 'trade',
            symbol: ['BTC/USD']
          }
        })
      )
    })

    socket.on('message', (payload: RawData) => {
      try {
        const message = JSON.parse(payload.toString()) as KrakenMessage

        if (message.success && message.result?.channel === 'trade') {
          this.emit('discover', { stream: 'spot', count: 1, symbols: ['BTC/USD'] })
          this.emit('ready', { stream: 'spot', symbolCount: 1, url: KRAKEN_URL })
          return
        }

        if (message.channel !== 'trade' || !Array.isArray(message.data)) {
          return
        }

        for (const update of message.data) {
          const timestamp = Date.parse(update.timestamp)

          if (!Number.isFinite(update.price) || !Number.isFinite(update.qty) || !Number.isFinite(timestamp) || update.price <= 0 || update.qty <= 0) {
            continue
          }

          const trade: TapeTrade = {
            exchange: 'KRAKEN',
            exchangeClass: 'cex',
            instrumentType: 'spot',
            symbol: update.symbol,
            timestamp,
            price: update.price,
            size: update.qty,
            notionalUsd: update.price * update.qty,
            side: update.side,
            tradeId: String(update.trade_id),
            raw: update
          }

          this.emit('trade', trade)
        }
      } catch (error) {
        this.emit('error', error)
      }
    })

    socket.on('error', (error: Error) => this.emit('error', error))
    socket.on('close', () => this.handleClose())
  }

  stop(): void {
    this.stopped = true

    if (this.reconnectTimer) {
      clearTimeout(this.reconnectTimer)
      this.reconnectTimer = undefined
    }

    this.socket?.close()
    this.socket = undefined
  }

  private handleClose(): void {
    this.socket = undefined

    if (this.stopped) {
      return
    }

    this.reconnectTimer = setTimeout(() => this.start(), 3_000)
    this.emit('warn', 'Reconnecting spot stream in 3s')
  }
}