const axios = require('axios')
const crypto = require('crypto')
const _ = require('lodash/fp')

const API_ENDPOINT = 'https://api.quadrigacx.com/v2'

let counter = -1
let lastTimestamp = Date.now()

function pad (num) {
  const asString = num.toString(10)
  if (num < 10) return '00' + asString
  if (num < 100) return '0' + asString
  return asString
}

function generateNonce () {
  const timestamp = Date.now()
  if (timestamp !== lastTimestamp) counter = -1
  lastTimestamp = timestamp
  counter = (counter + 1) % 1000
  return timestamp.toString(10) + pad(counter)
}

function authRequest (config, path, data) {
  if (!config.key || !config.secret || !config.clientId) {
    const err = new Error('Must provide key, secret and client ID')
    return Promise.reject(err)
  }

  data = data || {}

  const nonce = generateNonce()
  const msg = [nonce, config.clientId, config.key].join('')

  const signature = crypto
    .createHmac('sha256', Buffer.from(config.secret))
    .update(msg)
    .digest('hex')
    .toLowerCase()

  const signedData = _.merge(data, {
    key: config.key,
    signature,
    nonce
  })

  return request(path, 'POST', signedData)
}

function buildMarket (fiatCode, cryptoCode) {
  if (!_.includes(cryptoCode, ['BTC', 'ETH', 'LTC', 'BCH'])) {
    throw new Error(`Unsupported crypto: ${cryptoCode}`)
  }

  if (!_.includes(fiatCode, ['USD', 'CAD'])) {
    throw new Error(`Unsupported fiat: ${fiatCode}`)
  }

  let market = `${cryptoCode.toLowerCase()}_${fiatCode.toLowerCase()}`

  if (fiatCode === 'USD' && cryptoCode !== 'BTC') {
    throw new Error(`Unsupported market: ${market}`)
  }

  return market
}

function request (path, method, data) {
  const options = {
    method,
    data,
    url: API_ENDPOINT + path,
    headers: {
      'User-Agent': 'Mozilla/4.0 (compatible; Lamassu client)',
      'Content-Type': 'application/json; charset=utf-8'
    }
  }

  return axios(options)
    .then(r => {
      if (r.data.error) throw new Error(r.data.error.message)
      return r.data
    })
}

module.exports = {
  buildMarket,
  authRequest,
  request
}