// @flow

// NOTE: don't use Module here, since Module uses this class

import EventEmitter from 'events'

import { httpReq } from './uninstrumentedHttpUtils'

import type { MinimalMetricDimensions } from './types'


export type Metric = {
  statName: string, 
  value: number, 
  dims?: ?{}, 
  timestampMs?: ?number,
}

export type StatNameMode = 'measurements' | 'fields'

export default class InfluxDBClient extends EventEmitter {

  _influxDBHost: string
  _influxDBDBName: string
  _statNameMode: StatNameMode
  _flushIntervalMS: number
  _counterPoints: Map<string, number>
  _gaugePoints: Map<string, number>
  _timerPoints: Map<string, Array<number>>
  _baseDims: Object


  constructor(influxDBHost: string, influxDBDBName: string, statNameMode: StatNameMode, flushIntervalMS: ?number, baseDims?: ?Object) {
    super()

    this._influxDBHost = influxDBHost
    this._influxDBDBName = influxDBDBName
    this._statNameMode = statNameMode
    this._flushIntervalMS = flushIntervalMS || 0
    this._baseDims = baseDims || {}
    this._counterPoints = new Map()
    this._gaugePoints = new Map()
    this._timerPoints = new Map()

    if (this._flushIntervalMS) {
      setInterval(this.flushMetrics, this._flushIntervalMS)
    }
  }


  trackMetrics = async (metrics: Array<Metric>) => {
    metrics.forEach(({ statName, value, dims }) => {
      const filledDims = this._fillDims(dims)
      const metricKey = this._statNameMode === 'fields' ?
        `stat${`${Object.keys(filledDims).map(k => `,${k}=${filledDims[k]}`).join('')}`} ${statName}` :
        `${statName}${`${Object.keys(filledDims).map(k => `,${k}=${filledDims[k]}`).join('')}`} value`
      switch (filledDims.metricType) {
      case 'counters':
        this._counterPoints.set(metricKey, Number(this._counterPoints.get(metricKey) || 0) + Number(value))
        break
      case 'gauges':
        this._gaugePoints.set(metricKey, Number(value))
        break
      case 'timers':
        this._timerPoints.set(metricKey, [ ...(this._timerPoints.get(metricKey) || []), Number(value) ])
        break
      default:
        throw new Error(`Illegal metricType: '${filledDims.metricType}'`)
      }
    })

    //const body = `${statName}${ dims ? `${Object.keys(dims).map(k => `,${k}=${dims[k]}`).join('')}` : '' } value=${value}${ timestampMs ? ` ${timestampMs}000000` : '' }`

    // $FlowIgnore
    //const newMetricStrs = metrics.map(({ statName, value, dims, timestampMs }) => `stat${ dims ? `${Object.keys(dims).map(k => `,${k}=${dims[k]}`).join('')}` : '' } ${statName}=${value}${ timestampMs ? ` ${timestampMs}000000` : '' }`)
    
    if (!this._flushIntervalMS) {
      await this.flushMetrics()
    }
  }

  flushMetrics = async () => {
    try {
      if (this._counterPoints.size + this._gaugePoints.size + this._timerPoints.size === 0)
        return

      const pointsStr = [
        Array.from(this._counterPoints.keys()).map(key => `${key}=${ this._counterPoints.get(key) || 0 }`).join('\n'),
        Array.from(this._gaugePoints.keys()).map(key => `${key}=${ this._gaugePoints.get(key) || 0 }`).join('\n'),
        Array.from(this._timerPoints.keys()).map(key => `${key}=${ (this._timerPoints.get(key) || []).reduce((a, b) => a + b, 0) / (this._timerPoints.get(key) || []).length }`).join('\n'),
      ].join('\n')

      this._counterPoints = new Map()
      this._gaugePoints = new Map()
      this._timerPoints = new Map()

      // console.log('Tracking:\n' + pointsStr) // eslint-disable-line no-console

      await httpReq(`http://${this._influxDBHost}/write?db=${this._influxDBDBName}`, {
        method: 'POST',
        body: pointsStr,
        maxRetries: 1,
        timeout: 10000,
      })
    } catch (err) {
      console.error('InfluxDB error', (new Date()).toUTCString(), err.toString()) // eslint-disable-line no-console
      // TODO: make sure these errors are logged
      //this.emit('error', { err: err })
    }
  }

  _fillDims = (dims: ?{}): MinimalMetricDimensions => {
    return {
      ...this._baseDims,
      metricType: 'counters', // a metric is a counter by default
      ...dims,
    }
  } 

}