// @flow

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

import stringify from 'json-stringify-safe'
import _ from 'lodash'

import { httpReq } from './httpUtils'
import { padRight } from './stringUtils'

const LOG_FLUSH_INTERVAL_MS = 5 * 1000

type LoggerOptions = {
  noHTTPS?: boolean,
  host?: ?string,
  dataFieldsToPromote?: ?{ [id: string]: string },
  dataFieldsToRemove?: ?Array<string>, 
  systemMeta?: ?{},
}

export default class S3Logger {

  _logObjects: Array<Object> = []
  _logRecordNum: number = 0
  _options: LoggerOptions


  constructor(options: LoggerOptions) {
    this._options = options

    if (this._options.host) {
      setInterval(this.flushLogs, LOG_FLUSH_INTERVAL_MS)
    }
  }


  queueLogRecord = (logObj: Object): void => {
    try {
      const nowMS = Date.now()

      let { data, message, ...restLogObj } = logObj

      const objToPush = {
        event: message,

        ...restLogObj,

        record_num: ++this._logRecordNum,
        time_ms: nowMS,
        time_ts: new Date(nowMS).toISOString(),
      }

      if (data != null) {

        // make sure data is a object
        if (typeof data !== 'object') {
          data = {
            value: data.toString()
          }
        }

        // promote data fields
        if (this._options.dataFieldsToPromote) {
          Object.entries(this._options.dataFieldsToPromote).forEach(([logProp, dataPath]) => {
            // $FlowIgnore
            const dataVal = _.get(data, dataPath)
            if (dataVal !== undefined) {
              objToPush[logProp] = dataVal
            }
          })
        }

        // remove data fields
        if (this._options.dataFieldsToRemove) {
          this._options.dataFieldsToRemove.forEach(dataProp => {
            delete data[dataProp]
          })
        }

        // serialize data
        if (Object.keys(data).length > 0)
          objToPush.data = stringify(data)

      }

      // log to console
      console.log(`${objToPush.time_ts.substr(11, 12)}: ${padRight(objToPush.level, 5, ' ')} [${objToPush.module}] ${objToPush.event} ${objToPush.data || ''}`) // eslint-disable-line no-console
  
      this._logObjects.push(objToPush)
    } catch (err) {
      console.error('Failed to queue a log record', logObj, err) // eslint-disable-line no-console
    }
  }


  flushLogs = async (): Promise<void> => {
    try {
      if (!this._logObjects.length || !this._options.host)
        return

      const logsToFlush = this._logObjects
      this._logObjects = []

      await httpReq(`${this._options.noHTTPS ? 'http' : 'https'}://${this._options.host}/p1`, {
        method: 'POST', 
        body: {
          beacons: logsToFlush,
          common: this._options.systemMeta,
          client_sending_time_ms: Date.now(),
        },
        timeout: 10000,
      })

    } catch (err) {
      console.error('Failed to flush logs', (new Date()).toUTCString(), err) // eslint-disable-line no-console
    }
  }
}