forecast.coffee

KV_KEY = 'forecast-alert-datapoint'

module.exports = (robot) ->
  postWeatherAlert = (json, callback) ->
    postMessage = callback
    now = new Date()

    # This function posts an alert about the current forecast data always. It
    # doesn't determine if the alert should be posted.

    dataPoints = json['minutely']['data']

    dataPointsWithPrecipitation = []
    mostIntenseDataPoint = {}
    mostProbableDataPoint = {}

    for dataPoint in dataPoints
      intensity = dataPoint['precipIntensity'] || 0
      probability = dataPoint['precipProbability'] || 0

      if intensity > 0
        dataPointsWithPrecipitation.push(dataPoint)

        hightIntensity = mostIntenseDataPoint['precipIntensity'] || 0
        if intensity > hightIntensity
          mostIntenseDataPoint = dataPoint

        hightProbability = mostProbableDataPoint['precipProbability'] || 0
        if probability > hightProbability
          mostProbableDataPoint = dataPoint

    _minutes = dataPointsWithPrecipitation.length

    probability = mostProbableDataPoint['precipProbability']
    _percent = Math.round(probability * 100)

    intensity = mostIntenseDataPoint['precipIntensity']
    if intensity >= 0.4
      _intensity = 'heavy'
    else if intensity >= 0.1
      _intensity = 'moderate'
    else if intensity >= 0.02
      _intensity = 'light'
    else
      _intensity = 'very light'

    timestamp = mostIntenseDataPoint['time']
    date = new Date(timestamp * 1000)
    delta = (date - now)

    _delay = "#{Math.round(delta / 60 / 1000)}"

    _now = new Date().getTime()
    _link = "http://forecast.io/#/f/LAT,LNG/#{Math.round(_now / 1000)}"

    msg = "WEATHER: #{_percent}% chance of inclement weather in the next hour for at least #{_minutes} minutes. It will be worst in #{_delay} minutes (#{_intensity} precipitation). #{_link}"

    postMessage(msg, mostIntenseDataPoint)

  handleClear = (json, callback) ->
    postMessage = callback

    alertDataPoint = robot.brain.get(KV_KEY) || {}
    alertIntensity = alertDataPoint['precipIntensity'] || 0

    if alertIntensity == 0

      # This is where we end up most of the time (clear forecast currently
      # following a clear forecast previously); no need to do anything

      console.log '[Forecast] Continued clear weather.'

      return

    else

      # Forecast has cleared after a period of inclement weather; post a
      # notification (not checking time since last alert because this seems like
      # very important information, and should be posted regardless)

      console.log '[Forecast] Weather has cleared.'

      dataPoints = json['minutely']['data']
      dataPoint = dataPoints[0]

      msg = 'WEATHER: The weather should be clear for at least an hour.'

      postMessage(msg, dataPoint)

  handleNewWeather = (json, callback) ->
    isAnomaly = false

    # This is a new inclement weather forecast. As long as it doesn't seem to be
    # bogus data there should be an alert for it

    dataPointsWithPrecipitation = []
    mostIntenseDataPoint = {}
    totalIntensity = 0

    dataPoints = json['minutely']['data']

    for dataPoint in dataPoints
      intensity = dataPoint['precipIntensity'] || 0

      totalIntensity += intensity

      if intensity > 0
        dataPointsWithPrecipitation.push(dataPoint)

        hightIntensity = mostIntenseDataPoint['precipIntensity'] || 0
        mostIntenseDataPoint = dataPoint if intensity > hightIntensity

    isAnomaly = true if dataPointsWithPrecipitation.length < 5
    isAnomaly = true if mostIntenseDataPoint['precipProbability'] < 0.20
    isAnomaly = true if totalIntensity < (3 * mostIntenseDataPoint['precipIntensity'])

    if !isAnomaly

      console.log '[Forecast] Posting alert for new inclement weather'

      postWeatherAlert(json, callback)

  handleContinuingWeather = (json, callback) ->
    now = new Date()
    postMessage = callback

    alertDataPoint = robot.brain.get(KV_KEY) || {}
    alertIntensity = alertDataPoint['precipIntensity'] || 0
    alertTime = alertDataPoint['__alertTime']

    since = (now - alertTime)

    if since > (3 * 60 * 60 * 1000)

      # Three hours is long enough to post a new alert regardless of severity.
      # Not checking for anomalies because 3+ hours of bad weather is very
      # unlikely to be bad data

      console.log '[Forecast] Posting reminder alert'

      postWeatherAlert(json, callback)

    else

      # If it's been less than three hours only post an alert if the weather is
      # getting significantly worse or there's enough data to predict a break
      # in the weather

      mostIntenseDataPoint = {}

      dataPoints = json['minutely']['data']

      for dataPoint in dataPoints
        intensity = dataPoint['precipIntensity'] || 0

        totalIntensity += intensity

        if intensity > 0
          dataPointsWithPrecipitation.push(dataPoint)

          hightIntensity = mostIntenseDataPoint['precipIntensity'] || 0
          mostIntenseDataPoint = dataPoint if intensity > hightIntensity

      hightIntensity = mostIntenseDataPoint['precipIntensity']
      if hightIntensity > (2 * alertIntensity) && hightIntensity > 0.072

        # There's weather in the forecast that is at least twice as bad as the
        # weather was at the last alert so it's worth posting another alert

        console.log '[Forecast] Posting intensifying alert'

        postWeatherAlert(json, callback)

        return

      trailingClearDataPoints = []

      dataPoints.reverse()

      for dataPoint in dataPoints
        intensity = dataPoint['precipIntensity'] || 0

        break if intensity > 0

        trailingClearDataPoints.push(dataPoint)

      dataPoints.reverse()

      if trailingClearDataPoints.length > 30

        # If at least the last 30 minutes of the current forecast is clear post
        # an alert about the break in the weather. The currently cached data
        # point is getting rolled over with this notification so that the cache
        # still represents bad weather

        console.log '[Forecast] Posting weather break alert'

        msg = 'WEATHER: There should be a break in the weather for at least 30 minutes within the hour.'

        postMessage(msg, alertDataPoint)

  handleWeather = (json, callback) ->

    alertDataPoint = robot.brain.get(KV_KEY) || {}
    alertIntensity = alertDataPoint['precipIntensity'] || 0

    if alertIntensity == 0

      handleNewWeather(json, callback)

    else

      handleContinuingWeather(json, callback)

  handleJSON = (json, callback) ->

    if json['minutely']

      dataPoints = json['minutely']['data'] || []

      if dataPoints.length > 0

        totalIntensity = 0
        for dataPoint in dataPoints
          totalIntensity += (dataPoint['precipIntensity'] || 0)

        if totalIntensity == 0

          handleClear(json, callback)

        else

          handleWeather(json, callback)

  fetchForecast = (callback) ->

    forecastKey = process.env.FORECAST_KEY
    location = 'LAT,LNG'
    exclude = 'hourly,daily,flags'

    base_url = "https://api.forecast.io/forecast/#{forecastKey}/#{location}"
    url = "#{base_url}?units=us&exclude=#{exclude}"

    console.log "[Forecast] Requesting forecast data: #{url}"

    robot.http(url).get() (err, res, body) ->

      if !err
        json = JSON.parse(body)
        handleJSON(json, callback)

  forecast = ->
    now = new Date()

    isWeekday = (now.getDay() < 6)
    isBusinessHours = (now.getUTCHours() >= 11 && now.getUTCHours() <= 23)

    if isWeekday && isBusinessHours

      # Only run during business hours

      room = 'some_room@conf.hipchat.com'
      fetchForecast (msg, dataPoint) ->

        # Cache the data point related to this alert and send the message to
        # the room

        dataPoint['__alertTime'] = now
        robot.brain.set(KV_KEY, dataPoint)

        robot.messageRoom(room, msg)

    else

      # Remove the alert data cache between work days

      console.log '[Forecast] Sleeping'

      robot.brain.remove(KV_KEY)

  console.log '[Forecast] Starting weather service...'

  setInterval forecast, (5 * 60 * 1000)
  forecast()