#
# calc_gps_coords.py
#
# based on meta_device_tracker.py by oakbrad
# https://github.com/oakbrad/brad-homeassistant-config/blob/master/python_scripts/meta_device_tracker.py
#
# adapted GPS Haversine calculation from nathan rooy
# https://nathanrooy.github.io/posts/2016-09-07/haversine-with-python/
#
# Suggested max_gps_accuracy for Owntracks is 200m (656ft)
# https://www.home-assistant.io/components/device_tracker.owntracks/
#
# We'll use it too but use it to determine if the new value is greater-than current
# value to indicate significant movement. The idea behind this is to prevent false
# positive zone-transitions when stationary without line-of-sight of satellites
# and GPS lock drifts. Calculation is determined by using the Haversine formula. If
# the new value is greater-than current, we allow the meta_tracker to update otherwise
# we retain previous value.
#
MAX_GPS_METERS = 200

# Get Data from Automation Trigger
triggeredEntity = data.get('entity_id')
metatrackerName = "device_tracker." + data.get('meta_entity')
zoneEntity = data.get('zone_entity')

# Get current & new state
newState = hass.states.get(triggeredEntity)
currentState = hass.states.get(metatrackerName)
zoneState = hass.states.get(zoneEntity)

# Get New data & status
newSource = newState.attributes.get('source_type')
newStatus = newState.state

# Get new GPS data. If device_tracker.meta_entity has no previous
# meter value, create one.
newLatitude = newState.attributes.get('latitude')
newLongitude = newState.attributes.get('longitude')
newgpsAccuracy = newState.attributes.get('gps_accuracy')
newMeters = 1000 if newState.attributes.get('meters') is None \
  else newState.attributes.get('meters')

# Get current GPS data. If we have no data, assign new data.
currentLatitude = newLatitude if currentState.attributes.get('latitude') is None \
  else currentState.attributes.get('latitude')
currentLongitude = newLongitude if currentState.attributes.get('longitude') is None \
  else currentState.attributes.get('longitude')
currentgpsAccuracy = newgpsAccuracy if currentState.attributes.get('gps_accuracy') is None \
  else currentState.attributes.get('gps_accuracy')
currentMeters = 1000 if currentState.attributes.get('meters') is None \
  else currentState.attributes.get('meters')

# Get Zone data if it exists.
if zoneState is not None:
  zoneLatitude = zoneState.attributes.get('latitude')
  zoneLongitude = zoneState.attributes.get('longitude')
  zoneRadius = zoneState.attributes.get('radius')
  zoneName = zoneState.attributes.get('friendly_name')
  zoneTransition = data.get('zone_data')

# If GPS source, calculate GPS movement in meters
if newSource == 'gps':
  # If a zone trasition is triggered, use zone data to populate device_tracker.meta_entity
  # We set the distance for the zone to 0.5m to prevent GPS drift and lock the
  # device_tracker.meta_entity to the zone unless a leave event happens in which case we
  # begin calculating distance.
  if zoneState is not None:
    logger.info("GPS zone transition: %s (%s) [zone=%s lat=%f long=%f radius=%d]", metatrackerName[15:], \
	  zoneTransition, zoneName, zoneLatitude, zoneLongitude, zoneRadius)

    if zoneTransition == 'enter':
      finalLatitude = zoneLatitude
      finalLongitude = zoneLongitude
      finalgpsAccuracy = 1
      finalMeters = 0.5
      newStatus = zoneName
    else:
      finalLatitude = newLatitude
      finalLongitude = newLongitude
      finalgpsAccuracy = newgpsAccuracy
      finalMeters = 1000

      # Simple case-check for zone.home - if state was home, set not_home else
      # set state to zoneName. Ensure zone entity name matches in your config.
      if (newState.state == 'home' or newState.state == 'Home'):
        newStatus = 'not_home'
      else:
        newStatus = zoneName
  else:
    # Begin Haversine formula calculation. This calculation will take
    # newCoords and compare against currentCoords and determine the distance
    # in meters. As each calculation happens, if the result is smaller than
    # the last, keep it. The idea is that when in a particular zone, it allows
    # the device_tracker.meta_entity to zero in as close as possible and
    # eliminate GPS drift.
    R = 6371000
    phi_1 = math.radians(currentLatitude)
    phi_2 = math.radians(newLatitude)

    delta_phi = math.radians(newLongitude-currentLongitude)
    delta_lambda = math.radians(newLongitude-currentLongitude)

    a = math.sin(delta_phi/2.0)**2+\
      math.cos(phi_1)*math.cos(phi_2)*\
      math.sin(delta_lambda/2.0)**2
    c = 2*math.atan2(math.sqrt(a),math.sqrt(1-a))

    meters = round(R*c, 2)
    if (meters > MAX_GPS_METERS):
      logger.info("GPS met threshold for %s: %.2f meters (%d) [new=%f,%f old=%f,%f acc=%d state=%s]", metatrackerName[15:], \
	    meters, MAX_GPS_METERS, newLatitude, newLongitude, currentLatitude, currentLongitude, newgpsAccuracy, newStatus)
      finalLatitude = newLatitude
      finalLongitude = newLongitude
      finalgpsAccuracy = newgpsAccuracy
      finalMeters = meters
    else:
      # keep values that are lowest in meters from previous to ensure
      # we stay within a zone measurement similar to max_gps_accuracy
      if (meters != 0):
        logger.info("GPS below threshold for %s: %.2f meters (%d) [new=%f,%f old=%f,%f acc=%d meters=%.2f state=%s]", metatrackerName[15:], \
		  meters, MAX_GPS_METERS, newLatitude, newLongitude, currentLatitude, currentLongitude, currentgpsAccuracy, currentMeters, currentState.state)
      if (meters <= currentMeters and (newLatitude != currentLatitude or newLongitude != currentLongitude)):
        finalLatitude = newLatitude
        finalLongitude = newLongitude
        finalgpsAccuracy = newgpsAccuracy
        finalMeters = meters
      else:
        finalLatitude = currentState.attributes.get('latitude')
        finalLongitude = currentState.attributes.get('longitude')
        finalgpsAccuracy = currentState.attributes.get('gps_accuracy')
        finalMeters = currentState.attributes.get('meters')
else:
  # If not, keep last known coordinates.
  if newSource is not None:
    finalLatitude = currentState.attributes.get('latitude')
    finalLongitude = currentState.attributes.get('longitude')
    finalgpsAccuracy = currentState.attributes.get('gps_accuracy')
    finalMeters = currentState.attributes.get('meters')

# Get Battery
if newState.attributes.get('battery') is not None:
  newBattery = newState.attributes.get('battery')
elif currentState.attributes.get('battery') is not None:
  newBattery = currentState.attributes.get('battery')
else:
  newBattery = None

# Create device_tracker.meta_entity
hass.states.set(metatrackerName, newStatus, {
    'name': metatrackerName,
	'friendly_name': metatrackerName[15:],
    'source_type': newSource,
    'battery': newBattery,
    'gps_accuracy': finalgpsAccuracy,
    'latitude': finalLatitude,
    'longitude': finalLongitude,
	'meters': finalMeters,
    'last_update_source': triggeredEntity
})