#!/usr/bin/env python

import pytz
import sys

from datetime import datetime, timedelta

from aman.com import AircraftReport_pb2
from aman.config.AirportSequencing import AirportSequencing
from aman.formats.SctEseFormat import SctEseFormat
from aman.sys.WeatherModel import WeatherModel
from aman.types.PerformanceData import PerformanceData
from aman.types.Waypoint import Waypoint

class Inbound:
    def __init__(self, report : AircraftReport_pb2.AircraftReport, sequencingConfig : AirportSequencing, navData : SctEseFormat,
                 performanceData : PerformanceData, weatherModel : WeatherModel):
        self.Report = report
        self.CurrentPosition = report.position
        self.ReportTime = datetime.strptime(report.reportTime + '+0000', '%Y%m%d%H%M%S%z').replace(tzinfo = pytz.UTC)

        # search performance data -> fallback to A320
        if self.Report.aircraft.type in performanceData.Aircrafts:
            self.PerformanceData = performanceData.Aircrafts[self.Report.aircraft.type]
        if None == self.PerformanceData:
            self.PerformanceData = performanceData.Aircrafts['A320']

        self.findArrivalRunway(sequencingConfig)
        self.findArrivalRoute(navData)

        flightTime, flightTimeUntilIaf, trackmiles = self.secondsUntilTouchdown(weatherModel)

        # calculate the maximum time to gain (assumption: 10% speed increase by acceleration and shortcuts)
        avgSpeed = self.Report.distanceToIAF / (float(flightTimeUntilIaf.seconds) / 3600.0)
        self.MaximumTimeToGain = flightTimeUntilIaf - timedelta(minutes = (self.Report.distanceToIAF / (avgSpeed * 1.1)) * 60)
        avgSpeed = trackmiles / (float(flightTime.seconds) / 3600.0)
        self.MaximumTimeToGain += flightTime - timedelta(minutes = (trackmiles / (avgSpeed * 1.1)) * 60)

        # calculate the different arrival times
        self.InitialArrivalTime = self.ReportTime + flightTime
        self.EarliestArrivalTime = self.InitialArrivalTime - self.MaximumTimeToGain
        self.EstimatedArrivalTime = self.InitialArrivalTime
        self.EstimatedStarEntryTime = None

    def findArrivalRunway(self, sequencingConfig : AirportSequencing):
        self.PlannedRunway = None

        # find the nearest runway for an initial guess
        distance = 100000.0
        currentPosition = Waypoint(latitude = self.Report.position.latitude, longitude = self.Report.position.longitude)
        for runway in sequencingConfig.ActiveArrivalRunways:
            candidateDistance = runway.Runway.Start.haversine(currentPosition)
            if distance > candidateDistance:
                self.PlannedRunway = runway
                distance = candidateDistance

    def findArrivalRoute(self, navData : SctEseFormat):
        self.PlannedStar = None
        if None == self.PlannedRunway:
            return

        for arrivalRunway in navData.ArrivalRoutes:
            if arrivalRunway == self.PlannedRunway.Runway.Name:
                stars = navData.ArrivalRoutes[arrivalRunway]
                for star in stars:
                    if 0 != len(star.Route) and self.Report.initialApproachFix == star.Iaf.Name:
                        self.PlannedStar = star
                        return

    def secondsUntilTouchdown(self, weather : WeatherModel):
        if None == self.PlannedRunway or None == self.PlannedStar:
            return timedelta(seconds = 0)

        # calculate remaining trackmiles
        trackmiles = self.Report.distanceToIAF
        start = self.PlannedStar.Route[0]
        turnIndices = [ -1, -1 ]
        constraints = []
        for i in range(0, len(self.PlannedStar.Route)):
            # identified the base turn
            if True == self.PlannedStar.Route[i].BaseTurn:
                turnIndices[0] = i
            # identified the final turn
            elif -1 != turnIndices[0] and True == self.PlannedStar.Route[i].FinalTurn:
                turnIndices[1] = i
            # skip waypoints until the final turn point is found
            elif -1 != turnIndices[0] and -1 == turnIndices[1]:
                continue

            trackmiles += start.haversine(self.PlannedStar.Route[i]) * 0.539957

            # check if a new constraint is defined
            altitude = -1
            speed = -1
            if None != self.PlannedStar.Route[i].Altitude:
                altitude = self.PlannedStar.Route[i].Altitude
            if None != self.PlannedStar.Route[i].Speed:
                speed = self.PlannedStar.Route[i].Speed
            if -1 != altitude or -1 != speed:
                constraints.append([ trackmiles, altitude, speed ])

            start = self.PlannedStar.Route[i]

        # add the remaining distance from the last waypoint to the runway threshold
        trackmiles += start.haversine(self.PlannedRunway.Runway.Start)

        if turnIndices[0] > turnIndices[1] or (-1 == turnIndices[1] and -1 != turnIndices[0]):
            sys.stderr.write('Invalid constraint definition found for ' + self.PlannedStar.Name)
            sys.exit(-1)

        # calculate descend profile
        currentHeading = Waypoint(latitude = self.Report.position.latitude, longitude = self.Report.position.longitude).bearing(self.PlannedStar.Route[0])
        currentIAS = self.PerformanceData.ias(self.Report.dynamics.altitude, trackmiles)
        currentPosition = [ self.Report.dynamics.altitude, self.Report.dynamics.groundSpeed ]
        distanceToWaypoint = self.Report.distanceToIAF
        flightTimeUntilIafSeconds = 0
        flightTimeSeconds = 0
        nextWaypointIndex = 0
        flownDistance = 0.0

        while True:
            # check if a constraint cleanup is needed and if a speed-update is needed
            if 0 != len(constraints) and flownDistance >= constraints[0][0]:
                if -1 != constraints[0][2]:
                    currentIAS = min(constraints[0][2], self.PerformanceData.ias(self.Report.dynamics.altitude, trackmiles - flownDistance))
                    currentPosition[1] = min(weather.calculateGS(currentPosition[0], currentIAS, currentHeading), currentPosition[1])
                constraints.pop(0)

            # search next altitude constraint
            altitudeDistance = 0
            nextAltitude = 0
            for constraint in constraints:
                if -1 != constraint[1]:
                    altitudeDistance = constraint[0]
                    nextAltitude = constraint[1]
                    break

            # check if update of altitude and speed is needed on 3° glide
            if currentPosition[0] > nextAltitude and ((currentPosition[0] - nextAltitude) / 1000 * 3) > (altitudeDistance - flownDistance):
                oldGroundspeed = currentPosition[1]
                descendRate = (currentPosition[1] / 60) / 3 * 1000 / 6
                newAltitude = currentPosition[0] - descendRate
                if 0 > newAltitude:
                    newAltitude = 0

                currentPosition = [ newAltitude, min(weather.calculateGS(newAltitude, currentIAS, currentHeading), currentPosition[1]) ]
                distance = (currentPosition[1] + oldGroundspeed) / 2 / 60 / 6
            else:
                distance = currentPosition[1] / 60 / 6

            # update the statistics
            distanceToWaypoint -= distance
            flownDistance += distance
            newIAS = min(currentIAS, self.PerformanceData.ias(currentPosition[0], trackmiles - flownDistance))
            if newIAS < currentIAS:
                currentPosition[1] = min(weather.calculateGS(currentPosition[0], newIAS, currentHeading), currentPosition[1])
                currentIAS = newIAS

            flightTimeSeconds += 10
            if flownDistance <= self.Report.distanceToIAF:
                flightTimeUntilIafSeconds += 10
            if flownDistance >= trackmiles:
                break

            # check if we follow a new waypoint pair
            if 0 >= distanceToWaypoint:
                lastWaypointIndex = nextWaypointIndex
                nextWaypointIndex += 1

                # check if a skip from base to final turn waypoints is needed
                if -1 != turnIndices[0] and nextWaypointIndex > turnIndices[0] and nextWaypointIndex < turnIndices[1]:
                    nextWaypointIndex = turnIndices[1]

                # update the statistics
                if nextWaypointIndex < len(self.PlannedStar.Route):
                    distanceToWaypoint = self.PlannedStar.Route[lastWaypointIndex].haversine(self.PlannedStar.Route[nextWaypointIndex]) * 0.539957
                    currentHeading = self.PlannedStar.Route[lastWaypointIndex].bearing(self.PlannedStar.Route[nextWaypointIndex])
                    currentPosition[1] = min(weather.calculateGS(newAltitude, currentIAS, currentHeading), currentPosition[1])

        return timedelta(seconds = flightTimeSeconds), timedelta(seconds = flightTimeUntilIafSeconds), trackmiles