#!/usr/bin/env python

from datetime import timedelta

from aman.sys.aco.Configuration import Configuration
from aman.sys.aco.Constraints import SpacingConstraints
from aman.types.Inbound import Inbound

class RunwayManager:
    def __init__(self, configuration : Configuration):
        self.Spacings = SpacingConstraints()
        self.Configuration = configuration

        # initialize the tracker which inbound arrives at which runway
        self.RunwayInbounds = {}
        if None != configuration.PreceedingInbounds:
            for runway in configuration.PreceedingInbounds:
                self.RunwayInbounds[runway] = configuration.PreceedingInbounds[runway]
        for runway in configuration.RunwayConstraints.ActiveArrivalRunways:
            if not runway.Runway.Name in self.RunwayInbounds:
                self.RunwayInbounds[runway.Runway.Name] = None

    def validateWtc(inbound : Inbound):
        wtc = inbound.Report.aircraft.wtc.upper()
        if 'L' == wtc or 'M' == wtc or 'H' == None or 'J' == None:
            return wtc
        else:
            return None

    def calculateEarliestArrivalTime(self, runway : str, inbound : Inbound):
        if None == self.RunwayInbounds[runway]:
            return inbound.ArrivalCandidates[runway].EarliestArrivalTime

        preceedingInbound = self.RunwayInbounds[runway]

        # get the WTC constrained ETA
        wtcPre = RunwayManager.validateWtc(preceedingInbound)
        wtcThis = RunwayManager.validateWtc(inbound)
        if None == wtcPre or None == wtcThis:
            spacing = 3
        else:
            spacing = self.Spacings[wtcPre][wtcThis]
        delay = timedelta(minutes = spacing / (inbound.PerformanceData.SpeedApproach / 60))
        wtcEarliestArrivalTime = preceedingInbound.PlannedArrivalTime + delay

        # get the staggered time spacing
        dependentRunway = self.Configuration.RunwayConstraints.findDependentRunway(runway)
        if None != dependentRunway and None != self.RunwayInbounds[dependentRunway.Runway.Name]:
            # check if the one on the same runway lands before the one on the parallel runway
            if preceedingInbound.PlannedArrivalTime < self.RunwayInbounds[dependentRunway.Runway.Name].PlannedArrivalTime:
                delay = timedelta(minutes = 3 / (inbound.PerformanceData.SpeedApproach / 60))
                staggeredEarliestArrivalTime = self.RunwayInbounds[dependentRunway.Runway.Name].PlannedArrivalTime + delay
            # landing on the same runway
            else:
                staggeredEarliestArrivalTime = wtcEarliestArrivalTime
        # no neighbor or no dependent runway (IPA)
        else:
            staggeredEarliestArrivalTime = wtcEarliestArrivalTime

        # get the runway time spacing
        spacing = self.Configuration.RunwayConstraints.findRunway(runway).Spacing
        delay = timedelta(minutes = spacing / (inbound.PerformanceData.SpeedApproach / 60))
        runwayEarliestArrivalTime = preceedingInbound.PlannedArrivalTime + delay

        # the candidate with the latest ETA is used -> ensure all safety and procedure constraints
        candidate = max(max(wtcEarliestArrivalTime, staggeredEarliestArrivalTime), runwayEarliestArrivalTime)

        # check if inbound comes later than the latest possible ETA
        if candidate < inbound.ArrivalCandidates[runway].EarliestArrivalTime:
            return inbound.ArrivalCandidates[runway].EarliestArrivalTime
        # candidate fits into earliest arrival time or is later than this
        else:
            return candidate

    def selectArrivalRunway(self, inbound : Inbound):
        availableRunways = []
        for runway in self.Configuration.RunwayConstraints.ActiveArrivalRunways:
            availableRunways.append(runway)

        #if 1 < len(availableRunways):
            # TODO filter based on type
            # TODO filter based on airline
            # ensure that at least one runway is available

        # fallback to check if we have available runways
        if 0 == len(availableRunways):
            runway = self.Configuration.RunwayConstraints.ActiveArrivalRunways[0]
            return runway, self.calculateEarliestArrivalTime(runway.Runway.Name, inbound)

        # start with the beginning
        selectedRunway = None
        eta = None

        # get the runway with the earliest ETA
        for runway in availableRunways:
            candidate = self.calculateEarliestArrivalTime(runway.Runway.Name, inbound)
            if None == eta or eta > candidate:
                selectedRunway = runway.Runway
                eta = candidate

        return selectedRunway, eta