# Name: GetSolverProperties_01.py
# Description: Generate 3-minute service areas around fire stations at several
#               times of day to compare coverage differences due to varying
#               traffic conditions. Use GetSolverProperties to access the
#               Service Area layer's solver properties object, and update the
#               time of day property prior to each solve.
# Requirements: Network Analyst Extension

#Import system modules
import datetime
import arcpy
from arcpy import env

try:
    #Check out the Network Analyst extension license
    arcpy.CheckOutExtension("Network")

    #Set environment settings
    env.workspace = "C:/Data/SanFrancisco.gdb"
    env.overwriteOutput = True

    #Set local variables
    inNetworkDataset = "Transportation/Streets_ND"
    outNALayerName = "FireStationCoverage"
    outSAFC = "Analysis/outSAPolys"
    impedanceAttribute = "TravelTime"
    inFacilities = "Analysis/FireStations"
    timelist = [datetime.datetime(2013, 8, 23, 7, 0, 0),
                datetime.datetime(2013, 8, 23, 12, 30, 0),
                datetime.datetime(2013, 8, 23, 17, 30, 0),
                datetime.datetime(2013, 8, 23, 21, 0, 0)]

    #Create a new service area layer.
    outSAResultObject = arcpy.na.MakeServiceAreaLayer(inNetworkDataset, outNALayerName,
                                  impedanceAttribute, "TRAVEL_FROM", "3",
                                  "DETAILED_POLYS", "NO_MERGE",
                                  hierarchy = "NO_HIERARCHY")

    #Get the layer object from the result object. The service area layer can
    #now be referenced using the layer object.
    outNALayer = outSAResultObject.getOutput(0)

    #Get the names of all the sublayers within the service area layer.
    subLayerNames = arcpy.na.GetNAClassNames(outNALayer)
    #Store the layer names that we will use later
    facilitiesLayerName = subLayerNames["Facilities"]
    polygonsLayerName = subLayerNames["SAPolygons"]

    #The input data has a field for FireStationID that we want to transfer to
    #our analysis layer. Add the field, and then use field mapping to transfer
    #the values.
    arcpy.na.AddFieldToAnalysisLayer(outNALayer, facilitiesLayerName,
                                                    "FireStationID", "TEXT")
    fieldMappings = arcpy.na.NAClassFieldMappings(outNALayer,
                                                    facilitiesLayerName)
    fieldMappings["FireStationID"].mappedFieldName = "FireStationID"

    #Load the fire stations as facilities.
    arcpy.na.AddLocations(outNALayer, facilitiesLayerName, inFacilities,
                            fieldMappings, "",
                            exclude_restricted_elements = "EXCLUDE")

    #Get sublayers we will want to work with later
    FacilitiesSubLayer = arcpy.mapping.ListLayers(outNALayer,
                                                    facilitiesLayerName)[0]
    PolygonsSubLayer = arcpy.mapping.ListLayers(outNALayer,
                                                    polygonsLayerName)[0]

    # Add fields to the output Polygons sublayer. We will fill the values later.
    arcpy.na.AddFieldToAnalysisLayer(outNALayer, polygonsLayerName,
                                        "FireStationID", "TEXT")
    arcpy.na.AddFieldToAnalysisLayer(outNALayer, polygonsLayerName,
                                        "TimeOfDay", "TEXT")

    #Get the Service Area Layer's solver properties. This will allow us to
    #set individual properties later without re-creating the layer.
    SA_SolverProperties = arcpy.na.GetSolverProperties(outNALayer)

    #Solve the Service Area for each time of day in our time list
    for t in timelist:

        print "Now solving for time of day: " + t

        #Use the solver properties to set the time of day for the solve
        SA_SolverProperties.timeOfDay = t

        #Solve the service area layer
        arcpy.na.Solve(outNALayer)

        #Transfer the FireStationID field from the input Facilities to the
        #output Polygons
        arcpy.management.AddJoin(PolygonsSubLayer, "FacilityID",
                                        FacilitiesSubLayer, "ObjectID")
        arcpy.management.CalculateField(PolygonsSubLayer, "FireStationID",
                                        "!Facilities.FireStationID!", "PYTHON")
        arcpy.management.RemoveJoin(PolygonsSubLayer)

        #Populate the TimeOfDay field
        expression = '"' + t + '"'
        arcpy.management.CalculateField(PolygonsSubLayer, "TimeOfDay",
                                            expression, "PYTHON")

        #Append the polygons to the output feature class. If this was the first
        #solve, create the feature class.
        if not arcpy.Exists(outSAFC):
            arcpy.management.CopyFeatures(PolygonsSubLayer, outSAFC)
        else:
            arcpy.management.Append(PolygonsSubLayer, outSAFC)

    print "Script completed successfully"

except Exception as e:
    # If an error occurred, print line number and error message
    import traceback, sys
    tb = sys.exc_info()[2]
    print "An error occured on line %i" % tb.tb_lineno
    print str(e)