#! /usr/bin/env python

# Munter Time Calculation
#
# Rudimentary program written by ALV to implement the Munter time calculation

import sys
import argparse

class InvalidUnitsException(Exception):
    pass

rates = {
    'uphill': 4,
    'flat': 6, # or downhill on foot
    'downhill': 10,
    'bushwhacking': 2
}

unit_choices = ['metric', 'imperial']
travel_mode_choices = rates.keys()

def munter(distance, elevation, rate='flat', units='metric'):
    if units not in unit_choices:
        raise InvalidUnitsException

    if 'imperial' == units:
        # convert to metric
        distance = (distance * 1.609) # mi to km
        elevation = (elevation * .305) # ft to m

    time = (distance + (elevation / 100.0)) / rates[rate]

    return time

def main():
    parser = argparse.ArgumentParser(description='Munter Time Calculation')

    parser.add_argument('--distance', '-d', type=float, required=True,
        help='Distance (in km, by default)')
    parser.add_argument('--elevation', '-e', type=float, required=True,
        help='Elevation change (in m, by default)')
    parser.add_argument('--travel-mode', '-t', type=str,
        default='uphill', choices=travel_mode_choices, required=False,
        help='Travel mode (flat, by default)')
    parser.add_argument('--units', '-u', type=str, default='metric',
        required=False,
        choices=unit_choices,
        help='Units of input values')
    opts = parser.parse_args()

    distance = opts.distance
    elevation = opts.elevation
    units = opts.units
    travel_mode = opts.travel_mode

    print("Estimated Time (in hours) = %8.2f"
        % munter(distance, elevation, travel_mode, units=units))

if __name__ == "__main__":
    main()