import argparse
import time

def start_simulation(initial_portfolio, target_portfolio, growth_rate, investment_horizon, tolerance):
    # get a target monthly investment
    min_val = 0
    mid_val = 60000
    max_val = 240000

    while (min != max):
        balance = simulate(initial_portfolio, target_portfolio, growth_rate, investment_horizon, mid_val)
        if abs(target_portfolio - balance) < (tolerance * target_portfolio):
            return mid_val
        else:
           if balance < target_portfolio:
               min_val = mid_val
               mid_val = (max_val + min_val) / 2.0
           else:
               max_val = mid_val
               mid_val = (max_val + min_val) / 2.0

def simulate(initial, target, rate, time, contribution):
    portfolio = initial
    for year in xrange(time):
        portfolio += contribution
        portfolio *= rate
    return portfolio

if __name__ == '__main__':
    parser = argparse.ArgumentParser()

    parser.add_argument('-t', help='investment horizon', type=int)
    parser.add_argument('-r', help='growth rate (default=1.07)', type=float, default=1.07)
    parser.add_argument('-i', help='initial portfolio balance', type=int, default=0)
    parser.add_argument('-f', help='final target portfolio balance', type=int)
    parser.add_argument('--tolerance', help='difference between simulation goal and target portfolio balance', type=float, default=0.01)
    args = parser.parse_args()

    vals = [500000, 750000, 1000000, 1250000, 1500000, 1750000, 2000000, 2500000, 3000000]
    timeframes = [10, 15, 20, 25, 30, 35, 40]

    # uncomment these lines, comment the following set of lines to enter your specific info on the command line
    # start the program, calculate what our recurring monthly deposit should be
    # result = execute_test(args.i, args.f, args.r, args.t, args.tolerance)
    # output the recurring monthly deposit
    # print 'To save ${0:,.2f} in {1} years, invest ${2:,.2f} every month'.format(args.f, args.t, result / 12.0)

    # comment the following lines, uncomment the previous lines to enter your specific information instead
    print '-' * 80
    for val in vals:
        for time in timeframes:
            result = start_simulation(args.i, val, args.r, time, args.tolerance)
            print 'To save ${0:,.2f} in {1} years, invest ${2:,.2f} every month'.format(val, time, result / 12.0)
        print '-' * 80