#!/usr/bin/env python
"""
Calculates return on investment over time.

Usage:
    calc_roi [options]

Options:
    -h, --help                    This message
    -u, --unit-cost <uc>          Cost per panel (USD) [Default: 750]
    -i, --initial <ic>            Initial investment cost (USD) [Default: 9000]
    -i, --units <units>           Initial units purchased [Default: 15]
    -d, --degradation <deg>       Efficiency degradation per year % [Default: 0.007]
    -y, --years <years>           Years to calculate [Default: 25]
    -r, --return <return>         Annual return per unit (USD) [Default: 90]
    -p, --purchase                Purchase new units with profit [Default: True]
    -s, --sunset <year>           When to sunset a panel [Default: 100]
    -m, --margin <margin>         Percentage of revenue kept [Default: 80%]
    -c, --cease <year>            Year to cease purchasing new units [Default: 100]
"""


class Panel(object):

    """
    Solar Panel used for calculating roi per unit
    """

    @property
    def break_even(self):
        """ Year when this panel will break even """
        investment_return = 0
        for year in xrange(100):
            coeff = 1.0 - (self.degradation)
            margin = self.profit_margin
            revenue = self.annual_revenue
            investment_return += coeff * revenue * margin
            if investment_return >= self.investment:
                return year

    @property
    def age(self):
        """ age of panel """
        return self.start + self.year

    @property
    def roi(self):
        """ return on investment (%) """
        return self.investment / self.generated_revenue

    @property
    def degraded_revenue(self):
        """ degradation of panel in revenue """
        value = 0
        if self.age < self.sunset:
            coefficient = (1.0 - self.degradation * self.age)
            value = coefficient * self.annual_revenue * self.profit_margin
        return value

    def __init__(self, cost=750, year=0, revenue=2250 / 25, degradation=0.007, margin=0.8, sunset=100):
        """ Creates a unit which can be updated """
        self.investment = cost
        self.start = year
        self.year = 0
        self.profit_margin = 0.8
        self.degradation = degradation
        self.annual_revenue = revenue
        self.generated_revenue = 0
        self.sunset = sunset

    def update(self):
        """ Increments unit for this year """
        self.generated_revenue += self.degraded_revenue
        self.year += 1

    def __repr__(self):
        """ Panel at any point in time """
        args = {
            "years": self.years,
            "capital": self.investment,
            "return": self.generated_revenue,
            "roi": self.roi,
        }
        string = "<Panel age:{years}, capital:{investment}, "\
                 "return:{revenue}, roi:{roi}>"
        return string.format(args)


def calculate(args):
    unit_cost = args.get("--unit-cost")
    initial_cost = args.get("--initial")
    units_purchased = args.get("--units")
    degradation = args.get("--degradation")
    years = args.get("--years")
    annual_return = args.get("--return")
    purchase_new_units = args.get("--purchase", False)
    sunset = args.get("--sunset")
    margin = args.get("--margin")
    cease = args.get("--cease")

    cpu = initial_cost / units_purchased
    units = [Panel(cost=cpu,
                   revenue=annual_return,
                   degradation=degradation,
                   margin=margin,
                   sunset=sunset)
             for unit in xrange(units_purchased)]
    titles = ["year", "units", "monthly", "roi", "investment", "return"]
    print "{0:>4}: {1:>10} | {2:>16} | {3:<15} | ({4:>19}/{5:>19})".format(*titles)
    cumulative = 0
    for year in xrange(years):
        profit = sum(u.degraded_revenue for u in units)
        cumulative += profit
        if purchase_new_units and year < cease:
            while cumulative > unit_cost:
                panel = Panel(cost=unit_cost,
                              year=year,
                              revenue=annual_return,
                              degradation=degradation,
                              margin=margin,
                              sunset=sunset)
                units.append(panel)
                cumulative = cumulative - unit_cost
        data = {
            "units": sum(1 for u in units),
            "year": year,
            "cost": sum(u.investment for u in units),
            "profit": sum(u.generated_revenue for u in units),
            "monthly": sum(u.degraded_revenue/12.0 for u in units),
        }
        data["roi"] = data["profit"] / data["cost"]
        print("{year:>4}: {units:>10} | ${monthly:>15,} | {roi:<15} | (${cost:>18,}/${profit:>18,})".format(**data))
        for unit in units:
            unit.update()


if __name__ == "__main__":
    import docopt

    args = docopt.docopt(__doc__)
    for k, v in args.iteritems():
        try:
            if "." not in v:
                v = int(v)
                args[k] = v
            else:
                v = float(v)
                args[k] = v
        except:
            pass

    calculate(args)