#!/usr/bin/env python3

from numbers import Number
from typing import Callable

import constants


class Converter(object):
    def __init__(self,
                 name: str,
                 category: str,
                 to_canonical: Callable,
                 from_canonical: Callable,
                 unit: str) -> None:
        self.name = name
        self.category = category
        self.to_canonical = to_canonical
        self.from_canonical = from_canonical
        self.unit = unit

    def to_canonical(self, n: Number) -> Number:
        return self.to_canonical(n)

    def from_canonical(self, n: Number) -> Number:
        return self.from_canonical(n)

    def unit_suffix(self) -> str:
        return self.unit


conversion_catalog = {
    "Second": Converter("Second",
                        "time",
                        lambda s: s,
                        lambda s: s,
                        "s"),
    "Minute": Converter("Minute",
                        "time",
                        lambda m: (m * constants.SECONDS_PER_MINUTE),
                        lambda s: (s / constants.SECONDS_PER_MINUTE),
                        "m"),
    "Hour": Converter("Hour",
                      "time",
                      lambda h: (h * constants.SECONDS_PER_HOUR),
                      lambda s: (s / constants.SECONDS_PER_HOUR),
                      "h"),
    "Day": Converter("Day",
                     "time",
                     lambda d: (d * constants.SECONDS_PER_DAY),
                     lambda s: (s / constants.SECONDS_PER_DAY),
                     "d"),
    "Week": Converter("Week",
                      "time",
                      lambda w: (w * constants.SECONDS_PER_WEEK),
                      lambda s: (s / constants.SECONDS_PER_WEEK),
                      "w"),
    "Fahrenheit": Converter("Fahrenheit",
                            "temperature",
                            lambda f: (f - 32.0) * 0.55555555,
                            lambda c: c * 1.8 + 32.0,
                            "°F"),
    "Celsius": Converter("Celsius",
                         "temperature",
                         lambda c: c,
                         lambda c: c,
                         "°C"),
    "Kelvin": Converter("Kelvin",
                        "temperature",
                        lambda k: k - 273.15,
                        lambda c: c + 273.15,
                        "°K"),
}


def convert(magnitude: Number,
            from_thing: str,
            to_thing: str) -> Number:
    src = conversion_catalog.get(from_thing, None)
    dst = conversion_catalog.get(to_thing, None)
    if src is None or dst is None:
        raise ValueError("No known conversion")
    if src.category != dst.category:
        raise ValueError("Incompatible conversion")
    return _convert(magnitude, src, dst)


def _convert(magnitude: Number,
             from_unit: Converter,
             to_unit: Converter) -> Number:
    canonical = from_unit.to_canonical(magnitude)
    converted = to_unit.from_canonical(canonical)
    return converted


def sec_to_min(s: float) -> float:
    return convert(s, "Second", "Minute")


def sec_to_hour(s: float) -> float:
    return convert(s, "Second", "Hour")


def sec_to_day(s: float) -> float:
    return convert(s, "Second", "Day")


def sec_to_week(s: float) -> float:
    return convert(s, "Second", "Week")


def min_to_sec(m: float) -> float:
    return convert(m, "Minute", "Second")


def min_to_hour(m: float) -> float:
    return convert(m, "Minute", "Hour")


def min_to_day(m: float) -> float:
    return convert(m, "Minute", "Day")


def min_to_week(m: float) -> float:
    return convert(m, "Minute", "Week")


def hour_to_sec(h: float) -> float:
    return convert(h, "Hour", "Second")


def hour_to_min(h: float) -> float:
    return convert(h, "Hour", "Minute")


def hour_to_day(h: float) -> float:
    return convert(h, "Hour", "Day")


def hour_to_week(h: float) -> float:
    return convert(h, "Hour", "Week")


def day_to_sec(d: float) -> float:
    return convert(d, "Day", "Second")


def day_to_min(d: float) -> float:
    return convert(d, "Day", "Minute")


def day_to_hour(d: float) -> float:
    return convert(d, "Day", "Hour")


def day_to_week(d: float) -> float:
    return convert(d, "Day", "Week")


def week_to_sec(w: float) -> float:
    return convert(w, "Week", "Second")


def week_to_min(w: float) -> float:
    return convert(w, "Week", "Minute")


def week_to_hour(w: float) -> float:
    return convert(w, "Week", "Hour")


def week_to_day(w: float) -> float:
    return convert(w, "Week", "Day")


def f_to_c(temp_f: float) -> float:
    """Fahrenheit to Celsius."""
    return convert(temp_f, "Fahrenheit", "Celsius")


def c_to_f(temp_c: float) -> float:
    """Celsius to Fahrenheit."""
    return convert(temp_c, "Celsius", "Fahrenheit")