#!/usr/bin/env python3

from itertools import combinations, starmap
from math import gcd
from functools import reduce

from lib import vector

def lcm(a, b):
    return (a * b) // gcd(a, b)

def cmp(x, y):
    return (x < y) - (x > y) 

class Moon:
    def __init__(self, pos, vel=None):
        self.pos = vector(pos)
        if vel == None:
            vel = vector([0]*len(self.pos))
        self.vel = vector(vel)

    def restrict(self, i):
        return Moon((self.pos[i],), (self.vel[i],))

    def apply_gravity(self, b):
        self.vel += starmap(cmp, zip(self.pos, b.pos))

    def apply_velocity(self):
        self.pos += self.vel

    def copy(self):
        return Moon(self.pos, self.vel)

    def __len__(self):
        return len(self.pos)

    def energy(self):
        return sum(map(abs, self.pos)) * sum(map(abs, self.vel))

    def __eq__(self, other):
        return self.pos == other.pos and self.vel == other.vel

    def __ne__(self, other):
        return not self == other

    def __repr__(self):
        return "<{}>, <{}>".format(', '.join(map(str, self.pos)),
                                   ', '.join(map(str, self.vel)))


class System(tuple):

    def dimension(self):
        return min(len(m) for m in self)

    def restrict(self, i):
        return System(m.restrict(i) for m in self)

    def energy(self):
        return sum(m.energy() for m in self)

    def __repr__(self):
        return '\n'.join(map(str, self))

    def __next__(self):
        for a, b in combinations(self, 2):
            a.apply_gravity(b)
            b.apply_gravity(a)
        for m in self:
            m.apply_velocity()

    def copy(self):
        return System(m.copy() for m in self)


def simulate(sys, steps):
    sys = sys.copy()
    for i in range(steps):
        next(sys)
    return sys

def find_period(sys):
    if sys.dimension() == 1:
        future = sys.copy()
        next(future)
        step = 1
        while future != sys:
            next(future)
            step += 1
        return step
    return reduce(lcm, (find_period(sys.restrict(i))
                        for i in range(sys.dimension())))

 
def preproc(puzzle_input):
    parse = lambda line : Moon(int(x[2:]) for x in line[1:-1].split(', '))
    return System(map(parse, puzzle_input.split('\n')))

def partI(moons):
    return simulate(moons, 1000).energy()

def partII(moons):
    return int(find_period(moons))