import pygame
from pymunk.vec2d import Vec2d


def convert_colour(colour):
    if isinstance(colour, pygame.Color):
        return colour
    if isinstance(colour, tuple):
        return pygame.Color(*colour)
    if isinstance(colour, basestring):
        return pygame.Color(colour)
    raise ValueError()


def vec_from_angle(angle, length=1):
    vec = Vec2d(length, 0)
    vec.angle = angle
    return vec


def vec_with_length(coords, length=1):
    vec = Vec2d(coords)
    # Don't crash if we're created a zero length vector
    if vec.length != 0:
        vec.length = length
    return vec