prediction.py

"""
Predicting the collision of two cubes.
"""


def find_terms(a, b, c):
    if not a:
        return [(None, None)] if abs(b) <= c else None
    down, up = sorted(((c - b) / a, (-c - b) / a))
    if abs(a * (down - 1) + b) <= c:
        return [(None, down), (up, None)]
    return [(down, up)]


def predict(V1, P1, V2, P2, D):
    dVx = V1[0] - V2[0]
    dVy = V1[1] - V2[1]
    dPx = P1[0] - P2[0]
    dPy = P1[1] - P2[1]
    terms = []
    for dV, dP in [(dVx, dPx), (dVy, dPy)]:
        _terms = find_terms(dV, dP, D)
        if _terms is None:
            return
        terms.extend(_terms)

    down, up = None, None
    for td, tu in terms:
        if td > down:
            down = td
        if up is None or tu is not None and tu < up:
            up = tu

    if down <= up:
        return down, up


print predict((0, 0), (0, 0), (-1, 0), (10, 0), 1)