"""
This file provides a pseudo-random number generator identical to the one used in
Touhou 6: The Embodiment of Scarlet Devil.
It is the only truly reverse-engineered piece of code of this project,
as it is needed in order to retain compatibility with replay files produced by
the offical game code.

It has been reverse engineered from 102h.exe@0x41e780."""


#TODO: maybe some post-processing is missing


from time import time

class Random(object):
    def __init__(self, seed=None):
        if seed is None:
            seed = int(time.time() % 65536)
        self.counter = 0


    def set_seed(self, seed):
        self.seed = seed
        self.counter = 0


    def cycle(self):
        # Named this way because the actual return value may be different.
        # Further reverse engineering might be needed.
        x = ((seed ^ 0x9630) - 0x6553) & 0xffff
        self.seed = (((x & 0x0c000) >> 0xe) + x*4) & 0xffff
        self.counter += 1
        self.counter &= 0xffff
        return self.seed