"""Pluggable PRNG predictors for arena-battle token forensics.

The server computes: auth_token = "token_" + id + "_" + std::to_string(rand())
with NO srand() call => default-seeded PRNG, one draw per fighter, in id order.

Two predictors:
  GlibcRandom  - glibc TYPE_3 additive-feedback random() (Ubuntu 22.04 target)
  DarwinRandom - macOS/BSD rand() (Schrage multiplicative LCG) for local tests
"""

import sys

MASK32 = 0xFFFFFFFF


class GlibcRandom:
    """glibc random()/rand() TYPE_3: r[i] = (r[i-3] + r[i-31]) mod 2^32, out = r[i]>>1."""

    name = "glibc"

    def __init__(self, seed=1, n=200000):
        r = [0] * (344 + n)
        r[0] = seed & MASK32
        for i in range(1, 31):
            # r[i] = 16807 * r[i-1] mod 2147483647 (Schrage), result in [0, 2^31-2]
            hi, lo = divmod(r[i - 1], 127773)
            word = 16807 * lo - 2836 * hi
            if word < 0:
                word += 2147483647
            r[i] = word
        for i in range(31, 34):
            r[i] = r[i - 31]
        for i in range(34, 344 + n):
            r[i] = (r[i - 3] + r[i - 31]) & MASK32
        self.values = [x >> 1 for x in r[344:]]

    def index_of(self, value):
        return [i for i, v in enumerate(self.values) if v == value]


class DarwinRandom:
    """macOS rand(): Lehmer LCG next = 16807*next mod (2^31-1), out = next (seed 1)."""

    name = "darwin"

    def __init__(self, seed=1, n=200000):
        ctx = seed
        vals = []
        for _ in range(n):
            ctx = (16807 * ctx) % 2147483647
            vals.append(ctx)
        self.values = vals

    def index_of(self, value):
        return [i for i, v in enumerate(self.values) if v == value]


def get_predictor(name, n=200000):
    cls = {"glibc": GlibcRandom, "darwin": DarwinRandom}[name]
    return cls(1, n)


if __name__ == "__main__":
    g = get_predictor("glibc", 10)
    d = get_predictor("darwin", 10)
    print("glibc :", g.values[:5])
    print("darwin:", d.values[:5])
    assert g.values[:5] == [1804289383, 846930886, 1681692777, 1714636915, 1957747793], "glibc seq wrong"
    assert d.values[:5] == [16807, 282475249, 1622650073, 984943658, 1144108930], "darwin seq wrong"
    print("PREDICTORS OK", flush=True)