1"""
2Python pseudocode implementation of Solana proof-of-history.
3"""
4
5import hashlib
6
7
8class Poh:
9    def __init__(self, seed=bytes(32)):
10        self.state = bytes(seed)
11
12    def append(self):
13        msg = hashlib.sha256()
14        msg.update(self.state)
15        self.state = msg.digest()
16
17    def mixin(self, mixin):
18        assert len(mixin) == 32
19        msg = hashlib.sha256()
20        msg.update(self.state)
21        msg.update(mixin)
22        self.state = msg.digest()
23
24
25def test():
26    poh = Poh()
27    for _ in range(42):
28        poh.append()
29    poh.mixin(b"WAO.............................")
30    assert (
31        poh.state.hex()
32        == "18a244914fc9d21673ed92fc9edfbc4b00a9d630af352e0d8a4cac5846a344ce"
33    )
34
35
36if __name__ == "__main__":
37    test()
38