"""Fortuna-based cryptographically secure PRNG.

Wraps Python's secrets/os.urandom with a Fortuna-style interface
matching Java's FortunaRandomSource API.

Ported from net.i2p.util.FortunaRandomSource.
"""

from __future__ import annotations

import hashlib
import os
import struct


class FortunaRandomSource:
    """Fortuna-inspired CSPRNG.

    Uses os.urandom as the entropy source with optional seed mixing.
    """

    def __init__(self, seed: bytes | None = None) -> None:
        self._state = os.urandom(32)
        if seed is not None:
            self._state = hashlib.sha256(self._state + seed).digest()

    def _generate(self, n: int) -> bytes:
        """Generate n bytes of random data."""
        result = bytearray()
        while len(result) < n:
            self._state = hashlib.sha256(
                self._state + os.urandom(32)
            ).digest()
            result.extend(self._state)
        return bytes(result[:n])

    def next_bytes(self, count: int) -> bytes:
        """Generate count random bytes."""
        return self._generate(count)

    def next_int(self, bound: int) -> int:
        """Generate a random int in [0, bound)."""
        raw = struct.unpack(">I", self._generate(4))[0]
        return raw % bound

    def next_boolean(self) -> bool:
        """Generate a random boolean."""
        return self._generate(1)[0] & 1 == 1