"""Deterministic fixture helpers.

Fixture bytes are identity: the same (prefix, seed, size) always produces the

same content, and changing any of them is a fixture_version bump (ADR-0005).

"""

from __future__ import annotations

import shutil

from pathlib import Path

def write_pattern_file(path: Path, size: int, seed: str, binary: bool, prefix: str = "oakbench") -> None:

    path.parent.mkdir(parents=True, exist_ok=True)

    if binary:

        unit = (f"{prefix}:{seed}:".encode("utf-8") * 4096)[: 64 * 1024]

    else:

        line = f"{prefix} {seed} " + ("x" * 72) + "\n"

        unit = line.encode("utf-8") * max(1, (64 * 1024 // len(line)))

    remaining = size

    with path.open("wb") as fh:

        while remaining > 0:

            chunk = unit[: min(len(unit), remaining)]

            fh.write(chunk)

            remaining -= len(chunk)

def copy_fixture(src: Path, dest: Path, ignore_marker: bool = False) -> None:

    if dest.exists():

        shutil.rmtree(dest)

    ignore = shutil.ignore_patterns(".fixture-ready") if ignore_marker else None

    shutil.copytree(src, dest, ignore=ignore)