#!/usr/bin/env python3
"""Fixture и побайтная проверка транзакционного overwrite P19."""

from __future__ import annotations

import pathlib
import sys


def payload(seed: int, size: int) -> bytes:
    return bytes(((index * 29 + seed) & 0xFF) for index in range(size))


SOURCES = {
    "NORMAL.BIN": payload(11, 4097),
    "READONLY.BIN": payload(23, 8193),
    "ABSENT.BIN": payload(37, 17),
    "COLLIDE.BIN": payload(51, 4096),
    "ROLLBACK.BIN": payload(67, 4096),
}
OLD = {
    "NORMAL.BIN": b"old-normal-target",
    "READONLY.BIN": b"old-readonly-target",
    "COLLIDE.BIN": b"old-collision-target",
    "ROLLBACK.BIN": b"old-rollback-must-survive",
}
COLLISION = b"pre-existing backup name must survive"


def create(root: pathlib.Path) -> None:
    source = root / "SOURCE"
    target = root / "TARGET"
    source.mkdir(parents=True)
    target.mkdir(parents=True)
    for name, data in SOURCES.items():
        (source / name).write_bytes(data)
    for name, data in OLD.items():
        (target / name).write_bytes(data)
    (target / "~SB0000.BAK").write_bytes(COLLISION)


def verify(root: pathlib.Path) -> None:
    target = root / "TARGET"
    expected = {
        "NORMAL.BIN": SOURCES["NORMAL.BIN"],
        "READONLY.BIN": SOURCES["READONLY.BIN"],
        "COLLIDE.BIN": SOURCES["COLLIDE.BIN"],
        "ABSENT.BIN": SOURCES["ABSENT.BIN"],
        "RENAMED.BIN": SOURCES["ABSENT.BIN"],
        "ROLLBACK.BIN": OLD["ROLLBACK.BIN"],
        "~SB0000.BAK": COLLISION,
    }
    failures: list[str] = []
    for name, data in expected.items():
        path = target / name
        if not path.is_file() or path.read_bytes() != data:
            failures.append(f"неверный target {name}")
    unexpected = sorted(
        path.name for path in target.glob("~SB*.BAK")
        if path.name.upper() != "~SB0000.BAK"
    )
    if unexpected:
        failures.append(f"оставлены служебные backup: {unexpected!r}")
    result = root / "RESULT.TXT"
    text = result.read_text("ascii", errors="replace") if result.exists() else ""
    if "ALL PASS" not in text:
        failures.append("target-probe не записал ALL PASS")
    if failures:
        for failure in failures:
            print(f"FAIL: {failure}")
        raise SystemExit(1)
    print("PASS: transactional overwrite, readonly, collision and rollback.")


def main() -> None:
    if len(sys.argv) != 3 or sys.argv[1] not in {"create", "verify"}:
        raise SystemExit(f"usage: {sys.argv[0]} create|verify PATH")
    root = pathlib.Path(sys.argv[2])
    if sys.argv[1] == "create":
        create(root)
    else:
        verify(root)


if __name__ == "__main__":
    main()