"""runs 的快照收尾：`finish_snapshot` 只新建 finished.json，不改开跑时写的快照，也不收两次尾。"""

import json
from datetime import datetime
from pathlib import Path

import pytest

from cadx.runs import GitState, finish_snapshot, write_snapshot

_GIT = GitState(commit="a" * 40, short_commit="aaaaaaa", clean=True, diff_sha256="b" * 64)


def _snapshot(tmp_path: Path) -> Path:
    lock = tmp_path / "uv.lock"
    lock.write_text("lock", encoding="utf-8")
    config = tmp_path / "x.yaml"
    config.write_text("a: 1\n", encoding="utf-8")
    snapshot_dir = tmp_path / "snapshot"
    started = datetime(2026, 10, 16, 9, 0, 0).astimezone()
    write_snapshot(snapshot_dir, "run-1", _GIT, started, lock, {"x.yaml": config})
    return snapshot_dir


def test_finish_writes_separate_file_and_keeps_snapshot(tmp_path: Path) -> None:
    snapshot_dir = _snapshot(tmp_path)
    before = (snapshot_dir / "snapshot.json").read_bytes()
    finished = datetime(2026, 10, 16, 10, 0, 0).astimezone()
    finish_snapshot(snapshot_dir, finished, {"segment_cache_hits": 3})
    assert (snapshot_dir / "snapshot.json").read_bytes() == before
    record = json.loads((snapshot_dir / "finished.json").read_text(encoding="utf-8"))
    assert record == {"finished_at": finished.isoformat(), "segment_cache_hits": 3}


def test_finish_twice_or_with_finished_at_in_record_raises(tmp_path: Path) -> None:
    snapshot_dir = _snapshot(tmp_path)
    now = datetime(2026, 10, 16, 10, 0, 0).astimezone()
    with pytest.raises(ValueError, match="finished_at"):
        finish_snapshot(snapshot_dir, now, {"finished_at": "x"})
    assert not (snapshot_dir / "finished.json").exists()
    finish_snapshot(snapshot_dir, now, {})
    first = (snapshot_dir / "finished.json").read_bytes()
    with pytest.raises(FileExistsError):
        finish_snapshot(snapshot_dir, now, {"segment_cache_hits": 1})
    assert (snapshot_dir / "finished.json").read_bytes() == first