from __future__ import annotations

import importlib.util
import os
import sys
from pathlib import Path

import pytest


ROOT = Path(__file__).resolve().parents[2]
SCRIPT = ROOT / "scripts" / "release_backup_snapshot.py"


def load_snapshot_module():
    spec = importlib.util.spec_from_file_location("release_backup_snapshot_test", SCRIPT)
    assert spec is not None and spec.loader is not None
    module = importlib.util.module_from_spec(spec)
    sys.modules[spec.name] = module
    spec.loader.exec_module(module)
    return module


def test_snapshot_is_byte_complete_and_reuses_only_verified_backup_bytes(tmp_path: Path) -> None:
    snapshot = load_snapshot_module()
    source = tmp_path / "source"
    source.mkdir()
    (source / "same.bin").write_bytes(b"unchanged")
    (source / "changed.bin").write_bytes(b"before")
    (source / "empty").mkdir()

    prior = tmp_path / "prior"
    prior_manifest = tmp_path / "prior.tsv"
    snapshot.create_snapshot(source, prior, prior_manifest, label="storage")
    snapshot.verify_snapshot(prior, prior_manifest)

    (source / "changed.bin").write_bytes(b"after")
    current = tmp_path / "current"
    current_manifest = tmp_path / "current.tsv"
    snapshot.create_snapshot(
        source,
        current,
        current_manifest,
        label="storage",
        link_dest_snapshot=prior,
        link_dest_manifest=prior_manifest,
    )
    snapshot.verify_snapshot(current, current_manifest)

    assert os.path.samefile(prior / "same.bin", current / "same.bin")
    assert not os.path.samefile(prior / "changed.bin", current / "changed.bin")
    assert (current / "changed.bin").read_bytes() == b"after"
    assert (current / "empty").is_dir()


def test_snapshot_rejects_symlinked_content(tmp_path: Path) -> None:
    snapshot = load_snapshot_module()
    source = tmp_path / "source"
    source.mkdir()
    target = source / "target.bin"
    target.write_bytes(b"target")
    try:
        (source / "link.bin").symlink_to(target)
    except OSError:
        pytest.skip("Symlink creation is unavailable on this host")

    with pytest.raises(RuntimeError, match="refuses symlinked content"):
        snapshot.create_snapshot(source, tmp_path / "snapshot", tmp_path / "manifest.tsv", label="storage")


def test_snapshot_verification_rejects_changed_retained_bytes(tmp_path: Path) -> None:
    snapshot = load_snapshot_module()
    source = tmp_path / "source"
    source.mkdir()
    (source / "artifact.bin").write_bytes(b"retained")
    retained = tmp_path / "snapshot"
    manifest = tmp_path / "manifest.tsv"
    snapshot.create_snapshot(source, retained, manifest, label="storage")
    (retained / "artifact.bin").chmod(0o644)
    (retained / "artifact.bin").write_bytes(b"tampered")

    with pytest.raises(RuntimeError, match="checksum differs"):
        snapshot.verify_snapshot(retained, manifest)