mimic-big/backend/tests/unit/test_storage_blob.py

"""Content-addressed gzip blob store (D-012, MA2 streaming)."""

from __future__ import annotations

import gzip
import hashlib
import io

import pytest

from mimic.storage.blob import BlobTooLarge, blob_path, store_blob


def _stream(data: bytes) -> io.BytesIO:
    return io.BytesIO(data)


def test_blob_path_uses_two_byte_pairs(tmp_path) -> None:
    digest = "ab" + "cd" + "ef" * 30
    path = blob_path(tmp_path, digest)
    assert path == tmp_path / "ab" / "cd" / f"{digest}.gz"


def test_blob_path_rejects_invalid_digest(tmp_path) -> None:
    with pytest.raises(ValueError, match="invalid sha256"):
        blob_path(tmp_path, "not-a-digest")


def test_store_blob_writes_gzip_and_returns_digest(tmp_path) -> None:
    payload = b"hello world\n"
    expected = hashlib.sha256(payload).hexdigest()
    digest, path = store_blob(tmp_path, _stream(payload))
    assert digest == expected
    assert path == tmp_path / expected[0:2] / expected[2:4] / f"{expected}.gz"
    with gzip.open(path, "rb") as fh:
        assert fh.read() == payload


def test_store_blob_is_idempotent(tmp_path) -> None:
    payload = b"same content"
    digest1, path1 = store_blob(tmp_path, _stream(payload))
    mtime_before = path1.stat().st_mtime_ns
    digest2, path2 = store_blob(tmp_path, _stream(payload))
    assert digest1 == digest2
    assert path1 == path2
    assert path2.stat().st_mtime_ns == mtime_before


def test_store_blob_dedupes_distinct_payloads(tmp_path) -> None:
    _, p1 = store_blob(tmp_path, _stream(b"alpha"))
    _, p2 = store_blob(tmp_path, _stream(b"beta"))
    assert p1 != p2
    assert p1.exists()
    assert p2.exists()


def test_store_blob_raises_when_stream_exceeds_cap(tmp_path) -> None:
    too_big = b"A" * (1024 + 1)
    with pytest.raises(BlobTooLarge):
        store_blob(tmp_path, _stream(too_big), max_bytes=1024)
    # No tmp file left behind.
    leftovers = [p for p in tmp_path.iterdir() if p.name.startswith(".tmp-")]
    assert leftovers == []


def test_store_blob_handles_large_stream_in_chunks(tmp_path) -> None:
    # 1.5 MB payload — exercises the multi-chunk path (chunks are 64 KB).
    payload = (b"X" * 64 * 1024) * 24
    digest, path = store_blob(tmp_path, _stream(payload), max_bytes=2 * 1024 * 1024)
    assert digest == hashlib.sha256(payload).hexdigest()
    with gzip.open(path, "rb") as fh:
        assert fh.read() == payload


def test_store_blob_rejects_zero_or_negative_max(tmp_path) -> None:
    with pytest.raises(ValueError, match="max_bytes"):
        store_blob(tmp_path, _stream(b"x"), max_bytes=0)