signal-bot/tests/test_media_strip.py

# Copyright (c) 2026 Krzysztof Rudnicki. MIT licence.
"""The stripper, driven against stub binaries rather than the real exiftool.

Stubs, not mocks of ``subprocess``: the thing worth testing is that the gate
reads the *output back* and refuses on what it finds there, and a stub that
really writes a file and really prints a report exercises that end to end
without needing exiftool installed. ``scripts/e2e.sh`` runs the real one.
"""

from __future__ import annotations

import stat
from typing import TYPE_CHECKING

import pytest

from signal_bot.media_sniff import JPEG, MP4, SVG, WEBM, MediaKind
from signal_bot.media_strip import ExiftoolStripper

if TYPE_CHECKING:
    from pathlib import Path

CLEAN_REPORT = """[ExifTool]      ExifToolVersion                 : 13.55
[File]          FileName                        : out.jpg
[File]          MIMEType                        : image/jpeg
[Composite]     ImageSize                       : 48x48
"""

# A geotag as a phone actually writes it into an mp4: a QuickTime atom, which
# a gate looking only at "GPS" would wave straight through.
LEAKY_REPORT = """[File]          FileName                        : out.mp4
[QuickTime]     MajorBrand                      : MP4 Base Media v1
[QuickTime]     GPSCoordinates                  : 52.2297 21.0122 0
"""

# Lines the parser must simply skip rather than trip over.
NOISY_REPORT = """Warning: something exiftool felt like saying
[File]          FileName                        : out.jpg

======== out.jpg
[Composite]     ImageSize                       : 48x48
"""

STUB = """#!/usr/bin/env python3
import sys
args = sys.argv[1:]
if "-all=" in args:
    {strip}
else:
    sys.stdout.write({report!r})
sys.exit(0)
"""


def _stub(tmp_path: Path, name: str, *, strip: str, report: str = CLEAN_REPORT) -> str:
    """Write an executable stand-in for exiftool and return its path."""
    path = tmp_path / name
    path.write_text(STUB.format(strip=strip, report=report), encoding="utf-8")
    path.chmod(path.stat().st_mode | stat.S_IEXEC)
    return str(path)


COPIES = 'open(args[args.index("-o") + 1], "wb").write(open(args[-1], "rb").read())'
WRITES_NOTHING = "pass"
FAILS = "sys.exit(3)"


def test_a_clean_file_comes_back_stripped(tmp_path: Path) -> None:
    stripper = ExiftoolStripper(_stub(tmp_path, "ok", strip=COPIES))
    assert stripper.strip(b"\xff\xd8\xffdata", JPEG) == b"\xff\xd8\xffdata"


def test_a_tag_that_survived_the_strip_refuses_the_upload(tmp_path: Path) -> None:
    """The whole point: the exit code was 0 and the file is still dirty."""
    stripper = ExiftoolStripper(_stub(tmp_path, "leaky", strip=COPIES, report=LEAKY_REPORT))
    assert stripper.strip(b"\x00\x00\x00\x20ftypmp42", MP4) is None


def test_lines_that_are_not_tags_are_skipped(tmp_path: Path) -> None:
    stripper = ExiftoolStripper(_stub(tmp_path, "noisy", strip=COPIES, report=NOISY_REPORT))
    assert stripper.strip(b"\xff\xd8\xffdata", JPEG) == b"\xff\xd8\xffdata"


def test_a_strip_that_exits_nonzero_stores_nothing(tmp_path: Path) -> None:
    stripper = ExiftoolStripper(_stub(tmp_path, "fails", strip=FAILS))
    assert stripper.strip(b"\xff\xd8\xffdata", JPEG) is None


def test_a_strip_that_writes_no_output_stores_nothing(tmp_path: Path) -> None:
    """Exit 0 and no file is exactly the shape of the ffmpeg regression."""
    stripper = ExiftoolStripper(_stub(tmp_path, "silent", strip=WRITES_NOTHING))
    assert stripper.strip(b"\xff\xd8\xffdata", JPEG) is None


def test_a_report_that_fails_to_run_stores_nothing(tmp_path: Path) -> None:
    path = tmp_path / "half"
    path.write_text(
        "#!/usr/bin/env python3\n"
        "import sys\n"
        "args = sys.argv[1:]\n"
        'if "-all=" in args:\n'
        '    open(args[args.index("-o") + 1], "wb").write(open(args[-1], "rb").read())\n'
        "    sys.exit(0)\n"
        "sys.exit(4)\n",
        encoding="utf-8",
    )
    path.chmod(path.stat().st_mode | stat.S_IEXEC)
    assert ExiftoolStripper(str(path)).strip(b"\xff\xd8\xffdata", JPEG) is None


def test_a_missing_binary_refuses_rather_than_raising(tmp_path: Path) -> None:
    stripper = ExiftoolStripper(str(tmp_path / "not-here"))
    assert stripper.strip(b"\xff\xd8\xffdata", JPEG) is None


def test_no_exiftool_at_all_refuses_the_upload(monkeypatch: pytest.MonkeyPatch) -> None:
    """Never stores it dirty instead: a strip that cannot run is a refusal."""
    monkeypatch.setattr("signal_bot.media_strip.shutil.which", lambda _: None)
    assert ExiftoolStripper().strip(b"\xff\xd8\xffdata", JPEG) is None


@pytest.mark.parametrize("kind", [SVG, WEBM])
def test_the_two_unwritable_formats_are_stored_as_they_arrived(
    tmp_path: Path, kind: MediaKind
) -> None:
    """kuhy's decision of 2026-08-31, and it must not need exiftool at all."""
    stripper = ExiftoolStripper(str(tmp_path / "never-invoked"))
    payload = b"<svg><metadata>a name</metadata></svg>"
    assert stripper.strip(payload, kind) == payload