"""Lazy download and SHA256 pinning, exercised with local file:// URLs."""

from __future__ import annotations

import hashlib
from pathlib import Path

import pytest

from app.errors import Unsupported
from app.models import Backend, BackendSpec, ModelFile, Registry

from .conftest import make_settings


def _backend(source: Path, sha256: str, size: int, loads: list[dict[str, str]]) -> Backend:
    spec = BackendSpec(
        id="test-model",
        model="test-model",
        license="MIT",
        commercialUse=True,
        experimental=False,
        source=None,
        files=(ModelFile("weights.bin", source.as_uri(), sha256, size),),
    )
    return Backend(spec, lambda files, _settings: loads.append(files) or "runtime")


def test_downloads_once_and_verifies(media_root: Path, tmp_path: Path) -> None:
    source = tmp_path / "upstream.bin"
    source.write_bytes(b"weights" * 100)
    digest = hashlib.sha256(source.read_bytes()).hexdigest()
    loads: list[dict[str, str]] = []
    settings = make_settings(media_root, tmp_path, allow_model_download=True)
    registry = Registry(settings, backends={"embedFrames": _backend(source, digest, 700, loads)})
    assert registry.runtime("embedFrames") == "runtime"
    assert registry.runtime("embedFrames") == "runtime"
    assert len(loads) == 1
    cached = Path(loads[0]["weights.bin"])
    assert cached == tmp_path / "models" / "test-model" / "weights.bin"
    assert cached.read_bytes() == source.read_bytes()


def test_hash_mismatch_deletes_file_and_reports_unsupported(media_root: Path, tmp_path: Path) -> None:
    source = tmp_path / "tampered.bin"
    source.write_bytes(b"tampered")
    settings = make_settings(media_root, tmp_path, allow_model_download=True)
    backend = _backend(source, "0" * 64, 8, [])
    registry = Registry(settings, backends={"embedFrames": backend})
    with pytest.raises(Unsupported) as error:
        registry.runtime("embedFrames")
    assert "SHA256" in error.value.message
    assert not (tmp_path / "models" / "test-model" / "weights.bin").exists()
    assert registry.unavailable_reason(backend, "embedFrames") == error.value.message


def test_oversized_download_is_aborted(media_root: Path, tmp_path: Path) -> None:
    source = tmp_path / "big.bin"
    source.write_bytes(b"x" * 5000)
    settings = make_settings(media_root, tmp_path, allow_model_download=True)
    registry = Registry(settings, backends={"embedFrames": _backend(source, "0" * 64, 10, [])})
    with pytest.raises(Unsupported):
        registry.runtime("embedFrames")
    assert not list((tmp_path / "models" / "test-model").iterdir())


def test_offline_without_weights_is_unsupported(media_root: Path, tmp_path: Path) -> None:
    source = tmp_path / "w.bin"
    source.write_bytes(b"w")
    registry = Registry(
        make_settings(media_root, tmp_path), backends={"embedFrames": _backend(source, "0" * 64, 1, [])}
    )
    with pytest.raises(Unsupported) as error:
        registry.runtime("embedFrames")
    assert "MEDIA_MODEL_DOWNLOAD=0" in error.value.message