"""Local filesystem backend tests (ARTIFACT-STORE-WP-0001-T003)."""

from __future__ import annotations

from collections.abc import AsyncIterator
from pathlib import Path

import pytest

from artifactstore.identity import ContentAddress, digest_bytes
from artifactstore.storage import (
    LocalBackend,
    ObjectNotFoundError,
    clear_backends,
    get_backend,
    list_backends,
    register_backend,
)


async def _stream(data: bytes, chunk_size: int = 16) -> AsyncIterator[bytes]:
    for i in range(0, len(data), chunk_size):
        yield data[i : i + chunk_size]


def _ca_of(data: bytes) -> ContentAddress:
    return digest_bytes(data).primary.content_address


@pytest.fixture
def backend(tmp_path: Path) -> LocalBackend:
    return LocalBackend(tmp_path / "storage", backend_id="local")


async def _consume(it: AsyncIterator[bytes]) -> bytes:
    out = bytearray()
    async for chunk in it:
        out.extend(chunk)
    return bytes(out)


async def test_put_then_get_round_trips(backend: LocalBackend) -> None:
    data = b"hello world" * 100
    ca = _ca_of(data)

    receipt = await backend.put(ca, _stream(data))
    assert receipt.backend_id == "local"
    assert receipt.content_address == ca
    assert receipt.size_bytes == len(data)

    stream = await backend.get(ca)
    assert await _consume(stream) == data


async def test_object_key_layout_matches_blueprint(backend: LocalBackend) -> None:
    data = b"layout-check"
    ca = _ca_of(data)
    receipt = await backend.put(ca, _stream(data))
    digest = ca.to_digest()
    expected = f"{digest.algorithm}/{digest.hex[:2]}/{digest.hex[2:4]}/{digest.hex}"
    assert receipt.object_key == expected
    assert (backend.root / expected).is_file()


async def test_head_returns_metadata(backend: LocalBackend) -> None:
    data = b"abcde"
    ca = _ca_of(data)
    await backend.put(ca, _stream(data))
    meta = await backend.head(ca)
    assert meta.size_bytes == len(data)
    assert meta.content_address == ca
    assert meta.backend_id == "local"


async def test_head_missing_raises_object_not_found(backend: LocalBackend) -> None:
    ca = _ca_of(b"never-stored")
    with pytest.raises(ObjectNotFoundError):
        await backend.head(ca)


async def test_get_missing_raises_object_not_found(backend: LocalBackend) -> None:
    ca = _ca_of(b"never-stored")
    with pytest.raises(ObjectNotFoundError):
        await backend.get(ca)


async def test_put_is_idempotent(backend: LocalBackend) -> None:
    data = b"idempotent"
    ca = _ca_of(data)
    r1 = await backend.put(ca, _stream(data))
    r2 = await backend.put(ca, _stream(data))
    assert r1.size_bytes == r2.size_bytes == len(data)
    assert r1.content_address == r2.content_address


async def test_delete_returns_true_then_false(backend: LocalBackend) -> None:
    data = b"to-delete"
    ca = _ca_of(data)
    await backend.put(ca, _stream(data))

    first = await backend.delete(ca)
    assert first.deleted is True
    assert first.content_address == ca

    second = await backend.delete(ca)
    assert second.deleted is False


async def test_range_read_returns_subrange(backend: LocalBackend) -> None:
    data = bytes(range(100))  # 100 bytes 0..99
    ca = _ca_of(data)
    await backend.put(ca, _stream(data))

    stream = await backend.get(ca, byte_range=(10, 19))
    chunk = await _consume(stream)
    assert chunk == data[10:20]
    assert len(chunk) == 10


async def test_range_read_rejects_invalid_range(backend: LocalBackend) -> None:
    data = b"range-check"
    ca = _ca_of(data)
    await backend.put(ca, _stream(data))
    stream = await backend.get(ca, byte_range=(20, 5))
    with pytest.raises(ValueError):
        await _consume(stream)


async def test_health_reports_disk_usage(backend: LocalBackend) -> None:
    status = await backend.health()
    assert status.healthy is True
    assert status.free_bytes is not None
    assert status.total_bytes is not None
    assert status.free_bytes >= 0
    assert status.backend_id == "local"


async def test_health_reports_unhealthy_if_root_missing(tmp_path: Path) -> None:
    root = tmp_path / "vanished"
    backend = LocalBackend(root)
    # Remove the root directory after construction.
    root.rmdir()
    status = await backend.health()
    assert status.healthy is False
    assert "root" in status.detail


async def test_content_address_validation_blocks_path_traversal() -> None:
    # The ContentAddress constructor rejects malformed inputs before they
    # ever reach the backend.
    with pytest.raises(ValueError):
        ContentAddress("sha256:../etc/passwd")
    with pytest.raises(ValueError):
        ContentAddress("../sha256:deadbeef")


async def test_registry_register_get_list_clear(backend: LocalBackend) -> None:
    clear_backends()
    assert list_backends() == []

    register_backend(backend)
    assert list_backends() == ["local"]
    assert get_backend("local") is backend

    with pytest.raises(KeyError):
        get_backend("nope")

    clear_backends()
    assert list_backends() == []


async def test_idempotent_put_does_not_corrupt_existing(backend: LocalBackend) -> None:
    data = b"original-bytes"
    ca = _ca_of(data)
    await backend.put(ca, _stream(data))

    # A re-put with the same content address yields the same bytes back.
    await backend.put(ca, _stream(data))
    stream = await backend.get(ca)
    assert await _consume(stream) == data