"""S3-compatible backend tests (ARTIFACT-STORE-WP-0004)."""

from __future__ import annotations

from collections.abc import AsyncIterator
from typing import Any

import pytest

from artifactstore.identity import ContentAddress, digest_bytes
from artifactstore.storage import ObjectNotFoundError, S3Backend, S3BackendConfig


async def _stream(data: bytes, chunk_size: int = 4) -> AsyncIterator[bytes]:
    for i in range(0, len(data), chunk_size):
        yield data[i : i + chunk_size]


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


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


class FakeNotFoundError(Exception):
    def __init__(self) -> None:
        super().__init__("not found")
        self.response = {"Error": {"Code": "NoSuchKey"}}


class FakeBody:
    def __init__(self, data: bytes) -> None:
        self._data = data
        self._offset = 0

    async def read(self, size: int) -> bytes:
        if self._offset >= len(self._data):
            return b""
        chunk = self._data[self._offset : self._offset + size]
        self._offset += len(chunk)
        return chunk


class FakeS3Client:
    def __init__(self) -> None:
        self.objects: dict[str, bytes] = {}
        self.calls: list[tuple[str, dict[str, Any]]] = []
        self.uploads: dict[str, list[tuple[int, bytes]]] = {}

    async def __aenter__(self) -> FakeS3Client:
        return self

    async def __aexit__(self, *_exc: object) -> None:
        return None

    async def put_object(self, **kwargs: Any) -> None:
        self.calls.append(("put_object", kwargs))
        self.objects[kwargs["Key"]] = kwargs["Body"]

    async def create_multipart_upload(self, **kwargs: Any) -> dict[str, str]:
        self.calls.append(("create_multipart_upload", kwargs))
        upload_id = f"upload-{len(self.uploads) + 1}"
        self.uploads[upload_id] = []
        return {"UploadId": upload_id}

    async def upload_part(self, **kwargs: Any) -> dict[str, str]:
        self.calls.append(("upload_part", kwargs))
        self.uploads[kwargs["UploadId"]].append((kwargs["PartNumber"], kwargs["Body"]))
        return {"ETag": f"etag-{kwargs['PartNumber']}"}

    async def complete_multipart_upload(self, **kwargs: Any) -> None:
        self.calls.append(("complete_multipart_upload", kwargs))
        parts = self.uploads[kwargs["UploadId"]]
        self.objects[kwargs["Key"]] = b"".join(part for _num, part in sorted(parts))

    async def abort_multipart_upload(self, **kwargs: Any) -> None:
        self.calls.append(("abort_multipart_upload", kwargs))

    async def get_object(self, **kwargs: Any) -> dict[str, FakeBody]:
        self.calls.append(("get_object", kwargs))
        try:
            data = self.objects[kwargs["Key"]]
        except KeyError as exc:
            raise FakeNotFoundError from exc
        range_header = kwargs.get("Range")
        if range_header:
            bounds = str(range_header).removeprefix("bytes=").split("-", maxsplit=1)
            start = int(bounds[0])
            end = int(bounds[1])
            data = data[start : end + 1]
        return {"Body": FakeBody(data)}

    async def head_object(self, **kwargs: Any) -> dict[str, int]:
        self.calls.append(("head_object", kwargs))
        try:
            data = self.objects[kwargs["Key"]]
        except KeyError as exc:
            raise FakeNotFoundError from exc
        return {"ContentLength": len(data)}

    async def delete_object(self, **kwargs: Any) -> None:
        self.calls.append(("delete_object", kwargs))
        self.objects.pop(kwargs["Key"], None)

    async def head_bucket(self, **kwargs: Any) -> None:
        self.calls.append(("head_bucket", kwargs))


@pytest.fixture
def fake_client() -> FakeS3Client:
    return FakeS3Client()


@pytest.fixture
def backend(fake_client: FakeS3Client) -> S3Backend:
    return S3Backend(
        S3BackendConfig(
            endpoint_url="http://minio.test",
            region="us-east-1",
            bucket="artifacts",
            key_prefix="artifact-store",
            storage_class="STANDARD",
            sse="AES256",
            multipart_threshold_bytes=8,
            multipart_chunk_bytes=5,
        ),
        client_factory=lambda: fake_client,
        chunk_size=3,
    )


async def test_put_get_head_delete_round_trip(
    backend: S3Backend,
    fake_client: FakeS3Client,
) -> None:
    data = b"abc"
    ca = _ca(data)
    receipt = await backend.put(ca, _stream(data), size_hint=len(data))
    digest = ca.to_digest()
    assert receipt.object_key == (
        f"artifact-store/{digest.algorithm}/{digest.hex[:2]}/{digest.hex[2:4]}/{digest.hex}"
    )
    assert fake_client.calls[0][0] == "put_object"
    assert fake_client.calls[0][1]["StorageClass"] == "STANDARD"
    assert fake_client.calls[0][1]["ServerSideEncryption"] == "AES256"

    meta = await backend.head(ca)
    assert meta.size_bytes == len(data)

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

    await backend.delete(ca)
    with pytest.raises(ObjectNotFoundError):
        await backend.head(ca)


async def test_get_supports_range(backend: S3Backend, fake_client: FakeS3Client) -> None:
    data = b"0123456789"
    ca = _ca(data)
    await backend.put(ca, _stream(data), size_hint=len(data))

    stream = await backend.get(ca, byte_range=(2, 5))
    assert await _consume(stream) == b"2345"
    assert fake_client.calls[-1][1]["Range"] == "bytes=2-5"


async def test_put_uses_multipart_above_threshold(
    backend: S3Backend,
    fake_client: FakeS3Client,
) -> None:
    data = b"abcdefghijkl"
    ca = _ca(data)
    receipt = await backend.put(ca, _stream(data), size_hint=len(data))

    assert receipt.size_bytes == len(data)
    assert [name for name, _kwargs in fake_client.calls] == [
        "create_multipart_upload",
        "upload_part",
        "upload_part",
        "upload_part",
        "complete_multipart_upload",
    ]
    stream = await backend.get(ca)
    assert await _consume(stream) == data


async def test_health_uses_head_bucket(backend: S3Backend) -> None:
    status = await backend.health()
    assert status.healthy is True
    assert status.backend_id == "s3"