"""S3FileStorage — stores files in any S3-compatible object store."""

import tempfile
from collections.abc import AsyncGenerator, AsyncIterator
from contextlib import AbstractAsyncContextManager, asynccontextmanager
from pathlib import Path
from typing import Any

import aioboto3
import anyio
from botocore.exceptions import ClientError

from app.domain.entities.storage import ObjectStat
from app.domain.errors import StorageError

_EXT_CONTENT_TYPE: dict[str, str] = {
    "mp3": "audio/mpeg",
    "flac": "audio/flac",
    "m4a": "audio/mp4",
    "aac": "audio/aac",
    "ogg": "audio/ogg",
    "opus": "audio/ogg",
    "wav": "audio/wav",
    "wma": "audio/x-ms-wma",
    "aiff": "audio/aiff",
    "aif": "audio/aiff",
}


def _not_found(key: str, exc: Exception) -> StorageError:
    err = StorageError(f"Object not found: {key}")
    err.__cause__ = exc
    return err


def _is_404(exc: ClientError) -> bool:
    return exc.response["Error"]["Code"] in ("404", "NoSuchKey")


class S3FileStorage:
    def __init__(
        self,
        bucket: str,
        *,
        endpoint_url: str | None = None,
        region_name: str | None = None,
        access_key: str | None = None,
        secret_key: str | None = None,
    ) -> None:
        self._bucket = bucket
        self._endpoint_url = endpoint_url
        self._session: Any = aioboto3.Session(
            aws_access_key_id=access_key,
            aws_secret_access_key=secret_key,
            region_name=region_name,
        )

    def _client(self) -> Any:
        return self._session.client("s3", endpoint_url=self._endpoint_url)

    async def save_file(self, key: str, src_path: Path) -> int:
        async with await anyio.open_file(src_path, "rb") as f:
            content: bytes = await f.read()
        async with self._client() as s3:
            await s3.put_object(Bucket=self._bucket, Key=key, Body=content)
        return len(content)

    async def open_range(
        self, key: str, start: int, end: int | None
    ) -> tuple[AsyncIterator[bytes], int]:
        async with self._client() as s3:
            try:
                head = await s3.head_object(Bucket=self._bucket, Key=key)
            except ClientError as exc:
                if _is_404(exc):
                    raise _not_found(key, exc) from exc
                raise StorageError(str(exc)) from exc
        total_size: int = head["ContentLength"]

        range_header = f"bytes={start}-{end}" if end is not None else f"bytes={start}-"
        _bucket = self._bucket
        _key = key

        async def _stream() -> AsyncGenerator[bytes]:
            async with self._client() as s3:
                try:
                    resp = await s3.get_object(Bucket=_bucket, Key=_key, Range=range_header)
                except ClientError as exc:
                    raise StorageError(str(exc)) from exc
                body = resp["Body"]
                while True:
                    chunk: bytes = await body.read(65536)
                    if not chunk:
                        break
                    yield chunk

        return _stream(), total_size

    async def stat(self, key: str) -> ObjectStat:
        async with self._client() as s3:
            try:
                head = await s3.head_object(Bucket=self._bucket, Key=key)
            except ClientError as exc:
                if _is_404(exc):
                    raise _not_found(key, exc) from exc
                raise StorageError(str(exc)) from exc
        ext = Path(key).suffix.lower().lstrip(".")
        return ObjectStat(
            size=head["ContentLength"],
            content_type=head.get("ContentType") or _EXT_CONTENT_TYPE.get(ext),
        )

    async def exists(self, key: str) -> bool:
        async with self._client() as s3:
            try:
                await s3.head_object(Bucket=self._bucket, Key=key)
                return True
            except ClientError as exc:
                if _is_404(exc):
                    return False
                raise StorageError(str(exc)) from exc

    async def delete(self, key: str) -> None:
        async with self._client() as s3:
            try:
                await s3.delete_object(Bucket=self._bucket, Key=key)
            except ClientError as exc:
                raise StorageError(str(exc)) from exc

    async def disk_usage(self) -> None:
        # Object stores have no fixed-capacity volume to report.
        return None

    def as_local_path(self, key: str) -> AbstractAsyncContextManager[Path]:
        return self._as_local_path_cm(key)

    @asynccontextmanager
    async def _as_local_path_cm(self, key: str) -> AsyncGenerator[Path]:
        suffix = Path(key).suffix
        with tempfile.NamedTemporaryFile(suffix=suffix, delete=False) as f:
            tmp_path = Path(f.name)
        try:
            async with self._client() as s3:
                try:
                    resp = await s3.get_object(Bucket=self._bucket, Key=key)
                except ClientError as exc:
                    if _is_404(exc):
                        raise _not_found(key, exc) from exc
                    raise StorageError(str(exc)) from exc
                async with await anyio.open_file(tmp_path, "wb") as out:
                    body = resp["Body"]
                    while True:
                        chunk: bytes = await body.read(65536)
                        if not chunk:
                            break
                        await out.write(chunk)
            yield tmp_path
        finally:
            await anyio.Path(tmp_path).unlink(missing_ok=True)