# Copyright 2026 jCloud

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import httpx
from .exceptions import S3InternalServerError, S3ObjectNotFoundError, S3ObjectPermissionError
from typing import AsyncGenerator, Optional
from urllib.parse import urljoin

__all__ = [
    'S3Backend'
]

class S3Backend:
    '''
    A class representing an S3 compatible backend.

    :param url: The URL of the backend.
    :type url: str
    '''

    def __init__(self, url: str) -> None:
        self.url = url

    async def get_object(self, object_path: str, range: Optional[str] = None) -> AsyncGenerator[bytes]:
        '''
        Returns the bytes of an object.

        :param object_path: The path of the object. It consists of the
                            bucket name and the object key.
        :type object_path: str
        :param range: The bytes range as an RFC 9110-compliant string.
        :type range: Optional[str]

        :return: An iterator yielding the object bytes.
        :rtype: AsyncGenerator[bytes]
        '''

        if range is not None:
            headers = {
                'Range': f'bytes={range}'
            }
        else:
            headers = {}

        async with httpx.AsyncClient() as client:
            async with client.stream(
                    'GET',
                    urljoin(self.url, object_path),
                    headers = headers
            ) as response:
                if response.status_code == 404:
                    raise S3ObjectNotFoundError('Object not found', object_path = object_path)
                if response.status_code == 403:
                    raise S3ObjectPermissionError('Object access forbidden', object_path = object_path)
                if response.status_code // 100 == 5:
                    raise S3InternalServerError('Internal server error')

                async for chunk in response.aiter_bytes():
                    yield chunk