from __future__ import annotations
from io import BytesIO
from typing import BinaryIO, Dict, Optional

from .interface import StorageInterface


class AliyunOSSStorage(StorageInterface):
    """阿里云OSS存储适配器"""
    
    storage_type = "aliyun_oss"

    def __init__(self, config: dict):
        try:
            import oss2
        except ImportError:
            raise ImportError("请先安装 oss2: pip install oss2")

        self.access_key_id = config.get("access_key_id")
        self.access_key_secret = config.get("access_key_secret")
        self.endpoint = config.get("endpoint")
        self.bucket_name = config.get("bucket")
        
        if not all([self.access_key_id, self.access_key_secret, self.endpoint, self.bucket_name]):
            raise ValueError("阿里云OSS配置不完整，需要: access_key_id, access_key_secret, endpoint, bucket")

        auth = oss2.Auth(self.access_key_id, self.access_key_secret)
        self.bucket = oss2.Bucket(auth, self.endpoint, self.bucket_name)

    def upload(self, file_stream: BinaryIO, key: str, mime_type: Optional[str] = None) -> Dict:
        """上传文件到阿里云OSS（流式上传，避免内存溢出）"""
        headers = {}
        if mime_type:
            headers["Content-Type"] = mime_type

        # OSS SDK 的 put_object 支持传入文件对象，会自动流式上传
        # 不需要调用 read() 一次性读取到内存
        result = self.bucket.put_object(key, file_stream, headers=headers)
        
        return {
            "etag": result.etag,
            "request_id": result.request_id,
        }

    def append_chunk(self, key: str, chunk_stream: BinaryIO, offset: int) -> None:
        """追加写入数据块（OSS原生支持追加写）"""
        chunk_data = chunk_stream.read()
        
        # 第一次写入时使用append_object，后续也用append_object
        self.bucket.append_object(key, offset, chunk_data)

    def download(self, key: str) -> BinaryIO:
        """从阿里云OSS下载文件"""
        result = self.bucket.get_object(key)
        return BytesIO(result.read())

    def delete(self, key: str) -> None:
        """删除OSS文件"""
        self.bucket.delete_object(key)

    def exists(self, key: str) -> bool:
        """检查OSS文件是否存在"""
        return self.bucket.object_exists(key)

    def get_url(self, key: str, expires: int = 3600) -> str:
        """获取OSS文件访问URL（带签名）"""
        if expires == 0:
            # 永久URL（适用于公共读bucket）
            return f"https://{self.bucket_name}.{self.endpoint.replace('http://', '').replace('https://', '')}/{key}"
        
        # 生成带签名的临时URL
        return self.bucket.sign_url("GET", key, expires)

    # 预览与缩略图
    def get_preview_url(self, key: str, expires: int = 3600) -> str:
        """预览URL（等同于访问URL）"""
        return self.get_url(key, expires)

    def get_thumbnail_url(
        self,
        key: str,
        width: int = 200,
        height: int = 200,
        mode: str = "fit",
        expires: int = 3600,
    ) -> str:
        """使用 x-oss-process 图片处理签名URL。

        注意：图片处理参数必须参与签名，故通过 SDK 的 sign_url params 参数生成。
        """
        # 模式映射：fit -> lfit, fill -> fill, pad -> pad
        mode_map = {
            "fit": "lfit",
            "fill": "fill",
            "pad": "pad",
        }
        oss_mode = mode_map.get(mode, "lfit")
        
        # 使用图片处理 + 指定格式，避免覆盖 Content-Type（避免 0017-00000902 错误）
        # OSS 会依据 format 自动返回相应的 Content-Type
        process = (
            f"image/resize,m_{oss_mode},w_{max(1, int(width))},h_{max(1, int(height))}/format,png"
        )

        # 仅携带 x-oss-process 参与签名
        return self.bucket.sign_url("GET", key, expires, params={"x-oss-process": process})