from __future__ import annotations

import os
from io import BytesIO
from typing import BinaryIO, Dict, Optional

from .interface import StorageInterface


class TencentCOSStorage(StorageInterface):
    """腾讯云COS存储适配器"""
    
    storage_type = "tencent_cos"

    def __init__(self, config: dict):
        try:
            from qcloud_cos import CosConfig, CosS3Client
        except ImportError:
            raise ImportError("请先安装 cos-python-sdk-v5: pip install cos-python-sdk-v5")

        self.secret_id = config.get("secret_id")
        self.secret_key = config.get("secret_key")
        self.region = config.get("region")
        self.bucket_name = config.get("bucket")
        
        if not all([self.secret_id, self.secret_key, self.region, self.bucket_name]):
            raise ValueError("腾讯云COS配置不完整，需要: secret_id, secret_key, region, bucket")

        cos_config = CosConfig(
            Region=self.region,
            SecretId=self.secret_id,
            SecretKey=self.secret_key,
        )
        self.client = CosS3Client(cos_config)

    def upload(self, file_stream: BinaryIO, key: str, mime_type: Optional[str] = None) -> Dict:
        """上传文件到腾讯云COS"""
        response = self.client.put_object(
            Bucket=self.bucket_name,
            Key=key,
            Body=file_stream.read(),
            ContentType=mime_type or "application/octet-stream",
        )
        
        return {
            "etag": response.get("ETag", "").strip('"'),
            "version_id": response.get("VersionId"),
        }

    def append_chunk(self, key: str, chunk_stream: BinaryIO, offset: int) -> None:
        """
        追加写入数据块
        注意：COS不支持原生append，需要先下载再上传（或使用分片上传）
        这里采用简单的读-改-写策略
        """
        chunk_data = chunk_stream.read()
        
        # 如果文件已存在，先下载
        existing_data = b""
        if self.exists(key):
            try:
                response = self.client.get_object(Bucket=self.bucket_name, Key=key)
                existing_data = response["Body"].read()
            except Exception:
                pass
        
        # 合并数据
        if offset == 0:
            new_data = chunk_data
        else:
            new_data = existing_data[:offset] + chunk_data
        
        # 重新上传
        self.client.put_object(
            Bucket=self.bucket_name,
            Key=key,
            Body=new_data,
        )

    def download(self, key: str) -> BinaryIO:
        """从腾讯云COS下载文件"""
        response = self.client.get_object(Bucket=self.bucket_name, Key=key)
        return BytesIO(response["Body"].read())

    def delete(self, key: str) -> None:
        """删除COS文件"""
        self.client.delete_object(Bucket=self.bucket_name, Key=key)

    def exists(self, key: str) -> bool:
        """检查COS文件是否存在"""
        try:
            self.client.head_object(Bucket=self.bucket_name, Key=key)
            return True
        except Exception:
            return False

    def get_url(self, key: str, expires: int = 3600) -> str:
        """获取COS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}.cos.{self.region}.myqcloud.com/{key}"
        
        # 生成带签名的临时URL
        url = self.client.get_presigned_url(
            Method="GET",
            Bucket=self.bucket_name,
            Key=key,
            Expired=expires,
        )
        return url