import base64
import time
import oss2
from oss2.models import PolicyConditions  # 确保正确导入 PolicyConditions
from typing import Dict

class AliUtil:
    def __init__(self):
        # 从配置中读取阿里云 OSS 的配置
        self.endpoint = "your_endpoint"  # 替换为你的 OSS endpoint
        self.access_key_id = "your_access_key_id"  # 替换为你的 AccessKeyId
        self.access_key_secret = "your_access_key_secret"  # 替换为你的 AccessKeySecret

    def get_signature(self, bucket_name: str) -> Dict[str, str]:
        """
        获取临时访问 OSS 的签名
        :param bucket_name: bucket 名称，由前端传入（上传不同文件到不同文件夹）
        :return: 包含签名信息的字典
        """
        resp_map = {}
        # host 的格式为 bucketName.endpoint
        host = f"https://{bucket_name}.{self.endpoint}"
        # callbackUrl 为上传回调服务器的 URL，请将下面的 IP 和 Port 配置为您自己的真实信息。
        callback_url = ""
        dir = ""  # 用户上传文件时指定的前缀。

        # 初始化 OSS 客户端
        auth = oss2.Auth(self.access_key_id, self.access_key_secret)
        bucket = oss2.Bucket(auth, self.endpoint, bucket_name)

        try:
            # 设置过期时间为半小时 (1800 秒)
            expire_time = 60 * 30
            expire_end_time = int(time.time()) + expire_time

            # 设置 Policy 条件
            policy_conditions = PolicyConditions()
            policy_conditions.add_condition(PolicyConditions.CONTENT_LENGTH_RANGE, 0, 1048576000)  # 文件大小限制
            policy_conditions.add_condition(PolicyConditions.STARTS_WITH, PolicyConditions.KEY, dir)  # 文件前缀

            # 生成 Post Policy
            post_policy = bucket._make_post_policy(expire_end_time, policy_conditions)
            encoded_policy = base64.b64encode(post_policy.encode('utf-8')).decode('utf-8')

            # 计算签名
            post_signature = bucket._make_post_signature(post_policy)

            # 构建返回的签名信息
            resp_map["accessid"] = self.access_key_id
            resp_map["policy"] = encoded_policy
            resp_map["signature"] = post_signature
            resp_map["dir"] = dir
            resp_map["host"] = host
            resp_map["expire"] = str(expire_end_time)

            # 构建回调信息
            callback_body = {
                "callbackUrl": callback_url,
                "callbackBody": "filename=${object}&size=${size}&mimeType=${mimeType}&height=${imageInfo.height}&width=${imageInfo.width}",
                "callbackBodyType": "application/x-www-form-urlencoded"
            }
            base64_callback_body = base64.b64encode(str(callback_body).encode('utf-8')).decode('utf-8')
            resp_map["callback"] = base64_callback_body

        except Exception as e:
            print(f"Error: {e}")

        return resp_map