import os
import uuid
from datetime import datetime
from typing import Optional, BinaryIO
import oss2
from oss2.exceptions import OssError, NoSuchBucket, NoSuchKey
from config import settings


class OSSService:
    """阿里云OSS服务类"""
    
    def __init__(self):
        """初始化OSS客户端"""
        if not all([settings.oss_access_key_id, settings.oss_access_key_secret, settings.oss_bucket_name]):
            raise ValueError("OSS配置不完整，请检查环境变量")
        
        # 创建认证对象
        self.auth = oss2.Auth(settings.oss_access_key_id, settings.oss_access_key_secret)
        
        # 创建Bucket对象
        self.bucket = oss2.Bucket(self.auth, settings.oss_endpoint, settings.oss_bucket_name)
        
        # 验证bucket是否存在
        try:
            self.bucket.get_bucket_info()
        except NoSuchBucket:
            raise ValueError(f"Bucket '{settings.oss_bucket_name}' 不存在")
    
    def generate_object_key(self, original_filename: str, folder: str = "uploads") -> str:
        """生成OSS对象键名"""
        # 获取文件扩展名
        _, ext = os.path.splitext(original_filename)
        
        # 生成唯一文件名
        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
        unique_id = str(uuid.uuid4())[:8]
        filename = f"{timestamp}_{unique_id}{ext}"
        
        # 返回完整的对象键
        return f"{folder}/{filename}"
    
    def upload_file(self, file_content: bytes, object_key: str, content_type: str = None) -> dict:
        """
        上传文件到OSS
        
        Args:
            file_content: 文件内容
            object_key: OSS对象键
            content_type: 文件MIME类型
            
        Returns:
            包含上传结果的字典
        """
        try:
            # 设置文件头信息
            headers = {}
            if content_type:
                headers['Content-Type'] = content_type
            
            # 上传文件
            result = self.bucket.put_object(object_key, file_content, headers=headers)
            
            # 构造文件URL
            file_url = f"https://{settings.oss_bucket_name}.{settings.oss_endpoint.replace('http://', '').replace('https://', '')}/{object_key}"
            
            return {
                "success": True,
                "message": "文件上传成功",
                "object_key": object_key,
                "file_url": file_url,
                "etag": result.etag,
                "request_id": result.request_id
            }
            
        except OssError as e:
            return {
                "success": False,
                "message": f"上传失败: {e}",
                "error_code": e.code if hasattr(e, 'code') else 'Unknown'
            }
    
    def delete_file(self, object_key: str) -> dict:
        """
        删除OSS文件
        
        Args:
            object_key: OSS对象键
            
        Returns:
            删除结果字典
        """
        try:
            # 首先检查文件是否存在
            try:
                self.bucket.head_object(object_key)
            except NoSuchKey:
                return {
                    "success": False,
                    "message": f"文件不存在: {object_key}",
                    "error_code": "NoSuchKey"
                }
            
            # 文件存在，执行删除操作
            result = self.bucket.delete_object(object_key)
            return {
                "success": True,
                "message": "文件删除成功",
                "object_key": object_key,
                "request_id": result.request_id
            }
        except OssError as e:
            return {
                "success": False,
                "message": f"删除失败: {e}",
                "error_code": e.code if hasattr(e, 'code') else 'Unknown'
            }
    
    def get_file_info(self, object_key: str) -> dict:
        """
        获取文件信息
        
        Args:
            object_key: OSS对象键
            
        Returns:
            文件信息字典
        """
        try:
            head_result = self.bucket.head_object(object_key)
            
            return {
                "success": True,
                "object_key": object_key,
                "size": head_result.content_length,
                "last_modified": head_result.last_modified,
                "content_type": head_result.content_type,
                "etag": head_result.etag
            }
        except NoSuchKey:
            return {
                "success": False,
                "message": "文件不存在"
            }
        except OssError as e:
            return {
                "success": False,
                "message": f"获取文件信息失败: {e}"
            }
    
    def list_files(self, prefix: str = "", max_keys: int = 100) -> dict:
        """
        列出文件
        
        Args:
            prefix: 对象键前缀
            max_keys: 最大返回数量
            
        Returns:
            文件列表字典
        """
        try:
            files = []
            for obj in oss2.ObjectIterator(self.bucket, prefix=prefix, max_keys=max_keys):
                # 安全地处理 last_modified 字段
                last_modified_str = None
                if obj.last_modified:
                    if hasattr(obj.last_modified, 'isoformat'):
                        # 如果是 datetime 对象
                        last_modified_str = obj.last_modified.isoformat()
                    elif isinstance(obj.last_modified, (int, float)):
                        # 如果是时间戳，转换为 datetime 然后格式化
                        last_modified_str = datetime.fromtimestamp(obj.last_modified).isoformat()
                    else:
                        # 其他情况，尝试转换为字符串
                        last_modified_str = str(obj.last_modified)
                
                files.append({
                    "key": obj.key,
                    "size": obj.size,
                    "last_modified": last_modified_str,
                    "etag": obj.etag
                })
            
            return {
                "success": True,
                "files": files,
                "count": len(files)
            }
        except OssError as e:
            return {
                "success": False,
                "message": f"列出文件失败: {e}"
            }


# 全局OSS服务实例
oss_service = OSSService()