"""
阿里云OSS服务

全局单例服务，提供图片上传、下载等功能
配置从环境变量加载
"""
import os
import uuid
from urllib.parse import urlparse, quote, unquote
from datetime import datetime
from typing import Optional

import oss2
import requests


class OSSService:
    """
    阿里云OSS服务
    
    全局单例服务，提供图片上传功能
    """
    _instance: Optional['OSSService'] = None
    
    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
            cls._instance._initialized = False
        return cls._instance
    
    def __init__(self):
        if self._initialized:
            return
        
        self.access_key_id = os.getenv("OSS_ACCESS_KEY_ID")
        self.access_key_secret = os.getenv("OSS_ACCESS_KEY_SECRET")
        self.endpoint = os.getenv("OSS_ENDPOINT", "oss-cn-beijing.aliyuncs.com")
        self.bucket_name = os.getenv("OSS_BUCKET_NAME")
        self.bucket_domain = os.getenv("OSS_BUCKET_DOMAIN")
        self._bucket = None
        self._initialized = True
    
    @property
    def bucket(self):
        """延迟初始化bucket"""
        if self._bucket is None and self.access_key_id and self.access_key_secret and self.bucket_name:
            auth = oss2.Auth(self.access_key_id, self.access_key_secret)
            self._bucket = oss2.Bucket(auth, self.endpoint, self.bucket_name)
        return self._bucket
    
    def upload_image(self, image_data: bytes, prefix: str = "images") -> str:
        """
        上传图片到OSS
        
        Args:
            image_data: 图片二进制数据
            prefix: 存储路径前缀
            
        Returns:
            公开访问URL
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")
        
        object_key = self._generate_unique_filename(prefix)
        self.bucket.put_object(object_key, image_data)
        return f"https://{self.bucket_domain}/{object_key}"
    
    def upload_file(self, file_data: bytes, prefix: str = "uploads", original_filename: str = None) -> str:
        """
        上传文件到OSS
        
        Args:
            file_data: 文件二进制数据
            prefix: 存储路径前缀
            original_filename: 原始文件名（用于获取扩展名）
            
        Returns:
            公开访问URL
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")
        
        object_key = self._generate_unique_filename_with_ext(prefix, original_filename)
        headers = self._build_upload_headers(original_filename)
        self.bucket.put_object(object_key, file_data, headers=headers)
        return f"https://{self.bucket_domain}/{object_key}"

    def upload_file_stream(self, file_obj, prefix: str = "uploads", original_filename: str = None) -> str:
        """
        流式上传文件到OSS

        Args:
            file_obj: 文件对象
            prefix: 存储路径前缀
            original_filename: 原始文件名

        Returns:
            公开访问URL
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")

        object_key = self._generate_unique_filename_with_ext(prefix, original_filename)
        headers = self._build_upload_headers(original_filename)
        self.bucket.put_object(object_key, file_obj, headers=headers)
        return f"https://{self.bucket_domain}/{object_key}"
    
    def download_file(self, file_path: str) -> tuple[bytes, str]:
        """
        从OSS下载文件
        
        Args:
            file_path: 文件路径（不含域名）
            
        Returns:
            (文件内容, content_type)
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")
        
        if not self.bucket.object_exists(file_path):
            raise FileNotFoundError(f"文件不存在: {file_path}")
        
        result = self.bucket.get_object(file_path)
        content = result.read()
        content_type = result.headers.get('Content-Type', 'application/octet-stream')
        return content, content_type
    
    def get_signed_url(self, file_path: str, expires: int = 3600) -> str:
        """
        获取文件签名URL
        
        Args:
            file_path: 文件路径（不含域名）
            expires: 有效期（秒）
            
        Returns:
            签名URL
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")
        
        url = self.bucket.sign_url('GET', file_path, expires)
        return url.replace('http://', 'https://', 1)

    def generate_presigned_put_url(
        self,
        prefix: str = "uploads",
        original_filename: str = None,
        expires: int = 300,
        content_type: str = None
    ) -> dict:
        """
        生成预签名 PUT 上传 URL，供前端直传 OSS

        Args:
            prefix: 存储路径前缀
            original_filename: 原始文件名（用于保留扩展名）
            expires: 预签名 PUT URL 有效期（秒），默认 5 分钟
            content_type: 文件 Content-Type（可选，用于签名头）

        Returns:
            {
                "upload_url": 预签名 PUT URL（前端直接 PUT 到此地址）,
                "object_key": OSS 对象路径,
                "public_url": 上传完成后的公开访问 URL（bucket 公读时有效）,
                "access_url": 带签名的 GET URL（bucket 私有读时也可访问，有效期 24 小时）
            }
        """
        if not self.bucket:
            raise RuntimeError("OSS服务未正确配置")

        object_key = self._generate_unique_filename_with_ext(prefix, original_filename)

        headers = {}
        if content_type:
            headers["Content-Type"] = content_type

        # 注意：不将自定义元数据头加入签名，因为前端 PUT 直传不会携带这些头。
        # 否则签名不匹配会导致 OSS 返回 403 Forbidden。

        upload_url = self.bucket.sign_url(
            'PUT',
            object_key,
            expires,
            headers=headers if headers else None
        )
        upload_url = upload_url.replace('http://', 'https://', 1)

        public_url = f"https://{self.bucket_domain}/{object_key}"

        # 生成带签名的 GET URL（有效期 24 小时），供第三方服务（如 DashScope）访问私有文件
        access_url = self.bucket.sign_url('GET', object_key, 86400)
        access_url = access_url.replace('http://', 'https://', 1)

        return {
            "upload_url": upload_url,
            "object_key": object_key,
            "public_url": public_url,
            "access_url": access_url,
        }
    
    async def upload_from_url(self, image_url: str, prefix: str = "images") -> str:
        """
        从URL下载文件并上传到OSS
        
        Args:
            image_url: 文件URL
            prefix: 存储路径前缀
            
        Returns:
            OSS公开访问URL
        """
        response = requests.get(image_url, timeout=30)
        response.raise_for_status()
        content = response.content
        original_filename = self._infer_filename(image_url, response.headers.get("Content-Type"))
        ext_from_content = self._infer_extension_from_content(content)
        if ext_from_content and not original_filename.lower().endswith(ext_from_content):
            original_filename = f"downloaded{ext_from_content}"
        return self.upload_file(content, prefix, original_filename)

    def upload_from_url_sync(self, image_url: str, prefix: str = "images") -> str:
        """
        从URL下载文件并上传到OSS（同步版本，供后台线程调用）

        Args:
            image_url: 文件URL
            prefix: 存储路径前缀

        Returns:
            OSS公开访问URL
        """
        response = requests.get(image_url, timeout=120)
        response.raise_for_status()
        content = response.content
        original_filename = self._infer_filename(image_url, response.headers.get("Content-Type"))
        ext_from_content = self._infer_extension_from_content(content)
        if ext_from_content and not original_filename.lower().endswith(ext_from_content):
            original_filename = f"downloaded{ext_from_content}"
        return self.upload_file(content, prefix, original_filename)
    
    def _generate_unique_filename(self, prefix: str) -> str:
        """生成唯一文件名"""
        date_path = datetime.now().strftime('%Y%m%d')
        unique_id = uuid.uuid4().hex
        return f"{prefix}/{date_path}/{unique_id}.png"
    
    def _generate_unique_filename_with_ext(self, prefix: str, original_filename: str = None) -> str:
        """生成文件路径，使用 UUID 作为对象名并尽量保留原始扩展名"""
        date_path = datetime.now().strftime('%Y%m%d')
        unique_id = uuid.uuid4().hex
        if original_filename:
            safe_name = self.get_safe_original_filename(original_filename)
            _, ext = os.path.splitext(safe_name)
            if ext:
                return f"{prefix}/{date_path}/{unique_id}{ext.lower()}"
        return f"{prefix}/{date_path}/{unique_id}"

    def _build_upload_headers(self, original_filename: str = None) -> Optional[dict]:
        """构造上传头，持久化原始文件名元数据。"""
        safe_name = self.get_safe_original_filename(original_filename)
        if not safe_name:
            return None
        return {
            'x-oss-meta-original-filename': quote(safe_name, safe='')
        }

    def get_safe_original_filename(self, original_filename: Optional[str]) -> Optional[str]:
        """提取安全的原始文件名。"""
        if not original_filename:
            return None
        safe_name = os.path.basename(original_filename).strip()
        return safe_name or None

    def get_original_filename_from_headers(self, headers: Optional[dict], fallback: Optional[str] = None) -> Optional[str]:
        """从 OSS 响应头中读取上传时保存的原始文件名。"""
        if headers:
            for key, value in headers.items():
                if str(key).lower() == 'x-oss-meta-original-filename' and value:
                    try:
                        return unquote(str(value))
                    except Exception:
                        return str(value)
        return fallback

    def _infer_filename(self, file_url: str, content_type: Optional[str]) -> str:
        """Infer a filename from URL or content-type for OSS upload."""
        parsed = urlparse(file_url)
        name = os.path.basename(parsed.path)
        if name and "." in name:
            return name

        ext = ""
        if content_type:
            mime = content_type.split(";")[0].strip().lower()
            mime_map = {
                "video/mp4": ".mp4",
                "video/webm": ".webm",
                "video/quicktime": ".mov",
                "image/png": ".png",
                "image/jpeg": ".jpg",
                "image/jpg": ".jpg",
                "image/webp": ".webp",
                "audio/mpeg": ".mp3",
                "audio/wav": ".wav",
            }
            ext = mime_map.get(mime, "")

        return f"downloaded{ext or '.bin'}"

    def _infer_extension_from_content(self, content: bytes) -> Optional[str]:
        """Infer file extension from magic bytes (best-effort)."""
        if len(content) >= 12 and content[4:8] == b"ftyp":
            return ".mp4"
        if content.startswith(b"\x1A\x45\xDF\xA3"):
            return ".webm"
        if content.startswith(b"OggS"):
            return ".ogv"
        return None


# 延迟初始化的全局实例
_oss_service: Optional[OSSService] = None


def get_oss_service() -> OSSService:
    """获取OSS服务实例（用于依赖注入）"""
    global _oss_service
    if _oss_service is None:
        _oss_service = OSSService()
    return _oss_service