from dataclasses import dataclass
from typing import BinaryIO
from urllib.parse import quote, urlparse

import boto3
from botocore.config import Config
from django.conf import settings


@dataclass(frozen=True)
class StoredObject:
    bucket: str
    object_key: str
    content_type: str
    size_bytes: int


class TosStorage:
    def __init__(self) -> None:
        tos = settings.TOS
        self.bucket = tos["bucket"]
        self.client = boto3.client(
            "s3",
            endpoint_url=tos["endpoint"],
            aws_access_key_id=tos["access_key_id"],
            aws_secret_access_key=tos["secret_access_key"],
            region_name="cn-shanghai",
            config=Config(s3={"addressing_style": "virtual"}),
        )

    def upload_fileobj(self, *, fileobj: BinaryIO, object_key: str, content_type: str) -> StoredObject:
        fileobj.seek(0, 2)
        size = fileobj.tell()
        fileobj.seek(0)
        self.client.upload_fileobj(
            fileobj,
            self.bucket,
            object_key,
            # object_key 按 asset id 唯一、内容不可变 → 长效强缓存 + immutable:
            # 浏览器/CDN 永不重拉,前端重渲染(背景图重新赋值)也命中缓存,不再"每次生成全页图闪一下重载"。
            ExtraArgs={"ContentType": content_type, "CacheControl": "public, max-age=31536000, immutable"},
        )
        return StoredObject(
            bucket=self.bucket,
            object_key=object_key,
            content_type=content_type,
            size_bytes=size,
        )

    def presigned_get_url(self, *, object_key: str, expires_in: int = 3600) -> str:
        return self.client.generate_presigned_url(
            "get_object",
            Params={"Bucket": self.bucket, "Key": object_key},
            ExpiresIn=expires_in,
        )

    def public_url(self, *, object_key: str, bucket: str | None = None) -> str:
        """桶公读时的虚拟主机式直链:https://{bucket}.{host}/{key}。
        相比预签名 URL:不签名(省 boto3 客户端/签名开销)、且 URL 稳定可被浏览器/CDN 缓存
        (签名链每次都变、1h 过期,反而打不到缓存)。仅用于公开可读的预览图。"""
        host = urlparse(settings.TOS["endpoint"]).netloc
        return f"https://{bucket or self.bucket}.{host}/{quote(object_key, safe='/')}"