import os
from dataclasses import dataclass
from pathlib import Path
from typing import Optional, Tuple
from urllib.parse import urlparse, urlunparse


def _split_endpoint_bucket(endpoint: str) -> Tuple[str, str, str]:
    parsed = urlparse(endpoint)
    if not parsed.scheme or not parsed.netloc:
        return endpoint, "", ""

    path = (parsed.path or "").strip("/")
    if not path:
        return urlunparse((parsed.scheme, parsed.netloc, "", "", "", "")), "", ""

    parts = [part for part in path.split("/") if part]
    bucket = parts[0] if parts else ""
    base_prefix = "/".join(parts[1:]) if len(parts) > 1 else ""
    base_endpoint = urlunparse((parsed.scheme, parsed.netloc, "", "", "", ""))
    return base_endpoint, bucket, base_prefix


def _join_key(prefix: str, key: str) -> str:
    prefix = (prefix or "").strip("/")
    key = (key or "").lstrip("/")
    if not prefix:
        return key
    if not key:
        return prefix
    return f"{prefix}/{key}"


@dataclass(frozen=True)
class R2Config:
    endpoint_url: str
    bucket: str
    access_key_id: str
    secret_access_key: str
    base_prefix: str = ""


class R2Storage:
    def __init__(self, config: Optional[R2Config] = None):
        self.config = config or self._load_config_from_env()
        self._client = None

    @staticmethod
    def _load_config_from_env() -> R2Config:
        endpoint_raw = (os.getenv("R2_ENDPOINT") or os.getenv("R2_Endpoint") or "").strip()
        access_key_id = (os.getenv("R2_ACCESS_KEY_ID") or os.getenv("R2_ID") or "").strip()
        secret_access_key = (os.getenv("R2_SECRET_ACCESS_KEY") or os.getenv("R2_API") or "").strip()
        bucket = (os.getenv("R2_BUCKET") or "").strip()
        base_prefix = (os.getenv("R2_PREFIX") or "").strip()

        if endpoint_raw and not bucket:
            endpoint_url, bucket_from_path, prefix_from_path = _split_endpoint_bucket(endpoint_raw)
            bucket = bucket or bucket_from_path
            endpoint_raw = endpoint_url
            base_prefix = base_prefix or prefix_from_path

        endpoint_url = endpoint_raw
        if not endpoint_url or not bucket or not access_key_id or not secret_access_key:
            missing = []
            if not endpoint_url:
                missing.append("R2_ENDPOINT / R2_Endpoint")
            if not bucket:
                missing.append("R2_BUCKET (或把 bucket 放到 R2_Endpoint 的路径里)")
            if not access_key_id:
                missing.append("R2_ACCESS_KEY_ID / R2_ID")
            if not secret_access_key:
                missing.append("R2_SECRET_ACCESS_KEY / R2_API")
            raise ValueError(f"R2 配置缺失: {', '.join(missing)}")

        if secret_access_key.startswith("cfat_"):
            raise ValueError("R2_SECRET_ACCESS_KEY 看起来是 Cloudflare API Token（cfat_），不是 R2 的 S3 Secret Access Key。请在 Cloudflare 控制台生成 R2 的 S3 API 访问密钥并替换。")

        return R2Config(
            endpoint_url=endpoint_url,
            bucket=bucket,
            access_key_id=access_key_id,
            secret_access_key=secret_access_key,
            base_prefix=base_prefix,
        )

    def _get_client(self):
        if self._client is not None:
            return self._client

        try:
            import boto3
            from botocore.client import Config
        except Exception as exc:
            raise RuntimeError("缺少依赖 boto3，请先安装 requirements.txt") from exc

        self._client = boto3.client(
            "s3",
            endpoint_url=self.config.endpoint_url,
            aws_access_key_id=self.config.access_key_id,
            aws_secret_access_key=self.config.secret_access_key,
            region_name="auto",
            config=Config(signature_version="s3v4", s3={"addressing_style": "path"}),
        )
        return self._client

    def resolve_key(self, key: str) -> str:
        return _join_key(self.config.base_prefix, key)

    def exists(self, key: str) -> bool:
        client = self._get_client()
        resolved_key = self.resolve_key(key)
        try:
            client.head_object(Bucket=self.config.bucket, Key=resolved_key)
            return True
        except Exception as exc:
            try:
                from botocore.exceptions import ClientError
            except Exception:
                raise

            if isinstance(exc, ClientError):
                error = (exc.response or {}).get("Error") or {}
                code = str(error.get("Code") or "")
                if code in {"404", "NoSuchKey", "NotFound"}:
                    return False
            raise

    def upload_file(self, local_path: str | Path, key: str, content_type: Optional[str] = None) -> str:
        client = self._get_client()
        resolved_key = self.resolve_key(key)
        path = Path(local_path)
        if not path.exists():
            raise FileNotFoundError(str(path))

        kwargs = {}
        if content_type:
            kwargs["ContentType"] = content_type

        with path.open("rb") as handle:
            client.put_object(Bucket=self.config.bucket, Key=resolved_key, Body=handle, **kwargs)
        return resolved_key

    def download_file(self, key: str, local_path: str | Path) -> Path:
        client = self._get_client()
        resolved_key = self.resolve_key(key)
        path = Path(local_path)
        path.parent.mkdir(parents=True, exist_ok=True)
        response = client.get_object(Bucket=self.config.bucket, Key=resolved_key)
        body = response.get("Body")
        try:
            with path.open("wb") as handle:
                handle.write(body.read())
        finally:
            if body is not None:
                try:
                    body.close()
                except Exception:
                    pass
        return path

    def list_keys(self, prefix: str = "", max_keys: int = 20) -> list[str]:
        client = self._get_client()
        resolved_prefix = self.resolve_key(prefix) if prefix else ""
        params = {"Bucket": self.config.bucket, "MaxKeys": int(max_keys)}
        if resolved_prefix:
            params["Prefix"] = resolved_prefix
        response = client.list_objects_v2(**params)
        contents = response.get("Contents") or []
        return [item.get("Key", "") for item in contents if isinstance(item, dict) and item.get("Key")]

    def presign_get_url(self, key: str, expires_in: int = 3600) -> str:
        client = self._get_client()
        resolved_key = self.resolve_key(key)
        return client.generate_presigned_url(
            ClientMethod="get_object",
            Params={"Bucket": self.config.bucket, "Key": resolved_key},
            ExpiresIn=int(expires_in),
        )