from dataclasses import dataclass
from typing import Any, Dict, Iterable, Mapping, Optional, Tuple, Union

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

from request.proxy_config import apply_proxy

TimeoutType = Union[float, Tuple[float, float]]


class RequestClientError(Exception):
    """请求客户端通用异常。"""


class RequestConnectTimeout(RequestClientError):
    """连接超时。"""


class RequestTimeout(RequestClientError):
    """请求超时。"""


class RequestConnectionError(RequestClientError):
    """连接错误。"""


class RequestSSLError(RequestClientError):
    """SSL 错误。"""


@dataclass
class ResponseData:
    # 只保留采集侧稳定需要的字段，避免直接向上层泄露原始 Response 对象
    status_code: int
    text: str
    url: str
    headers: Dict[str, str]


class RequestsClient:
    """
    统一 requests 客户端：
    - 自动应用代理配置
    - 支持可选重试
    - 对外抛出统一异常类型
    """

    def __init__(
        self,
        headers: Optional[Mapping[str, str]] = None,
        *,
        retry_total: int = 0,
        retry_backoff_factor: float = 0.0,
        retry_status_forcelist: Optional[Iterable[int]] = None,
        retry_allowed_methods: Optional[Iterable[str]] = None,
        default_timeout: Optional[TimeoutType] = None,
    ) -> None:
        self._base_headers: Dict[str, str] = dict(headers or {})
        self.retry_total = int(retry_total)
        self.retry_backoff_factor = float(retry_backoff_factor)
        self.retry_status_forcelist = tuple(retry_status_forcelist or ())
        self.retry_allowed_methods = tuple(retry_allowed_methods or ("GET", "POST"))
        self.default_timeout = default_timeout
        self._session = self._build_session()

    def _build_session(self) -> requests.Session:
        session = requests.Session()
        # 统一从 proxy_settings.json 注入代理，并屏蔽系统环境代理干扰
        apply_proxy(session)
        if self.retry_total > 0:
            # 适配器级重试：主要处理连接波动与指定状态码的瞬时失败
            retries = Retry(
                total=self.retry_total,
                backoff_factor=self.retry_backoff_factor,
                status_forcelist=self.retry_status_forcelist,
                allowed_methods=frozenset(self.retry_allowed_methods),
                raise_on_status=False,
            )
            adapter = HTTPAdapter(max_retries=retries)
            session.mount("https://", adapter)
            session.mount("http://", adapter)
        if self._base_headers:
            # 基础头只在建 session 时注入，业务请求可通过 headers 临时覆盖
            session.headers.update(self._base_headers)
        return session

    @property
    def headers(self):
        return self._session.headers

    @property
    def proxies(self) -> Dict[str, str]:
        return dict(self._session.proxies)

    def refresh(self) -> None:
        # 强制重建 session，用于 403/连接异常后的“换连接”场景
        self.close()
        self._session = self._build_session()

    def close(self) -> None:
        try:
            self._session.close()
        except Exception:
            pass

    def clone(self) -> "RequestsClient":
        # 线程场景建议 clone：复用同配置，但使用独立连接池
        clone_client = RequestsClient(
            headers=dict(self.headers),
            retry_total=self.retry_total,
            retry_backoff_factor=self.retry_backoff_factor,
            retry_status_forcelist=self.retry_status_forcelist,
            retry_allowed_methods=self.retry_allowed_methods,
            default_timeout=self.default_timeout,
        )
        return clone_client

    def request_text(
        self,
        method: str,
        url: str,
        *,
        timeout: Optional[TimeoutType] = None,
        verify: bool = True,
        headers: Optional[Mapping[str, str]] = None,
        **kwargs: Any,
    ) -> ResponseData:
        response = None
        # 调用方未传 timeout 时，回退到客户端默认超时
        real_timeout = self.default_timeout if timeout is None else timeout
        try:
            response = self._session.request(
                method=method,
                url=url,
                timeout=real_timeout,
                verify=verify,
                headers=headers,
                **kwargs,
            )
            return ResponseData(
                status_code=response.status_code,
                text=response.text,
                url=response.url,
                headers=dict(response.headers),
            )
        # 把 requests 的具体异常统一收敛，业务层无需依赖 requests.exceptions
        except requests.exceptions.ConnectTimeout as exc:
            raise RequestConnectTimeout(str(exc)) from exc
        except requests.exceptions.Timeout as exc:
            raise RequestTimeout(str(exc)) from exc
        except requests.exceptions.ConnectionError as exc:
            raise RequestConnectionError(str(exc)) from exc
        except requests.exceptions.SSLError as exc:
            raise RequestSSLError(str(exc)) from exc
        except requests.exceptions.RequestException as exc:
            raise RequestClientError(str(exc)) from exc
        finally:
            if response is not None:
                # 立即释放底层连接，避免大量采集时连接堆积
                response.close()

    def get_text(self, url: str, **kwargs: Any) -> ResponseData:
        return self.request_text("GET", url, **kwargs)

    def post_text(self, url: str, **kwargs: Any) -> ResponseData:
        return self.request_text("POST", url, **kwargs)