import json
import logging
import re
from http.client import HTTPResponse
from ssl import SSLContext
from typing import Dict, Union, List, Optional
from urllib.error import HTTPError
from urllib.request import Request, urlopen

from slack.errors import SlackRequestError
from .internal_utils import _build_body, _build_request_headers, _debug_log_response
from .webhook_response import WebhookResponse
from ..web import get_user_agent
from ..web.classes.attachments import Attachment
from ..web.classes.blocks import Block


class WebhookClient:
    logger = logging.getLogger(__name__)

    def __init__(
        self,
        url: str,
        timeout: int = 30,
        ssl: Optional[SSLContext] = None,
        proxy: Optional[str] = None,
        default_headers: Optional[Dict[str, str]] = None,
        user_agent_prefix: Optional[str] = None,
        user_agent_suffix: Optional[str] = None,
    ):
        """API client for Incoming Webhooks and response_url
        :param url: a complete URL to send data (e.g., https://hooks.slack.com/XXX)
        :param timeout: request timeout (in seconds)
        :param ssl: ssl.SSLContext to use for requests
        :param proxy: proxy URL (e.g., localhost:9000, http://localhost:9000)
        :param default_headers: request headers to add to all requests
        :param user_agent_prefix: prefix for User-Agent header value
        :param user_agent_suffix: suffix for User-Agent header value
        """
        self.url = url
        self.timeout = timeout
        self.ssl = ssl
        self.proxy = proxy
        self.default_headers = default_headers if default_headers else {}
        self.default_headers["User-Agent"] = get_user_agent(
            user_agent_prefix, user_agent_suffix
        )

    def send(
        self,
        *,
        text: Optional[str] = None,
        attachments: Optional[List[Union[Dict[str, any], Attachment]]] = None,
        blocks: Optional[List[Union[Dict[str, any], Block]]] = None,
        response_type: Optional[str] = None,
        headers: Optional[Dict[str, str]] = None,
    ) -> WebhookResponse:
        """Performs a Slack API request and returns the result.
        :param text: the text message (even when having blocks, setting this as well is recommended as it works as fallback)
        :param attachments: a collection of attachments
        :param blocks: a collection of Block Kit UI components
        :param response_type: the type of message (either 'in_channel' or 'ephemeral')
        :param headers: request headers to append only for this request
        :return: API response
        """
        return self.send_dict(
            body={
                "text": text,
                "attachments": attachments,
                "blocks": blocks,
                "response_type": response_type,
            },
            headers=headers,
        )

    def send_dict(
        self, body: Dict[str, any], headers: Optional[Dict[str, str]] = None
    ) -> WebhookResponse:
        """Performs a Slack API request and returns the result.
        :param body: json data structure (it's still a dict at this point),
            if you give this argument, body_params and files will be skipped
        :param headers: request headers to append only for this request
        :return: API response
        """
        return self._perform_http_request(
            body=_build_body(body),
            headers=_build_request_headers(self.default_headers, headers),
        )

    def _perform_http_request(
        self, *, body: Dict[str, any], headers: Dict[str, str]
    ) -> WebhookResponse:
        """Performs an HTTP request and parses the response.
        :param url: a complete URL to send data (e.g., https://hooks.slack.com/XXX)
        :param body: request body data
        :param headers: complete set of request headers
        :return: API response
        """
        body = json.dumps(body)
        headers["Content-Type"] = "application/json;charset=utf-8"

        if self.logger.level <= logging.DEBUG:
            self.logger.debug(
                f"Sending a request - url: {self.url}, body: {body}, headers: {headers}"
            )
        try:
            url = self.url
            # for security (BAN-B310)
            if url.lower().startswith("http"):
                req = Request(
                    method="POST", url=url, data=body.encode("utf-8"), headers=headers
                )
                if self.proxy is not None:
                    host = re.sub("^https?://", "", self.proxy)
                    req.set_proxy(host, "http")
                    req.set_proxy(host, "https")
            else:
                raise SlackRequestError(f"Invalid URL detected: {url}")

            # NOTE: BAN-B310 is already checked above
            resp: HTTPResponse = urlopen(  # skipcq: BAN-B310
                req, context=self.ssl, timeout=self.timeout,
            )
            charset: str = resp.headers.get_content_charset() or "utf-8"
            response_body: str = resp.read().decode(charset)
            resp = WebhookResponse(
                url=url,
                status_code=resp.status,
                body=response_body,
                headers=resp.headers,
            )
            _debug_log_response(self.logger, resp)
            return resp

        except HTTPError as e:
            charset = e.headers.get_content_charset()
            body: str = e.read().decode(charset)  # read the response body here
            resp = WebhookResponse(
                url=url, status_code=e.code, body=body, headers=e.headers,
            )
            if e.code == 429:
                # for backward-compatibility with WebClient (v.2.5.0 or older)
                resp.headers["Retry-After"] = resp.headers["retry-after"]
            _debug_log_response(self.logger, resp)
            return resp

        except Exception as err:
            self.logger.error(f"Failed to send a request to Slack API server: {err}")
            raise err
