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

from slack_sdk.errors import SlackRequestError
from slack_sdk.models.attachments import Attachment
from slack_sdk.models.blocks import Block
from .internal_utils import (
    _build_body,
    _build_request_headers,
    _debug_log_response,
    get_user_agent,
)
from .webhook_response import WebhookResponse
from slack_sdk.http_retry import default_retry_handlers
from slack_sdk.http_retry.handler import RetryHandler
from slack_sdk.http_retry.request import HttpRequest as RetryHttpRequest
from slack_sdk.http_retry.response import HttpResponse as RetryHttpResponse
from slack_sdk.http_retry.state import RetryState
from ..proxy_env_variable_loader import load_http_proxy_from_env


class WebhookClient:
    url: str
    timeout: int
    ssl: Optional[SSLContext]
    proxy: Optional[str]
    default_headers: Dict[str, str]
    logger: logging.Logger
    retry_handlers: List[RetryHandler]

    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,
        logger: Optional[logging.Logger] = None,
        retry_handlers: Optional[List[RetryHandler]] = None,
    ):
        """API client for Incoming Webhooks and `response_url`

        https://api.slack.com/messaging/webhooks

        Args:
            url: Complete URL to send data (e.g., `https://hooks.slack.com/XXX`)
            timeout: Request timeout (in seconds)
            ssl: `ssl.SSLContext` to use for requests
            proxy: Proxy URL (e.g., `localhost:9000`, `http://localhost:9000`)
            default_headers: Request headers to add to all requests
            user_agent_prefix: Prefix for User-Agent header value
            user_agent_suffix: Suffix for User-Agent header value
            logger: Custom logger
            retry_handlers: Retry handlers
        """
        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
        )
        self.logger = logger if logger is not None else logging.getLogger(__name__)
        self.retry_handlers = (
            retry_handlers if retry_handlers is not None else default_retry_handlers()
        )

        if self.proxy is None or len(self.proxy.strip()) == 0:
            env_variable = load_http_proxy_from_env(self.logger)
            if env_variable is not None:
                self.proxy = env_variable

    def send(
        self,
        *,
        text: Optional[str] = None,
        attachments: Optional[Sequence[Union[Dict[str, any], Attachment]]] = None,
        blocks: Optional[Sequence[Union[Dict[str, any], Block]]] = None,
        response_type: Optional[str] = None,
        replace_original: Optional[bool] = None,
        delete_original: Optional[bool] = None,
        unfurl_links: Optional[bool] = None,
        unfurl_media: Optional[bool] = None,
        headers: Optional[Dict[str, str]] = None,
    ) -> WebhookResponse:
        """Performs a Slack API request and returns the result.

        Args:
            text: The text message
                (even when having blocks, setting this as well is recommended as it works as fallback)
            attachments: A collection of attachments
            blocks: A collection of Block Kit UI components
            response_type: The type of message (either 'in_channel' or 'ephemeral')
            replace_original: True if you use this option for response_url requests
            delete_original: True if you use this option for response_url requests
            unfurl_links: Option to indicate whether text url should unfurl
            unfurl_media: Option to indicate whether media url should unfurl
            headers: Request headers to append only for this request

        Returns:
            Webhook response
        """
        return self.send_dict(
            # It's fine to have None value elements here
            # because _build_body() filters them out when constructing the actual body data
            body={
                "text": text,
                "attachments": attachments,
                "blocks": blocks,
                "response_type": response_type,
                "replace_original": replace_original,
                "delete_original": delete_original,
                "unfurl_links": unfurl_links,
                "unfurl_media": unfurl_media,
            },
            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.

        Args:
            body: JSON data structure (it's still a dict at this point),
                if you give this argument, body_params and files will be skipped
            headers: Request headers to append only for this request
        Returns:
            Webhook 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:
        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}"
            )

        url = self.url
        # NOTE: Intentionally ignore the `http_verb` here
        # Slack APIs accepts any API method requests with POST methods
        req = Request(
            method="POST", url=url, data=body.encode("utf-8"), headers=headers
        )
        resp = None
        last_error = None

        retry_state = RetryState()
        counter_for_safety = 0
        while counter_for_safety < 100:
            counter_for_safety += 1
            # If this is a retry, the next try started here. We can reset the flag.
            retry_state.next_attempt_requested = False

            try:
                resp = self._perform_http_request_internal(url, req)
                # The resp is a 200 OK response
                return resp

            except HTTPError as e:
                # read the response body here
                charset = e.headers.get_content_charset() or "utf-8"
                response_body: str = e.read().decode(charset)
                resp = WebhookResponse(
                    url=url,
                    status_code=e.code,
                    body=response_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)

                # Try to find a retry handler for this error
                retry_request = RetryHttpRequest.from_urllib_http_request(req)
                retry_response = RetryHttpResponse(
                    status_code=e.code,
                    headers={k: [v] for k, v in e.headers.items()},
                    data=response_body.encode("utf-8")
                    if response_body is not None
                    else None,
                )
                for handler in self.retry_handlers:
                    if handler.can_retry(
                        state=retry_state,
                        request=retry_request,
                        response=retry_response,
                        error=e,
                    ):
                        if self.logger.level <= logging.DEBUG:
                            self.logger.info(
                                f"A retry handler found: {type(handler).__name__} for {req.method} {req.full_url} - {e}"
                            )
                        handler.prepare_for_next_attempt(
                            state=retry_state,
                            request=retry_request,
                            response=retry_response,
                            error=e,
                        )
                        break

                if retry_state.next_attempt_requested is False:
                    return resp

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

                # Try to find a retry handler for this error
                retry_request = RetryHttpRequest.from_urllib_http_request(req)
                for handler in self.retry_handlers:
                    if handler.can_retry(
                        state=retry_state,
                        request=retry_request,
                        response=None,
                        error=err,
                    ):
                        if self.logger.level <= logging.DEBUG:
                            self.logger.info(
                                f"A retry handler found: {type(handler).__name__} for {req.method} {req.full_url} - {err}"
                            )
                        handler.prepare_for_next_attempt(
                            state=retry_state,
                            request=retry_request,
                            response=None,
                            error=err,
                        )
                        self.logger.info(
                            f"Going to retry the same request: {req.method} {req.full_url}"
                        )
                        break

                if retry_state.next_attempt_requested is False:
                    raise err

        if resp is not None:
            return resp
        raise last_error

    def _perform_http_request_internal(self, url: str, req: Request):
        opener: Optional[OpenerDirector] = None
        # for security (BAN-B310)
        if url.lower().startswith("http"):
            if self.proxy is not None:
                if isinstance(self.proxy, str):
                    opener = urllib.request.build_opener(
                        ProxyHandler({"http": self.proxy, "https": self.proxy}),
                        HTTPSHandler(context=self.ssl),
                    )
                else:
                    raise SlackRequestError(
                        f"Invalid proxy detected: {self.proxy} must be a str value"
                    )
        else:
            raise SlackRequestError(f"Invalid URL detected: {url}")

        # NOTE: BAN-B310 is already checked above
        resp: Optional[HTTPResponse] = None
        if opener:
            resp = opener.open(req, timeout=self.timeout)  # skipcq: BAN-B310
        else:
            resp = 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
