slack.py

import hashlib
import hmac
from http import HTTPStatus
import json
import logging
import math
import re
import time
from typing import Any, Awaitable, Callable, Dict, List, Optional, Text

from rasa.core.channels.channel import InputChannel, OutputChannel, UserMessage
from rasa.shared.constants import DOCS_URL_CONNECTORS_SLACK
from rasa.shared.exceptions import InvalidConfigException, RasaException
import rasa.shared.utils.io
from sanic import Blueprint, response
from sanic.request import Request
from sanic.response import HTTPResponse
from slack import WebClient

logger = logging.getLogger(__name__)


class SlackBot(OutputChannel):
    """A Slack communication channel"""

    @classmethod
    def name(cls) -> Text:
        return "slack"

    def __init__(
        self,
        token: Text,
        slack_channel: Optional[Text] = None,
        thread_id: Optional[Text] = None,
        proxy: Optional[Text] = None,
    ) -> None:

        self.slack_channel = slack_channel
        self.thread_id = thread_id
        self.proxy = proxy
        self.client = WebClient(token, run_async=True, proxy=proxy)
        super().__init__()

    @staticmethod
    def _get_text_from_slack_buttons(buttons: List[Dict]) -> Text:
        return "".join([b.get("title", "") for b in buttons])

    async def _post_message(self, channel: Text, **kwargs: Any) -> None:
        if self.thread_id:
            await self.client.chat_postMessage(
                channel=channel, **kwargs, thread_ts=self.thread_id
            )
        else:
            await self.client.chat_postMessage(channel=channel, **kwargs)

    async def send_text_message(
        self, recipient_id: Text, text: Text, **kwargs: Any
    ) -> None:
        recipient = self.slack_channel or recipient_id
        for message_part in text.strip().split("\n\n"):
            await self._post_message(
                channel=recipient, as_user=True, text=message_part, type="mrkdwn"
            )

    async def send_image_url(
        self, recipient_id: Text, image: Text, **kwargs: Any
    ) -> None:
        recipient = self.slack_channel or recipient_id
        image_block = {"type": "image", "image_url": image, "alt_text": image}

        await self._post_message(
            channel=recipient, as_user=True, text=image, blocks=[image_block]
        )

    async def send_attachment(
        self, recipient_id: Text, attachment: Dict[Text, Any], **kwargs: Any
    ) -> None:
        recipient = self.slack_channel or recipient_id
        await self._post_message(
            channel=recipient, as_user=True, attachments=[attachment], **kwargs
        )

    async def send_text_with_buttons(
        self,
        recipient_id: Text,
        text: Text,
        buttons: List[Dict[Text, Any]],
        **kwargs: Any,
    ) -> None:
        recipient = self.slack_channel or recipient_id

        text_block = {"type": "section", "text": {"type": "plain_text", "text": text}}

        if len(buttons) > 5:
            rasa.shared.utils.io.raise_warning(
                "Slack API currently allows only up to 5 buttons. "
                "Since you added more than 5, slack will ignore all of them."
            )
            return await self.send_text_message(recipient, text, **kwargs)

        button_block = {"type": "actions", "elements": []}
        for button in buttons:
            button_block["elements"].append(
                {
                    "type": "button",
                    "text": {"type": "plain_text", "text": button["title"]},
                    "value": button["payload"],
                }
            )

        await self._post_message(
            channel=recipient,
            as_user=True,
            text=text,
            blocks=[text_block, button_block],
        )

    async def send_custom_json(
        self, recipient_id: Text, json_message: Dict[Text, Any], **kwargs: Any
    ) -> None:
        channel = json_message.get("channel", self.slack_channel or recipient_id)
        json_message.setdefault("as_user", True)
        await self._post_message(channel=channel, **json_message)


class SlackInput(InputChannel):
    """Slack input channel implementation. Based on the HTTPInputChannel."""

    @classmethod
    def name(cls) -> Text:
        return "slack"

    @classmethod
    def from_credentials(cls, credentials: Optional[Dict[Text, Any]]) -> InputChannel:
        if not credentials:
            cls.raise_missing_credentials_exception()

        return cls(
            credentials.get("slack_token"),
            credentials.get("slack_channel"),
            credentials.get("proxy"),
            credentials.get("slack_retry_reason_header", "x-slack-retry-reason"),
            credentials.get("slack_retry_number_header", "x-slack-retry-num"),
            credentials.get("errors_ignore_retry", None),
            credentials.get("use_threads", False),
            credentials.get("slack_signing_secret", ""),
        )

    def __init__(
        self,
        slack_token: Text,
        slack_channel: Optional[Text] = None,
        proxy: Optional[Text] = None,
        slack_retry_reason_header: Optional[Text] = None,
        slack_retry_number_header: Optional[Text] = None,
        errors_ignore_retry: Optional[List[Text]] = None,
        use_threads: Optional[bool] = False,
        slack_signing_secret: Text = "",
    ) -> None:
        """Create a Slack input channel.

        Needs a couple of settings to properly authenticate and validate
        messages. Details to setup:

        https://github.com/slackapi/python-slackclient

        Args:
            slack_token: Your Slack Authentication token. You can create a
                Slack app and get your Bot User OAuth Access Token
                `here <https://api.slack.com/slack-apps>`_.
            slack_channel: the string identifier for a channel to which
                the bot posts, or channel name (e.g. '#bot-test')
                If not set, messages will be sent back
                to the "App" DM channel of your bot's name.
            proxy: A Proxy Server to route your traffic through
            slack_retry_reason_header: Slack HTTP header name indicating reason
                that slack send retry request.
            slack_retry_number_header: Slack HTTP header name indicating
                the attempt number.
            errors_ignore_retry: Any error codes given by Slack
                included in this list will be ignored.
                Error codes are listed
                `here <https://api.slack.com/events-api#errors>`_.
            use_threads: If set to `True`, your bot will send responses in Slack as
                a threaded message. Responses will appear as a normal Slack message
                if set to `False`.
            slack_signing_secret: Slack creates a unique string for your app and
                shares it with you. This allows us to verify requests from Slack
                with confidence by verifying signatures using your signing secret.

        """
        self.slack_token = slack_token
        self.slack_channel = slack_channel
        self.proxy = proxy
        self.errors_ignore_retry = errors_ignore_retry or ("http_timeout",)
        self.retry_reason_header = slack_retry_reason_header
        self.retry_num_header = slack_retry_number_header
        self.use_threads = use_threads
        self.slack_signing_secret = slack_signing_secret

        self._validate_credentials()

    def _validate_credentials(self) -> None:
        """Raises exceptions if the connector is not properly configured."""
        if not self.slack_signing_secret:
            raise InvalidConfigException(
                f"Your slack bot is missing a configured signing secret. Running a "
                f"bot without a signing secret is insecure and was removed. "
                f"You need to add a `slack_signing_secret` parameter to your channel "
                f"configuration. "
                f"More info at {DOCS_URL_CONNECTORS_SLACK} ."
            )

    @staticmethod
    def _is_app_mention(slack_event: Dict) -> bool:
        try:
            return slack_event["event"]["type"] == "app_mention"
        except KeyError:
            return False

    @staticmethod
    def _is_direct_message(slack_event: Dict) -> bool:
        try:
            return slack_event["event"]["channel_type"] == "im"
        except KeyError:
            return False

    @staticmethod
    def _is_user_message(slack_event: Dict[Text, Any]) -> bool:
        return (
            slack_event.get("event") is not None
            and (
                slack_event.get("event", {}).get("type") == "message"
                or slack_event.get("event", {}).get("type") == "app_mention"
            )
            and slack_event.get("event", {}).get("text")
            and not slack_event.get("event", {}).get("bot_id")
        ) or SlackInput._is_init_message(slack_event)

    @staticmethod
    def _is_init_message(slack_event: Dict[Text, Any]) -> bool:
        """
        This method determines if a message sent is an initial message
        from Slack when the user opens up the window with chatbot conversation.

        This can happen multiple times throughout the conversation and the user 
        needs to handle this on the chatbot side only actually invoking 
        init intent e.g. if a certain time (like 24 hours) have passed since
        last time welcome message (=init intent) display.

        By default the init intent is not invoked as this message is normally
        not invoked by Slack. For this method to work it needs to be subscribed
        to in event subscription. 
        Args:
            slack_event: event from slack saying that user has started chatbot interaction
        """
        return (
            slack_event.get("event") is not None
            and slack_event.get("event", {}).get("type") == "app_home_opened"
        )

    @staticmethod
    def _sanitize_user_message(
        text: Text, uids_to_remove: Optional[List[Text]]
    ) -> Text:
        """Remove superfluous/wrong/problematic tokens from a message.

        Probably a good starting point for pre-formatting of user-provided text
        to make NLU's life easier in case they go funky to the power of extreme

        In the current state will just drop self-mentions of bot itself

        Args:
            text: raw message as sent from slack
            uids_to_remove: a list of user ids to remove from the content

        Returns:
            str: parsed and cleaned version of the input text
        """

        uids_to_remove = uids_to_remove or []

        for uid_to_remove in uids_to_remove:
            # heuristic to format majority cases OK
            # can be adjusted to taste later if needed,
            # but is a good first approximation
            for regex, replacement in [
                (fr"<@{uid_to_remove}>\s", ""),
                (fr"\s<@{uid_to_remove}>", ""),  # a bit arbitrary but probably OK
                (fr"<@{uid_to_remove}>", " "),
            ]:
                text = re.sub(regex, replacement, text)

        # Find multiple mailto or http links like
        # <mailto:xyz@rasa.com|xyz@rasa.com> or
        # <http://url.com|url.com> in text and substitute
        # it with original content
        pattern = r"(\<(?:mailto|http|https):\/\/.*?\|.*?\>)"
        match = re.findall(pattern, text)

        if match:
            for remove in match:
                replacement = remove.split("|")[1]
                replacement = replacement.replace(">", "")
                text = text.replace(remove, replacement)
        return text.strip()

    @staticmethod
    def _is_interactive_message(payload: Dict) -> bool:
        """Check wheter the input is a supported interactive input type."""

        supported = [
            "button",
            "select",
            "static_select",
            "external_select",
            "conversations_select",
            "users_select",
            "channels_select",
            "overflow",
            "datepicker",
            "multi_static_select",
        ]
        if payload.get("actions"):
            action_type = payload["actions"][0].get("type")
            if action_type in supported:
                return True
            elif action_type:
                logger.warning(
                    "Received input from a Slack interactive component of type "
                    f"'{payload['actions'][0]['type']}', for which payload parsing is not yet supported."
                )
        return False

    @staticmethod
    def _get_text_from_multi_select(action: Dict) -> Optional[Text]:
        values = []
        for val in action.get("selected_options"):
            values.append(val.get("value"))
        return ",".join(values)

    @staticmethod
    def _get_interactive_response(action: Dict) -> Optional[Text]:
        """Parse the payload for the response value."""

        if action["type"] == "button":
            return action.get("value")
        elif action["type"] == "select":
            return action.get("selected_options", [{}])[0].get("value")
        elif action["type"] == "static_select":
            return action.get("selected_option", {}).get("value")
        elif action["type"] == "external_select":
            return action.get("selected_option", {}).get("value")
        elif action["type"] == "conversations_select":
            return action.get("selected_conversation")
        elif action["type"] == "users_select":
            return action.get("selected_user")
        elif action["type"] == "channels_select":
            return action.get("selected_channel")
        elif action["type"] == "overflow":
            return action.get("selected_option", {}).get("value")
        elif action["type"] == "datepicker":
            return action.get("selected_date")
        elif action["type"] == "multi_static_select":
            return SlackInput._get_text_from_multi_select(action)

    async def process_message(
        self,
        request: Request,
        on_new_message: Callable[[UserMessage], Awaitable[Any]],
        text: Text,
        sender_id: Optional[Text],
        metadata: Optional[Dict],
    ) -> Any:
        """Slack retries to post messages up to 3 times based on
        failure conditions defined here:
        https://api.slack.com/events-api#failure_conditions
        """
        retry_reason = request.headers.get(self.retry_reason_header)
        retry_count = request.headers.get(self.retry_num_header)
        if retry_count and retry_reason in self.errors_ignore_retry:
            logger.warning(
                f"Received retry #{retry_count} request from slack"
                f" due to {retry_reason}."
            )

            return response.text(
                None, status=HTTPStatus.CREATED, headers={"X-Slack-No-Retry": 1}
            )

        if metadata is not None:
            output_channel = metadata.get("out_channel")
            if self.use_threads:
                thread_id = metadata.get("thread_id")
            else:
                thread_id = None
        else:
            output_channel = None
            thread_id = None

        try:
            user_msg = UserMessage(
                text,
                self.get_output_channel(output_channel, thread_id),
                sender_id,
                input_channel=self.name(),
                metadata=metadata,
            )

            await on_new_message(user_msg)
        except Exception as e:
            logger.error(f"Exception when trying to handle message.{e}")
            logger.error(str(e), exc_info=True)

        return response.text("")

    def get_metadata(self, request: Request) -> Dict[Text, Any]:
        """Extracts the metadata from a slack API event.

        Slack Documentation: https://api.slack.com/types/event

        Args:
            request: A `Request` object that contains a slack API event in the body.

        Returns:
            Metadata extracted from the sent event payload. This includes the output
                channel for the response, and users that have installed the bot.
        """
        content_type = request.headers.get("content-type")

        # Slack API sends either a JSON-encoded or a URL-encoded body depending on the
        # content
        if content_type == "application/json":
            # if JSON-encoded message is received
            slack_event = request.json
            event = slack_event.get("event", {})
            thread_id = event.get("thread_ts", event.get("ts"))

            users = []
            if "authed_users" in slack_event:
                users = slack_event.get("authed_users")
            elif (
                "authorizations" in slack_event
                and len(slack_event.get("authorizations")) > 0
            ):
                users.append(slack_event.get("authorizations")[0].get("user_id"))

            return {
                "out_channel": event.get("channel"),
                "thread_id": thread_id,
                "users": users,
            }

        if content_type == "application/x-www-form-urlencoded":
            # if URL-encoded message is received
            output = request.form
            payload = json.loads(output["payload"][0])
            message = payload.get("message", {})
            thread_id = message.get("thread_ts", message.get("ts"))

            users = []
            if payload.get("user", {}).get("id"):
                users.append(payload.get("user", {}).get("id"))

            return {
                "out_channel": payload.get("channel", {}).get("id"),
                "thread_id": thread_id,
                "users": users,
            }

        return {}

    def is_request_from_slack_authentic(self, request: Request) -> bool:
        """Validate a request from Slack for its authenticity.

        Checks if the signature matches the one we expect from Slack. Ensures
        we don't process request from a third-party disguising as slack.

        Args:
            request: incoming request to be checked

        Returns:
            `True` if the request came from Slack.
        """

        try:
            slack_signing_secret = bytes(self.slack_signing_secret, "utf-8")

            slack_signature = request.headers.get("X-Slack-Signature", "")
            slack_request_timestamp = request.headers.get(
                "X-Slack-Request-Timestamp", "0"
            )

            if abs(time.time() - int(slack_request_timestamp)) > 60 * 5:
                # The request timestamp is more than five minutes from local time.
                # It could be a replay attack, so let's ignore it.
                return False

            prefix = f"v0:{slack_request_timestamp}:".encode("utf-8")
            basestring = prefix + request.body
            digest = hmac.new(
                slack_signing_secret, basestring, hashlib.sha256
            ).hexdigest()
            computed_signature = f"v0={digest}"

            return hmac.compare_digest(computed_signature, slack_signature)
        except Exception as e:
            logger.error(
                f"Failed to validate slack request authenticity. "
                f"Assuming invalid request. Error: {e}"
            )
            return False

    def blueprint(
        self, on_new_message: Callable[[UserMessage], Awaitable[Any]]
    ) -> Blueprint:
        slack_webhook = Blueprint("slack_webhook", __name__)

        @slack_webhook.route("/", methods=["GET"])
        async def health(_: Request) -> HTTPResponse:
            return response.json({"status": "ok"})

        @slack_webhook.route("/webhook", methods=["GET", "POST"])
        async def webhook(request: Request) -> HTTPResponse:
            content_type = request.headers.get("content-type")

            if not self.is_request_from_slack_authentic(request):
                return response.text(
                    "Message is not properly signed with a valid "
                    "X-Slack-Signature header",
                    status=HTTPStatus.BAD_REQUEST,
                )

            # Slack API sends either a JSON-encoded or a URL-encoded body
            # depending on the content

            if content_type == "application/json":
                # if JSON-encoded message is received
                output = request.json
                event = output.get("event", {})
                user_message = event.get("text", "")
                sender_id = event.get("user", "")
                metadata = self.get_metadata(request)

                if "challenge" in output:
                    return response.json(output.get("challenge"))

                if not self._is_user_message(output):
                    logger.debug(
                        "Received message from Slack which doesn't look like "
                        "a user message. Skipping message."
                    )
                    return response.text("Bot message delivered.")
                if self._is_init_message(output):
                    logger.debug("Init message recieved - sending to /init intent")
                    user_message = "/init"
                if not self._is_supported_channel(output, metadata):
                    logger.warning(
                        f"Received message on unsupported channel: {metadata['out_channel']}"
                    )
                    return response.text("channel not supported.")

                return await self.process_message(
                    request,
                    on_new_message,
                    text=self._sanitize_user_message(user_message, metadata["users"]),
                    sender_id=sender_id,
                    metadata=metadata,
                )
            elif content_type == "application/x-www-form-urlencoded":
                # if URL-encoded message is received
                output = request.form
                payload = json.loads(output["payload"][0])

                if self._is_interactive_message(payload):
                    sender_id = payload["user"]["id"]
                    text = self._get_interactive_response(payload["actions"][0])
                    if text is not None:
                        metadata = self.get_metadata(request)
                        return await self.process_message(
                            request, on_new_message, text, sender_id, metadata
                        )
                    if payload["actions"][0]["type"] == "button":
                        # link buttons don't have "value", don't send their clicks to
                        # bot
                        return response.text("User clicked link button")
                return response.text(
                    "The input message could not be processed.",
                    status=HTTPStatus.INTERNAL_SERVER_ERROR,
                )

            return response.text("Bot message delivered.")

        return slack_webhook

    def _is_supported_channel(self, slack_event: Dict, metadata: Dict) -> bool:
        return (
            self._is_direct_message(slack_event)
            or self._is_app_mention(slack_event)
            or metadata["out_channel"] == self.slack_channel
            or self._is_init_message(slack_event)
        )

    def get_output_channel(
        self, channel: Optional[Text] = None, thread_id: Optional[Text] = None
    ) -> OutputChannel:
        channel = channel or self.slack_channel
        return SlackBot(self.slack_token, channel, thread_id, self.proxy)

    def set_output_channel(self, channel: Text) -> None:
        self.slack_channel = channel