# Webhooks for external integrations.
import re
from typing import Any, Dict, Text, Optional

from django.http import HttpRequest, HttpResponse
from django.utils.translation import ugettext as _

from zerver.decorator import api_key_only_webhook_view
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_error, json_success
from zerver.lib.webhooks.common import check_send_webhook_message
from zerver.models import UserProfile

@api_key_only_webhook_view("AppFollow")
@has_request_variables
def api_appfollow_webhook(request: HttpRequest, user_profile: UserProfile,
                          payload: Dict[str, Any]=REQ(argument_type="body")) -> HttpResponse:
    message = payload["text"]
    app_name = re.search('\A(.+)', message).group(0)
    topic = app_name

    check_send_webhook_message(request, user_profile, topic,
                               body=convert_markdown(message))
    return json_success()

def convert_markdown(text: Text) -> Text:
    # Converts Slack-style markdown to Zulip format
    # Implemented mainly for AppFollow messages
    # Not ready for general use as some edge-cases not handled
    # Convert Bold
    text = re.sub(r'(?:(?<=\s)|(?<=^))\*(.+?\S)\*(?=\s|$)', r'**\1**', text)
    # Convert Italics
    text = re.sub(r'\b_(\s*)(.+?)(\s*)_\b', r'\1*\2*\3', text)
    # Convert Strikethrough
    text = re.sub(r'(?:(?<=\s)|(?<=^))~(.+?\S)~(?=\s|$)', r'~~\1~~', text)

    return text

# Webhooks for external integrations.
import re
from typing import Any, Dict, Text, Optional

from django.http import HttpRequest, HttpResponse
from django.utils.translation import ugettext as _

from zerver.decorator import api_key_only_webhook_view
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_error, json_success
from zerver.lib.webhooks.common import check_send_webhook_message
from zerver.models import UserProfile

@api_key_only_webhook_view("AppFollow")
@has_request_variables
def api_appfollow_webhook(request: HttpRequest, user_profile: UserProfile,
                          payload: Dict[str, Any]=REQ(argument_type="body")) -> HttpResponse:
    message = payload["text"]
    app_name_search = re.search('\A(.+)', message)
    assert app_name_search is not None
    app_name = app_name_search.group(0)
    topic = app_name

    check_send_webhook_message(request, user_profile, topic,
                               body=convert_markdown(message))
    return json_success()

def convert_markdown(text: Text) -> Text:
    # Converts Slack-style markdown to Zulip format
    # Implemented mainly for AppFollow messages
    # Not ready for general use as some edge-cases not handled
    # Convert Bold
    text = re.sub(r'(?:(?<=\s)|(?<=^))\*(.+?\S)\*(?=\s|$)', r'**\1**', text)
    # Convert Italics
    text = re.sub(r'\b_(\s*)(.+?)(\s*)_\b', r'\1*\2*\3', text)
    # Convert Strikethrough
    text = re.sub(r'(?:(?<=\s)|(?<=^))~(.+?\S)~(?=\s|$)', r'~~\1~~', text)

    return text

Add assert for re search being None in appfollow webhook.