#!/usr/bin/env python3
from __future__ import print_function

import requests
import re
import argparse
import sys
import os

from six.moves.configparser import ConfigParser
from typing import Any, Dict, MutableMapping, Optional, Text

# Scans zulip repositary for issues that don't have any `area` labels.
# GitHub API token is required as GitHub limits unauthenticated
# requests to 60/hour. There is a good chance that this limit is
# bypassed in consecutive attempts.
# The api token can be generated here
# https://github.com/settings/tokens/new?description=Zulip%20Issue%20Label%20Checker
#
# Copy conf.ini-template to conf.ini and populate with your api token.
#
# usage: python check-issue-labels
# Pass --force as an argument to run without a token.

def get_config():
    # type: () -> ConfigParser
    config = ConfigParser()
    config.read(os.path.join(os.path.dirname(os.path.abspath(__file__)), 'conf.ini'))
    return config

def area_labeled(issue):
    # type: (Dict[str, Any]) -> bool
    for label in issue["labels"]:
        label_name = str(label["name"])
        if "area:" in label_name:
            return True
    return False

def is_issue(item):
    # type: (Dict[str, Any]) -> bool
    return "issues" in item["html_url"]

def get_next_page_url(link_header):
    # type: (str) -> Optional[str]
    matches = re.findall(r'\<(\S+)\>; rel=\"next\"', link_header)
    try:
        return matches[0]
    except IndexError:
        return None

def check_issue_labels():
    # type: () -> None
    parser = argparse.ArgumentParser()
    parser.add_argument('--force', action="store_true", dest="force", default=False)
    args = parser.parse_args()

    if not args.force:
        config = get_config()
        try:
            token = config.get('github', 'api_token')
        except KeyError:
            print("Error fetching GitHub api token. Copy conf.ini-template to conf.ini and populate with "
                  "your api token. If you want to continue without using a token use --force.")
            sys.exit(1)

    next_page_url = 'https://api.github.com/repos/zulip/zulip/issues'  # type: Optional[Text]
    unlabeled_issue_urls = []
    while next_page_url:
        try:
            if args.force:
                response = requests.get(next_page_url)
            else:
                response = requests.get(next_page_url, headers={'Authorization': 'token %s' % token})
            if response.status_code == 401:
                sys.exit("Error. Please check the token.")
            if response.status_code == 403:
                sys.exit("403 Error. This is generally caused when API limit is exceeded. You use an api "
                         "token to overcome this limit.")
        except requests.exceptions.RequestException as e:
            print(e)
            sys.exit(1)

        next_page_url = get_next_page_url(response.headers["Link"])
        for item in response.json():
            if is_issue(item) and not area_labeled(item):
                unlabeled_issue_urls.append(item["html_url"])

    if len(unlabeled_issue_urls):
        print("The following issues don't have any area labels associated with it")
        print("\n".join(unlabeled_issue_urls))
    else:
        print("No GitHub issues found with missing area labels.")

if __name__ == '__main__':
    check_issue_labels()