import argparse
import os
import time

from github import Github


GITHUB_TOKEN = os.getenv('GITHUB_TOKEN')


def get_mergeable_state(pr_number):
    """Get mergeable state of the PR https://docs.github.com/en/graphql/reference/enums#mergestatestatus"""
    github_api = Github(GITHUB_TOKEN)
    db_repo = github_api.get_repo("theorchard/database")

    # github calculates mergeable state when the api request occurs, so might need to retry a fetch if stale
    attempt = 1
    while (attempt < 3):
        pr = db_repo.get_pull(pr_number)
        mergeable_state = pr.mergeable_state

        if mergeable_state != 'unknown':
            return mergeable_state

        print('PR {} status is currently unknown, sleeping and retrying.'.format(
            pr_number))
        time.sleep(5)
        attempt = attempt + 1
    raise Exception('PR {} has a mergeable_state of unknown. Please give '
                    'GitHub a minute to finish calculating this state.')
    

def is_pr_mergeable(pr_number, raise_exception):
    
    pr_mergeable_state = get_mergeable_state(pr_number)
    print('The status of PR {} is {}'.format(pr_number, pr_mergeable_state))
    
    if pr_mergeable_state != 'clean':
        message = 'PR {} is not mergeable, blocking deploy'.format(pr_number)
        if raise_exception:
            raise Exception(message)
        print(message)
        return False
    print('This PR is mergeable')
    return True


def main(*args):
    parser = argparse.ArgumentParser()
    parser.add_argument(
        '--pr-number',
        type=int,
        required=True,
        help='Pull Request to check if mergeable')
    parser.add_argument(
        '--raise-exception',
        action='store_true',
        help='Raise exception if PR is not mergeable')
    args = parser.parse_args()
    is_pr_mergeable(args.pr_number, args.raise_exception)


if __name__ == '__main__':
    main()