import argparse
import re
import sys
import os
from github import Github
from github.GithubException import UnknownObjectException

try:
    github_token = os.environ["GITHUB_TOKEN"]
except KeyError:
    print("Please set the 'GITHUB_TOKEN' environment variable")
    sys.exit(1)


def parser():
    parser = argparse.ArgumentParser()
    parser.add_argument('--repository', type=str, required=True,
                        help='Github repository name (e.g., scylladb/scylladb)')
    parser.add_argument('--commit_before_merge', type=str, required=True, help='Git commit ID to start labeling from ('
                                                                               'newest commit).')
    parser.add_argument('--commit_after_merge', type=str, required=True,
                        help='Git commit ID to end labeling at (oldest '
                             'commit, exclusive).')
    parser.add_argument('--update_issue', type=bool, default=False, help='Set True to update issues when backport was '
                                                                         'done')
    parser.add_argument('--ref', type=str, required=True, help='PR target branch')
    return parser.parse_args()


def add_comment_and_close_pr(pr, comment):
    if pr.state == 'open':
        pr.create_issue_comment(comment)
        pr.edit(state="closed")


def mark_backport_done(repo, ref_pr_number, branch):
    pr = repo.get_pull(int(ref_pr_number))
    label_to_remove = f'backport/{branch}'
    label_to_add = f'{label_to_remove}-done'
    current_labels = [label.name for label in pr.get_labels()]
    if label_to_remove in current_labels:
        pr.remove_from_labels(label_to_remove)
    if label_to_add not in current_labels:
        pr.add_to_labels(label_to_add)


def main():
    # This script is triggered by a push event to either the master branch or a branch named branch-x.y (where x and y represent version numbers). Based on the pushed branch, the script performs the following actions:
    # - When ref branch is `master`, it will add the `promoted-to-master` label, which we need later for the auto backport process
    # - When ref branch is `branch-x.y` (which means we backported a patch), it will replace in the original PR the `backport/x.y` label with `backport/x.y-done` and will close the backport PR (Since GitHub close only the one referring to default branch)
    args = parser()
    pr_pattern = re.compile(r'Closes .*#([0-9]+)')
    target_branch = re.search(r'branch-(\d+\.\d+)', args.ref)
    g = Github(github_token)
    repo = g.get_repo(args.repository, lazy=False)
    commits = repo.compare(head=args.commit_after_merge, base=args.commit_before_merge)
    processed_prs = set()
    # Print commit information
    for commit in commits.commits:
        print(f'Commit sha is: {commit.sha}')
        match = pr_pattern.search(commit.commit.message)
        if match:
            pr_number = int(match.group(1))
            if pr_number in processed_prs:
                continue
            if target_branch:
                pr = repo.get_pull(pr_number)
                branch_name = target_branch[1]
                refs_pr = re.findall(r'Refs (?:#|https.*?)(\d+)', pr.body)
                if refs_pr:
                    print(f'branch-{target_branch.group(1)}, pr number is: {pr_number}')
                    # 1. change the backport label of the parent PR to note that
                    #    we've merge the corresponding backport PR
                    # 2. close the backport PR and leave a comment on it to note
                    #    that it has been merged with a certain git commit,
                    ref_pr_number = refs_pr[0]
                    mark_backport_done(repo, ref_pr_number, branch_name)
                    comment = f'Closed via {commit.sha}'
                    add_comment_and_close_pr(pr, comment)
            else:
                try:
                    pr = repo.get_pull(pr_number)
                    pr.add_to_labels('promoted-to-master')
                    print(f'master branch, pr number is: {pr_number}')
                except UnknownObjectException:
                    print(f'{pr_number} is not a PR but an issue, no need to add label')
            processed_prs.add(pr_number)


if __name__ == "__main__":
    main()