assign.yml

name: Assign Bot

# Lets external contributors self-assign to issues via `/assign` comments
# and release them via `/unassign`. Scoped to issues labeled `good first
# issue` or `help wanted`; caps at 2 assignees per issue. GITHUB_TOKEN
# with `issues: write` is sufficient — no PAT.

on:
  issue_comment:
    types: [created]

permissions:
  issues: write

jobs:
  assign:
    name: handle /assign and /unassign
    runs-on: ubuntu-latest
    # Skip PR comments — issue_comment fires for both issues and PRs, and
    # `issue.pull_request` is present only on PR comments.
    if: >-
      !github.event.issue.pull_request &&
      (startsWith(github.event.comment.body, '/assign') ||
       startsWith(github.event.comment.body, '/unassign'))
    steps:
      - uses: actions/github-script@v9
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const body = context.payload.comment.body || '';
            const firstLine = body.split(/\r?\n/)[0].trim();

            // Exact, case-sensitive match on the first line. Anything else
            // (e.g. `/assign me`, `/ASSIGN`, quoted mentions) is a no-op.
            let command;
            if (firstLine === '/assign') {
              command = 'assign';
            } else if (firstLine === '/unassign') {
              command = 'unassign';
            } else {
              core.info(`no-op: first line "${firstLine}" is not an exact /assign or /unassign`);
              return;
            }

            const { owner, repo } = context.repo;
            const issue_number = context.payload.issue.number;
            const user = context.payload.comment.user.login;
            const labels = (context.payload.issue.labels || []).map(l => l.name);

            const ALLOWED_LABELS = ['good first issue', 'help wanted'];
            const MAX_ASSIGNEES = 2;

            const hasGatingLabel = labels.some(n => ALLOWED_LABELS.includes(n));
            if (!hasGatingLabel) {
              core.info(`no-op: issue #${issue_number} is not labeled ${ALLOWED_LABELS.join(' or ')}`);
              return;
            }

            const reply = async (body) => {
              await github.rest.issues.createComment({
                owner, repo, issue_number, body,
              });
            };

            try {
              if (command === 'assign') {
                const current = (context.payload.issue.assignees || []).map(a => a.login);
                if (current.includes(user)) {
                  await reply(`@${user} you are already assigned to this issue.`);
                  return;
                }
                if (current.length >= MAX_ASSIGNEES) {
                  await reply(
                    `Sorry @${user}, this issue already has ${current.length} assignees ` +
                    `(cap is ${MAX_ASSIGNEES}). Please wait for one to free up or pick another issue.`
                  );
                  return;
                }
                await github.rest.issues.addAssignees({
                  owner, repo, issue_number, assignees: [user],
                });
                await reply(`Assigned to @${user}. Thanks for picking this up!`);
              } else {
                await github.rest.issues.removeAssignees({
                  owner, repo, issue_number, assignees: [user],
                });
                await reply(`Released by @${user}. The issue is open for others.`);
              }
            } catch (err) {
              core.warning(`assign-bot failed: ${err.message}`);
              await reply(
                `Sorry @${user}, the assign bot hit an error: \`${err.message}\`. ` +
                `A maintainer can assign manually.`
              );
            }