name: Commit linter

on: [pull_request_target]

# Make sure to update Meta/lint-commit.sh to match this script when adding new checks!
# (… but don't accept overlong 'fixup!' commit descriptions.)

jobs:
  lint_commits:
    runs-on: ubuntu-22.04
    if: always() && github.repository == 'SerenityOS/serenity'

    steps:
      - name: Lint PR commits
        uses: actions/github-script@v6
        with:
          script: |
            const excludedBotIds = [
              49699333,  // dependabot[bot]
            ];
            const rules = [
              {
                pattern: /^[^\r]*$/,
                error: "Commit message contains CRLF line breaks (only unix-style LF linebreaks are allowed)",
              },
              {
                pattern: /^.+(\r?\n(\r?\n.*)*)?$/,
                error: "Empty line between commit title and body is missing",
              },
              {
                pattern: /^.{0,72}(?:\r?\n(?:(.{0,72})|(.*?([a-z]+:\/\/)?(([a-zA-Z0-9_]|-)+\.)+[a-z]{2,}(:\d+)?([a-zA-Z_0-9@:%\+.~\?&/=]|-)+).*?))*$/,
                error: "Commit message lines are too long (maximum allowed is 72 characters, except for URLs)",
              },
              {
                pattern: /^((?!^Merge branch )[\s\S])*$/,
                error: "Commit is a git merge commit, use the rebase command instead",
              },
              {
                pattern: /^\S.*?\S: .+/,
                error: "Missing category in commit title (if this is a fix up of a previous commit, it should be squashed)",
              },
              {
                pattern: /^\S.*?: [A-Z0-9]/,
                error: "First word of commit after the subsystem is not capitalized",
              },
              {
                pattern: /^.+[^.\n](\r?\n.*)*$/,
                error: "Commit title ends in a period",
              },
              {
                pattern: /^((?!Signed-off-by: )[\s\S])*$/,
                error: "Commit body contains a Signed-off-by tag",
              },
            ];

            const { repository, pull_request } = context.payload;

            // NOTE: This maxes out at 250 commits. If this becomes a problem, see:
            // https://octokit.github.io/rest.js/v18#pulls-list-commits
            const opts = github.rest.pulls.listCommits.endpoint.merge({
              owner: repository.owner.login,
              repo: repository.name,
              pull_number: pull_request.number,
            });
            const commits = await github.paginate(opts);

            const errors = [];
            for (const { sha, commit: { message }, author } of commits) {
              if (author !== null && excludedBotIds.includes(author.id)) {
                continue;
              }
              const commitErrors = [];
              for (const { pattern, error } of rules) {
                if (!pattern.test(message)) {
                  commitErrors.push(error);
                }
              }
              if (commitErrors.length > 0) {
                const title = message.split("\n")[0];
                errors.push([`${title} (${sha}):`, ...commitErrors].join("\n  "));
              }
            }

            if (errors.length > 0) {
              core.setFailed(`One or more of the commits in this PR do not match the code submission policy:\n\n${errors.join("\n")}`);
            }

      - name: Comment on PR
        if: ${{ failure() && !github.event.pull_request.draft }}
        uses: IdanHo/comment-on-pr@5f51df338210754f519f721f8320d8f72525a4d0
        env:
          GITHUB_TOKEN: ${{ secrets.BUGGIEBOT_TOKEN }}
        with:
          msg: "Hello!\n\nOne or more of the commit messages in this PR do not match the SerenityOS [code submission policy](https://github.com/SerenityOS/serenity/blob/master/CONTRIBUTING.md#code-submission-policy), please check the `lint_commits` CI job for more details on which commits were flagged and why.\nPlease do not close this PR and open another, instead modify your commit message(s) with [git commit --amend](https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/changing-a-commit-message) and force push those changes to update this PR."