pr-title-bot.yml

name: PR Title Bot

on:
  pull_request_target:
    types:
      - opened
      - synchronize
      - reopened
  workflow_dispatch:
    inputs:
      pr_number:
        description: "PR number to rewrite (leave blank to process all open PRs)"
        required: false
        type: number

permissions:
  pull-requests: write
  contents: read

jobs:
  discover:
    runs-on: ubuntu-latest
    outputs:
      pr_numbers: ${{ steps.list.outputs.pr_numbers }}
    steps:
      - name: Determine target PRs
        id: list
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          REPO: ${{ github.repository }}
        run: |
          set -euo pipefail

          if [[ -n "${{ github.event.pull_request.number }}" ]]; then
            numbers="[${{ github.event.pull_request.number }}]"
          elif [[ -n "${{ inputs.pr_number }}" ]]; then
            numbers="[${{ inputs.pr_number }}]"
          else
            numbers=$(gh pr list --repo "$REPO" --state open --limit 1000 --json number --jq '[.[].number]')
          fi

          echo "Targeting PRs: $numbers"
          echo "pr_numbers=$numbers" >> "$GITHUB_OUTPUT"

  rewrite:
    needs: discover
    if: needs.discover.outputs.pr_numbers != '[]'
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        pr_number: ${{ fromJson(needs.discover.outputs.pr_numbers) }}
    concurrency:
      group: pr-title-bot-${{ matrix.pr_number }}
      cancel-in-progress: true
    steps:
      - name: Rewrite title and label from plugin diff
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          REPO: ${{ github.repository }}
          PR_NUMBER: ${{ matrix.pr_number }}
        run: |
          set -euo pipefail

          HEAD_SHA=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json headRefOid --jq '.headRefOid')

          files=$(gh api "repos/$REPO/pulls/$PR_NUMBER/files" --paginate \
            --jq '.[] | select(.filename | startswith("plugins/")) | "\(.status)\t\(.filename)\t\(.sha)"')

          if [[ -z "$files" ]]; then
            echo "No plugin files changed; skipping."
            exit 0
          fi

          plugin_paths=$(printf '%s\n' "$files" | cut -f2 | awk -F/ '{print $1"/"$2}' | sort -u)
          plugin_count=$(printf '%s\n' "$plugin_paths" | grep -c .)

          if [[ "$plugin_count" -ne 1 ]]; then
            echo "PR touches $plugin_count plugin directories; skipping title rewrite."
            exit 0
          fi

          plugin_path=$plugin_paths
          line=$(printf '%s\n' "$files" | awk -F'\t' -v p="$plugin_path" '$2==p {print; exit}')
          status=$(printf '%s' "$line" | cut -f1)
          submodule_sha=$(printf '%s' "$line" | cut -f3)

          case "$status" in
            added)
              verb="Add"
              label="plugin-addition"
              other_label="plugin-update"
              ;;
            modified)
              verb="Update"
              label="plugin-update"
              other_label="plugin-addition"
              ;;
            *)
              echo "Unhandled file status '$status' for $plugin_path; skipping."
              exit 0
              ;;
          esac

          submodule_url=$(gh api "repos/$REPO/contents/.gitmodules?ref=$HEAD_SHA" --jq '.content' | base64 -d \
            | awk -v p="$plugin_path" '
                $0 ~ ("\\[submodule \"" p "\"\\]") { found=1; next }
                found && /^\[submodule/ { found=0 }
                found && /url[ \t]*=/ { sub(/^[ \t]*url[ \t]*=[ \t]*/, ""); print; exit }
              ')

          if [[ -z "$submodule_url" ]]; then
            echo "Could not resolve submodule URL for $plugin_path; skipping."
            exit 0
          fi

          sub_repo=$(printf '%s' "$submodule_url" | tr -d '\r' | sed -E 's/[[:space:]]+$//' \
            | sed -E 's#^https://github\.com/##' | sed -E 's#\.git$##' | sed -E 's#/$##')

          common_name=$(gh api "repos/$sub_repo/contents/plugin.json?ref=$submodule_sha" --jq '.content' 2>/dev/null \
            | base64 -d 2>/dev/null | jq -r '.common_name // empty' 2>/dev/null || true)

          if [[ -z "$common_name" ]]; then
            common_name=$(basename "$plugin_path" | sed -E 's/[-_]+/ /g' | sed -E 's/(^|[ ])([a-z])/\1\u\2/g')
            echo "::warning::Could not read common_name from plugin.json for $sub_repo@$submodule_sha; falling back to '$common_name'."
          fi

          new_title="$verb $common_name"
          current_title=$(gh pr view "$PR_NUMBER" --repo "$REPO" --json title --jq '.title')

          if [[ "$current_title" != "$new_title" ]]; then
            gh pr edit "$PR_NUMBER" --repo "$REPO" --title "$new_title"
          fi

          gh pr edit "$PR_NUMBER" --repo "$REPO" --add-label "$label" --remove-label "$other_label"