name: Restore Wiki Pages Deleted by Others

# The gollum event only fires on page create/update, never on deletion,
# so deletions can only be caught by polling the wiki git history.

on:
  schedule:
    - cron: "*/10 * * * *"
  gollum:
  workflow_dispatch:

permissions:
  contents: write
  issues: write

concurrency:
  group: wiki-guard
  cancel-in-progress: false

jobs:
  restore:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout wiki repository
        uses: actions/checkout@v7
        with:
          repository: ${{ github.repository }}.wiki
          path: wiki
          fetch-depth: 0

      - name: Restore pages deleted by non-maintainer
        id: restore
        run: |
          cd wiki
          git config core.quotePath false

          # Any author email under this domain is the maintainer and may delete pages.
          OWNER_DOMAIN="neilpang.com"

          : > ../restored.txt

          # Paths deleted within the recent window (rolling; the cron runs
          # every 10 minutes, so 7 days gives ample overlap without
          # resurrecting old deletions the maintainer already accepted).
          # --no-renames makes a rename count as a deletion of the old path,
          # so a page renamed by a non-maintainer is restored under its
          # original name (the new name stays -- creating pages is allowed).
          git log --since="7 days ago" --diff-filter=D --no-renames --name-only --format= \
            | sort -u \
            | while IFS= read -r f; do
                if [ -z "$f" ] || [ -e "$f" ]; then
                  continue
                fi
                # The most recent commit (in full history) that deleted this path.
                del="$(git log -1 --diff-filter=D --no-renames --format=%H -- "$f")"
                if [ -z "$del" ]; then
                  continue
                fi
                ae="$(git show -s --format=%ae "$del" | tr 'A-Z' 'a-z')"
                case "$ae" in
                  *@"$OWNER_DOMAIN")
                    continue
                    ;;
                esac
                an="$(git show -s --format=%an "$del")"
                echo "Restoring: $f (deleted in $del by $an <$ae>)"
                git checkout "$del^" -- "$f"
                printf '%s\n' "- \`$f\` deleted in $del by $an <$ae>" >> ../restored.txt
              done

          if [ -s ../restored.txt ]; then
            git config user.name "github-actions[bot]"
            git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
            git commit -m "Restore pages deleted by non-maintainer"
            git push origin HEAD || { git pull --rebase && git push origin HEAD; }
            {
              echo "The following wiki pages were deleted or renamed by someone other than the maintainer and have been restored automatically:"
              echo ""
              cat ../restored.txt
              echo ""
              echo "Wiki: https://github.com/${GITHUB_REPOSITORY}/wiki"
            } > ../restore-msg.txt
            echo "restored=true" >> "$GITHUB_OUTPUT"
          else
            echo "No unauthorized deletions found."
            echo "restored=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Create issue to notify Neilpang
        if: steps.restore.outputs.restored == 'true'
        uses: peter-evans/create-issue-from-file@v6
        with:
          title: "Wiki pages restored after unauthorized deletion"
          content-filepath: ./restore-msg.txt
          assignees: Neilpang