name: cleanup caches by a branch
on:
  pull_request:
    types:
      - closed
  workflow_dispatch:

jobs:
  cleanup:
    runs-on: ubuntu-22.04
    permissions:
      # `actions:write` permission is required to delete caches
      #   See also: https://docs.github.com/en/rest/actions/cache?apiVersion=2022-11-28#delete-a-github-actions-cache-for-a-repository-using-a-cache-id
      actions: write
      contents: read
    steps:
      - name: Check out code
        uses: actions/checkout@v4

      - name: Cleanup
        run: |
          gh extension install actions/gh-actions-cache

          REPO=${{ github.repository }}
          BRANCH=refs/pull/${{ github.event.pull_request.number }}/merge

          echo "Fetching list of cache key"
          cacheKeysForPR=$(gh actions-cache list -R $REPO -B $BRANCH | cut -f 1 )

          ## Setting this to not fail the workflow while deleting cache keys.
          set +e
          echo "Deleting caches..."
          for cacheKey in $cacheKeysForPR
          do
              gh actions-cache delete $cacheKey -R $REPO -B $BRANCH --confirm
          done
          echo "Done"
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}