name: cleanup caches by branch
on:
  pull_request:
    types:
      - closed
jobs:
  cleanup:
    runs-on: ubuntu-latest
    steps:
      - name: Check out code
        uses: actions/checkout@v3
        
      - name: Cleanup
        run: |
          gh extension install actions/gh-actions-cache
          
          REPO=${{ github.repository }}

          # get the branch
          BRANCH="refs/pull/${{ github.event.pull_request.number }}/merge"

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

          # set this to not fail the workflow while deleting cache keys
          set +e

          # delete cache key
          for cacheKey in $cacheKeysForPR
          do
              gh actions-cache delete $cacheKey -R $REPO -B $BRANCH --confirm
          done
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}