name: Generate sha256 hashes for release files

on:
  release:
    types: [published]

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: write
    env:
      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      TAG: ${{ github.event.release.tag_name }}
    steps:
    - name: Generate and upload SHA256 hashes
      run: |
        # Download every asset attached to this release, compute SHA256 hashes,
        # and upload the result back to the same release as
        # Files-SHA256-Hashes.txt. Excludes any pre-existing hash file so a
        # re-run does not re-hash its own previous output.
        mkdir release-assets
        cd release-assets
        gh release download "$TAG" --repo "$GITHUB_REPOSITORY"
        find . -maxdepth 1 -type f ! -name 'Files-SHA256-Hashes.txt' -print0 \
          | xargs -0 sha256sum > ../Files-SHA256-Hashes.txt
        cd ..
        gh release upload "$TAG" Files-SHA256-Hashes.txt \
          --repo "$GITHUB_REPOSITORY" --clobber