name: "Build system config"
on:
  pull_request:
  workflow_dispatch:
  push:
    branches: [ main ]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v3
      with:
        fetch-depth: 0
    - name: Install Nix
      uses: DeterminateSystems/nix-installer-action@v4
    - name: Run the Magic Nix Cache
      uses: DeterminateSystems/magic-nix-cache-action@v2
    - name: nix flake check
      run: |
        nix flake check --no-build
        echo "## \`nix flake check\` succeeded" >> $GITHUB_STEP_SUMMARY
        echo "" >> $GITHUB_STEP_SUMMARY
    - name: Discover nixosConfigurations
      run: |
        echo Discovered the following system configs
        nix flake show . --json | jq ".nixosConfigurations|keys[]" -r
    - name: Build systems
      run: |
        echo "## Builds succeeded" >> $GITHUB_STEP_SUMMARY
        echo "" >> $GITHUB_STEP_SUMMARY
        echo "| Host | Out path |" >> $GITHUB_STEP_SUMMARY
        echo "| ---- | -------- |" >> $GITHUB_STEP_SUMMARY
        for host in $(nix flake show . --json | jq ".nixosConfigurations|keys[]" -r); do
          echo "::group::Building ${host}"
          drv=".#nixosConfigurations.$host.config.system.build.toplevel"
          build_cmd="nix build ${drv}"
          #cachix watch-exec chaos-jetzt-nixfiles -- $build_cmd
          $build_cmd
          echo "::endgroup::"
          out_path=$($build_cmd --print-out-paths)
          echo -e "\x1b[32;1mSuccessfully built .#nixosConfigurations.${host}\x1b[0m"
          echo "| ${host} | \`${out_path}\` |" >> $GITHUB_STEP_SUMMARY
        done
    - name: Diff closures
      # Since this is only triggered by pushes to main, no need to compare to main for pushes
      if: github.event_name != 'push'
      run: |
        # Compare to pull_request_target or, if this has no PR-Target, main
        target_ref="${GITHUB_BASE_REF-main}"
        target_ref="origin/${target_ref/#refs\/heads\//}"
        if [[ $GITHUB_REF == "target/refs/main" ]]; then
          # If triggered on main, compare with the previous commit
          target_ref="$(git log  HEAD~1 -1 --format=format:"%H")"
        fi
        echo -e "## Closure differences\n" >> $GITHUB_STEP_SUMMARY
        echo "_Comparing current $(git rev-parse --abbrev-ref HEAD) ($(git rev-parse --verify HEAD)) to ${target_ref} ($(git rev-parse $target_ref))_" | tee -a $GITHUB_STEP_SUMMARY
        for host in $(nix flake show . --json | jq ".nixosConfigurations|keys[]" -r); do
          echo "::group::Diff-closures for ${host}"
          drv="nixosConfigurations.$host.config.system.build.toplevel"
          diff_cmd="nix store diff-closures git+file:.?ref=${target_ref}#${drv} .#${drv}"
          # Get the nice and colorfull output for the logs, running twice won't (significantly) prolong the runtime
          $diff_cmd
          echo -e "<details>\n<summary>Diff for ${host}</summary>\n"  >> $GITHUB_STEP_SUMMARY
          echo '```' >> $GITHUB_STEP_SUMMARY
          # Strip color codes so that the summary stays readable
          $diff_cmd | sed -e 's/\x1b\[[0-9;]*m//g' >> $GITHUB_STEP_SUMMARY
          echo '```' >> $GITHUB_STEP_SUMMARY
          echo -e "\n</details>" >> $GITHUB_STEP_SUMMARY
          echo "::endgroup::"
        done