name: Diff Nix Flake

on:
  pull_request:

permissions:
  contents: read
  pull-requests: write
  actions: read

jobs:
  diff:
    name: ${{ matrix.host }} (${{ matrix.system }})
    runs-on: ${{ matrix.os }}

    strategy:
      fail-fast: false
      matrix:
        include:
          - os: ubuntu-latest
            system: x86_64-linux
            target_attr: nixosConfigurations
            host: earthy
          - os: ubuntu-24.04-arm
            system: aarch64-linux
            target_attr: nixosConfigurations
            host: anemone
          - os: ubuntu-latest
            system: x86_64-linux
            target_attr: nixosConfigurations
            host: lily
          - os: ubuntu-latest
            system: x86_64-linux
            target_attr: nixosConfigurations
            host: zinnia
          - os: macos-latest
            system: aarch64-darwin
            target_attr: darwinConfigurations
            host: starling

    steps:
      - name: Checkout
        uses: actions/checkout@v6
        with:
          persist-credentials: false

      - name: Install Nix
        uses: cachix/install-nix-action@v31
        with:
          github_access_token: ${{ secrets.GITHUB_TOKEN }}

      - uses: DeterminateSystems/magic-nix-cache-action@v14

      - name: Generate Nix Diff
        uses: 42willow/nix-diff-action@main
        with:
          mode: diff-only
          attributes: |
            - displayName: "${{ matrix.host }} (${{ matrix.system }})"
              attribute: "${{ matrix.target_attr }}.${{ matrix.host }}.config.system.build.toplevel"

  comment:
    name: Post Comment
    needs: diff
    if: github.event_name == 'pull_request'
    runs-on: ubuntu-latest
    steps:
      - name: Aggregate and Post Diffs
        uses: 42willow/nix-diff-action@main
        with:
          mode: comment-only
          github-token: ${{ secrets.GITHUB_TOKEN }}