name: Example

on:
  workflow_dispatch:

jobs:
  eval:
    name: Evaluate flake
    runs-on: ubuntu-latest

    outputs:
      matrix: ${{ steps.generate.outputs.matrix }}

    steps:
      - uses: actions/checkout@v4

      - name: Install Nix
        uses: DeterminateSystems/nix-installer-action@v9

      - name: Generate matrix
        id: generate
        run: |
          set -eu

          echo "matrix=$(nix eval --show-trace --json .#workflowMatrix)" >> "$GITHUB_OUTPUT"

  build:
    needs: eval

    strategy:
      fail-fast: false
      matrix: ${{ fromJSON(needs.eval.outputs.matrix) }}

    name: Build (${{matrix.attr}})
    runs-on: ${{ matrix.os }}

    steps:
      - uses: actions/checkout@v4

      - name: Setup Qemu
        if: matrix.arch == 'aarch64'
        uses: docker/setup-qemu-action@v3
        with:
          platforms: "arm64"

      - name: Install Nix
        if: matrix.arch != 'aarch64'
        uses: DeterminateSystems/nix-installer-action@v9

      - name: Install Nix (with aarch64)
        if: matrix.arch == 'aarch64'
        uses: DeterminateSystems/nix-installer-action@v9
        with:
          extra-conf: "extra-platforms = aarch64-linux arm-linux"

      - name: Build ${{ matrix.attr }}
        run: nix build -L .#${{ matrix.attr }}