# This file was mostly copied from nixpkgs's check-nix-format.yml,
# which itself wsa mostly copied from nixpkgs's check-maintainers-sorted.yaml.

name: Check that Nix files are formatted

on:
  pull_request:
    types: [opened, synchronize, reopened]
  push:
    branches:
      - main
      - 'push-action/**'
  merge_group:
permissions:
  contents: read

jobs:
  nixos:
    name: nixfmt-check
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
        with:
          fetch-depth: 2
      - name: Calculate changed files
        id: changed-files
        run: echo "changed_files=$(git diff --name-only -r HEAD^1 HEAD | xargs)" >> $GITHUB_OUTPUT
      - uses: cachix/install-nix-action@fd24c48048070c1be9acd18c9d369a83f0fe94d7 # v31
        with:
          extra_nix_config: sandbox = true
          nix_path: nixpkgs=channel:nixpkgs-unstable
      - name: Install nixfmt
        run: "nix-env -f '<nixpkgs>' -iAP nixfmt-rfc-style"
      - name: Check that Nix files are formatted according to the RFC style
        run: |
          # List of changed files
          changed_files="${{ steps.changed-files.outputs.changed_files }}"
          
          # Convert the string of changed files into an array
          IFS=' ' read -r -a files <<< "$changed_files"
          
          # A variable to track failures
          failure=0
          
          # Function to check the file and run nixfmt
          check_file() {
            local file="$1"
            if [[ -f "$file" ]]; then
              if ! nixfmt --check "$file"; then
                echo "::error file=$file::Formatting check failed for $file" >&2
                failure=1
              fi
            else
              echo "File does not exist: $file" >&2
            fi
          }
          
          # Export the function and failure variable for parallel execution
          export -f check_file
          export failure
          
          # Run the checks in parallel
          printf "%s\n" "${files[@]}" | xargs -n 1 -P "$(nproc)" -I {} bash -c 'check_file "$@"' _ {}
          
          # Exit with a status of 1 if any checks failed
          if [[ $failure -eq 1 ]]; then
            exit 1
          fi