name: Docker

on:
  workflow_run:
    workflows: [crane]
    branches: [main]
    types:
      - completed
  # schedule:
  #   - cron: 0 0 * * 1
  # push:
  #   branches: ["main"]
  #   # Publish semver tags as releases.
  #   tags: [ 'v*.*.*' ]
  # pull_request:
  #   branches: [ "main" ]

env:
  # Use docker.io for Docker Hub if empty
  REGISTRY: ghcr.io
  # github.repository as <account>/<repo>
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build:
    runs-on: ubuntu-latest
    # https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#running-a-workflow-based-on-the-conclusion-of-another-workflow
    if: ${{ github.event.workflow_run.conclusion == 'success' }}
    permissions:
      contents: read
      packages: write
      # This is used to complete the identity challenge
      # with sigstore/fulcio when running outside of PRs.
      id-token: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v3

      # Install Nix
      - name: Install Nix
        uses: DeterminateSystems/nix-installer-action@main
      - uses: DeterminateSystems/magic-nix-cache-action@main

      # Set up BuildKit Docker container builder to be able to build
      # multi-platform images and export cache
      # https://github.com/docker/setup-buildx-action
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      # Login against a Docker registry except on PR
      # https://github.com/docker/login-action
      - name: Log into registry ${{ env.REGISTRY }}
        if: github.event_name != 'pull_request'
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GHCR_TOKEN }}

      # Extract metadata (tags, labels) for Docker
      # https://github.com/docker/metadata-action
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      # Build Nix package
      - name: Build Nix package
        run: nix build .#dockerImage

      # https://github.com/orgs/community/discussions/25768#discussioncomment-3249183
      - name: Downcase REPO
        run: |
          echo "REPO=${GITHUB_REPOSITORY,,}" >>${GITHUB_ENV}

      # Build and push Docker image with Buildx (don't push on PR)
      # https://github.com/docker/build-push-action
      - name: Build and push Docker image
        id: build-and-push
        uses: docker/build-push-action@v5
        with:
          context: ./result
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ env.REGISTRY }}/${{ env.REPO }}:latest
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max