name: Docker Build & Publish

on:
  push:
    branches: [ "main", "master" ]
    # Publish semver tags as releases.
    tags: [ 'v*.*.*' ]
  pull_request:
    branches: [ "main", "master" ]

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
    permissions:
      contents: read
      packages: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      # Set up Docker Buildx (required for caching)
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      # Login against GHCR
      - 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.GITHUB_TOKEN }}
      
      # Login against Docker Hub (Optional fallback if secrets exist)
      - name: Log into Docker Hub
        if: github.event_name != 'pull_request' && secrets.DOCKER_USERNAME != ''
        uses: docker/login-action@v3
        with:
          registry: docker.io
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}

      # 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 }}
            docker.io/${{ env.IMAGE_NAME }}
          tags: |
            type=raw,value=edge,enable={{is_default_branch}}
            type=ref,event=tag
            type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/') }}

      # 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: .
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max

      # Update Docker Hub Description (README)
      # https://github.com/peter-evans/dockerhub-description
      - name: Update Docker Hub Description
        if: github.event_name != 'pull_request'
        uses: peter-evans/dockerhub-description@v4
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}
          repository: ${{ env.IMAGE_NAME }}
          short-description: ${{ github.event.repository.description }}
          readme-filepath: ./DOCKER_README.md