name: docker
on:
  push:
    branches:
      - 'master'
    tags:
      - 'v*.*.*'
  pull_request:
    types:
      - opened
      - synchronize
  workflow_dispatch:
    inputs:
      use_cache:
        description: "Use build cache"
        required: true
        type: boolean
        default: true

env:
  REGISTRY: ghcr.io
  # ghcr.io/OWNER/REPO
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
      id-token: write
      attestations: write

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

      - name: Set up QEMU
        uses: docker/setup-qemu-action@v3

      # Workaround: https://github.com/docker/build-push-action/issues/461
      - name: Setup 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.GITHUB_TOKEN }}

      # Extract metadata (tags, labels) for Docker
      # For some reason the title have to be set manually
      # https://github.com/docker/metadata-action
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          labels: |
            org.opencontainers.image.title=Oxipng
          annotations: |
            org.opencontainers.image.title=Oxipng

      # Build and push Docker image with Buildx (don't push on PR)
      # Cache isn't used for tags and on workflow_dispatch if specified
      # https://github.com/docker/build-push-action
      - name: Build and push Docker image
        id: build-and-push
        uses: docker/build-push-action@v6
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          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
          no-cache: ${{ (github.event_name == 'workflow_dispatch' && !inputs.use_cache) || startsWith(github.ref, 'refs/tags/') }}

      # Attest the build provenance
      # TODO: enable push to registry when referrers API will be supported by ghcr.io
      - name: Attest Build Provenance
        if: github.event_name != 'pull_request'
        uses: actions/attest-build-provenance@v1
        with:
          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          subject-digest: ${{ steps.build-and-push.outputs.digest }}
          push-to-registry: false