name: Build and Push Container Image

"on":
  workflow_call:
    inputs:
      registry:
        type: string
        required: false
        default: ghcr.io
        description: The container registry FQDN.
      image_name:
        type: string
        required: true
        description: The suffix for the image name, without the registry and without the repository path.
      context:
        type: string
        required: true
        description: The path to the context to start `docker build` into.
      target:
        type: string
        required: false
        default: ""
        description: The Dockerfile target stage to build the image for.
      arm64_reuse_amd64_build_arg:
        type: string
        required: false
        default: ""
        description: "Build arg name to pass first amd64 tag to arm64 build (skips arch-independent build steps)"

# see https://docs.github.com/en/enterprise-cloud@latest/actions/how-tos/use-cases-and-examples/publishing-packages/publishing-docker-images#publishing-images-to-github-packages
jobs:
  docker-build-push:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
      attestations: write
      id-token: write
    steps:
      - name: Checkout repository
        uses: actions/checkout@v6
      - name: Set up QEMU
        uses: docker/setup-qemu-action@v3
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
      - name: Log in to the Container registry
        uses: docker/login-action@v3
        with:
          registry: ${{ inputs.registry }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ inputs.registry }}/${{ github.repository }}-${{ inputs.image_name }}
          tags: |
            type=ref,event=branch
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
      - name: Generate platform-specific tags
        id: platform-tags
        run: |
          AMD64_TAGS=$(echo "${{ steps.meta.outputs.tags }}" | sed 's/$/-amd64/')
          ARM64_TAGS=$(echo "${{ steps.meta.outputs.tags }}" | sed 's/$/-arm64/')
          FIRST_AMD64_TAG=$(echo "${{ steps.meta.outputs.tags }}" | head -1)-amd64
          {
            echo "amd64<<EOF"
            echo "$AMD64_TAGS"
            echo "EOF"
            echo "arm64<<EOF"
            echo "$ARM64_TAGS"
            echo "EOF"
            echo "amd64_first=$FIRST_AMD64_TAG"
          } >> "$GITHUB_OUTPUT"
      - name: Build and push (amd64)
        uses: docker/build-push-action@v6
        with:
          context: ${{ inputs.context }}
          target: ${{ inputs.target }}
          platforms: linux/amd64
          push: true
          provenance: false
          tags: ${{ steps.platform-tags.outputs.amd64 }}
          labels: ${{ steps.meta.outputs.labels }}
      - name: Build and push (arm64)
        uses: docker/build-push-action@v6
        with:
          context: ${{ inputs.context }}
          target: ${{ inputs.target }}
          platforms: linux/arm64
          push: true
          provenance: false
          tags: ${{ steps.platform-tags.outputs.arm64 }}
          labels: ${{ steps.meta.outputs.labels }}
          build-args: |
            ${{ inputs.arm64_reuse_amd64_build_arg && format('{0}={1}', inputs.arm64_reuse_amd64_build_arg, steps.platform-tags.outputs.amd64_first) || '' }}
      - name: Create multi-arch manifests
        id: create-manifest
        run: |
          IMAGE="${{ inputs.registry }}/${{ github.repository }}-${{ inputs.image_name }}"
          readarray -t TAGS <<< "${{ steps.meta.outputs.tags }}"
          FIRST_TAG=""
          for tag in "${TAGS[@]}"; do
            [ -z "$tag" ] && continue
            docker buildx imagetools create -t "$tag" \
              "${tag}-amd64" "${tag}-arm64"
            if [ -z "$FIRST_TAG" ]; then
              FIRST_TAG="$tag"
            fi
          done
          # Get the digest of the multi-arch manifest for attestation
          # Note: --format '{{.Manifest.Digest}}' is broken (docker/buildx#1175),
          # so we compute it from the raw manifest JSON instead.
          if [ -n "$FIRST_TAG" ]; then
            DIGEST="sha256:$(docker buildx imagetools inspect "$FIRST_TAG" --raw | sha256sum | awk '{print $1}')"
            echo "digest=$DIGEST" >> "$GITHUB_OUTPUT"
          fi
      # This pushes a signed SLSA provenance attestation to the registry,
      # tagged as sha256-<digest>. It proves the image was built by this
      # workflow from this repo. Verified with: gh attestation verify <image>
      - name: Generate artifact attestation
        uses: actions/attest-build-provenance@v2
        with:
          subject-name: ${{ inputs.registry }}/${{ github.repository }}-${{ inputs.image_name }}
          subject-digest: ${{ steps.create-manifest.outputs.digest }}
          push-to-registry: true
      - name: Delete all untagged container images
        uses: actions/delete-package-versions@v5
        with:
          package-name: messages-${{ inputs.image_name }}
          package-type: 'container'
          min-versions-to-keep: 0
          delete-only-untagged-versions: true
