name: Publish to ghcr

# This workflow is a modification of a example.
# @ see: https://docs.docker.com/build/ci/github-actions/multi-platform/#distribute-build-across-multiple-runners

on:
  push:
    branches: ["main"]
    tags: ["v*.*.*"]

env:
  # Use docker.io for Docker Hub if empty
  REGISTRY_IMAGE: ghcr.io/sourcebot-dev/sourcebot

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
      # This is used to complete the identity challenge
      # with sigstore/fulcio when running outside of PRs.
      id-token: write
    strategy:
      matrix:
        platform:
          - linux/amd64
          - linux/arm64

    steps:
      - name: Prepare
        run: |
          platform=${{ matrix.platform }}
          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV

      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          submodules: "true"

      # 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_IMAGE }}

      # Install the cosign tool except on PR
      # https://github.com/sigstore/cosign-installer
      - name: Install cosign
        uses: sigstore/cosign-installer@v3.5.0
        with:
          cosign-release: "v2.2.4"

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Login to GitHub Packages Docker Registry
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build Docker image
        id: build
        uses: docker/build-push-action@v6
        with:
          context: .
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max
          platforms: ${{ matrix.platform }}
          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
          build-args: |
            SOURCEBOT_VERSION=${{ github.ref_name }}

      - name: Export digest
        run: |
          mkdir -p /tmp/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "/tmp/digests/${digest#sha256:}"

      - name: Upload digest
        uses: actions/upload-artifact@v4
        with:
          name: digests-${{ env.PLATFORM_PAIR }}
          path: /tmp/digests/*
          if-no-files-found: error
          retention-days: 1

      # Sign the resulting Docker image digest except on PRs.
      # This will only write to the public Rekor transparency log when the Docker
      # repository is public to avoid leaking data.  If you would like to publish
      # transparency data even for private images, pass --force to cosign below.
      # https://github.com/sigstore/cosign
      - name: Sign the published Docker image
        env:
          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
          TAGS: ${{ steps.meta.outputs.tags }}
          DIGEST: ${{ steps.build.outputs.digest }}
        # This step uses the identity token to provision an ephemeral certificate
        # against the sigstore community Fulcio instance.
        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}
  
  merge:
    runs-on: ubuntu-latest
    permissions:
      packages: write
    needs:
      - build
    steps:
      - name: Download digests
        uses: actions/download-artifact@v4
        with:
          path: /tmp/digests
          pattern: digests-*
          merge-multiple: true
      
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3
      
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY_IMAGE }}

      - name: Login to GitHub Packages Docker Registry
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      
      - name: Create manifest list and push
        working-directory: /tmp/digests
        run: |
          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
      
      - name: Inspect image
        run: |
          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}