name: "Docker: Branch image"

on:
  push:
    branches:
      - main
      - dev
    paths:
      - "Dockerfile"
      - ".dockerignore"
      - "app/**"
      - "components/**"
      - "contexts/**"
      - "hooks/**"
      - "lib/**"
      - "stores/**"
      - "locales/**"
      - "public/**"
      - "package.json"
      - "package-lock.json"
      - ".github/workflows/docker-publish.yml"
  workflow_dispatch:

# Jobs that need more (the registry push, the attestation) say so themselves.
permissions:
  contents: read

jobs:
  prepare:
    name: Prepare
    runs-on: ubuntu-latest
    outputs:
      image_name: ${{ steps.set.outputs.image_name }}
    steps:
      - name: Set image name
        id: set
        env:
          REF_NAME: ${{ github.ref_name }}
          REPOSITORY: ${{ github.repository }}
        run: |
          if [ "$REF_NAME" = "main" ]; then
            echo "image_name=ghcr.io/${REPOSITORY}-beta" >> "$GITHUB_OUTPUT"
          else
            echo "image_name=ghcr.io/${REPOSITORY}-${REF_NAME}" >> "$GITHUB_OUTPUT"
          fi

  build:
    name: Build (${{ matrix.platform == 'linux/amd64' && 'amd64' || 'arm64' }})
    needs: prepare
    strategy:
      fail-fast: false
      matrix:
        include:
          - platform: linux/amd64
            runner: ubuntu-latest
          - platform: linux/arm64
            runner: ubuntu-24.04-arm
    runs-on: ${{ matrix.runner }}
    permissions:
      contents: read
      packages: write

    steps:
      - name: Checkout
        uses: actions/checkout@v7

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v4

      - name: Log in to GHCR
        uses: docker/login-action@v4
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Extract metadata
        id: meta
        uses: docker/metadata-action@v6
        with:
          images: ${{ needs.prepare.outputs.image_name }}

      - name: Build and push by digest
        id: build
        uses: docker/build-push-action@v7
        with:
          context: .
          platforms: ${{ matrix.platform }}
          labels: ${{ steps.meta.outputs.labels }}
          build-args: |
            GIT_COMMIT=${{ github.sha }}
          outputs: type=image,name=${{ needs.prepare.outputs.image_name }},push-by-digest=true,name-canonical=true,push=true
          cache-from: type=gha,scope=${{ matrix.platform }}
          cache-to: type=gha,mode=max,scope=${{ matrix.platform }}

      - 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@v7
        with:
          name: digests-${{ matrix.platform == 'linux/amd64' && 'amd64' || 'arm64' }}
          path: /tmp/digests/*
          if-no-files-found: error
          retention-days: 1

  merge:
    name: Merge manifest
    runs-on: ubuntu-latest
    needs: [prepare, build]
    permissions:
      contents: read
      packages: write
      id-token: write
      attestations: write

    steps:
      - name: Download digests
        uses: actions/download-artifact@v8
        with:
          path: /tmp/digests
          pattern: digests-*
          merge-multiple: true

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v4

      - name: Log in to GHCR
        uses: docker/login-action@v4
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Extract metadata
        id: meta
        uses: docker/metadata-action@v6
        with:
          images: ${{ needs.prepare.outputs.image_name }}
          tags: |
            type=raw,value=latest
            type=sha

      - 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") \
            $(printf '${{ needs.prepare.outputs.image_name }}@sha256:%s ' *)

      - name: Inspect image
        id: inspect
        run: |
          docker buildx imagetools inspect ${{ needs.prepare.outputs.image_name }}:${{ steps.meta.outputs.version }}
          digest=$(docker buildx imagetools inspect ${{ needs.prepare.outputs.image_name }}:${{ steps.meta.outputs.version }} --format '{{json .Manifest}}' | jq -r .digest)
          echo "digest=$digest" >> "$GITHUB_OUTPUT"

      # Signed build provenance, pushed to GHCR next to the image:
      # `gh attestation verify oci://<image>:<tag> --owner bulwarkmail`.
      - name: Attest build provenance
        uses: actions/attest@v4
        with:
          subject-name: ${{ needs.prepare.outputs.image_name }}
          subject-digest: ${{ steps.inspect.outputs.digest }}
          push-to-registry: true
          create-storage-record: false