docker-publish.yml

name: Docker Publish

on:
  push:
    branches:
      - main
    tags:
      - 'v*.*.*'
      - 'v*.*.*-*'
  pull_request:

env:
  IMAGE: tapflow/tapflow

jobs:
  # Build each architecture on its own native runner. arm64 used to build under
  # QEMU emulation on an amd64 runner, where the native module compile could hang
  # for hours; native runners remove the emulation entirely.
  build:
    runs-on: ${{ matrix.runner }}
    strategy:
      fail-fast: false
      matrix:
        include:
          - platform: linux/amd64
            runner: ubuntu-24.04
          - platform: linux/arm64
            runner: ubuntu-24.04-arm
    env:
      HAS_DOCKERHUB: ${{ secrets.DOCKERHUB_TOKEN != '' && secrets.DOCKERHUB_USERNAME != '' }}
    steps:
      - name: Prepare platform name
        run: echo "PLATFORM_PAIR=${platform//\//-}" >> "$GITHUB_ENV"
        env:
          platform: ${{ matrix.platform }}

      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Warn when Docker Hub credentials are missing
        if: github.event_name != 'pull_request' && env.HAS_DOCKERHUB != 'true'
        run: echo "::warning::DOCKERHUB_USERNAME/DOCKERHUB_TOKEN are not set — building the image for validation but skipping push."

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

      - name: Log in to Docker Hub
        if: github.event_name != 'pull_request' && env.HAS_DOCKERHUB == 'true'
        uses: docker/login-action@v3
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Extract metadata (labels) for Docker
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.IMAGE }}

      - name: Build image (push by digest when publishing)
        id: build
        uses: docker/build-push-action@v5
        with:
          context: .
          file: ./Dockerfile
          platforms: ${{ matrix.platform }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha,scope=${{ env.PLATFORM_PAIR }}
          cache-to: type=gha,mode=max,scope=${{ env.PLATFORM_PAIR }}
          # Publish: push a per-architecture image by digest (merged into a manifest
          # list in the merge job). Otherwise (PR / no credentials): build for
          # validation only, keeping just the cache.
          outputs: ${{ (github.event_name != 'pull_request' && env.HAS_DOCKERHUB == 'true') && format('type=image,name={0},push-by-digest=true,name-canonical=true,push=true', env.IMAGE) || 'type=cacheonly' }}

      - name: Export digest
        if: github.event_name != 'pull_request' && env.HAS_DOCKERHUB == 'true'
        run: |
          mkdir -p "${{ runner.temp }}/digests"
          digest="${{ steps.build.outputs.digest }}"
          touch "${{ runner.temp }}/digests/${digest#sha256:}"

      - name: Upload digest
        if: github.event_name != 'pull_request' && env.HAS_DOCKERHUB == 'true'
        uses: actions/upload-artifact@v4
        with:
          name: digests-${{ env.PLATFORM_PAIR }}
          path: ${{ runner.temp }}/digests/*
          if-no-files-found: error
          retention-days: 1

  # Combine the per-architecture digests into a single multi-arch manifest list.
  # Only runs for real publishes; PRs and credential-less builds validate only.
  merge:
    needs: build
    if: github.event_name != 'pull_request'
    runs-on: ubuntu-latest
    env:
      HAS_DOCKERHUB: ${{ secrets.DOCKERHUB_TOKEN != '' && secrets.DOCKERHUB_USERNAME != '' }}
    steps:
      - name: Note validation-only build
        if: env.HAS_DOCKERHUB != 'true'
        run: echo "::warning::No Docker Hub credentials — per-architecture validation builds succeeded, nothing to publish."

      - name: Download digests
        if: env.HAS_DOCKERHUB == 'true'
        uses: actions/download-artifact@v4
        with:
          path: ${{ runner.temp }}/digests
          pattern: digests-*
          merge-multiple: true

      - name: Set up Docker Buildx
        if: env.HAS_DOCKERHUB == 'true'
        uses: docker/setup-buildx-action@v3

      - name: Log in to Docker Hub
        if: env.HAS_DOCKERHUB == 'true'
        uses: docker/login-action@v3
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Extract metadata (tags) for Docker
        id: meta
        if: env.HAS_DOCKERHUB == 'true'
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.IMAGE }}
          tags: |
            type=edge,branch=main
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=sha

      - name: Create manifest list and push
        if: env.HAS_DOCKERHUB == 'true'
        working-directory: ${{ runner.temp }}/digests
        run: |
          # shellcheck disable=SC2046  # intentional split: expand -t flags and per-digest refs
          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.IMAGE }}@sha256:%s ' *)

      - name: Inspect image
        if: env.HAS_DOCKERHUB == 'true'
        run: docker buildx imagetools inspect ${{ env.IMAGE }}:${{ steps.meta.outputs.version }}