ci.yml

# Written using
# https://docs.docker.com/build/ci/github-actions/multi-platform/
# and
# https://github.com/sredevopsorg/multi-arch-docker-github-workflow/blob/main/.github/workflows/multi-build.yaml
name: CI

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

env:
  # The name of the Docker image to be built and pushed to GHCR
  # The image name is derived from the GitHub repository name and the GitHub Container Registry (GHCR) URL.
  # The image name will be in the format: ghcr.io/<owner>/<repo>
  GHCR_IMAGE: ghcr.io/${{ github.repository }}

jobs:

  build:

    strategy:
      fail-fast: false
      matrix:
        include:
        - arch: amd64
          runner: ubuntu-latest
        - arch: arm64
          runner: ubuntu-24.04-arm
    runs-on: ${{ matrix.runner }}

    steps:
      - name: Lowercase the image name
        run: echo "GHCR_IMAGE=${GHCR_IMAGE,,}" >> $GITHUB_ENV

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

      - name: Extract metadata for publishing image
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.GHCR_IMAGE }}

      - name: Build and export to Docker local cache
        uses: docker/build-push-action@v6
        with:
          # Need load and tags so we can test it below
          load: true
          tags: tag_for_testing

      - name: Test cli works in cached runtime image
        run: docker run --rm tag_for_testing uvx pycowsay 'hello ubuntu-devcontainer!'

      - name: Log in to GitHub Docker Registry
        if: github.ref_type == 'tag'
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build and push by digest
        if: github.ref_type == 'tag'
        id: build
        uses: docker/build-push-action@v6
        with:
          labels: ${{ steps.meta.outputs.labels }}
          annotations: ${{ steps.meta.outputs.annotations }}
          outputs: type=image,name=${{ env.GHCR_IMAGE }},push-by-digest=true,name-canonical=true,push=true,oci-mediatypes=true

      - name: Export digest
        if: github.ref_type == 'tag'
        run: |
          mkdir -p ${{ runner.temp }}/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "${{ runner.temp }}/digests/${digest#sha256:}"

      - name: Upload digest
        if: github.ref_type == 'tag'
        uses: actions/upload-artifact@v6
        with:
          name: digests-linux-${{ matrix.arch }}
          path: ${{ runner.temp }}/digests/*
          if-no-files-found: error

  merge:
    runs-on: ubuntu-latest
    needs:
      - build
    if: github.ref_type == 'tag'

    steps:
      - name: Lowercase the image name
        run: echo "GHCR_IMAGE=${GHCR_IMAGE,,}" >> $GITHUB_ENV

      - name: Download digests
        uses: actions/download-artifact@v7
        with:
          path: ${{ runner.temp }}/digests
          pattern: digests-*
          merge-multiple: true

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

      - name: Create tags for publishing image
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.GHCR_IMAGE }}
          tags: |
            type=ref,event=tag
            type=raw,value=latest
            type=raw,value=noble

      - name: Log in to GitHub 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: ${{ runner.temp }}/digests
        run: |
          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.GHCR_IMAGE }}@sha256:%s ' *)

      - name: Inspect image
        run: |
          docker buildx imagetools inspect ${{ env.GHCR_IMAGE }}:${{ steps.meta.outputs.version }}