docker-build.yml

# This workflow is for building and possibly pushing the docker image for
# a commit tagged by a version number.  It is triggered either manually or by
# a tag event of type "v*.*.*", which is intended for new releases. Currently,
# pushing to ghcr.io can happen only to commits tagged by a version number. This
# is intended to associate every docker image with a version number. This means
# that there is no option to push the image for the latest commit, even though
# we can build the image for testing purposes. 
#
# Manual trigger
#   In Actions, go to "Docker image build" and click
#   "Run workflow" and choose from the following options.
#   Options:
#    - 'Build latest commit': for testing for the latest commit
#    - 'Build existing version': for testing a particular version 
#    - 'Build + push existing version': for publishing a particular version
#
# Tag event
#   In a tag event of type "v*.*.*", such as new release or retagging, this work
#   flow is triggered to build and publish the image for the tagged version
#   number.
#
# The image can be pulled by one of the following commands.
#
# docker pull ghcr.io/smithlabcode/dnmtools:latest
# docker pull ghcr.io/smithlabcode/dnmtools:<7-DIGIT SHA>
# docker pull ghcr.io/smithlabcode/dnmtools:v<VERSION NUMBER> (e.g. v1.3.0)


name: Docker image build

on: 
  workflow_dispatch:
    branches: ['master']
    inputs:
      build_option:
        description: 'Build/push option'
        required: true
        default: 'Build latest commit'
        type: choice
        options:
        - 'Build latest commit'
        - 'Build existing version'
        - 'Build + push existing version'
      version:
        description: 'Version number: "v*.*.*" 
                      (latest version if not specified)'
        required: false

  push:
    tags:
      - 'v*.*.*'

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:

  build-and-push:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write

    steps:

      - name: Checkout current repository to get latest version
        uses: actions/checkout@v3
        with:
          fetch-depth: 0 # Needed to get tags information

      # Copy Dockerfile in case the commit to be used does not have it 
      # This is to be used to build older versions that didn't have Dockerfile.
      # This temporary Dockerfile should not be needed for new versions.
      - name: Copy Dockerfile to Temporary File
        run: |
          cp Dockerfile /tmp/Dockerfile 
          
      - name: 'Get latest version'
        run: |
          echo "LATEST_VERSION=$(git describe --abbrev=0 --tags)" >> $GITHUB_ENV
          
      - name: Set version for manual trigger
        if: github.event_name == 'workflow_dispatch'
        run: |
          if [[ "${{ github.event.inputs.version }}" == "" ]]; then
            echo "VERSION=${{env.LATEST_VERSION}}" >> $GITHUB_ENV
          else
            echo "VERSION=${{ github.event.inputs.version }}" >> $GITHUB_ENV
          fi

      - name: Set version for tag trigger 
        if: startsWith(github.ref, 'refs/tags/v')
        run: echo "VERSION=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV 

      - name: "Set commit hash"
        run: |
          if [[ "${{ github.event.inputs.build_option }}" == \
                                        "Build latest commit" ]]; then
            COMMIT_HASH=${{ github.sha }}
          else
            # for specified version in manual trigger or tag event
            COMMIT_HASH=$(git rev-parse ${{ env.VERSION }})
          fi
          SHA=$(git rev-parse --short "${COMMIT_HASH}")
          echo "COMMIT_HASH=${COMMIT_HASH}" >> $GITHUB_ENV 
          echo "SHA=${SHA}" >> $GITHUB_ENV

      - name: "Checkout the commit: ${{ env.SHA }}"
        uses: actions/checkout@v3
        with:
          ref: ${{ env.COMMIT_HASH }}
          submodules: 'recursive'
          
      - name: Log in to the Container registry
        uses: docker/login-action@v2
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Decide whether to push the image to ghcr.io
        run: |
          if [[ "${{ github.event.inputs.build_option }}" == \
                          "Build + push existing version" ]] || 
             [[ "${{ github.event_name }}" == "push" ]]; then
            echo "PUSH=true" >> $GITHUB_ENV 
          else
            echo "PUSH=false" >> $GITHUB_ENV
          fi

      # The default tags are the SHA hash and the version number.
      # Below command adds the "latest" tag if the version number is the latest.
      - name: Determine image tags
        env: 
          IMAGE_TAGS: "${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.SHA }},${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ env.VERSION }}"
        run: |
          if [ "${{ env.VERSION }}" == "${{ env.LATEST_VERSION }}" ]; then
            echo "IMAGE_TAGS=${{ env.IMAGE_TAGS }},${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest" >> $GITHUB_ENV
          else
            echo "IMAGE_TAGS=${{ env.IMAGE_TAGS }}" >> $GITHUB_ENV
          fi

      - name: Use temp.Dockerfile if Dockerfile doesn't exist
        run: |
          if [ -f Dockerfile ]; then
            echo "DOCKERFILE=./Dockerfile" >> $GITHUB_ENV
          else
            echo "DOCKERFILE=/tmp/Dockerfile" >> $GITHUB_ENV
          fi

      - name: 'Build Docker image (push: ${{ env.PUSH }}, dockerfile: ${{ env.DOCKERFILE }})'
        uses: docker/build-push-action@v4
        with:
          context: .
          file: ${{ env.DOCKERFILE }}
          push: ${{ env.PUSH }}
          tags: |
            ${{ env.IMAGE_TAGS }}