name: Build and Publish Docker Image

on:
  push:
    branches: ['main']

# Defines two custom environment variables for the workflow. These are used for the Container registry domain, and
# a name for the Docker image that this workflow builds.
env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  build-and-push-image:
    runs-on: ubuntu-latest

    # Sets the permissions granted to the `GITHUB_TOKEN` for the actions in this job.
    permissions:
      contents: read
      packages: write
      attestations: write
      id-token: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      # Uses the `docker/login-action` action to log in to the Container registry registry using the account and
      # password that will publish the packages. Once published, the packages are scoped to the account defined here.
      - name: Log in to the Container registry
        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ secrets.USERNAME }}
          password: ${{ secrets.TOKEN }}

      # This step uses https://github.com/docker/metadata-action#about to extract tags and labels that will be applied
      # to the specified image. The `id` "meta" allows the output of this step to be referenced in a subsequent step.
      # The `images` value provides the base name for the tags and labels.
      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}

      # This step uses the `docker/build-push-action` action to build the image, based on your repository's `Dockerfile`.
      # If the build succeeds, it pushes the image to GitHub Packages. It uses the `context` parameter to define the
      # build's context as the set of files located in the specified path. For more information, see 
      # https://github.com/docker/build-push-action#usage in the README of the `docker/build-push-action` repository.
      # It uses the `tags` and `labels` parameters to tag and label the image with the output of the "meta" step.
      - name: Build and push Docker image
        id: push
        uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
      
      # This step generates an artifact attestation for the image, which is an unforgeable statement about where and
      # how it was built. It increases supply chain security for people who consume the image. For more information,
      # see: /actions/security-guides/using-artifact-attestations-to-establish-provenance-for-builds 
      - name: Generate artifact attestation
        uses: actions/attest-build-provenance@v1
        with:
          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}
          subject-digest: ${{ steps.push.outputs.digest }}
          push-to-registry: true