docker-build.yaml

name: Build kubectl image
on:
  schedule:
    # This will run the job daily at 00:13 UTC
    - cron: "13 0 * * *"
  workflow_dispatch:

env:
  REGISTRY: ghcr.io
  REGCTL_VERSION: v0.5.7
  SEMVER_VERSION: 3.4.0

defaults:
  run:
    shell: bash

jobs:
  prepare-matrix:
    name: Prepare matrix
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.prepare-matrix.outputs.matrix }}
      build: ${{ steps.prepare-matrix.outputs.build }}
      repository: ${{ steps.prepare-repository-name.outputs.repository }}
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

      - name: Setup regctl
        uses: regclient/actions/regctl-installer@main
        with:
          release: ${{ env.REGCTL_VERSION }}
          install-dir: ${{ runner.temp }}/bin

      - name: Setup semver
        uses: sap/cs-actions/setup-semver@main
        with:
          version: ${{ env.SEMVER_VERSION }}
          install-directory: ${{ runner.temp }}/bin

      - name: Prepare repository name
        id: prepare-repository-name
        run: |
          repository=$REGISTRY/${{ github.repository }}
          echo "repository=${repository,,}" >> $GITHUB_OUTPUT

      - name: Log in to the registry
        run: |
          regctl registry login $REGISTRY --user ${{ github.actor }} --pass-stdin <<< ${{ github.token }}

      - name: Fetch k8s versions
        id: fetch-k8s-versions
        run: |
          page=1

          while true; do
            release_info=$(curl \
              --silent \
              --header "Accept: application/vnd.github+json" \
              --header "Authorization: Bearer ${{ github.token }}" \
              --header "X-GitHub-Api-Version: 2022-11-28" \
              "https://api.github.com/repos/kubernetes/kubernetes/tags?page=${page}&per_page=100"
            )
            tag_names=$(echo "${release_info}" | grep "name" | awk '{ print substr($2, 2, length($2)-3) }')

            [[ "${tag_names}" == "" ]] && break

            tag_names=$(echo "$tag_names" | grep -vE 'alpha|beta|rc')
            echo "${tag_names}" | awk '/^v1\.[2-9][6-9]\..*/||/^v[2-9]\..*/' | sort -V >> k8s_released_versions.txt
            sed -i '/^$/d' k8s_released_versions.txt

            ((page=page+1))
          done
        shell: bash {0}

      - name: Fetch built versions
        id: fetch-built-versions
        run: |
          regctl tag list ${{ steps.prepare-repository-name.outputs.repository }} | sort -V > gh_com_tags.txt

      - name: Print unbuilt versions and prepare matrix
        id: prepare-matrix
        run: |
          unbuilt_versions=$(comm -23 <(sort k8s_released_versions.txt) <(sort gh_com_tags.txt) | tr '\n' ',' | sed 's/,$//')

          if [[ "${unbuilt_versions}" == "" ]]
          then
            echo "All the released k8s versions were built already"
            exit 0
          else
            echo "Unbuilt versions: $unbuilt_versions"
            echo "matrix={\"k8s-version\":[$(echo $unbuilt_versions | sed 's/\([^,]*\)/"\1"/g')]}" >> $GITHUB_OUTPUT
            echo "build=true" >> $GITHUB_OUTPUT
          fi

  build-image:
    name: Build image
    if: needs.prepare-matrix.outputs.build == 'true'
    needs: prepare-matrix
    runs-on: ubuntu-latest
    strategy:
      matrix: ${{fromJson(needs.prepare-matrix.outputs.matrix)}}
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4

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

      - name: Log in to the Container registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ github.token }}

      - name: Build and push docker image
        uses: docker/build-push-action@v5
        with:
          platforms: linux/amd64,linux/arm64
          context: .
          file: ./Dockerfile
          tags: ${{ needs.prepare-matrix.outputs.repository }}:${{ matrix['k8s-version'] }}
          cache-from: |
            type=gha,scope=sha-${{ github.sha }}
            type=gha,scope=${{ github.ref_name }}
            type=gha,scope=${{ github.base_ref || 'main' }}
            type=gha,scope=main
          cache-to: |
            type=gha,scope=sha-${{ github.sha }},mode=max
            type=gha,scope=${{ github.ref_name }},mode=max
          build-args: "KUBECTL_VERSION=${{ matrix['k8s-version'] }}"
          push: true