name: Docker Image

on:
  workflow_dispatch:
    inputs:
      version:
        description: "Image version/tag to publish, for example v1.0.0-beta"
        required: false
        type: string
      image_name:
        description: "Image name without registry. Defaults to owner/repo."
        required: false
        type: string
  push:
    tags: ["v*"]

env:
  REGISTRY: ghcr.io
  DEFAULT_IMAGE_NAME: ${{ github.repository }}
  DOCKERFILE: ./docker/Dockerfile
  BUILD_CONTEXT: .
  CACHE_SCOPE: docker-image
  STABLE_FLOATING_TAG: latest
  PRERELEASE_FLOATING_TAG: beta
  PRERELEASE_PATTERN: (alpha|beta|rc)

permissions:
  contents: read
  packages: write
  attestations: write
  id-token: write

jobs:
  build:
    name: Build (${{ matrix.arch }})
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        include:
          - arch: amd64
            platform: linux/amd64
          - arch: arm64
            platform: linux/arm64
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          fetch-tags: true
          persist-credentials: false

      - name: Set build metadata
        shell: bash
        env:
          INPUT_VERSION: ${{ github.event.inputs.version }}
          INPUT_IMAGE_NAME: ${{ github.event.inputs.image_name }}
        run: |
          set -euo pipefail

          pointed_tag="$(git tag --points-at HEAD --list 'v*' | sort -V | tail -n1)"
          input_version="${INPUT_VERSION//[[:space:]]/}"
          image_name="${INPUT_IMAGE_NAME:-$DEFAULT_IMAGE_NAME}"

          if [[ "$GITHUB_REF" == refs/tags/* ]]; then
            version="$GITHUB_REF_NAME"
          elif [[ -n "$input_version" ]]; then
            version="$input_version"
          elif [[ -n "$pointed_tag" ]]; then
            version="$pointed_tag"
          else
            echo "workflow_dispatch requires a version input when HEAD is not tagged" >&2
            exit 1
          fi

          if [[ ! -f "$DOCKERFILE" ]]; then
            echo "Dockerfile not found: $DOCKERFILE" >&2
            exit 1
          fi

          if [[ ! -d "$BUILD_CONTEXT" ]]; then
            echo "Docker context not found: $BUILD_CONTEXT" >&2
            exit 1
          fi

          {
            echo "IMAGE=${REGISTRY}/${image_name,,}"
            echo "VERSION=$version"
            echo "BUILD_DATE=$(date -u +'%Y-%m-%dT%H:%M:%SZ')"
            echo "VCS_REF=$GITHUB_SHA"
          } >> "$GITHUB_ENV"

      - name: Set up QEMU
        uses: docker/setup-qemu-action@v3

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

      - name: Log in to registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build and push digest
        id: build
        uses: docker/build-push-action@v6
        with:
          context: ${{ env.BUILD_CONTEXT }}
          file: ${{ env.DOCKERFILE }}
          platforms: ${{ matrix.platform }}
          outputs: type=image,name=${{ env.IMAGE }},push-by-digest=true,name-canonical=true,push=true
          build-args: |
            VERSION=${{ env.VERSION }}
            BUILD_DATE=${{ env.BUILD_DATE }}
            VCS_REF=${{ env.VCS_REF }}
          labels: |
            org.opencontainers.image.title=${{ github.event.repository.name }}
            org.opencontainers.image.source=${{ github.server_url }}/${{ github.repository }}
            org.opencontainers.image.revision=${{ github.sha }}
            org.opencontainers.image.version=${{ env.VERSION }}
            org.opencontainers.image.created=${{ env.BUILD_DATE }}
          cache-from: type=gha,scope=${{ env.CACHE_SCOPE }}-${{ matrix.arch }}
          cache-to: type=gha,mode=max,ignore-error=true,timeout=20m,scope=${{ env.CACHE_SCOPE }}-${{ matrix.arch }}

      - name: Export digest
        shell: bash
        env:
          DIGEST: ${{ steps.build.outputs.digest }}
        run: |
          set -euo pipefail
          mkdir -p /tmp/image-digests
          touch "/tmp/image-digests/${DIGEST#sha256:}"

      - name: Upload digest
        uses: actions/upload-artifact@v4
        with:
          name: image-digests-${{ matrix.arch }}
          path: /tmp/image-digests/*
          if-no-files-found: error
          retention-days: 1

      - name: Generate artifact attestation
        uses: actions/attest-build-provenance@v2
        with:
          subject-name: ${{ env.IMAGE }}
          subject-digest: ${{ steps.build.outputs.digest }}
          push-to-registry: true

  merge:
    name: Merge multi-arch manifest
    runs-on: ubuntu-latest
    needs: build
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          fetch-tags: true
          persist-credentials: false

      - name: Set build metadata
        shell: bash
        env:
          INPUT_VERSION: ${{ github.event.inputs.version }}
          INPUT_IMAGE_NAME: ${{ github.event.inputs.image_name }}
        run: |
          set -euo pipefail

          pointed_tag="$(git tag --points-at HEAD --list 'v*' | sort -V | tail -n1)"
          input_version="${INPUT_VERSION//[[:space:]]/}"
          image_name="${INPUT_IMAGE_NAME:-$DEFAULT_IMAGE_NAME}"

          if [[ "$GITHUB_REF" == refs/tags/* ]]; then
            version="$GITHUB_REF_NAME"
          elif [[ -n "$input_version" ]]; then
            version="$input_version"
          elif [[ -n "$pointed_tag" ]]; then
            version="$pointed_tag"
          else
            echo "workflow_dispatch requires a version input when HEAD is not tagged" >&2
            exit 1
          fi

          if [[ ! -f "$DOCKERFILE" ]]; then
            echo "Dockerfile not found: $DOCKERFILE" >&2
            exit 1
          fi

          if [[ ! -d "$BUILD_CONTEXT" ]]; then
            echo "Docker context not found: $BUILD_CONTEXT" >&2
            exit 1
          fi

          {
            echo "IMAGE=${REGISTRY}/${image_name,,}"
            echo "VERSION=$version"
          } >> "$GITHUB_ENV"

      - name: Download digests
        uses: actions/download-artifact@v4
        with:
          path: /tmp/image-digests
          pattern: image-digests-*
          merge-multiple: true

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

      - name: Log in to registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Create and push manifest list
        working-directory: /tmp/image-digests
        shell: bash
        run: |
          set -euo pipefail
          shopt -s nullglob

          references=()
          for digest in *; do
            references+=("${IMAGE}@sha256:${digest}")
          done

          if [[ ${#references[@]} -eq 0 ]]; then
            echo "No digests found in /tmp/image-digests" >&2
            exit 1
          fi

          floating_tag="$STABLE_FLOATING_TAG"
          if [[ "$VERSION" =~ $PRERELEASE_PATTERN ]]; then
            floating_tag="$PRERELEASE_FLOATING_TAG"
          fi

          docker buildx imagetools create \
            -t "${IMAGE}:${VERSION}" \
            -t "${IMAGE}:${floating_tag}" \
            "${references[@]}"

      - name: Inspect image
        run: docker buildx imagetools inspect "${IMAGE}:${VERSION}"