name: Publish Docker image

on:
  workflow_dispatch:
  push:
    tags:
      - "v*"

permissions: {}

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}

jobs:
  push_to_registry:
    name: Push Docker image to GHCR
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
      id-token: write
    steps:
      - name: Check out the repo
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
        with:
          persist-credentials: false

      - name: Set up QEMU
        uses: docker/setup-qemu-action@96fe6ef7f33517b61c61be40b68a1882f3264fb8 # v4.2.0
        with:
          platforms: linux/amd64,linux/arm64

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0

      - name: Log in to the Container registry
        uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@dc802804100637a589fabce1cb79ff13a1411302
        with:
          images: ghcr.io/${{ github.repository }}

      - uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2

      - name: Build and push Docker image
        id: build
        uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          provenance: mode=max
          sbom: true

      - name: Sign image by digest
        env:
          DIGEST: ${{ steps.build.outputs.digest }}
          IMAGE: ghcr.io/${{ github.repository }}
        run: |
          set -euo pipefail
          [[ "$DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]
          cosign sign --yes "${IMAGE}@${DIGEST}"

      - name: Verify BuildKit attestations and extract SPDX predicates
        env:
          DIGEST: ${{ steps.build.outputs.digest }}
          IMAGE: ghcr.io/${{ github.repository }}
        run: |
          set -euo pipefail
          reference="${IMAGE}@${DIGEST}"
          docker buildx imagetools inspect "$reference" --format '{{ json .Provenance }}' > provenance.json
          docker buildx imagetools inspect "$reference" --format '{{ json .SBOM }}' > sbom.json

          for platform in linux/amd64 linux/arm64; do
            jq -e --arg p "$platform" '.[$p].SLSA | type == "object" and length > 0' \
              provenance.json >/dev/null
            jq -e --arg p "$platform" '.[$p].SPDX' sbom.json > "sbom-${platform//\//-}.spdx.json"
          done

      - name: Attest platform SBOMs by digest
        env:
          DIGEST: ${{ steps.build.outputs.digest }}
          IMAGE: ghcr.io/${{ github.repository }}
        run: |
          set -euo pipefail
          [[ "$DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]
          reference="${IMAGE}@${DIGEST}"
          for predicate in sbom-linux-amd64.spdx.json sbom-linux-arm64.spdx.json; do
            cosign attest --yes --type spdxjson --predicate "$predicate" "$reference"
          done