release.yml

name: Release

# Builds and publishes a multi-arch container image to GHCR.
#
# Triggers:
#   - push to main         → ghcr.io/<owner>/gluco-hub:edge + :sha-<short>
#   - push of a v* tag     → :X.Y.Z, :X.Y, :X, :latest, :sha-<short>
#   - pull_request         → build-only verification on both arches (no push)
#   - workflow_dispatch    → manual republish
#
# Architecture: separate native-runner jobs per platform (amd64 on
# ubuntu-latest, arm64 on ubuntu-24.04-arm) push by digest, then a
# merge job assembles the multi-arch manifest, signs it keyless with
# cosign, and attaches a SLSA build-provenance attestation. This is
# materially faster than QEMU emulation for a Rust workload.

on:
  push:
    branches: [main]
    tags: ['v*']
  pull_request:
    branches: [main]
  workflow_dispatch:

# Don't cancel a release in flight if a newer commit lands — the
# in-flight build might be the one a user is about to pull. PRs are
# safe to cancel on rebase.
concurrency:
  group: release-${{ github.ref }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository_owner }}/gluco-hub

jobs:
  build:
    name: build (${{ matrix.platform }})
    runs-on: ${{ matrix.runner }}
    permissions:
      contents: read
      packages: write       # push image layers by digest (no-op on PRs)
    strategy:
      fail-fast: false
      matrix:
        include:
          - platform: linux/amd64
            runner: ubuntu-latest
          - platform: linux/arm64
            runner: ubuntu-24.04-arm
    steps:
      - uses: actions/checkout@v4

      - name: Compute env
        run: |
          echo "BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ)" >> "$GITHUB_ENV"
          # platform "linux/arm64" → "linux-arm64", used as artifact suffix
          echo "PLATFORM_PAIR=${PLATFORM//\//-}" >> "$GITHUB_ENV"
        env:
          PLATFORM: ${{ matrix.platform }}

      - uses: docker/setup-buildx-action@v3

      - name: Log in to GHCR
        if: github.event_name != 'pull_request'
        uses: docker/login-action@v4
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      # Only labels here — tags are computed in the merge job and applied
      # via `buildx imagetools create -t <tag> ...`. Per-arch builds push
      # by digest and have no human-readable tag of their own.
      - name: Compute image labels
        id: meta
        uses: docker/metadata-action@v6
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          labels: |
            org.opencontainers.image.licenses=AGPL-3.0-or-later

      - name: Build & push by digest
        id: build
        uses: docker/build-push-action@v7
        with:
          context: .
          platforms: ${{ matrix.platform }}
          labels: ${{ steps.meta.outputs.labels }}
          build-args: |
            GLUCO_HUB_GIT_SHA=${{ github.sha }}
            BUILD_DATE=${{ env.BUILD_DATE }}
          # Per-platform cache scope so the two matrix jobs don't evict
          # each other.
          cache-from: type=gha,scope=${{ env.PLATFORM_PAIR }}
          cache-to: type=gha,mode=max,scope=${{ env.PLATFORM_PAIR }}
          # PRs build but don't push. Non-PR runs push by digest only —
          # the merge job assembles the multi-arch manifest with proper
          # tags. `name-canonical=true` ensures the digest is recorded
          # against the canonical image name.
          outputs: |
            ${{ github.event_name == 'pull_request'
              && 'type=cacheonly'
              || format('type=image,name={0}/{1},push-by-digest=true,name-canonical=true,push=true', env.REGISTRY, env.IMAGE_NAME) }}
          # Provenance default for public repos is mode=max since
          # build-push-action v6 — leaving implicit. SBOM must be opted
          # into explicitly.
          sbom: true

      - name: Export digest
        if: github.event_name != 'pull_request'
        run: |
          mkdir -p /tmp/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "/tmp/digests/${digest#sha256:}"

      - name: Upload digest
        if: github.event_name != 'pull_request'
        uses: actions/upload-artifact@v4
        with:
          name: digest-${{ env.PLATFORM_PAIR }}
          path: /tmp/digests/*
          if-no-files-found: error
          retention-days: 1

  merge:
    name: merge & publish manifest
    if: github.event_name != 'pull_request'
    needs: build
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write       # push manifest list to GHCR
      id-token: write       # cosign keyless OIDC + attestation signing
      attestations: write   # GitHub Artifact Attestations
    steps:
      - name: Download digests
        uses: actions/download-artifact@v4
        with:
          path: /tmp/digests
          pattern: digest-*
          merge-multiple: true

      - uses: docker/setup-buildx-action@v3

      - name: Log in to GHCR
        uses: docker/login-action@v4
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Compute image metadata
        id: meta
        uses: docker/metadata-action@v6
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          tags: |
            type=edge,branch=main
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=semver,pattern={{major}}
            type=sha,format=short

      - name: Create manifest list & push
        working-directory: /tmp/digests
        run: |
          docker buildx imagetools create \
            $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)

      - name: Inspect manifest
        run: |
          docker buildx imagetools inspect \
            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}

      - name: Resolve manifest digest
        id: manifest
        run: |
          digest=$(docker buildx imagetools inspect \
            "${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}" \
            --format '{{json .Manifest.Digest}}' | tr -d '"')
          echo "digest=${digest}" >> "$GITHUB_OUTPUT"

      - name: Install cosign
        uses: sigstore/cosign-installer@v4.1.2

      # Sign the manifest-list digest. One signature covers every tag
      # pointing at the same digest — re-tagging doesn't invalidate it.
      - name: Sign image (keyless)
        env:
          IMAGE: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          DIGEST: ${{ steps.manifest.outputs.digest }}
        run: |
          cosign sign --yes \
            -a "repo=${{ github.repository }}" \
            -a "workflow=${{ github.workflow }}" \
            -a "ref=${{ github.sha }}" \
            "${IMAGE}@${DIGEST}"

      # Pushes a Sigstore-signed SLSA provenance bundle to the registry,
      # discoverable in the GitHub UI and verifiable via:
      #   gh attestation verify oci://ghcr.io/<owner>/gluco-hub:<tag> \
      #     --owner <owner>
      - name: Attest build provenance
        uses: actions/attest-build-provenance@v4
        with:
          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          subject-digest: ${{ steps.manifest.outputs.digest }}
          push-to-registry: true