name: Build SilverMetal Linux ISO (reproducibility-gated)

# M1.1 exit-criterion check. Builds the ISO twice from a clean checkout in
# isolated directories and gates on byte-identical SHA256. On a tag push, the
# verified ISO and its SHA256SUMS are attached to a Gitea release.
#
# Two-stage:
#   1. builder-image — rebuilds linux/build/docker/Dockerfile.builder, pushes
#      to docker-registry.silverlabs.uk/silvermetal-builder:m1.1-<sha>, and
#      surfaces the resulting digest as a job output. This is what previously
#      had to be done by hand on 10.0.0.51 between every iter.
#   2. build-and-verify — reproducibility-gated double build, using the
#      digest from step 1 via the BUILDER_IMAGE env override that build.sh
#      already supports (and validates is digest-form).
#
# The release-upload pattern (create-if-not-exists then attach asset) is
# lifted from SilverLABS/SilverVPN/.gitea/workflows/build-linux-client.yaml
# lines 77-117. Keep them in sync if either changes.

on:
  push:
    branches: [main]
    paths:
      - 'linux/**'
      - 'shared/branding/linux-iso-meta.yaml'
      - '.gitea/workflows/build-iso-linux.yaml'
    tags:
      - 'v*'
  pull_request:
    branches: [main]
    paths:
      - 'linux/**'
      - 'shared/branding/linux-iso-meta.yaml'
      - '.gitea/workflows/build-iso-linux.yaml'
  workflow_dispatch:

# Two reproducibility-gated builds in flight at once would just compete for
# loop devices on the privileged runner. Serialise per ref.
concurrency:
  group: build-iso-linux-${{ github.ref }}
  cancel-in-progress: true

jobs:
  builder-image:
    # Build + push the silvermetal-builder image on the runner host's docker
    # daemon (DooD via /var/run/docker.sock, mounted into the act_runner job
    # container by linux/build/runner/docker-compose.yml). The runner host
    # is also already authenticated to docker-registry.silverlabs.uk via
    # /root/.docker (mounted read-only into the runner) so `docker push`
    # works without an explicit login step here.
    runs-on: silvermetal-builder
    timeout-minutes: 30
    outputs:
      digest: ${{ steps.push.outputs.digest }}
      image:  ${{ steps.push.outputs.image }}

    steps:
      - name: Checkout
        uses: actions/checkout@v4
        # No submodules needed for the builder image — its build context is
        # only linux/build/docker/.

      - name: Build & push silvermetal-builder
        id: push
        env:
          REGISTRY: docker-registry.silverlabs.uk
          REPO: silvermetal-builder
        run: |
          set -eu
          TAG="m1.1-${GITHUB_SHA::12}"
          IMAGE="${REGISTRY}/${REPO}:${TAG}"
          LATEST="${REGISTRY}/${REPO}:latest"

          echo "Building ${IMAGE}"
          docker build \
            -f linux/build/docker/Dockerfile.builder \
            -t "${IMAGE}" \
            -t "${LATEST}" \
            linux/build/docker

          echo "Pushing ${IMAGE}"
          docker push "${IMAGE}"
          docker push "${LATEST}"

          # docker inspect's RepoDigests is "repo@sha256:...". Take the
          # entry that matches the registry/repo we just pushed to (there
          # may be multiple if the image has been pushed elsewhere too).
          DIGEST=$(docker inspect --format '{{range .RepoDigests}}{{println .}}{{end}}' "${IMAGE}" \
            | grep "^${REGISTRY}/${REPO}@" \
            | head -n1 \
            | sed 's/.*@//')
          if [ -z "${DIGEST}" ]; then
            echo "::error::failed to resolve digest for ${IMAGE}" >&2
            docker inspect "${IMAGE}" >&2 || true
            exit 1
          fi
          echo "Pushed digest: ${DIGEST}"

          {
            echo "digest=${DIGEST}"
            echo "image=${REGISTRY}/${REPO}@${DIGEST}"
          } >> "${GITHUB_OUTPUT}"

  build-and-verify:
    # Self-hosted, privileged-capable. Setup procedure documented in
    # linux/build/README.md ("Self-hosted runner setup").
    needs: builder-image
    runs-on: silvermetal-builder
    timeout-minutes: 240
    env:
      # Override build.sh's compiled-in pin with the digest we just built &
      # pushed. build.sh validates the @sha256: form on line ~37 — the
      # composed value below satisfies that.
      BUILDER_IMAGE: ${{ needs.builder-image.outputs.image }}

    steps:
      - name: Checkout (with submodules)
        uses: actions/checkout@v4
        with:
          submodules: recursive
          fetch-depth: 0   # need history so SOURCE_DATE_EPOCH = HEAD commit time

      - name: Show pinned inputs
        run: |
          set -eu
          echo "commit=$(git rev-parse HEAD)"
          cat linux/build/config/snapshot-pin.env
          echo "builder image (this run): ${BUILDER_IMAGE}"
          echo "Dockerfile.builder FROM/snapshot:"
          grep -E '^FROM |^ARG APT_SNAPSHOT_URL' linux/build/docker/Dockerfile.builder

      - name: Build A
        env:
          BUILD_DIR: ${{ github.workspace }}/build-a
        run: linux/build/scripts/build.sh

      - name: Build B (clean second build)
        env:
          BUILD_DIR: ${{ github.workspace }}/build-b
        run: linux/build/scripts/build.sh

      - name: Compare SHA256
        id: compare
        run: |
          set -eu
          A=$(sha256sum "${{ github.workspace }}/build-a"/*.iso | cut -d' ' -f1)
          B=$(sha256sum "${{ github.workspace }}/build-b"/*.iso | cut -d' ' -f1)
          echo "A=${A}"
          echo "B=${B}"
          echo "iso_sha256=${A}" >> "${GITHUB_OUTPUT}"
          if [ "${A}" != "${B}" ]; then
            echo "::error::ISO SHA256 mismatch — A=${A} B=${B}"
            ISO_A="$(ls "${{ github.workspace }}/build-a"/*.iso | head -n1)" \
            ISO_B="$(ls "${{ github.workspace }}/build-b"/*.iso | head -n1)" \
            REPORT_DIR="${{ github.workspace }}/divergence" \
              linux/build/scripts/diagnose-divergence.sh
            exit 1
          fi
          echo "Reproducibility gate PASSED at ${A}"

      - name: Upload divergence report on failure
        if: failure()
        uses: actions/upload-artifact@v3
        with:
          name: divergence-report-${{ github.run_id }}
          path: ${{ github.workspace }}/divergence
          if-no-files-found: ignore
          retention-days: 14

      - name: Stage release artefacts
        if: startsWith(github.ref, 'refs/tags/')
        run: |
          set -eu
          mkdir -p release
          cp "${{ github.workspace }}/build-a"/*.iso        release/
          cp "${{ github.workspace }}/build-a"/SHA256SUMS   release/
          cp "${{ github.workspace }}/build-a"/BUILD_INFO   release/
          cp "${{ github.workspace }}/build-a"/snapshot-pin.env release/snapshot-pin.env
          ls -la release/

      - name: Upload to Gitea release (tag only)
        if: startsWith(github.ref, 'refs/tags/')
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          set -eu
          TAG="${{ github.ref_name }}"
          API="${{ github.server_url }}/api/v1"
          REPO="${{ github.repository }}"

          # Create-if-not-exists, then attach assets. Pattern lifted from
          # SilverLABS/SilverVPN build-linux-client.yaml:89-115.
          RELEASE_ID=$(curl -s "${API}/repos/${REPO}/releases/tags/${TAG}" \
            -H "Authorization: token ${GITHUB_TOKEN}" \
            | jq -r '.id // empty' 2>/dev/null || true)

          if [ -z "${RELEASE_ID}" ] || [ "${RELEASE_ID}" = "0" ]; then
            RESPONSE=$(curl -s -w "\n%{http_code}" -X POST "${API}/repos/${REPO}/releases" \
              -H "Authorization: token ${GITHUB_TOKEN}" \
              -H "Content-Type: application/json" \
              -d "{\"tag_name\":\"${TAG}\",\"name\":\"SilverMetal Linux ${TAG}\",\"body\":\"Reproducibility-verified ISO. SHA256 in SHA256SUMS asset.\",\"draft\":false,\"prerelease\":true}")
            HTTP_CODE=$(echo "${RESPONSE}" | tail -1)
            BODY=$(echo "${RESPONSE}" | sed '$d')
            if [ "${HTTP_CODE}" -ge 400 ]; then
              echo "ERROR: Failed to create release (${HTTP_CODE}): ${BODY}"
              exit 1
            fi
            RELEASE_ID=$(echo "${BODY}" | jq -r '.id')
            echo "Created release ID: ${RELEASE_ID}"
          else
            echo "Found existing release ID: ${RELEASE_ID}"
          fi

          for asset in release/*; do
            name=$(basename "${asset}")
            echo "Attaching ${name}"
            curl -sf -X POST \
              "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=${name}" \
              -H "Authorization: token ${GITHUB_TOKEN}" \
              -H "Content-Type: application/octet-stream" \
              --data-binary "@${asset}"
          done