name: SLSA Build L1 (provenance attestation)

# SLSA v1.0 Build L1 requires that provenance EXISTS describing how the
# artifact was built and is DISTRIBUTED to consumers
# (https://slsa.dev/spec/v1.0/levels#build-l1).
#
# The previous job was a no-op stub (`run: echo "SLSA L1 supply-chain checks OK"`)
# which emitted no provenance and therefore did not satisfy Build L1.
#
# This workflow now:
#   1. Builds the same a11oy-uds-<version>.tar.zst artifact produced by
#      uds-sign-release.yml (git archive | zstd).
#   2. Generates an in-toto v1 SLSA provenance attestation for that artifact
#      via actions/attest-build-provenance. The attestation is signed with the
#      SAME Sigstore keyless flow already used for release signing
#      (GitHub OIDC -> Fulcio short-lived cert -> Rekor transparency log).
#   3. Uploads the provenance bundle (.intoto.jsonl) as a release asset so it
#      is distributed to consumers alongside the artifact.
#
# Doctrine v6: no echo stubs, verifiable provenance only.

on:
  workflow_dispatch:
    inputs:
      tag_name:
        description: 'Release tag to attest (e.g. uds-v0.3.0). Optional on push.'
        required: false
        type: string
  release:
    types: [published]

permissions:
  contents: read

jobs:
  provenance:
    name: Build artifact + attest SLSA provenance
    runs-on: ubuntu-latest
    permissions:
      id-token: write     # OIDC token -> Sigstore Fulcio keyless signing
      contents: write      # upload provenance + write attestation to release
      attestations: write  # store the attestation in the repo attestations API
      actions: read
    steps:
      - name: Resolve tag name
        id: tag
        run: |
          if [[ "${{ github.event_name }}" == "release" ]]; then
            TAG="${{ github.event.release.tag_name }}"
          else
            TAG="${{ inputs.tag_name }}"
          fi
          if [[ -z "${TAG}" ]]; then
            # No tag context (e.g. manual dispatch on main): attest the current ref.
            TAG="$(git rev-parse --short HEAD 2>/dev/null || echo main)"
            VERSION="0.0.0-dev-${TAG}"
          else
            VERSION="${TAG#uds-v}"
          fi
          echo "tag=${TAG}" >> "$GITHUB_OUTPUT"
          echo "version=${VERSION}" >> "$GITHUB_OUTPUT"
          echo "tarball=a11oy-uds-${VERSION}.tar.zst" >> "$GITHUB_OUTPUT"

      - name: Checkout
        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
        with:
          ref: ${{ steps.tag.outputs.tag }}
          fetch-depth: 0

      - name: Build tar.zst (same artifact as uds-sign-release.yml)
        id: build
        run: |
          VERSION="${{ steps.tag.outputs.version }}"
          TARBALL="${{ steps.tag.outputs.tarball }}"
          echo "Building ${TARBALL}..."
          git archive \
            --format=tar \
            --prefix="a11oy-uds-${VERSION}/" \
            HEAD \
            | zstd -19 -T0 -o "${TARBALL}"
          echo "Built ${TARBALL}: $(wc -c < "${TARBALL}") bytes"
          echo "tarball_path=${PWD}/${TARBALL}" >> "$GITHUB_OUTPUT"

      - name: Generate SLSA provenance attestation (Sigstore keyless)
        id: attest
        uses: actions/attest-build-provenance@a2bbfa25375fe432b6a289bc6b6cd05ecd0c4c32 # v4.1.0
        with:
          subject-path: ${{ steps.build.outputs.tarball_path }}

      - name: Stage provenance as a distributable .intoto.jsonl
        id: prov
        run: |
          VERSION="${{ steps.tag.outputs.version }}"
          PROV_OUT="a11oy-uds-${VERSION}.tar.zst.intoto.jsonl"
          # actions/attest-build-provenance writes the signed in-toto v1 bundle
          # to a file whose path is exported as bundle-path.
          cp "${{ steps.attest.outputs.bundle-path }}" "${PROV_OUT}"
          echo "Provenance bundle: ${PROV_OUT} ($(wc -c < "${PROV_OUT}") bytes)"
          echo "prov_file=${PROV_OUT}" >> "$GITHUB_OUTPUT"

      - name: Upload provenance to the GitHub release (distribute to consumers)
        if: github.event_name == 'release'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          TAG="${{ steps.tag.outputs.tag }}"
          PROV_OUT="${{ steps.prov.outputs.prov_file }}"
          gh release upload "${TAG}" "${PROV_OUT}" \
            --clobber \
            --repo szl-holdings/a11oy
          echo "Provenance distributed as a release asset on ${TAG}."

      - name: Upload provenance as workflow artifact (dispatch runs)
        if: github.event_name != 'release'
        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
        with:
          name: ${{ steps.prov.outputs.prov_file }}
          path: ${{ steps.prov.outputs.prov_file }}
          retention-days: 90

      - name: Print verification instructions
        run: |
          VERSION="${{ steps.tag.outputs.version }}"
          echo "=== Verify SLSA provenance ==="
          echo "slsa-verifier verify-artifact \\"
          echo "  --provenance-path a11oy-uds-${VERSION}.tar.zst.intoto.jsonl \\"
          echo "  --source-uri github.com/szl-holdings/a11oy \\"
          echo "  a11oy-uds-${VERSION}.tar.zst"
          echo ""
          echo "Or with the GitHub CLI (uses the repo attestations API + Rekor):"
          echo "  gh attestation verify a11oy-uds-${VERSION}.tar.zst --repo szl-holdings/a11oy"