name: Trivy Multi-Arch CVE Delta Comparison
description: Downloads and verifies Trivy, extracts multi-platform SBOMs, and computes a consolidated set-based CVE delta report

inputs:
  head-image:
    description: Head container image reference (e.g. host/server/gitea:git-12345678)
    required: true
  target-image:
    description: Target baseline container image reference (e.g. host/server/gitea:latest)
    required: true
  target-branch:
    description: Target branch name for delta heading (e.g. main)
    required: false
    default: main
  trivy-version:
    description: Trivy binary version to install and verify
    required: false
    default: 0.74.0   # trivy-version
  output-delta:
    description: Output markdown file for CVE delta report
    required: false
    default: cve-delta.md
  output-summary:
    description: Output markdown file for full vulnerability summary
    required: false
    default: cve-summary.md
  write-summary:
    description: Whether to append the generated reports to the job summary ($GITHUB_STEP_SUMMARY)
    required: false
    default: 'true'

outputs:
  delta-report:
    description: Path to CVE delta markdown report
    value: ${{ inputs.output-delta }}
  summary-report:
    description: Path to full vulnerability markdown report
    value: ${{ inputs.output-summary }}

runs:
  using: composite
  steps:
  - name: Prepare Cache Keys
    id: vars
    shell: bash
    run: echo "date=$(date -u +%Y-%m-%d)" >> "$GITHUB_OUTPUT"

  - name: Cache Trivy (Binary & Vulnerability DB)
    uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830     # v4.3.0
    with:
      path: |
        ~/.cache/trivy-bin
        ~/.cache/trivy
      key: trivy-${{ inputs.trivy-version }}-${{ runner.os }}-${{ runner.arch }}-${{ steps.vars.outputs.date }}
      restore-keys: |
        trivy-${{ inputs.trivy-version }}-${{ runner.os }}-${{ runner.arch }}-

  - name: Install and Verify Trivy
    shell: bash
    run: |
      mkdir -p "$HOME/.cache/trivy-bin" "$HOME/.local/bin"
      echo "$HOME/.local/bin" >> "$GITHUB_PATH"

      ARCH=$(uname -m)
      case "$ARCH" in
        x86_64) T_ARCH="64bit" ;;
        aarch64|arm64) T_ARCH="ARM64" ;;
        *) echo "Unsupported architecture: $ARCH"; exit 1 ;;
      esac
      tarball="trivy_${{ inputs.trivy-version }}_Linux-${T_ARCH}.tar.gz"
      checksums_file="${{ github.action_path }}/checksums.txt"

      if [ -f "$HOME/.cache/trivy-bin/${tarball}" ] && (cd "$HOME/.cache/trivy-bin" && grep "  ${tarball}$" "$checksums_file" | sha256sum -c -); then
        echo "Cached Trivy archive verified against lockfile."
      else
        echo "Archive missing or checksum mismatch; downloading..."
        curl -sfLO "https://github.com/aquasecurity/trivy/releases/download/v${{ inputs.trivy-version }}/${tarball}" --output-dir "$HOME/.cache/trivy-bin"
        (cd "$HOME/.cache/trivy-bin" && grep "  ${tarball}$" "$checksums_file" | sha256sum -c -)
      fi

      tar -xzf "$HOME/.cache/trivy-bin/${tarball}" -C "$HOME/.local/bin" trivy
      chmod +x "$HOME/.local/bin/trivy"

  - name: Extract Multi-Platform SBOMs
    shell: bash
    run: |
      export PATH="$HOME/.local/bin:$PATH"
      mkdir -p sboms/head sboms/target

      cleanup_file() {
        local f="$1"
        if [ ! -s "$f" ] || [ "$(cat "$f" 2>/dev/null)" = "null" ]; then
          rm -f "$f"
        fi
      }

      # Extract platform SBOMs for head image
      echo "Extracting platform SBOMs for head image: ${{ inputs.head-image }}..."
      docker buildx imagetools inspect "${{ inputs.head-image }}" \
        --format '{{ json (index .SBOM "linux/amd64").SPDX }}' > sboms/head/sbom-amd64.spdx.json 2>/dev/null || true
      cleanup_file sboms/head/sbom-amd64.spdx.json

      docker buildx imagetools inspect "${{ inputs.head-image }}" \
        --format '{{ json (index .SBOM "linux/arm64").SPDX }}' > sboms/head/sbom-arm64.spdx.json 2>/dev/null || true
      cleanup_file sboms/head/sbom-arm64.spdx.json

      # If single-arch, extract root .SPDX
      if [ ! -f sboms/head/sbom-amd64.spdx.json ] && [ ! -f sboms/head/sbom-arm64.spdx.json ]; then
        docker buildx imagetools inspect "${{ inputs.head-image }}" \
          --format '{{ json .SBOM.SPDX }}' > sboms/head/sbom-amd64.spdx.json 2>/dev/null || true
        cleanup_file sboms/head/sbom-amd64.spdx.json
      fi

      # Fallback to generating head SBOM with Trivy if attestation missing
      if [ ! -f sboms/head/sbom-amd64.spdx.json ] && [ ! -f sboms/head/sbom-arm64.spdx.json ]; then
        echo "Head image lacks SBOM attestation; generating with Trivy..."
        trivy image --format spdx-json --output sboms/head/sbom-amd64.spdx.json "${{ inputs.head-image }}" || true
        cleanup_file sboms/head/sbom-amd64.spdx.json
      fi

      # Extract platform SBOMs for target image
      echo "Extracting platform SBOMs for target image: ${{ inputs.target-image }}..."
      docker buildx imagetools inspect "${{ inputs.target-image }}" \
        --format '{{ json (index .SBOM "linux/amd64").SPDX }}' > sboms/target/sbom-amd64.spdx.json 2>/dev/null || true
      cleanup_file sboms/target/sbom-amd64.spdx.json

      docker buildx imagetools inspect "${{ inputs.target-image }}" \
        --format '{{ json (index .SBOM "linux/arm64").SPDX }}' > sboms/target/sbom-arm64.spdx.json 2>/dev/null || true
      cleanup_file sboms/target/sbom-arm64.spdx.json

      if [ ! -f sboms/target/sbom-amd64.spdx.json ] && [ ! -f sboms/target/sbom-arm64.spdx.json ]; then
        docker buildx imagetools inspect "${{ inputs.target-image }}" \
          --format '{{ json .SBOM.SPDX }}' > sboms/target/sbom-amd64.spdx.json 2>/dev/null || true
        cleanup_file sboms/target/sbom-amd64.spdx.json
      fi

      # Fallback to generating target SBOM with Trivy if attestation missing
      if [ ! -f sboms/target/sbom-amd64.spdx.json ] && [ ! -f sboms/target/sbom-arm64.spdx.json ]; then
        echo "Target image lacks SBOM attestation; attempting to generate with Trivy..."
        trivy image --format spdx-json --output sboms/target/sbom-amd64.spdx.json "${{ inputs.target-image }}" || true
        cleanup_file sboms/target/sbom-amd64.spdx.json
      fi

      # Expose extracted head SBOMs to workspace root for workflow artifact uploads
      [ -f sboms/head/sbom-amd64.spdx.json ] && cp sboms/head/sbom-amd64.spdx.json sbom-amd64.spdx.json || true
      [ -f sboms/head/sbom-arm64.spdx.json ] && cp sboms/head/sbom-arm64.spdx.json sbom-arm64.spdx.json || true

  - name: Scan Multi-Platform SBOMs and Generate Delta
    shell: bash
    run: |
      export PATH="$HOME/.local/bin:$PATH"
      mkdir -p cve-reports/head cve-reports/target

      # Scan each available head SBOM
      for f in sboms/head/sbom-*.spdx.json; do
        [ -f "$f" ] || continue
        arch=$(basename "$f" .spdx.json | sed 's/sbom-//')
        echo "Scanning head SBOM for architecture: $arch"
        trivy sbom --format json --output "cve-reports/head/cve-${arch}.json" "$f" || true
      done

      # Scan each available target SBOM
      for f in sboms/target/sbom-*.spdx.json; do
        [ -f "$f" ] || continue
        arch=$(basename "$f" .spdx.json | sed 's/sbom-//')
        echo "Scanning target SBOM for architecture: $arch"
        trivy sbom --format json --output "cve-reports/target/cve-${arch}.json" "$f" || true
      done

      # Run multi-arch set-based diff
      node "${{ github.action_path }}/cve-diff.js" \
        "cve-reports/target" \
        "cve-reports/head" \
        "${{ inputs.target-branch }}" > "${{ inputs.output-delta }}" || true

      # Generate full markdown summary report for primary platform
      primary_sbom=""
      if [ -f sboms/head/sbom-amd64.spdx.json ]; then
        primary_sbom="sboms/head/sbom-amd64.spdx.json"
      elif [ -f sboms/head/sbom-arm64.spdx.json ]; then
        primary_sbom="sboms/head/sbom-arm64.spdx.json"
      fi

      if [ -n "$primary_sbom" ]; then
        trivy sbom \
          --format template \
          --template "@${{ github.action_path }}/markdown.tpl" \
          --output "${{ inputs.output-summary }}" \
          "$primary_sbom" || true
      fi

  - name: Publish Reports to Step Summary
    shell: bash
    run: |
      if [ "${{ inputs.write-summary }}" = "true" ] && [ -n "${GITHUB_STEP_SUMMARY:-}" ]; then
        if [ -f "${{ inputs.output-delta }}" ]; then
          cat "${{ inputs.output-delta }}" >> "$GITHUB_STEP_SUMMARY"
        fi
        if [ -f "${{ inputs.output-summary }}" ]; then
          cat "${{ inputs.output-summary }}" >> "$GITHUB_STEP_SUMMARY"
        fi
      fi