name: 🔏 Sign PDFs

# Can be triggered:
#   1. Automatically after build.yml completes on main
#   2. Manually, pointing at a specific build run to pull PDFs from
on:
  # workflow_run:
  #   workflows: ["📖 Build PDFs"]
  #   types: [completed]
  #   branches: [main]
  workflow_dispatch:
    inputs:
      build_run_id:
        description: 'build.yml run ID to download PDFs from (leave blank for latest)'
        required: false
        type: string

permissions:
  actions:  read    # download artifacts from other runs
  contents: write   # needed to commit export/ files back to the repo

jobs:
  sign:
    name: Hash & Sign PDFs
    # On workflow_run, only proceed if the build actually succeeded
    # if: >
    #   github.event_name == 'workflow_dispatch' ||
    #   github.event.workflow_run.conclusion == 'success'
    runs-on: ubuntu-latest
    outputs:
      light_sha256: ${{ steps.hashes.outputs.light_sha256 }}
      dark_sha256:  ${{ steps.hashes.outputs.dark_sha256 }}
      light_b2:     ${{ steps.hashes.outputs.light_b2 }}
      dark_b2:      ${{ steps.hashes.outputs.dark_b2 }}

    steps:
      - name: 🛠️ Checkout (for pgp/ key reference only)
        uses: actions/checkout@v4
        with:
          sparse-checkout: pgp

      # Download PDFs from the manually specified run ID (required for manual dispatch)
      - name: 📥 Resolve source run ID
        id: src
        run: |
          if [ -z "${{ inputs.build_run_id }}" ]; then
            echo "::error::build_run_id is required — provide the build.yml run ID to pull PDFs from."
            exit 1
          fi
          echo "run_id=${{ inputs.build_run_id }}" >> $GITHUB_OUTPUT

      - name: 📥 Download PDF artifacts
        uses: actions/download-artifact@v4
        with:
          name:    pdfs
          path:    export/
          run-id:  ${{ steps.src.outputs.run_id }}
          github-token: ${{ secrets.GITHUB_TOKEN }}

      - name: 📋 List downloaded files
        run: ls -lh export/

      # ------------------------------------------------------------------ #
      #  Hash
      # ------------------------------------------------------------------ #
      - name: #️⃣ Hash PDFs
        id: hashes
        run: |
          cd export

          for f in thgtoa.pdf thgtoa-dark.pdf; do
            [ -f "$f" ] || continue
            sha256sum "$f" | awk '{print $1}' > "${f}.sha256"
            b2sum     "$f" | awk '{print $1}' > "${f}.b2"
          done

          # Combined files (only include files that exist)
          sha256sum thgtoa.pdf thgtoa-dark.pdf 2>/dev/null > sha256sums.txt || \
            sha256sum thgtoa.pdf               2>/dev/null > sha256sums.txt
          b2sum     thgtoa.pdf thgtoa-dark.pdf 2>/dev/null > b2sums.txt     || \
            b2sum     thgtoa.pdf               2>/dev/null > b2sums.txt

          # Expose individual hashes as outputs (empty string if file absent)
          light_sha256=$(cat thgtoa.pdf.sha256      2>/dev/null || echo "")
          dark_sha256=$(cat  thgtoa-dark.pdf.sha256 2>/dev/null || echo "")
          light_b2=$(cat     thgtoa.pdf.b2          2>/dev/null || echo "")
          dark_b2=$(cat      thgtoa-dark.pdf.b2     2>/dev/null || echo "")

          echo "light_sha256=$light_sha256" >> $GITHUB_OUTPUT
          echo "dark_sha256=$dark_sha256"   >> $GITHUB_OUTPUT
          echo "light_b2=$light_b2"         >> $GITHUB_OUTPUT
          echo "dark_b2=$dark_b2"           >> $GITHUB_OUTPUT

          echo "--- SHA-256 ---"
          cat sha256sums.txt
          echo "--- BLAKE2b ---"
          cat b2sums.txt

      # ------------------------------------------------------------------ #
      #  GPG sign (maintainer-verifiable detached signatures for release)
      # ------------------------------------------------------------------ #
      - name: 🔑 Install GPG
        run: |
          sudo apt-get update -qq
          sudo apt-get install -y gnupg

      - name: 🔏 Import GPG signing key
        env:
          GPG_PRIVATE_KEY: ${{ secrets.GPG_PRIVATE_KEY }}
          GPG_PASSPHRASE:  ${{ secrets.GPG_PASSPHRASE }}
        run: |
          echo "$GPG_PRIVATE_KEY" | gpg --batch --import
          echo "$GPG_PASSPHRASE" | gpg --batch --yes --passphrase-fd 0 \
            --pinentry-mode loopback --list-secret-keys

      - name: 🔏 Sign PDFs and hash files
        env:
          GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
        run: |
          sign() {
            local file="$1"
            [ -f "$file" ] || return 0
            echo "$GPG_PASSPHRASE" | gpg --batch --yes --passphrase-fd 0 \
              --pinentry-mode loopback \
              --detach-sign --armor --output "${file}.sig" "$file"
            echo "Signed: $file"
          }
          sign export/thgtoa.pdf
          sign export/thgtoa-dark.pdf
          sign export/sha256sums.txt
          sign export/b2sums.txt

      # ------------------------------------------------------------------ #
      #  Commit export/ back to main
      # ------------------------------------------------------------------ #
      - name: 📦 Checkout full repo for commit
        uses: actions/checkout@v4
        with:
          ref: main
          fetch-depth: 0
          path: repo

      - name: 📂 Copy export files into repo
        run: cp -v export/* repo/export/

      - name: 🔏 Configure SSH commit signing
        run: |
          mkdir -p ~/.ssh
          echo "${{ secrets.ACTIONS_SSH_SIGNING_KEY }}" > ~/.ssh/signing_key
          chmod 600 ~/.ssh/signing_key
          git config --global gpg.format ssh
          git config --global user.signingKey ~/.ssh/signing_key
          git config --global commit.gpgSign true
          git config --global user.name  "github-actions[bot]"
          git config --global user.email "github-actions[bot]@users.noreply.github.com"

      - name: 📤 Commit and push export/ to main
        working-directory: repo
        run: |
          git add export/
          if git diff --cached --quiet; then
            echo "Nothing to commit — export/ is already up to date."
          else
            git commit -S -m "chore(export): update PDFs, hashes and signatures [skip ci]"
            git push origin main
          fi

      # ------------------------------------------------------------------ #
      #  Upload — PDFs + all signatures and hashes together
      # ------------------------------------------------------------------ #
      - name: 📤 Upload signatures artifact
        uses: actions/upload-artifact@v4
        with:
          name: signatures
          path: |
            export/sha256sums.txt
            export/b2sums.txt
            export/thgtoa.pdf.sha256
            export/thgtoa-dark.pdf.sha256
            export/thgtoa.pdf.b2
            export/thgtoa-dark.pdf.b2
            export/thgtoa.pdf.sig
            export/thgtoa-dark.pdf.sig
            export/sha256sums.txt.sig
            export/b2sums.txt.sig
          if-no-files-found: error
          retention-days: 90
          compression-level: 0

      - name: 📤 Upload signed PDFs artifact
        uses: actions/upload-artifact@v4
        with:
          name: pdfs-signed
          path: |
            export/thgtoa.pdf
            export/thgtoa-dark.pdf
          if-no-files-found: warn
          retention-days: 90
          compression-level: 0