name: LaTeX Diff

on:
  workflow_dispatch:
    inputs:
      base_branch:
        description: 'Base branch (older version)'
        required: true
        default: 'main'
      compare_branch:
        description: 'Compare branch (new version)'
        required: true
        default: 'dev'

jobs:
  latexdiff:
    runs-on: ubuntu-latest
    container:
      image: ghcr.io/xu-cheng/texlive-full:latest
      options: --user root  # allow package install if needed

    steps:
      - name: Checkout base branch
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.inputs.base_branch }}
          path: base

      - name: Checkout compare branch
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.inputs.compare_branch }}
          path: compare

      - name: Install flatex (Python flattener)
        run: |
          apk add --no-cache py3-pip  # if Alpine base
          pip install flatex

      - name: Create output folder
        run: mkdir -p diff_output

      - name: Flatten base branch
        run: |
          flatex base/latex/main.tex > diff_output/base_flat.tex

      - name: Flatten compare branch
        run: |
          flatex compare/latex/main.tex > diff_output/compare_flat.tex

      - name: Generate diff.tex using latexdiff
        run: |
          latexdiff diff_output/base_flat.tex diff_output/compare_flat.tex > diff_output/diff.tex

      - name: Compile diff.tex to PDF
        working-directory: diff_output
        run: |
          xelatex -interaction=nonstopmode diff.tex
          xelatex -interaction=nonstopmode diff.tex

      - name: Upload diff output files
        uses: actions/upload-artifact@v4
        with:
          name: latex-diff-output
          path: diff_output/