name: Build and deploy documentation

on:
  push:
    # Runs on pushes targeting the release branches
    branches:
      - main
      - nixos-24.05

  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:

# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
permissions:
  contents: read
  pages: write
  id-token: write

# Allow one concurrent deployment
concurrency:
  group: "pages"
  cancel-in-progress: true

jobs:
  deploy:
    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}
    runs-on: ubuntu-latest
    timeout-minutes: 40

    env:
      repo: ${{ github.repository }}
      repoName: ${{ github.event.repository.name }}
      out: docs-build

    steps:
      - name: Install nix
        uses: cachix/install-nix-action@v26
        with:
          nix_path: nixpkgs=channel:nixos-unstable

      - name: Configure cachix
        uses: cachix/cachix-action@v15
        with:
          name: nix-community
          authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"

      - name: Build docs
        run: |
          set -ex

          # 1: branch
          # 2: install dir (relative to /nixvim/)
          build() {
            branch="$1"
            dir="${2:+/$2}"
            flakeref="github:${repo}${branch:+/$branch}"
            baseHref="/${repoName}${dir}/"
            installDir="${out}${dir}"

            # Build docs for the given flake ref, overriding baseHref in the derivation args
            nix build --impure \
                --argstr flakeref "$flakeref" \
                --argstr baseHref "$baseHref" \
                --expr '
                  {
                    flakeref,
                    baseHref,
                    system ? builtins.currentSystem,
                  }:
                  let
                    flake = builtins.getFlake flakeref;
                    packages = flake.outputs.packages.${system};
                  in
                  packages.docs.override {
                    inherit baseHref;
                  }
                '

            # Copy the result to the install dir
            mkdir -p "$installDir"
            cp -r result/share/doc/* "$installDir"
          }

          # Install main-branch docs at the top-level
          build 'main' ''

          # Install 24.05 docs under 'stable'
          # TODO: consider having `<release>` instead of `stable`
          build 'nixos-24.05' 'stable'

      - name: Upload artifact
        uses: actions/upload-pages-artifact@v3
        with:
          path: "docs-build"

      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4