nix-flake/modules/docs.nix

{ inputs, self, ... }: let
  mkDocsDerivation = { pkgs, doBuild ? true }: let
    inherit (pkgs) lib stdenv mkdocs python314Packages;

    mkOptionsDocFromModule = commandName: module: let
      eval = lib.evalModules {
        modules = [ module ];
        args = { inherit pkgs; };
      };

      optionsDoc = pkgs.nixosOptionsDoc {
        inherit (eval) options;
      };
    in pkgs.runCommand commandName {} ''
      cat ${optionsDoc.optionsCommonMark} >> $out
    '';

    indexMd = let
      rawText = ''
        ## Hello world
        Welcome to the site!
      '';
    in pkgs.runCommand "index.md" {} ''
      echo "${rawText}" >> $out
    '';

    nixosOptionsMd = mkOptionsDocFromModule "nixos-options.md" self.nixosModules.options;
    homeOptionsMd = mkOptionsDocFromModule "home-options.md" self.homeModules.options;

    mkDocsConfig = ''
      site_name: greyweather's nix flake options
      nav:
        - Home: 'index.md'
        - Options:
          - NixOS: 'nixos-options.md'
          - Home Manager: 'home-options.md'
      theme: material
    '';

    mkDocsYml = pkgs.runCommand "mkdocs.yml" {} ''
      echo "${mkDocsConfig}" >> $out
    '';
  in stdenv.mkDerivation {
    src = self;
    name = if doBuild then "docs" else "docs-md";
    buildInput = [
      mkDocsYml
      indexMd
      nixosOptionsMd
      homeOptionsMd
    ];
    nativeBuildInputs = [
      mkdocs
      python314Packages.mkdocs-material
      python314Packages.pygments
    ];
    buildPhase = ''
      mkdir docs-build
      cd docs-build
      ln -s ${mkDocsYml} "./mkdocs.yml"
      mkdir docs
      ln -s ${indexMd} "./docs/index.md"
      ln -s ${nixosOptionsMd} "./docs/nixos-options.md"
      ln -s ${homeOptionsMd} "./docs/home-options.md"
      # generate the site
      ${if doBuild then "mkdocs build" else ""}
    '';
    installPhase = if doBuild then ''
      mv site $out
    '' else ''
      cp -r . $out
    '';
  };
in {
  perSystem = { pkgs, ... }: {
    packages.docs = mkDocsDerivation { inherit pkgs; };
    packages.docs-md = mkDocsDerivation { inherit pkgs; doBuild = false; };
  };
}