{
  pkgs,
  lib,
  inputs,
  ...
}:

let
  nixosConfiguration = lib.nixosSystem {
    inherit (pkgs) system;
    modules = [
      inputs.home-manager.nixosModules.home-manager
      inputs.self.nixosModules.stylix
      ./settings.nix
    ];
  };

  homeManagerConfiguration = inputs.home-manager.lib.homeManagerConfiguration {
    inherit pkgs;
    modules = [
      inputs.self.homeManagerModules.stylix
      ./settings.nix
      {
        home = {
          homeDirectory = "/home/book";
          stateVersion = "22.11";
          username = "book";
        };
      }
    ];
  };

  # TODO: Include Nix Darwin options

  makeOptionsDoc =
    { configuration, pathFilter }:
    (pkgs.nixosOptionsDoc {
      inherit (configuration) options;
      transformOptions =
        let
          commit = inputs.self.rev or "master";
          declarationPrefix = toString inputs.self;
        in
        option:
        option
        // {
          declarations = map (
            declaration:
            let
              declarationString = toString declaration;
              declarationWithoutprefix = lib.removePrefix "${declarationPrefix}/" declarationString;
            in
            lib.throwIfNot (lib.hasPrefix declarationPrefix declarationString)
              "declaration not in ${declarationPrefix}: ${declarationString}"
              {
                name = "<${declarationWithoutprefix}>";
                url = "https://github.com/danth/stylix/blob/${commit}/${declarationWithoutprefix}";
              }
          ) option.declarations;

          visible = option.visible && lib.any pathFilter option.declarations;
        };
    }).optionsCommonMark;

  # The documentation for options which aren't linked to a specific module
  makePlatformsOptionsDoc =
    configuration:
    makeOptionsDoc {
      inherit configuration;
      pathFilter =
        path:
        lib.hasPrefix "${inputs.self}/" path
        && !lib.hasPrefix "${inputs.self}/modules/" path;
    };

  # Returns an attribute set of module names and their corresponding option
  # documentation.
  makeModuleOptionsDoc =
    configuration:
    lib.mapAttrs (
      module: _:
      makeOptionsDoc {
        inherit configuration;
        pathFilter = lib.hasPrefix "${inputs.self}/modules/${module}/";
      }
    ) (builtins.readDir "${inputs.self}/modules");

  nixosModuleOptionsDoc = makeModuleOptionsDoc nixosConfiguration;
  homeManagerModuleOptionsDoc = makeModuleOptionsDoc homeManagerConfiguration;

  modulePageScript = lib.pipe "${inputs.self}/modules" [
    builtins.readDir
    (lib.mapAttrsToList (
      module: _: ''
        writeModulePage \
          ${module} \
          ${homeManagerModuleOptionsDoc.${module}} \
          ${nixosModuleOptionsDoc.${module}}
      ''
    ))
    lib.concatStrings
  ];

in
pkgs.stdenvNoCC.mkDerivation {
  name = "stylix-book";
  src = ./.;
  buildInputs = with pkgs; [
    mdbook
    mdbook-alerts
  ];

  patchPhase = ''
    # The generated documentation has headings at level 2, but we want level 3
    # so they can be nested under the sections for each module system.
    REDUCE_HEADINGS='s/^## /### /'

    function writeOptions() {
      platformName="$1"
      optionsFile="$2"
      outputFile="$3"

      printf '\n## %s options\n' "$platformName" >>"$outputFile"

      if [[ -s "$optionsFile" ]]; then
        sed \
          --expression "$REDUCE_HEADINGS" \
          <"$optionsFile" \
          >>"$outputFile"
      else
        printf '*%s*\n' "None provided." >>"$outputFile"
      fi
    }

    function writeModulePage() {
      moduleName="$1"
      homeManagerOptionsFile="$2"
      nixosOptionsFile="$3"

      readmeFile="${inputs.self}/modules/$moduleName/README.md"
      page="options/modules/$moduleName.md"
      outputFile="src/$page"

      if [[ -f $outputFile ]]; then
        printf \
          '%s should not be used. Move it to %s\n' \
          "docs/src/options/modules/$moduleName.md" \
          "modules/$moduleName/README.md" \
          >&2
        exit 1

      elif [[ -f $readmeFile ]]; then
        cp --no-preserve=mode,ownership "$readmeFile" "$outputFile"

      else
        printf \
          '%s\n' \
          "# $moduleName" \
          '> [!NOTE]' \
          "> This module doesn't include any additional documentation." \
          '> You can browse the options it provides below.' \
          >>"$outputFile"
      fi

      writeOptions 'Home Manager' "$homeManagerOptionsFile" "$outputFile"
      writeOptions 'NixOS' "$nixosOptionsFile" "$outputFile"

      printf '  - [%s](%s)\n' "$moduleName" "$page" >>src/SUMMARY.md
    }

    cp ${../README.md} src/README.md
    cp ${../gnome.png} src/gnome.png
    cp ${../kde.png} src/kde.png

    mkdir --parents src/options/platforms
    writeOptions 'Home Manager' ${(makePlatformsOptionsDoc homeManagerConfiguration)} src/options/platforms/home_manager.md
    writeOptions 'NixOS' ${(makePlatformsOptionsDoc nixosConfiguration)} src/options/platforms/nixos.md

    mkdir --parents src/options/modules
    ${modulePageScript}
  '';

  buildPhase = "mdbook build --dest-dir $out";
}