{ lib, config, pkgs, ... }:
let
   t = v: builtins.trace v v;
   filterAttrs' = l: lib.filterAttrs (v:  _: builtins.elem v l);
  cfg = config.retronix.emulationstation;

  attrToXml = attrs: lib.concatLines (lib.mapAttrsToList (k: v: "<${k}>${builtins.toString v}</${k}>") attrs);

  gameTemplate = game: let
    attr = [
      "path"
      "name"
      "sortname"
      "desc"
      "image"
      "video"
      "marquee"
      "thumbnail"
      "rating"
      "releasedate"
      "developer"
      "publisher"
      "genre"
      "players"
      "favorite"
      "hidden"
      "kidgame"
      "playcount"
      "lastplayed"
    ];
    args = game.meta // { path = "@out@/${game.name}.sh"; };
  in ''
    <game>
    ${attrToXml (filterAttrs' attr args)}
    </game>
  '';

  systemTemplate = args: let
    attr = [
      "name"
      "fullname"
      "path"
      "extension"
      "command"
      "platform"
      "theme"
    ];
  in ''
    <system>
    ${attrToXml (filterAttrs' attr args)}
    </system>
  '';

  mkSystemPath = name: games: let
    gamelist = ''
      <?xml version="1.0"?>
      <gameList>
      ${lib.concatLines (builtins.map gameTemplate games)}
      </gameList>
    '';
    symlinkCommands = builtins.map (
      v: "ln -s ${v}/${v.launchPath} $out/${v.name}.sh"
    ) games;

  in pkgs.runCommand "${name}-roms" {
    inherit gamelist symlinkCommands;
    passAsFile = [
      "gamelist"
    ];
  } ''
    mkdir -p $out
    cp $gamelistPath $out/gamelist.xml
    substituteAllInPlace $out/gamelist.xml

    ${lib.concatLines symlinkCommands}
  '';

  sectionOptions = lib.types.submodule ({config, name, ...}: {
    freeformType = with lib.types; attrsOf str;
    options = {
      name = lib.mkOption {
        type = lib.types.str;
        default = name;
      };
      fullname = lib.mkOption {
        type = lib.types.str;
        default = name;
      };
      path = lib.mkOption {
        type = lib.types.path;
      };
      command = lib.mkOption {
        type = lib.types.str;
        default = "%ROM%";
      };
      extension = lib.mkOption {
        type = lib.types.str;
      };
      games = lib.mkOption {
        type = lib.types.listOf lib.types.package;
        description = "Takes attributes of `games` tag in gamelist.xml";
      };
    };
    config = {
      path = mkSystemPath config.name config.games;
    };
  });
in {
  options = {
    retronix = {
      emulationstation = {
        systemCfgFile = lib.mkOption {
          type = lib.types.path;
        };
        inputCfgFile = lib.mkOption {
          type = lib.types.path;
        };
        settingsCfgFile = lib.mkOption {
          type = lib.types.path;
        };
        themesDir = lib.mkOption {
          type =  lib.types.path;
        };
        themes = lib.mkOption {
          type = lib.types.attrsOf lib.types.path;
          default = {};
        };
        inputCfg = lib.mkOption {
          type = lib.types.str;
          default = "";
        };
        homeDir = lib.mkOption {
          internal = true;
          type = lib.types.path;
        };
        extraConfigFiles = lib.mkOption {
          type = with lib.types; listOf path;
          default = [];
          description = ''
            Must be store paths.
            Directory structure will be merged.
          '';
        };
        cli = lib.mkOption {
          type = lib.types.package;
        };
      };
      systems = lib.mkOption {
        type = lib.types.attrsOf (sectionOptions);
        default = {};
      };
    };
  };
  config = {

    retronix.emulationstation = {
      systemCfgFile = pkgs.writeTextDir "es_systems.cfg" ''
        <?xml version="1.0"?>
        <systemList>
        ${lib.concatLines (lib.mapAttrsToList (_: systemTemplate) config.retronix.systems)}
        </systemList>
      '';
      inputCfgFile = lib.mkDefault (pkgs.writeTextDir "es_input.cfg" cfg.inputCfg);
      themesDir = let
        copyCommands = lib.concatLines (lib.mapAttrsToList (k: v: "cp -r ${v} $out/themes/${k}") cfg.themes);
      in pkgs.runCommand "es-themes" {} ''
        mkdir -p $out/themes
        ${copyCommands}
        '';
      homeDir = pkgs.symlinkJoinSubdir {
        name = "es-config-dir";
        subdir = ".emulationstation";
        paths = [
          cfg.systemCfgFile
          cfg.inputCfgFile
          cfg.settingsCfgFile
          cfg.themesDir
        ] ++ cfg.extraConfigFiles;
      };
      cli = pkgs.writeShellScript "emulationstation" "${pkgs.emulationstationPatched}/bin/emulationstation --home ${cfg.homeDir} --gamelist-only";
    };
  };

}