{ config, lib, ... }:

let
  cfg = config.programs.xonsh;

in
with lib;
{
  options = {
    programs.xonsh = {
      enable = mkEnableOption "Enable the xonsh program";

      sessionVariables = mkOption {
        type = types.attrs;
        default = { };
        example = {
          XONSH_TRACE_SUBPROC = true;
        };
        description = ''
          Environment variables that will be set for the Xonsh session.
        '';
      };

      aliases = mkOption {
        type = types.attrsOf types.str;
        default = { };
        example = literalExpression ''
          {
          	ll = "ls -l";
          	la = "ls -a";
          }
        '';
        description = ''
          An attribute set that maps aliases (the top level attribute names in
          this option) to command strings or directly to build outputs.
        '';
      };

      configHeader = mkOption {
        type = types.lines;
        default = "";
        example = literalExpression ''
          import os
          import sys
        '';
        description = "An arbitrary string to put at the top of the config file";
      };

      configFooter = mkOption {
        type = types.lines;
        default = "";
        example = literalExpression ''
          def _some_method(args):
          	do_command()
          	some_other_thing()
          aliases['some_method'] = _some_method
        '';
        description = "An arbitrary string to put at the end of the config file";
      };
    };
  };

  config =
    let
      shortAliases = concatStringsSep "\n" (mapAttrsToList (k: v: "aliases['${k}']=r'${v}'") cfg.aliases);

      listToPythonList =
        let
          listInternals = args: concatStringsSep "\n" (map (v: "'${v}'") args);
        in
        list: "[${listInternals list}]";

      sessionVars = concatStringsSep "\n" (
        mapAttrsToList (
          k: v:
          if builtins.typeOf v == "string" then
            "\$${k} = '${v}'"
          else if builtins.typeOf v == "list" then
            "\$${k} = ${listToPythonList}"
          else if builtins.typeOf v == "int" then
            "\$${k} = ${toString v}"
          else
            ""
        ) cfg.sessionVariables
      );

    in
    mkIf cfg.enable {

      home.file.".xonshrc".text = ''
        ${cfg.configHeader}

        ${sessionVars}

        ${shortAliases}

        ${cfg.configFooter}
      '';
    };
}