{ config, lib, pkgs, ... }:

with lib;

let

  cfg = config.programs.bash;

in

{
  options = {
    programs.bash = {
      enable = mkEnableOption "GNU Bourne-Again SHell";

      historySize = mkOption {
        type = types.int;
        default = 10000;
        description = "Number of history lines to keep in memory.";
      };

      historyFileSize = mkOption {
        type = types.int;
        default = 100000;
        description = "Number of history lines to keep on file.";
      };

      historyControl = mkOption {
        type = types.listOf (types.enum [
          "erasedups"
          "ignoredups"
          "ignorespace"
        ]);
        default = [];
        description = "Controlling how commands are saved on the history list.";
      };

      historyIgnore = mkOption {
        type = types.listOf types.str;
        default = [];
        description = "List of commands that should not be saved to the history list.";
      };

      shellOptions = mkOption {
        type = types.listOf types.str;
        default = [
          # Append to history file rather than replacing it.
          "histappend"

          # check the window size after each command and, if
          # necessary, update the values of LINES and COLUMNS.
          "checkwinsize"

          # Extended globbing.
          "extglob"
          "globstar"

          # Warn if closing shell with running jobs.
          "checkjobs"
        ];
        description = "Shell options to set.";
      };

      shellAliases = mkOption {
        default = {};
        example = { ll = "ls -l"; ".." = "cd .."; };
        description = ''
          An attribute set that maps aliases (the top level attribute names in
          this option) to command strings or directly to build outputs. The
          aliases are added to all users' shells.
        '';
        type = types.attrs;
      };

      enableAutojump = mkOption {
        default = false;
        type = types.bool;
        description = "Enable the autojump navigation tool.";
      };

      profileExtra = mkOption {
        default = "";
        type = types.lines;
        description = "Extra commands that should be added to .profile.";
      };

      initExtra = mkOption {
        default = "";
        type = types.lines;
        description = "Extra commands that should be added to .bashrc.";
      };
    };
  };

  config = (
    let
      aliasesStr = concatStringsSep "\n" (
        mapAttrsToList (k: v: "alias ${k}='${v}'") cfg.shellAliases
      );

      shoptsStr = concatStringsSep "\n" (
        map (v: "shopt -s ${v}") cfg.shellOptions
      );

      export = n: v: "export ${n}=\"${toString v}\"";
      exportIfNonNull = n: v: optionalString (v != null) (export n v);
      exportIfNonEmpty = n: v: optionalString (v != "") (export n v);

      histControlStr = concatStringsSep ":" cfg.historyControl;
      histIgnoreStr = concatStringsSep ":" cfg.historyIgnore;

      envVarsStr = concatStringsSep "\n" (
        mapAttrsToList export config.home.sessionVariables
      );
    in mkIf cfg.enable {
      home.file.".bash_profile".text = ''
        # -*- mode: sh -*-

        # include .profile if it exists
        [[ -f ~/.profile ]] && . ~/.profile

        # include .bashrc if it exists
        [[ -f ~/.bashrc ]] && . ~/.bashrc
      '';

      home.file.".profile".text = ''
        # -*- mode: sh -*-

        ${envVarsStr}

        ${cfg.profileExtra}
      '';

      home.file.".bashrc".text = ''
        # -*- mode: sh -*-

        # Skip if not running interactively.
        [ -z "$PS1" ] && return

        ${export "HISTSIZE" cfg.historySize}
        ${export "HISTFILESIZE" cfg.historyFileSize}
        ${exportIfNonEmpty "HISTCONTROL" histControlStr}
        ${exportIfNonEmpty "HISTIGNORE" histIgnoreStr}

        ${shoptsStr}

        ${aliasesStr}

        ${cfg.initExtra}

        ${optionalString cfg.enableAutojump
          ". ${pkgs.autojump}/share/autojump/autojump.bash"}
      '';

      home.packages =
        optional (cfg.enableAutojump) pkgs.autojump;
    }
  );
}