{
  inputs,
  cell,
  namespace,
}: {
  config,
  lib,
  pkgs,
  ...
}: let
  cfg = config."${namespace}".shells;
in {
  options."${namespace}".shells = {
    enable = lib.mkOption {
      type = lib.types.bool;
      description = "Enable umbrella shell configuration";
      default = true;
      example = false;
    };
    shellInitExtra = lib.mkOption {
      type = lib.types.str;
      description = "Extra shell init. The syntax should be sh-compliant";
      default = "";
      example = ''
        # X11 support for WSL
        export DISPLAY=$(ip route list default | awk '{print $3}'):0
        export LIBGL_ALWAYS_INDIRECT=1
      '';
    };
    shellAliases = lib.mkOption {
      type = lib.types.attrs;
      description = "Shell command aliases";
      default = {};
      example = {
        nixGL = "nixGLIntel";
      };
    };
  };
  config = lib.mkIf cfg.enable {
    # nix: Propagates the environment with packages and vars when enter (children of)
    # a directory with shell.nix-compatible and .envrc
    programs.direnv = {
      enable = true;
      nix-direnv.enable = true;
      # nix-direnv.enableFlakes = true; # must remove. this will always be supported.
    };
    # z <path> as smarter cd
    programs.zoxide = {
      enable = true;
      enableZshIntegration = true;
    };
    programs.tmux = {
      enable = true;
      plugins = let inherit (pkgs.tmuxPlugins) cpu net-speed; in [cpu net-speed];
      extraConfig = builtins.readFile "${inputs.self}/native_configs/tmux/tmux.conf";
    };
    xdg.configFile."tmux/tmux.conf".text = lib.mkOrder 600 ''
      set -g status-right '#{cpu_bg_color} CPU: #{cpu_icon} #{cpu_percentage} | %a %h-%d %H:%M '
    '';
    # Colored ls
    programs.exa = {
      enable = true;
      enableAliases = true;
    };
    # Make the shell look beautiful
    programs.starship = {
      enable = true;
      enableZshIntegration = true;
      settings = let
        native = builtins.fromTOML (builtins.readFile "${inputs.self}/native_configs/starship/starship.toml");
        patch-nix = pkgs.lib.recursiveUpdate native {
          # WARNING: home-manager fails on here for some reason. Likely not at the
          # validation phase (type-checking), but at evaluation phaase (stringify)
          # I'm thinking when `settings` are evaluated, it has some sort of
          # recursive processing before it gets turned into a toml
          # c.commands = [
          #   ["nix" "run" "nixpkgs#clang" "--" "--version"]
          #   ["nix" "run" "nixpkgs#gcc" "--" "--version"]
          # ];
          c.disabled = true;
        };
      in
        patch-nix;
    };
    # Fuzzy finder. `fzf` for TUI, `fzf -f '<fuzzy query>'` for UNIX piping
    programs.fzf.enable = true;
    programs.bash = {
      enable = true;
      enableCompletion = true;
      initExtra = cfg.shellInitExtra or "";
    };
    programs.zsh = {
      enable = true;
      enableCompletion = true;
      enableAutosuggestions = true;
      shellAliases =
        {
          nix-rebuild = "sudo nixos-rebuild switch";
          hm-switch = "home-manager switch --flake";
        }
        // (cfg.shellAliases or {});
      history = {
        size = 10000;
        path = "${config.xdg.dataHome}/zsh/history";
      };
      oh-my-zsh = {
        enable = true;
        plugins = [
          "git" # git command aliases: https://github.com/ohmyzsh/ohmyzsh/tree/master/plugins/git#aliases
          "command-not-found" # suggests which package to install; does not support nixos (we have solution already)
          "gitignore" # `gi list` -> `gi java >>.gitignore`
          "ripgrep" # adds completion for `rg`
          "rust" # compe for rustc/cargo
          "poetry" # compe for poetry - Python's cargo
        ];
      };
      sessionVariables = {
        # Vim mode on the terminal
        # VI_MODE_RESET_PROMPT_ON_MODE_CHANGE = true;
        # VI_MODE_SET_CURSOR = true;
        # ZVM_VI_ESCAPE_BINDKEY = "";
        ZVM_READKEY_ENGINE = "$ZVM_READKEY_ENGINE_NEX";
        ZVM_KEYTIMEOUT = 0.004; # 40ms, or subtly around 25 FPS. I'm a gamer :)
        ZVM_ESCAPE_KEYTIMEOUT = 0.004; # 40ms, or subtly around 25 FPS. I'm a gamer :)
      };
      initExtra =
        (cfg.shellInitExtra or "")
        + ''
          source ${pkgs.zsh-vi-mode}/share/zsh-vi-mode/zsh-vi-mode.plugin.zsh
        '';
    };
  };
}