{ config, options, pkgs, lib, ... }:
with lib;
with lib.custom;
let
    cfg = config.modules.shell.zsh;
    configDir = config.dotfiles.configDir;
in {
    options.modules.shell.zsh = with types; {
        enable = mkBoolOpt false;

        aliases = mkOpt (attrsOf (either str path)) {};

        rcInit = mkOpt' lines "" ''
            Zsh lines to be written to $XDG_CONFIG_HOME/zsh/extra.zshrc and sourced by
            $XDG_CONFIG_HOME/zsh/.zshrc
        '';
        envInit = mkOpt' lines "" ''
            Zsh lines to be written to $XDG_CONFIG_HOME/zsh/extra.zshenv and sourced
            by $XDG_CONFIG_HOME/zsh/.zshenv
        '';

        rcFiles  = mkOpt (listOf (either str path)) [];
        envFiles = mkOpt (listOf (either str path)) [];
    };

    config = mkIf cfg.enable {
        users.defaultUserShell = pkgs.zsh;

        programs.zsh = {
            enable = true;
            enableCompletion = true;
            # I init completion myself, because enableGlobalCompInit initializes it
            # too soon, which means commands initialized later in my config won't get
            # completion, and running compinit twice is slow.
            enableGlobalCompInit = false;
            promptInit = "";
        };

        user.packages = with pkgs; [
            zsh
            nix-zsh-completions
            bat
            nnn
            exa
            fasd
            fd
            fzf
            jq
            ripgrep
            tldr
        ];

        env = {
            ZDOTDIR   = "$XDG_CONFIG_HOME/zsh";
            ZSH_CACHE = "$XDG_CACHE_HOME/zsh";
            ZGEN_DIR  = "$XDG_DATA_HOME/zgenom";
        };

        home.configFile = {
            # Write it recursively so other modules can write files to it
            "zsh" = { source = "${configDir}/zsh"; recursive = true; };

            # Why am I creating extra.zsh{rc,env} when I could be using extraInit?
            # Because extraInit generates those files in /etc/profile, and mine just
            # write the files to ~/.config/zsh; where it's easier to edit and tweak
            # them in case of issues or when experimenting.
            "zsh/extra.zshrc".text =
            let
                aliasLines = mapAttrsToList (n: v: "alias ${n}=\"${v}\"") cfg.aliases;
            in ''
                # This file was autogenerated, do not edit it!
                ${concatStringsSep "\n" aliasLines}
                ${concatMapStrings (path: "source '${path}'\n") cfg.rcFiles}
                ${cfg.rcInit}
            '';

            "zsh/extra.zshenv".text = ''
                # This file is autogenerated, do not edit it!
                ${concatMapStrings (path: "source '${path}'\n") cfg.envFiles}
                ${cfg.envInit}
            '';
        };

        system.userActivationScripts.cleanupZgen = ''
            rm -rf $ZSH_CACHE
            rm -fv $ZGEN_DIR/init.zsh{,.zwc}
        '';
    };
}