# Global theme configuration - use `tt dark` or `tt light` to switch.
  is_dark = true;

  # Global theme configuration - can be overridden by specialisations.
  is_dark = if config.themeOverride != null
           then config.themeOverride
           else false;  # Default to light.

  # helpers

  # Helpers.

  # Separate option for specialisation override.
  options.themeOverride = mkOption {
    type = types.nullOr types.bool;
    default = null;
    description = "Force dark or light theme (used by specialisations)";
  };

  # Export theme info as env var.
  config.environment.variables.THEME_MODE = variant;

  # Export theme info as environment variable.
  config.environment.variables.THEME_MODE        = variant;
  config.environment.sessionVariables.THEME_MODE = variant;

{ config, lib, ... }: let
  inherit (lib) mkIf;
in {
  config = mkIf config.isDesktopNotWsl {
    # Specialisations for system-level theme switching.
    specialisation = {
      dark-theme = {
        configuration = {
          # Force dark theme.
          themeOverride = lib.mkForce true;
          # For identification.
          system.nixos.tags = [ "dark-theme" ];
          # Include the light theme specialisation in dark theme.
          specialisation.light-theme = {
            configuration = {
              themeOverride = lib.mkForce false;
              system.nixos.tags = [ "light-theme" ];
            };
          };
        };
      };
      # Light theme specialisation.
      light-theme = {
        configuration = {
          # Force light theme.
          themeOverride = lib.mkForce false;
          # For identification.
          system.nixos.tags = [ "light-theme" ];
          # Include the dark theme specialisation in light theme.
          specialisation.dark-theme = {
            configuration = {
              themeOverride = lib.mkForce true;
              system.nixos.tags = [ "dark-theme" ];
            };
          };
        };
      };
    };
    # Home Manager specialisations for user-level theme switching.
    home-manager.sharedModules = [{
      specialisation = {
        dark = {
          configuration = {
            # Override theme to dark in home-manager.
            home.sessionVariables.THEME_MODE = "dark";
          };
        };
        light = {
          configuration = {
            # Override theme to light in home-manager.
            home.sessionVariables.THEME_MODE = "light";
          };
        };
      };
    }];
  };
}

    # determine current theme from nix theme file
    let theme_file = $"($env.HOME)/nixos/modules/common/theme.nix"
    let current_theme = try {
        let content = open $theme_file
        if ($content | str contains "is_dark = true;") {
            "dark"
        } else {
            "light"
        }
    } catch {
        "light"
    }
    # use provided theme or toggle current
    let new_theme = if $theme != null {
        if $theme in ["light", "dark"] {
            $theme
        } else {
            print $"Invalid theme: ($theme). Use 'light' or 'dark'"
            return
        }

    # Use provided theme.
    let new_theme = if $theme in ["light", "dark"] {
        $theme

        if $current_theme == "light" { "dark" } else { "light" }

        print_notify $"Invalid theme: '($theme)'. Use 'light' or 'dark'."
        return

    print $"Switching from ($current_theme) to ($new_theme) theme..."

    print_notify $"Switching to ($new_theme) theme."

    # update centralized theme file

    # Use NixOS specialisations for theme switching.
    # Always switch to base system first, then to target specialisation if needed.

        let content = open $theme_file

        ^sudo /nix/var/nix/profiles/system/bin/switch-to-configuration switch

        let updated = if $new_theme == "dark" {
            $content | str replace "is_dark = false;" "is_dark = true;"

        print_notify $"Activating ($new_theme) specialisation."
        if $new_theme == "dark" {
            ^sudo /run/current-system/specialisation/dark-theme/bin/switch-to-configuration switch

            $content | str replace "is_dark = true;" "is_dark = false;"

            ^sudo /run/current-system/specialisation/light-theme/bin/switch-to-configuration switch

        $updated | save $theme_file --force
        print $"updated theme to ($new_theme)"

        print $"failed to update theme: ($e.msg)"

        print_notify $"Failed to switch theme: ($e.msg)"

    # update system dark mode marker

    # Update system dark mode marker and environment variable.

        print "dark mode activated"

        print_notify "Dark mode activated."

        print "light mode activated"

        print_notify "Light mode activated."

        # rebuild nixos config to apply themes
        print "Rebuilding nixos config to apply themes... (this may take a moment)"
        nu $"($env.HOME)/rebuild.nu"

    print "Theme switch completed!"

    print_notify($"Theme switch to ($new_theme) completed!")
}

def print_notify [message: string] {
    print $"[Theme Switcher]: ($message)"

        ^dunstify "Theme Switch" $"Switched to ($new_theme) theme."

        ^dunstify "[Theme Switcher]" $"($message)"

}

# check current theme
def current-theme [] {
    let theme_file = $"($env.HOME)/nixos/modules/common/theme.nix"
    try {
        let content = open $theme_file
        if ($content | str contains "is_dark = true;") {
            "dark"
        } else {
            "light"
        }
    } catch {
        "light"
    }