nix_config/home/modules/firefox.nix

{
  config,
  lib,
  pkgs,
  ...
}:
with lib; let
  cfg = config.local.apps.firefox;
in {
  options.local.apps.firefox = {
    enable = mkEnableOption "firefox settings";

    workspace = mkOption {
      type = types.nullOr types.str;
      default = null;
      description = ''
        Workspace in which Firefox should open. If not set, Firefox will not open at startup.
      '';
    };
  };

  config = mkIf cfg.enable {
    programs.firefox.enable = true;

    xdg = {
      mimeApps = {
        enable = true;
        defaultApplications = {
          "text/uri-list" = with pkgs; ["firefox"];
          "x-scheme-handler/http" = with pkgs; ["firefox"];
          "x-scheme-handler/https" = with pkgs; ["firefox"];
        };
      };
    };

    xsession.windowManager.i3.config.startup = optional (cfg.workspace != null) {
      command = "${lib.getExe pkgs.i3-gaps} 'workspace ${cfg.workspace}; exec ${lib.getExe pkgs.firefox}'";
    };
  };
}