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

with lib;

let cfg = config.services.tailscale;
in {
  meta.maintainers = with maintainers; [ danderson mbaillie ];

  options.services.tailscale = {
    enable = mkEnableOption "Tailscale client daemon";

    port = mkOption {
      type = types.port;
      default = 41641;
      description = "The port to listen on for tunnel traffic (0=autoselect).";
    };

    interfaceName = mkOption {
      type = types.str;
      default = "tailscale0";
      description = ''The interface name for tunnel traffic. Use "userspace-networking" (beta) to not use TUN.'';
    };

    permitCertUid = mkOption {
      type = types.nullOr types.nonEmptyStr;
      default = null;
      description = "Username or user ID of the user allowed to to fetch Tailscale TLS certificates for the node.";
    };

    package = mkOption {
      type = types.package;
      default = pkgs.tailscale;
      defaultText = literalExpression "pkgs.tailscale";
      description = "The package to use for tailscale";
    };
  };

  config = mkIf cfg.enable {
    environment.systemPackages = [ cfg.package ]; # for the CLI
    systemd.packages = [ cfg.package ];
    systemd.services.tailscaled = {
      wantedBy = [ "multi-user.target" ];
      path = [ pkgs.openresolv pkgs.procps ];
      serviceConfig.Environment = [
        "PORT=${toString cfg.port}"
        ''"FLAGS=--tun ${lib.escapeShellArg cfg.interfaceName}"''
      ] ++ (lib.optionals (cfg.permitCertUid != null) [
        "TS_PERMIT_CERT_UID=${cfg.permitCertUid}"
      ]);
    };
  };
}