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

with pkgs;
with lib;

let
  cfg = config.services.connman;
  configFile = pkgs.writeText "connman.conf" ''
    [General]
    NetworkInterfaceBlacklist=${concatStringsSep "," cfg.networkInterfaceBlacklist}

    ${cfg.extraConfig}
  '';
  enableIwd = cfg.wifi.backend == "iwd";
in {

  imports = [
    (mkRenamedOptionModule [ "networking" "connman" ] [ "services" "connman" ])
  ];

  ###### interface

  options = {

    services.connman = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = ''
          Whether to use ConnMan for managing your network connections.
        '';
      };

      enableVPN = mkOption {
        type = types.bool;
        default = true;
        description = ''
          Whether to enable ConnMan VPN service.
        '';
      };

      extraConfig = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Configuration lines appended to the generated connman configuration file.
        '';
      };

      networkInterfaceBlacklist = mkOption {
        type = with types; listOf str;
        default = [ "vmnet" "vboxnet" "virbr" "ifb" "ve" ];
        description = ''
          Default blacklisted interfaces, this includes NixOS containers interfaces (ve).
        '';
      };

      wifi = {
        backend = mkOption {
          type = types.enum [ "wpa_supplicant" "iwd" ];
          default = "wpa_supplicant";
          description = ''
            Specify the Wi-Fi backend used.
            Currently supported are <option>wpa_supplicant</option> or <option>iwd</option>.
          '';
        };
      };

      extraFlags = mkOption {
        type = with types; listOf str;
        default = [ ];
        example = [ "--nodnsproxy" ];
        description = ''
          Extra flags to pass to connmand
        '';
      };

      package = mkOption {
        type = types.path;
        description = "The connman package / build flavor";
        default = connman;
        example = literalExample "pkgs.connmanFull";
      };

    };

  };

  ###### implementation

  config = mkIf cfg.enable {

    assertions = [{
      assertion = !config.networking.useDHCP;
      message = "You can not use services.connman with networking.useDHCP";
    }{
      # TODO: connman seemingly can be used along network manager and
      # connmanFull supports this - so this should be worked out somehow
      assertion = !config.networking.networkmanager.enable;
      message = "You can not use services.connman with networking.networkmanager";
    }];

    environment.systemPackages = [ cfg.package ];

    systemd.services.connman = {
      description = "Connection service";
      wantedBy = [ "multi-user.target" ];
      after = [ "syslog.target" ] ++ optional enableIwd "iwd.service";
      requires = optional enableIwd "iwd.service";
      serviceConfig = {
        Type = "dbus";
        BusName = "net.connman";
        Restart = "on-failure";
        ExecStart = toString ([
          "${cfg.package}/sbin/connmand"
          "--config=${configFile}"
          "--nodaemon"
        ] ++ optional enableIwd "--wifi=iwd_agent"
          ++ cfg.extraFlags);
        StandardOutput = "null";
      };
    };

    systemd.services.connman-vpn = mkIf cfg.enableVPN {
      description = "ConnMan VPN service";
      wantedBy = [ "multi-user.target" ];
      after = [ "syslog.target" ];
      before = [ "connman" ];
      serviceConfig = {
        Type = "dbus";
        BusName = "net.connman.vpn";
        ExecStart = "${cfg.package}/sbin/connman-vpnd -n";
        StandardOutput = "null";
      };
    };

    systemd.services.net-connman-vpn = mkIf cfg.enableVPN {
      description = "D-BUS Service";
      serviceConfig = {
        Name = "net.connman.vpn";
        before = [ "connman" ];
        ExecStart = "${cfg.package}/sbin/connman-vpnd -n";
        User = "root";
        SystemdService = "connman-vpn.service";
      };
    };

    networking = {
      useDHCP = false;
      wireless = {
        enable = mkIf (!enableIwd) true;
        iwd = mkIf enableIwd {
          enable = true;
        };
      };
      networkmanager.enable = false;
    };
  };
}