# Based on https://github.com/jgillich/nixos/blob/master/services/ppp.nix
# Tipps and tricks under https://www.hackster.io/munoz0raul/how-to-use-gsm-3g-4g-in-embedded-linux-systems-9047cf#toc-configuring-the-ppp-files-5
# TODO: http://www.embeddedpi.com/documentation/3g-4g-modems/raspberry-pi-sierra-wireless-mc7455-modem-raw-ip-qmi-interface-setup
{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.wwan;
  mbim-ip = pkgs.writeScriptBin "mbim-ip" readFile ./wwan/mbim-ip.bash;
  mbim-ip-configured = pkgs.writeScriptBin "mbim-ip-configured" ''
    #!${pkgs.stdenv.shell}
    MBIM_BINARY=${pkgs.libmbim}/bin/mbimcli
    MBIM_INTERFACE=${cfg.mbimInterface}
    exec ${mbim-ip} $@
  '';
in
{
  options = {
    services.wwan = {
      enable = mkEnableOption "wwan client service";

      config = mkOption {
        type = types.attrsOf (types.submodule (
          {
            options = {
              apn = mkOption {
                type    = types.str;
                description = ''
                    APN domain of provider.
                '';
              };

              apnUser = mkOption {
                type    = types.str;
                default = "";
                description = ''
                    APN username (optional).
                '';
              };

            apnPass = mkOption {
                type    = types.str;
                default = "";
                description = ''
                    APN password (optional).
                '';
              };

            apnAuth = mkOption {
                type    = types.enum;
                values = [ "PAP" "CHAP" "MSCHAPV2" "" ];
                default = "";
                description = ''
                    APN authentication type, one of ${concatMapStringsSep ", " show values} (optional).
                '';
              };

            mbimProxy = mkOption {
                type    = types.bool;
                default = true;
                description = ''
                    Whether to use the mbim proxy or not.
                '';
              };

              mbimInterface = mkOption {
                type = types.path;
                default = /dev/cdc-wdm0
                description = "MBIM Interface which the connection will use.";
              };

              networkInterface = mkOption {
                type = types.str;
                description = "Name of the WWAN network interface";
              };
            };
          }
        ));

        default = {};

        example = literalExample ''
          {
            wwan = {
              apn = "gprs.swisscom.ch";
              networkInterface = "wwp0s19u1u3i12";
            };
          }
        '';

        description = ''
          Configuration for WWAN connectivity using a MBIM capable card.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    systemd.services."wwan" = {
      description = "WWAN connectivity";
      wantedBy = [ "network.target" ];
      wants = [ "sys-subsystem-net-devices-${cfg.networkInterface}.device"];

      serviceConfig = {
        ExecStart = "@${pkgs.libmbim}/bin/mbim-network ${toString cfg.mbimInterface} start";
        ExecStop =  "@${pkgs.libmbim}/bin/mbim-network ${toString cfg.mbimInterface} stop";

        # MBIM networking is a special fellow - it gets the IP address for us,
        # but we need to manually set it to the interface
        ExecStartPost = "@${mbim-ip-configured} start ${cfg.networkInterface}";
        ExecStopPre =   "@${mbim-ip-configured} stop  ${cfg.networkInterface}";

        RemainAfterExit = true;
      };
    };

    environment.etc."/etc/mbim-network.conf".text = ''
      APN=${cfg.apnUser}
      APN_USER=${cfg.apnUser}
      APN_PASS=${cfg.apnPass}
      APN_AUTH=${cfg.apnAuth}
      PROXY=${optionalString cfg.proxy "yes"}
    '';
  };
}