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

with lib;

let
  cfg = config.networking.wireless;
  configFile = if cfg.networks != {} then pkgs.writeText "wpa_supplicant.conf" ''
    ${optionalString cfg.userControlled.enable ''
      ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=${cfg.userControlled.group}
      update_config=1''}
    ${concatStringsSep "\n" (mapAttrsToList (ssid: networkConfig: let
      psk = if networkConfig.psk != null
        then ''"${networkConfig.psk}"''
        else networkConfig.pskRaw;
    in ''
      network={
        ssid="${ssid}"
        ${optionalString (psk != null) ''psk=${psk}''}
        ${optionalString (psk == null) ''key_mgmt=NONE''}
      }
    '') cfg.networks)}
  '' else "/etc/wpa_supplicant.conf";
in {
  options = {
    networking.wireless = {
      enable = mkEnableOption "wpa_supplicant";

      interfaces = mkOption {
        type = types.listOf types.str;
        default = [];
        example = [ "wlan0" "wlan1" ];
        description = ''
          The interfaces <command>wpa_supplicant</command> will use. If empty, it will
          automatically use all wireless interfaces.
        '';
      };

      driver = mkOption {
        type = types.str;
        default = "nl80211,wext";
        description = "Force a specific wpa_supplicant driver.";
      };

      networks = mkOption {
        type = types.attrsOf (types.submodule {
          options = {
            psk = mkOption {
              type = types.nullOr types.str;
              default = null;
              description = ''
                The network's pre-shared key in plaintext defaulting
                to being a network without any authentication.

                Be aware that these will be written to the nix store
                in plaintext!

                Mutually exclusive with <varname>pskRaw</varname>.
              '';
            };

            pskRaw = mkOption {
              type = types.nullOr types.str;
              default = null;
              description = ''
                The network's pre-shared key in hex defaulting
                to being a network without any authentication.

                Mutually exclusive with <varname>psk</varname>.
              '';
            };
          };
        });
        description = ''
          The network definitions to automatically connect to when
           <command>wpa_supplicant</command> is running. If this
           parameter is left empty wpa_supplicant will use
          /etc/wpa_supplicant.conf as the configuration file.
        '';
        default = {};
        example = literalExample ''
          { echelon = {
              psk = "abcdefgh";
            };
            "free.wifi" = {};
          }
        '';
      };

      userControlled = {
        enable = mkOption {
          type = types.bool;
          default = false;
          description = ''
            Allow normal users to control wpa_supplicant through wpa_gui or wpa_cli.
            This is useful for laptop users that switch networks a lot and don't want
            to depend on a large package such as NetworkManager just to pick nearby
            access points.

            When using a declarative network specification you cannot persist any
            settings via wpa_gui or wpa_cli.
          '';
        };

        group = mkOption {
          type = types.str;
          default = "wheel";
          example = "network";
          description = "Members of this group can control wpa_supplicant.";
        };
      };
    };
  };

  config = mkMerge [
    (mkIf cfg.enable {
      assertions = flip mapAttrsToList cfg.networks (name: cfg: {
        assertion = cfg.psk == null || cfg.pskRaw == null;
        message = ''networking.wireless."${name}".psk and networking.wireless."${name}".pskRaw are mutually exclusive'';
      });

      environment.systemPackages =  [ pkgs.wpa_supplicant ];

      services.dbus.packages = [ pkgs.wpa_supplicant ];

      # FIXME: start a separate wpa_supplicant instance per interface.
      systemd.services.wpa_supplicant = let
        ifaces = cfg.interfaces;
        deviceUnit = interface: [ "sys-subsystem-net-devices-${interface}.device" ];
      in {
        description = "WPA Supplicant";

        after = [ "network-interfaces.target" ] ++ lib.concatMap deviceUnit ifaces;
        requires = lib.concatMap deviceUnit ifaces;
        wantedBy = [ "network.target" ];

        path = [ pkgs.wpa_supplicant ];

        script = ''
          ${if ifaces == [] then ''
            for i in $(cd /sys/class/net && echo *); do
              DEVTYPE=
              source /sys/class/net/$i/uevent
              if [ "$DEVTYPE" = "wlan" -o -e /sys/class/net/$i/wireless ]; then
                ifaces="$ifaces''${ifaces:+ -N} -i$i"
              fi
            done
          '' else ''
            ifaces="${concatStringsSep " -N " (map (i: "-i${i}") ifaces)}"
          ''}
          exec wpa_supplicant -s -u -D${cfg.driver} -c ${configFile} $ifaces
        '';
      };

      powerManagement.resumeCommands = ''
        ${config.systemd.package}/bin/systemctl try-restart wpa_supplicant
      '';

      # Restart wpa_supplicant when a wlan device appears or disappears.
      services.udev.extraRules = ''
        ACTION=="add|remove", SUBSYSTEM=="net", ENV{DEVTYPE}=="wlan", RUN+="${config.systemd.package}/bin/systemctl try-restart wpa_supplicant.service"
      '';
    })
    {
      meta.maintainers = with lib.maintainers; [ globin ];
    }
  ];
}