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

with lib;

let
  package = if cfg.allowAuxiliaryImperativeNetworks
    then pkgs.wpa_supplicant_ro_ssids
    else pkgs.wpa_supplicant;

  cfg = config.networking.wireless;

  mkNetwork = ssid: opts:
  let
    quote = x: ''"${x}"'';
    indent = x: "  " + x;

    pskString = if opts.psk != null
      then quote opts.psk
      else opts.pskRaw;

    options = [
      "ssid=${quote ssid}"
    ] ++ optional opts.hidden "scan_ssid=1"
      ++ optional (pskString == null && opts.auth == null) "key_mgmt=NONE"
      ++ optional (pskString != null) "psk=${pskString}"
      ++ optionals (opts.auth != null) (filter (x: x != "") (splitString "\n" opts.auth))
      ++ optional (opts.priority != null) "priority=${toString opts.priority}"
      ++ optional (opts.extraConfig != "") opts.extraConfig;
  in ''
    network={
    ${concatMapStringsSep "\n" indent options}
    }
  '';

  generatedConfig = concatStringsSep "\n" (
    (mapAttrsToList mkNetwork cfg.networks)
    ++ optional cfg.userControlled.enable (concatStringsSep "\n"
      [ "ctrl_interface=/run/wpa_supplicant"
        "ctrl_interface_group=${cfg.userControlled.group}"
        "update_config=1"
      ])
    ++ optional (cfg.extraConfig != "") cfg.extraConfig);

  configFile =
    if cfg.networks != {} || cfg.extraConfig != "" || cfg.userControlled.enable
      then pkgs.writeText "wpa_supplicant.conf" generatedConfig
      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.";
      };

      allowAuxiliaryImperativeNetworks = mkEnableOption "support for imperative & declarative networks" // {
        description = ''
          Whether to allow configuring networks "imperatively" (e.g. via
          <package>wpa_supplicant_gui</package>) and declaratively via
          <xref linkend="opt-networking.wireless.networks" />.

          Please note that this adds a custom patch to <package>wpa_supplicant</package>.
        '';
      };

      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>.
              '';
            };

            auth = mkOption {
              type = types.nullOr types.str;
              default = null;
              example = ''
                key_mgmt=WPA-EAP
                eap=PEAP
                identity="user@example.com"
                password="secret"
              '';
              description = ''
                Use this option to configure advanced authentication methods like EAP.
                See
                <citerefentry>
                  <refentrytitle>wpa_supplicant.conf</refentrytitle>
                  <manvolnum>5</manvolnum>
                </citerefentry>
                for example configurations.

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

            hidden = mkOption {
              type = types.bool;
              default = false;
              description = ''
                Set this to <literal>true</literal> if the SSID of the network is hidden.
              '';
              example = literalExample ''
                { echelon = {
                    hidden = true;
                    psk = "abcdefgh";
                  };
                }
              '';
            };

            priority = mkOption {
              type = types.nullOr types.int;
              default = null;
              description = ''
                By default, all networks will get same priority group (0). If some of the
                networks are more desirable, this field can be used to change the order in
                which wpa_supplicant goes through the networks when selecting a BSS. The
                priority groups will be iterated in decreasing priority (i.e., the larger the
                priority value, the sooner the network is matched against the scan results).
                Within each priority group, networks will be selected based on security
                policy, signal strength, etc.
              '';
            };

            extraConfig = mkOption {
              type = types.str;
              default = "";
              example = ''
                bssid_blacklist=02:11:22:33:44:55 02:22:aa:44:55:66
              '';
              description = ''
                Extra configuration lines appended to the network block.
                See
                <citerefentry>
                  <refentrytitle>wpa_supplicant.conf</refentrytitle>
                  <manvolnum>5</manvolnum>
                </citerefentry>
                for available options.
              '';
            };

          };
        });
        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 = {                   # SSID with no spaces or special characters
              psk = "abcdefgh";
            };
            "echelon's AP" = {            # SSID with spaces and/or special characters
               psk = "ijklmnop";
            };
            "free.wifi" = {};             # Public wireless network
          }
        '';
      };

      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.";
        };
      };

      extraConfig = mkOption {
        type = types.str;
        default = "";
        example = ''
          p2p_disabled=1
        '';
        description = ''
          Extra lines appended to the configuration file.
          See
          <citerefentry>
            <refentrytitle>wpa_supplicant.conf</refentrytitle>
            <manvolnum>5</manvolnum>
          </citerefentry>
          for available options.
        '';
      };
    };
  };

  config = mkIf cfg.enable {
    assertions = flip mapAttrsToList cfg.networks (name: cfg: {
      assertion = with cfg; count (x: x != null) [ psk pskRaw auth ] <= 1;
      message = ''options networking.wireless."${name}".{psk,pskRaw,auth} are mutually exclusive'';
    });

    environment.systemPackages = [ package ];

    services.dbus.packages = [ package ];

    hardware.wirelessRegulatoryDatabase = true;

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

      after = lib.concatMap deviceUnit ifaces;
      before = [ "network.target" ];
      wants = [ "network.target" ];
      requires = lib.concatMap deviceUnit ifaces;
      wantedBy = [ "multi-user.target" ];
      stopIfChanged = false;

      path = [ package pkgs.udev ];

      script = let
        configStr = if cfg.allowAuxiliaryImperativeNetworks
          then "-c /etc/wpa_supplicant.conf -I ${configFile}"
          else "-c ${configFile}";
      in ''
        if [ -f /etc/wpa_supplicant.conf -a "/etc/wpa_supplicant.conf" != "${configFile}" ]; then
          echo >&2 "<3>/etc/wpa_supplicant.conf present but ignored. Generated ${configFile} is used instead."
        fi

        iface_args="-s -u -D${cfg.driver} ${configStr}"

        ${if ifaces == [] then ''
          # detect interfaces automatically

          # check if there are no wireless interface
          if ! find -H /sys/class/net/* -name wireless | grep -q .; then
            # if so, wait until one appears
            echo "Waiting for wireless interfaces"
            grep -q '^ACTION=add' < <(stdbuf -oL -- udevadm monitor -s net/wlan -pu)
            # Note: the above line has been carefully written:
            # 1. The process substitution avoids udevadm hanging (after grep has quit)
            #    until it tries to write to the pipe again. Not even pipefail works here.
            # 2. stdbuf is needed because udevadm output is buffered by default and grep
            #    may hang until more udev events enter the pipe.
          fi

          # add any interface found to the daemon arguments
          for name in $(find -H /sys/class/net/* -name wireless | cut -d/ -f 5); do
            echo "Adding interface $name"
            args+="''${args:+ -N} -i$name $iface_args"
          done
        '' else ''
          # add known interfaces to the daemon arguments
          args="${concatMapStringsSep " -N " (i: "-i${i} $iface_args") ifaces}"
        ''}

        # finally start daemon
        exec wpa_supplicant $args
      '';
    };

    powerManagement.resumeCommands = ''
      /run/current-system/systemd/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+="/run/current-system/systemd/bin/systemctl try-restart wpa_supplicant.service"
    '';
  };

  meta.maintainers = with lib.maintainers; [ globin ];
}