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

with lib;

let

  cfg = config.services.bitlbee;
  bitlbeeUid = config.ids.uids.bitlbee;

  bitlbeePkg = pkgs.bitlbee.override {
    enableLibPurple = cfg.libpurple_plugins != [];
    enablePam = cfg.authBackend == "pam";
  };

  bitlbeeConfig = pkgs.writeText "bitlbee.conf"
    ''
    [settings]
    RunMode = Daemon
    ConfigDir = ${cfg.configDir}
    DaemonInterface = ${cfg.interface}
    DaemonPort = ${toString cfg.portNumber}
    AuthMode = ${cfg.authMode}
    AuthBackend = ${cfg.authBackend}
    Plugindir = ${pkgs.bitlbee-plugins cfg.plugins}/lib/bitlbee
    ${lib.optionalString (cfg.hostName != "") "HostName = ${cfg.hostName}"}
    ${lib.optionalString (cfg.protocols != "") "Protocols = ${cfg.protocols}"}
    ${cfg.extraSettings}

    [defaults]
    ${cfg.extraDefaults}
    '';

  purple_plugin_path =
    lib.concatMapStringsSep ":"
      (plugin: "${plugin}/lib/pidgin/:${plugin}/lib/purple-2/")
      cfg.libpurple_plugins
    ;

in

{

  ###### interface

  options = {

    services.bitlbee = {

      enable = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Whether to run the BitlBee IRC to other chat network gateway.
          Running it allows you to access the MSN, Jabber, Yahoo! and ICQ chat
          networks via an IRC client.
        '';
      };

      interface = mkOption {
        type = types.str;
        default = "127.0.0.1";
        description = lib.mdDoc ''
          The interface the BitlBee daemon will be listening to.  If `127.0.0.1`,
          only clients on the local host can connect to it; if `0.0.0.0`, clients
          can access it from any network interface.
        '';
      };

      portNumber = mkOption {
        default = 6667;
        type = types.port;
        description = lib.mdDoc ''
          Number of the port BitlBee will be listening to.
        '';
      };

      authBackend = mkOption {
        default = "storage";
        type = types.enum [ "storage" "pam" ];
        description = lib.mdDoc ''
          How users are authenticated
            storage -- save passwords internally
            pam -- Linux PAM authentication
        '';
      };

      authMode = mkOption {
        default = "Open";
        type = types.enum [ "Open" "Closed" "Registered" ];
        description = lib.mdDoc ''
          The following authentication modes are available:
            Open -- Accept connections from anyone, use NickServ for user authentication.
            Closed -- Require authorization (using the PASS command during login) before allowing the user to connect at all.
            Registered -- Only allow registered users to use this server; this disables the register- and the account command until the user identifies himself.
        '';
      };

      hostName = mkOption {
        default = "";
        type = types.str;
        description = lib.mdDoc ''
          Normally, BitlBee gets a hostname using getsockname(). If you have a nicer
          alias for your BitlBee daemon, you can set it here and BitlBee will identify
          itself with that name instead.
        '';
      };

      plugins = mkOption {
        type = types.listOf types.package;
        default = [];
        example = literalExpression "[ pkgs.bitlbee-facebook ]";
        description = lib.mdDoc ''
          The list of bitlbee plugins to install.
        '';
      };

      libpurple_plugins = mkOption {
        type = types.listOf types.package;
        default = [];
        example = literalExpression "[ pkgs.purple-matrix ]";
        description = lib.mdDoc ''
          The list of libpurple plugins to install.
        '';
      };

      configDir = mkOption {
        default = "/var/lib/bitlbee";
        type = types.path;
        description = lib.mdDoc ''
          Specify an alternative directory to store all the per-user configuration
          files.
        '';
      };

      protocols = mkOption {
        default = "";
        type = types.str;
        description = lib.mdDoc ''
          This option allows to remove the support of protocol, even if compiled
          in. If nothing is given, there are no restrictions.
        '';
      };

      extraSettings = mkOption {
        default = "";
        type = types.lines;
        description = lib.mdDoc ''
          Will be inserted in the Settings section of the config file.
        '';
      };

      extraDefaults = mkOption {
        default = "";
        type = types.lines;
        description = lib.mdDoc ''
          Will be inserted in the Default section of the config file.
        '';
      };

    };

  };

  ###### implementation

  config =  mkMerge [
    (mkIf config.services.bitlbee.enable {
      systemd.services.bitlbee = {
        environment.PURPLE_PLUGIN_PATH = purple_plugin_path;
        description = "BitlBee IRC to other chat networks gateway";
        after = [ "network.target" ];
        wantedBy = [ "multi-user.target" ];

        serviceConfig = {
          DynamicUser = true;
          StateDirectory = "bitlbee";
          ReadWritePaths = [ cfg.configDir ];
          ExecStart = "${bitlbeePkg}/sbin/bitlbee -F -n -c ${bitlbeeConfig}";
        };
      };

      environment.systemPackages = [ bitlbeePkg ];

    })
    (mkIf (config.services.bitlbee.authBackend == "pam") {
      security.pam.services.bitlbee = {};
    })
  ];

}