%%%----------------------------------------------------------------------
%%% File    : mod_caps.erl
%%% Author  : Magnus Henoch <henoch@dtek.chalmers.se>
%%% Purpose : Request and cache Entity Capabilities (XEP-0115)
%%% Created : 7 Oct 2006 by Magnus Henoch <henoch@dtek.chalmers.se>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2010   ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%% 2009, improvements from ProcessOne to support correct PEP handling
%%% through s2s, use less memory, and speedup global caps handling
%%%----------------------------------------------------------------------

-module(mod_caps).
-author('henoch@dtek.chalmers.se').

-behaviour(gen_server).
-behaviour(gen_mod).

-export([read_caps/1,
	 caps_stream_features/2,
	 disco_features/5,
	 disco_identity/5,
	 disco_info/5,
	 get_features/1]).

%% gen_mod callbacks
-export([start/2, start_link/2,
	 stop/1]).

%% gen_server callbacks
-export([init/1,
	 handle_info/2,
	 handle_call/3,
	 handle_cast/2,
	 terminate/2,
	 code_change/3
	]).

-include_lib("exmpp/include/exmpp.hrl").

%% hook handlers
-export([user_send_packet/3]).

-include("ejabberd.hrl").

-define(PROCNAME, ejabberd_mod_caps).

-record(caps, {node, version, exts}).
-record(caps_features, {node_pair, features = []}).

-record(state, {host}).

%%====================================================================
%% API
%%====================================================================
start_link(Host, Opts) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    gen_server:start_link({local, Proc}, ?MODULE, [Host, Opts], []).

start(Host, Opts) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    ChildSpec =
	{Proc,
	 {?MODULE, start_link, [Host, Opts]},
	 transient,
	 1000,
	 worker,
	 [?MODULE]},
    supervisor:start_child(ejabberd_sup, ChildSpec).

stop(Host) ->
    Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
    gen_server:call(Proc, stop),
    supervisor:terminate_child(ejabberd_sup, Proc),
    supervisor:delete_child(ejabberd_sup, Proc).

%% get_features returns a list of features implied by the given caps
%% record (as extracted by read_caps) or 'unknown' if features are
%% not completely collected at the moment.
get_features(nothing) ->
    [];
get_features(#caps{node = Node, version = Version, exts = Exts}) ->
    SubNodes = [Version | Exts],
    lists:foldl(
      fun(SubNode, Acc) ->
	      BinaryNode = node_to_binary(Node, SubNode),
	      case cache_tab:lookup(caps_features, BinaryNode,
				    caps_read_fun(BinaryNode)) of
		  error ->
		      Acc;
		  {ok, Features} ->
		      binary_to_features(Features) ++ Acc
	      end
      end, [], SubNodes).

%% read_caps takes a list of XML elements (the child elements of a
%% <presence/> stanza) and returns an opaque value representing the
%% Entity Capabilities contained therein, or the atom nothing if no
%% capabilities are advertised.
read_caps(Els) ->
    read_caps(Els, nothing).
read_caps([#xmlel{ns = ?NS_CAPS, name = 'c'} = El | Tail], _Result) ->
    Node = exmpp_xml:get_attribute_as_list(El, 'node', ""),
    Version = exmpp_xml:get_attribute_as_list(El, 'ver', ""),
    Exts = string:tokens(exmpp_xml:get_attribute_as_list(El, 'ext', ""), " "),
    read_caps(Tail, #caps{node = Node, version = Version, exts = Exts});
read_caps([#xmlel{ns = ?NS_MUC_USER, name = 'x'} | _Tail], _Result) ->
    nothing;
read_caps([_ | Tail], Result) ->
    read_caps(Tail, Result);
read_caps([], Result) ->
    Result.

%%====================================================================
%% Hooks
%%====================================================================
user_send_packet(From, To, #xmlel{name = 'presence', attrs = Attrs, children = Els}) ->
    case exmpp_jid:bare_compare(From, To) of
	true ->
	    Type = exmpp_xml:get_attribute_from_list_as_list(Attrs, 'type', ""),
	    if Type == ""; Type == "available" ->
		    case read_caps(Els) of
			nothing ->
			    ok;
			#caps{version = Version, exts = Exts} = Caps ->
			    Server = exmpp_jid:prep_domain_as_list(From),
			    feature_request(Server, From, Caps, [Version | Exts])
		    end;
	    true ->
		    ok
	    end;
	false ->
	    ok
    end;
user_send_packet(_From, _To, _Packet) ->
    ok.

caps_stream_features(Acc, MyHost) ->
    case make_my_disco_hash(MyHost) of
	"" ->
	    Acc;
	Hash ->
	    [#xmlel{name = c,
		    ns = ?NS_CAPS,
		    attrs = [?XMLATTR(hash, "sha-1"),
			     ?XMLATTR(node, ?EJABBERD_URI),
			     ?XMLATTR(ver, Hash)]} | Acc]
    end.

disco_features(_Acc, From, To, <<?EJABBERD_URI, $#, _/binary>>, Lang) ->
    ejabberd_hooks:run_fold(disco_local_features,
			    exmpp_jid:domain(To),
			    empty,
			    [From, To, <<>>, Lang]);
disco_features(Acc, _From, _To, _Node, _Lang) ->
    Acc.

disco_identity(_Acc, From, To, <<?EJABBERD_URI, $#, _/binary>>, Lang) ->
    ejabberd_hooks:run_fold(disco_local_identity,
			    exmpp_jid:domain(To),
			    [],
			    [From, To, <<>>, Lang]);
disco_identity(Acc, _From, _To, _Node, _Lang) ->
    Acc.

disco_info(_Acc, Host, Module, <<?EJABBERD_URI, $#, _/binary>>, Lang) ->
    ejabberd_hooks:run_fold(disco_info,
			    list_to_binary(Host),
			    [],
			    [Host, Module, <<>>, Lang]);
disco_info(Acc, _Host, _Module, _Node, _Lang) ->
    Acc.

%%====================================================================
%% gen_server callbacks
%%====================================================================
init([Host, Opts]) ->
    case catch mnesia:table_info(caps_features, storage_type) of
	{'EXIT', _} ->
	    ok;
	disc_only_copies ->
	    ok;
	_ ->
	    mnesia:delete_table(caps_features)
    end,
    mnesia:create_table(caps_features,
			[{disc_only_copies, [node()]},
			 {local_content, true},
			 {attributes, record_info(fields, caps_features)}]),
    mnesia:add_table_copy(caps_features, node(), disc_only_copies),
    MaxSize = gen_mod:get_opt(cache_size, Opts, 1000),
    LifeTime = gen_mod:get_opt(cache_life_time, Opts, timer:hours(24) div 1000),
    cache_tab:new(caps_features, [{max_size, MaxSize}, {life_time, LifeTime}]),
    HostB = list_to_binary(Host),
    ejabberd_hooks:add(user_send_packet, HostB, ?MODULE, user_send_packet, 75),
    ejabberd_hooks:add(c2s_stream_features, HostB,
		       ?MODULE, caps_stream_features, 75),
    ejabberd_hooks:add(s2s_stream_features, HostB,
		       ?MODULE, caps_stream_features, 75),
    ejabberd_hooks:add(disco_local_features, HostB,
		       ?MODULE, disco_features, 75),
    ejabberd_hooks:add(disco_local_identity, HostB,
		       ?MODULE, disco_identity, 75),
    ejabberd_hooks:add(disco_info, HostB,
		       ?MODULE, disco_info, 75),
    {ok, #state{host = Host}}.

handle_call(stop, _From, State) ->
    {stop, normal, ok, State};
handle_call(_Req, _From, State) ->
    {reply, {error, badarg}, State}.

handle_cast(_Msg, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

terminate(_Reason, State) ->
    HostB = list_to_binary(State#state.host),
    ejabberd_hooks:delete(user_send_packet, HostB, ?MODULE, user_send_packet, 75),
    ejabberd_hooks:delete(c2s_stream_features, HostB,
			  ?MODULE, caps_stream_features, 75),
    ejabberd_hooks:delete(s2s_stream_features, HostB,
			  ?MODULE, caps_stream_features, 75),
    ejabberd_hooks:delete(disco_local_features, HostB,
			  ?MODULE, disco_features, 75),
    ejabberd_hooks:delete(disco_local_identity, HostB,
			  ?MODULE, disco_identity, 75),
    ejabberd_hooks:delete(disco_info, HostB,
			  ?MODULE, disco_info, 75),
    ok.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%====================================================================
%% Aux functions
%%====================================================================
feature_request(Host, From, Caps, [SubNode | Tail] = SubNodes) ->
    Node = Caps#caps.node,
    BinaryNode = node_to_binary(Node, SubNode),
    case cache_tab:lookup(caps_features, BinaryNode,
			  caps_read_fun(BinaryNode)) of
	error ->
	    IQ = #iq{type = get,
		     iq_ns = ?NS_JABBER_CLIENT,
		     payload = #xmlel{ns = ?NS_DISCO_INFO, name = 'query',
				 attrs = [?XMLATTR('node', Node ++ "#" ++ SubNode)]}},
	    F = fun(IQReply) ->
			feature_response(
			  IQReply, Host, From, Caps, SubNodes)
		end,
	    ejabberd_local:route_iq(
	      exmpp_jid:make("", Host, ""), From, IQ, F);
	_ ->
	    feature_request(Host, From, Caps, Tail)
    end;
feature_request(_Host, _From, _Caps, []) ->
    ok.

feature_response(#iq{type = result, payload = El},
		 Host, From, Caps, [SubNode | SubNodes]) ->
    Features = lists:flatmap(
		fun(#xmlel{name = 'feature', attrs = FAttrs}) ->
			[exmpp_xml:get_attribute_from_list_as_list(FAttrs, 'var', "")];
		   (_) ->
			[]
		end, El#xmlel.children),
    BinaryNode = node_to_binary(Caps#caps.node, SubNode),
    BinaryFeatures = features_to_binary(Features),
    cache_tab:insert(
      caps_features, BinaryNode, BinaryFeatures,
      caps_write_fun(BinaryNode, BinaryFeatures)),
    feature_request(Host, From, Caps, SubNodes);
feature_response(timeout, _Host, _From, _Caps, _SubNodes) ->
    ok;
feature_response(_IQResult, Host, From, Caps, [SubNode | SubNodes]) ->
    %% We got type=error or invalid type=result stanza, so
    %% we cache empty feature not to probe the client permanently
    BinaryNode = node_to_binary(Caps#caps.node, SubNode),
    cache_tab:insert(caps_features, BinaryNode, [],
		     caps_write_fun(BinaryNode, [])),
    feature_request(Host, From, Caps, SubNodes).

node_to_binary(Node, SubNode) ->
    {list_to_binary(Node), list_to_binary(SubNode)}.

features_to_binary(L) -> [list_to_binary(I) || I <- L].
binary_to_features(L) -> [binary_to_list(I) || I <- L].

caps_read_fun(Node) ->
    fun() ->
	    case mnesia:dirty_read({caps_features, Node}) of
		[#caps_features{features = Features}] ->
		    {ok, Features};
		_ ->
		    error
	    end
    end.

caps_write_fun(Node, Features) ->
    fun() ->
	    mnesia:dirty_write(
	      #caps_features{node_pair = Node,
			     features = Features})
    end.

make_my_disco_hash(Host) ->
    JID = exmpp_jid:make(Host),
    case {ejabberd_hooks:run_fold(disco_local_features,
				  Host,
				  empty,
				  [JID, JID, <<>>, <<>>]),
	  ejabberd_hooks:run_fold(disco_local_identity,
				  Host,
				  [],
				  [JID, JID, <<>>, <<>>]),
	  ejabberd_hooks:run_fold(disco_info,
				  Host,
				  [],
				  [Host, undefined, <<>>, <<>>])} of
	{{result, Features}, Identities, Info} ->
	    Feats = lists:map(
		      fun({{Feat, _Host}}) ->
			      #xmlel{name = feature,
				     attrs = [?XMLATTR(var, Feat)]};
			 (Feat) ->
			      #xmlel{name = feature,
				     attrs = [?XMLATTR(var, Feat)]}
		      end, Features),
	    make_disco_hash(Identities ++ Info ++ Feats, sha1);
	_Err ->
	    ""
    end.

make_disco_hash(DiscoEls, Algo) when Algo == sha1 ->
    Concat = [concat_identities(DiscoEls),
	      concat_features(DiscoEls),
	      concat_info(DiscoEls)],
    base64:encode_to_string(crypto:sha(Concat)).

concat_features(Els) ->
    lists:usort(
      lists:flatmap(
	fun(#xmlel{name = feature} = El) ->
		[[exmpp_xml:get_attribute(El, var, <<>>), $<]];
	   (_) ->
		[]
	end, Els)).

concat_identities(Els) ->
    lists:sort(
      lists:flatmap(
	fun(#xmlel{name = identity} = El) ->
		[[exmpp_xml:get_attribute_as_binary(El, category, <<>>), $/,
		  exmpp_xml:get_attribute_as_binary(El, type, <<>>), $/,
		  exmpp_xml:get_attribute_as_binary(El, lang, <<>>), $/,
		  exmpp_xml:get_attribute_as_binary(El, name, <<>>), $<]];
	   (_) ->
		[]
	end, Els)).

concat_info(Els) ->
    lists:sort(
      lists:flatmap(
	fun(#xmlel{name = x, ns = ?NS_DATA_FORMS, children = Fields} = El) ->
		case exmpp_xml:get_attribute_as_list(El, 'type', "") of
		    "result" ->
			[concat_xdata_fields(Fields)];
		    _ ->
			[]
		end;
	   (_) ->
		[]
	end, Els)).

concat_xdata_fields(Fields) ->
    [Form, Res] =
	lists:foldl(
	  fun(#xmlel{name = field, children = Els} = El,
	      [FormType, VarFields] = Acc) ->
		  case exmpp_xml:get_attribute_as_binary(El, var, <<>>) of
		      <<>> ->
			  Acc;
		      <<"FORM_TYPE">> ->
			  [exmpp_xml:get_path(
			     El, [{element, value}, cdata]), VarFields];
		      Var ->
			  [FormType,
			   [[[Var, $<],
			     lists:sort(
			       lists:flatmap(
				 fun(#xmlel{name = value} = VEl) ->
					 [[exmpp_xml:get_cdata(VEl), $<]];
				    (_) ->
					 []
				 end, Els))] | VarFields]]
		  end;
	     (_, Acc) ->
		  Acc
	  end, [<<>>, []], Fields),
    [Form, $<, lists:sort(Res)].