Adds minimal rule tracing functionality

apps/htoad/src/htoad.erl

@@ -29,6 +29,8 @@ assert(Fact) when is_list(Fact); is_tuple(Fact) ->
     htoad_engine:assert(?ENGINE, Fact).
 
 assert(Engine, Fact) when is_list(Fact); is_tuple(Fact) ->
+    {Fun, Args} = seresye_engine:get_fired_rule(Engine),
+    htoad_trace:assert(Engine, Fun, Args, Fact),
     seresye_engine:assert(Engine, Fact).
 
 retract(Fact) when is_list(Fact); is_tuple(Fact) ->

apps/htoad/src/htoad_app.erl

@@ -20,6 +20,7 @@ start(_StartType, _StartArgs) ->
             init:stop(),
             {ok, self()};
         _ ->
+            ets:new(htoad_trace, [named_table, public, bag]),
             process_args(Args),
             Result = htoad_sup:start_link(Args),
             [ htoad:assert({load, File}) || File <- Files ],

apps/htoad/src/htoad_engine.erl

@@ -17,6 +17,7 @@
 -export([start/0, start/1, start/2, stop/1, get_engine/1,
          add_rules/2, add_rule/2, add_rule/3, assert/2, get_kb/1,
          get_rules_fired/1, get_client_state/1,
+         set_hooks/2, get_fired_rule/1,
          set_client_state/2, query_kb/2, remove_rule/2, retract/2]).
 
 %% gen_server callbacks
@@ -35,6 +36,9 @@ start(Name) ->
 start(Name, ClientState) ->
     seresye_sup:start_engine(Name, ClientState).
 
+set_hooks(Name, Hooks) when is_list(Hooks) ->
+    gen_server:cast(Name, {set_hooks, Hooks}).
+
 set_client_state(Name, NewState) ->
     gen_server:cast(Name, {set_client_state, NewState}).
 
@@ -75,6 +79,9 @@ remove_rule(Name, Rule) ->
 get_rules_fired(Name) ->
     gen_server:call(Name, get_rules_fired).
 
+get_fired_rule(Name) ->
+    gen_server:call(Name, get_fired_rule).    
+
 get_kb(Name) ->
     gen_server:call(Name, get_kb).
 
@@ -175,6 +182,15 @@ handle_call(get_rules_fired, _From, State0) ->
                 {error, {Type, Reason}}
         end,
     {reply, Reply, State0};
+handle_call(get_fired_rule, _From, State0) ->
+    Reply =
+        try
+            seresye_engine:get_fired_rule(State0)
+        catch
+            Type:Reason ->
+                {error, {Type, Reason}}
+        end,
+    {reply, Reply, State0};
 handle_call(get_engine, _From, State0) ->
     {reply, State0, State0};
 handle_call(get_kb, _From, State0) ->
@@ -196,6 +212,9 @@ handle_call({query_kb, Pattern}, _From, State0) ->
         end,
     {reply, Reply, State0}.
 
+handle_cast({set_hooks, Hooks}, State) ->
+    {noreply, seresye_engine:set_hooks(State, Hooks)};
+
 handle_cast({set_client_state, CS}, State) ->
     {noreply, seresye_engine:set_client_state(State, CS)}.
 

apps/htoad/src/htoad_sup.erl

@@ -18,7 +18,10 @@ start_link(Args) ->
     esupervisor:start_link({local, ?MODULE}, ?MODULE, [Args]).
 
 start_seresye() ->
-    htoad_engine:start(?ENGINE).
+    {ok, Pid} = htoad_engine:start(?ENGINE),
+    htoad_engine:set_hooks(?ENGINE,[{before_rule, fun htoad_trace:rule/3}]),
+    {ok, Pid}.
+
 
 %% ===================================================================
 %% Supervisor callbacks

apps/htoad/src/htoad_trace.erl

@@ -0,0 +1,23 @@
+-module(htoad_trace).
+-export([rule/3, assert/4]).
+
+-include_lib("htoad/include/htoad.hrl").
+
+rule(_Engine, Fun, Args) ->
+    Info = erlang:fun_info(Fun),
+    Key = {rule,
+           proplists:get_value(module, Info),
+           proplists:get_value(name, Info),
+           proplists:get_value(arity, Info)},
+    ets:insert(htoad_trace, [{{facts, Args}, Key}|[ {{fact, Arg}, Key} || Arg <- Args ]]).
+
+assert(Engine, Fun, Args, Facts) when is_list(Facts) ->
+    [ assert(Engine, Fun, Args, Fact) || Fact <- Facts ];
+assert(_Engine, Fun, _Args, Fact) ->
+    Info = erlang:fun_info(Fun),
+    Key = {rule,
+           proplists:get_value(module, Info),
+           proplists:get_value(name, Info),
+           proplists:get_value(arity, Info)},
+    ets:insert(htoad_trace, {Key, {fact, Fact}}).
+