caching works correctly

src/fd_cache.erl

@@ -0,0 +1,120 @@
+% @doc storing map #{cookie := Context}
+-module(fd_cache).
+
+-behavior(gen_server).
+
+-export([
+    start_link/0,
+    query/1, set/2, unset/1,
+    %%---
+    %% everything below here runs in process context
+    %%--
+    %% gen_server callbacks
+    init/1, handle_call/3, handle_cast/2, handle_info/2,
+    code_change/3, terminate/2
+]).
+
+-include("$zx_include/zx_logger.hrl").
+
+-type context() :: wfc_eval_context:context().
+
+-record(s,
+        {cookies = #{} :: #{Cookie :: binary() := context()}}).
+% -type state() :: #s{}.
+
+
+%%--------------------------------
+%% api (runs in context of caller)
+%%--------------------------------
+
+-spec start_link() -> {ok, pid()} | {error, term()}.
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, none, []).
+
+
+
+-spec query(Cookie) -> {ok, Context} | error
+    when Cookie  :: binary(),
+         Context :: context().
+
+query(Cookie) ->
+    gen_server:call(?MODULE, {query, Cookie}).
+
+
+
+-spec set(Cookie, Context) -> ok
+    when Cookie  :: binary(),
+         Context :: context().
+
+set(Cookie, Context) ->
+    gen_server:cast(?MODULE, {set, Cookie, Context}).
+
+
+-spec unset(Cookie) -> ok
+    when Cookie  :: binary().
+
+unset(Cookie) ->
+    gen_server:cast(?MODULE, {unset, Cookie}).
+
+
+%%----------------------
+%% gen-server bs
+%%----------------------
+
+
+
+init(none) ->
+    log(info, "starting fd_cache"),
+    InitState = #s{},
+    {ok, InitState}.
+
+
+handle_call({query, Cookie}, _, State) ->
+    Result = do_query(Cookie, State),
+    {reply, Result, State};
+handle_call(Unexpected, From, State) ->
+    tell("~tp: unexpected call from ~tp: ~tp", [?MODULE, Unexpected, From]),
+    {noreply, State}.
+
+
+handle_cast({set, Cookie, Context}, State) ->
+    NewState = do_set(Cookie, Context, State),
+    {noreply, NewState};
+handle_cast({unset, Cookie}, State) ->
+    NewState = do_unset(Cookie, State),
+    {noreply, NewState};
+handle_cast(Unexpected, State) ->
+    tell("~tp: unexpected cast: ~tp", [?MODULE, Unexpected]),
+    {noreply, State}.
+
+
+handle_info(Unexpected, State) ->
+    tell("~tp: unexpected info: ~tp", [?MODULE, Unexpected]),
+    {noreply, State}.
+
+
+code_change(_, State, _) ->
+    {ok, State}.
+
+terminate(_, _) ->
+    ok.
+
+
+%%---------------------
+%% doers
+%%---------------------
+
+do_set(Cookie, Context, State = #s{cookies = Cookies}) ->
+    NewCookies = maps:put(Cookie, Context, Cookies),
+    NewState   = State#s{cookies = NewCookies},
+    NewState.
+
+
+do_unset(Cookie, State = #s{cookies = Cookies}) ->
+    NewCookies = maps:remove(Cookie, Cookies),
+    NewState   = State#s{cookies = NewCookies},
+    NewState.
+
+
+do_query(Cookie, _State = #s{cookies = Cookies}) ->
+    maps:find(Cookie, Cookies).

src/fd_client.erl

@@ -263,34 +263,52 @@ default_css(Sock) ->
             http_err(Sock, 500)
     end.
 
-wfcin(Sock, #request{enctype = json, body = #{"wfcin" := Input}}) ->
+wfcin(Sock, #request{enctype = json,
+                     cookies = Cookies,
+                     body = #{"wfcin" := Input}}) ->
     tell("wfcin good request: ~tp", [Input]),
-    RespObj =
+    {Cookie, Ctx0} = ctx(Cookies),
+    {RespObj, NewCtx} =
+        %% FIXME: this should really be a new process
         try
             case wfc_read:expr(Input) of
-                %% FIXME support multiple expressions
                 {ok, Expr, _Rest} ->
-                    case wfc_eval:eval(Expr, wfc_eval_context:default()) of
-                        {ok, noop, _NewContext}     -> jsgud("<noop>");
-                        {ok, Sentence, _NewContext} -> jsgud(wfc_pp:sentence(Sentence));
-                        {error, Message}            -> jsbad(Message)
+                    case wfc_eval:eval(Expr, Ctx0) of
+                        {ok, noop, Ctx1}     -> {jsgud("<noop>"), Ctx1};
+                        {ok, Sentence, Ctx1} -> {jsgud(wfc_pp:sentence(Sentence)), Ctx1};
+                        {error, Message}     -> {jsbad(Message), Ctx0}
                     end;
                 {error, Message} ->
-                    jsbad(Message)
+                    {jsbad(Message), Ctx0}
             end
         catch
             error:E:S ->
                 ErrorMessage = unicode:characters_to_list(io_lib:format("parser crashed: ~p:~p", [E, S])),
-                jsbad(ErrorMessage)
+                {jsbad(ErrorMessage), Ctx0}
         end,
+    % update cache with new context
+    ok = fd_cache:set(Cookie, NewCtx),
     Body    = zj:encode(RespObj),
-    Response = #response{headers = [{"content-type", "application/json"}],
+    Response = #response{headers = [{"content-type", "application/json"},
+                                    {"set-cookie",   ["wfc=", Cookie]}],
                          body    = Body},
     respond(Sock, Response);
 wfcin(Sock, Request) ->
     tell("wfcin: bad request: ~tp", [Request]),
     http_err(Sock, 400).
 
+
+ctx(#{<<"wfc">> := Cookie}) ->
+    case fd_cache:query(Cookie) of
+        {ok, Context} -> {Cookie, Context};
+        error         -> {Cookie, wfc_eval_context:default()}
+    end;
+ctx(_) ->
+    {new_cookie(), wfc_eval_context:default()}.
+
+new_cookie() ->
+    binary:encode_hex(crypto:strong_rand_bytes(8)).
+
 jsgud(X) ->
     #{"ok"     => true,
       "result" => X}.

src/fd_sup.erl

@@ -42,5 +42,11 @@ init([]) ->
                  5000,
                  supervisor,
                  [fd_clients]},
-    Children  = [Clients],
+    Cache     = {fd_cache,
+                 {fd_cache, start_link, []},
+                 permanent,
+                 5000,
+                 worker,
+                 [fd_cache]},
+    Children  = [Clients, Cache],
     {ok, {RestartStrategy, Children}}.

src/wfc_eval.erl

@@ -59,6 +59,11 @@ eval_sexp(Args = [{snowflake, <<"define">>}, {pattern, Pat}, Expr], Ctx0) ->
         Error ->
             Error
     end;
+eval_sexp(_Args = [{snowflake, <<"undefine">>}, {pattern, Pat}], Ctx0) ->
+    case wfc_eval_context:undefine(Pat, Ctx0) of
+        {ok, NewContext} -> {ok, noop, NewContext};
+        Error            -> Error
+    end;
 eval_sexp([{snowflake, SF} | Args], Ctx0) ->
     % first evaluate the arguments individually
     case eval_sexp_args(Args, Ctx0, []) of

src/wfc_eval_context.erl

@@ -9,6 +9,7 @@
     default/0,
     default_snowflakes/0,
     define/3,
+    undefine/2,
     resolve_pattern/2,
     resolve_snowflake/2
 ]).
@@ -33,6 +34,7 @@ default() ->
 default_snowflakes() ->
     #{<<"and">>     => fun wfc:mul/1,
       <<"xor">>     => fun wfc:add/1,
+      <<"implies">> => fun snf_implies/1,
       <<"ior">> =>
             fun IOR([S1 | Rest]) ->
                     case IOR(Rest) of
@@ -46,10 +48,6 @@ default_snowflakes() ->
             fun ([S]) -> {ok, sf_not(S)};
                 (Bad) -> {error, wfc_utils:str("not/1: wrong number of arguments: ~p", [Bad])}
             end,
-      <<"implies">> =>
-            fun ([A, B]) -> {ok, sf_implies(A, B)};
-                (Bad)    -> {error, wfc_utils:str("implies/2: wrong number of arguments: ~p", [Bad])}
-            end,
       <<"impliedby">> =>
             fun ([A, B]) -> {ok, sf_impliedby(A, B)};
                 (Bad)    -> {error, wfc_utils:str("impliedby/2: wrong number of arguments: ~p", [Bad])}
@@ -60,6 +58,10 @@ default_snowflakes() ->
             end
      }.
 
+snf_implies([A, B]) -> {ok, sf_implies(A, B)};
+snf_implies(Bad)    -> {error, wfc_utils:str("implies/2: wrong number of arguments: ~p", [Bad])}.
+
+
 sf_ior(A, B) ->
     wfc_sftt:appl_ttf(fun ttf_ior/2, [A, B]).
 
@@ -93,14 +95,18 @@ define(Pat, Sentence, Ctx = #ctx{patterns = OldPatterns}) ->
     NewPatterns = maps:put(Pat, Sentence, OldPatterns),
     {ok, Ctx#ctx{patterns = NewPatterns}}.
 
+undefine(Pat, Ctx = #ctx{patterns = OldPatterns}) ->
+    NewPatterns = maps:remove(Pat, OldPatterns),
+    {ok, Ctx#ctx{patterns = NewPatterns}}.
+
 resolve_pattern(Pat, Ctx = #ctx{patterns = Patterns}) ->
     case maps:find(Pat, Patterns) of
-        error -> {error, wfc_utils:str("wfc_eval_context:resolve_pattern: not found: ~w; context: ~w", [Pat, Ctx])};
+        error -> {error, wfc_utils:str("wfc_eval_context:resolve_pattern: not found: ~s; context: ~w", [Pat, Ctx])};
         Result -> Result
     end.
 
 resolve_snowflake(SF, Ctx = #ctx{snowflakes = Snowflakes}) ->
     case maps:find(SF, Snowflakes) of
-        error -> {error, wfc_utils:str("wfc_eval_context:resolve_snowflake: not found: ~w; context: ~w", [SF, Ctx])};
+        error -> {error, wfc_utils:str("wfc_eval_context:resolve_snowflake: not found: ~s; context: ~w", [SF, Ctx])};
         Result -> Result
     end.