caching works correctly

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}.