Create subject subsystem on server

server/src/session_server.erl

@@ -39,7 +39,7 @@ handle_info({'EXIT', Pid, Reason},
 	Response = case Reason of
 				   {response, Value} -> Value;
 				   _ ->
-					   io:format("Request handling error: ~p~n", [Reason]),
+					   io:format("Error handling request: ~p~n", [Reason]),
 					   {error, serverError}
 			   end,
 	send(Socket, TransactionId, Response),
@@ -63,6 +63,13 @@ handle_request(Request) ->
 
 map_request({ping, 'NULL'}) ->
 	{response, {ack, 'NULL'}};
+map_request({logSession, {'Session', Subject, Type, Timestamp, Minutes}}) ->
+	Session = {unicode:characters_to_list(Subject),
+			   Type, Timestamp, Minutes},
+	case subject_router:log_session(Session) of
+		ok -> {response, {ack, 'NULL'}};
+		{error, invalid_subject} -> {response, {error, invalidArguments}}
+	end;
 map_request(_) ->
 	{response, {error, invalidArguments}}.
 

server/src/study_system_server_app.erl

@@ -9,7 +9,11 @@
 start(_StartType, _StartArgs) ->
 	Port = application:get_env(study_system_server, port, 12888),
 	{ok, CertDir} = application:get_env(study_system_server, cert_dir),
-	proto_sup:start_link(Port, CertDir).
+	{ok, _Pid} = pg:start(study_system_server),
+	study_system_server_sup:start_link(Port, CertDir),
+	subject_sup:start_subject("Cybernetics"),
+	subject_sup:start_subject("Physics"),
+	subject_sup:start_subject("Linguistics").
 
 stop(_State) ->
 	ok.

server/src/study_system_server_sup.erl

@@ -0,0 +1,35 @@
+% Copyright (c) Camden Dixie O'Brien
+% SPDX-License-Identifier: AGPL-3.0-only
+
+-module(study_system_server_sup).
+-behaviour(supervisor).
+
+-export([start_link/2]).
+-export([init/1]).
+
+start_link(Port, CertDir) ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, [Port, CertDir]).
+
+init([Port, CertDir]) ->
+	SupFlags = #{strategy => one_for_one,
+				 intensity => 5,
+				 period => 10},
+	ChildSpecs = [#{id => subject_router,
+					start => {subject_router, start_link, []},
+					restart => permanent,
+					shutdown => 5000,
+					type => worker,
+					modules => [subject_router]},
+				  #{id => subject_sup,
+					start => {subject_sup, start_link, []},
+					restart => permanent,
+					shutdown => 5000,
+					type => supervisor,
+					modules => [subject_sup]},
+				  #{id => proto_sup,
+					start => {proto_sup, start_link, [Port, CertDir]},
+					restart => permanent,
+					shutdown => 5000,
+					type => supervisor,
+					modules => [proto_sup]}],
+	{ok, {SupFlags, ChildSpecs}}.

server/src/subject_router.erl

@@ -0,0 +1,75 @@
+% Copyright (c) Camden Dixie O'Brien
+% SPDX-License-Identifier: AGPL-3.0-only
+
+-module(subject_router).
+-behaviour(gen_server).
+
+-export([start_link/0, log_session/1]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+		 terminate/2, code_change/3]).
+
+start_link() ->
+	gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+log_session(Session) ->
+	gen_server:call(?MODULE, {log_session, Session}).
+
+init([]) ->
+	{MonitorRef, Pids} = pg:monitor(study_system_server, subject_servers),
+	SubjectTable = ets:new(subject_table, [private]),
+	register_servers(SubjectTable, Pids),
+	{ok, #{monitor_ref => MonitorRef,
+		   subject_table => SubjectTable}}.
+
+handle_call({log_session, {Subject, Type, Timestamp, Minutes}},
+			_From, State = #{subject_table := SubjectTable}) ->
+	case ets:lookup(SubjectTable, Subject) of
+		[{Subject, Pid}] ->
+			Pid ! {new_session, Type, Timestamp, Minutes},
+			{reply, ok, State};
+		[] ->
+			{reply, {error, invalid_subject}, State}
+	end;
+handle_call(_Request, _From, State) ->
+	{reply, ok, State}.
+
+handle_cast(_Msg, State) ->
+	{noreply, State}.
+
+handle_info({Ref, join, subject_servers, Pids},
+			State = #{monitor_ref := MonitorRef,
+					  subject_table := SubjectTable})
+  when Ref =:= MonitorRef ->
+	register_servers(SubjectTable, Pids),
+	{noreply, State};
+handle_info({Ref, leave, subject_servers, Pids},
+			State = #{monitor_ref := MonitorRef,
+					  subject_table := SubjectTable})
+  when Ref =:= MonitorRef ->
+	deregister_servers(SubjectTable, Pids),
+	{noreply, State};
+handle_info(_Info, State) ->
+	{noreply, State}.
+
+terminate(_Reason, _State) ->
+	ok.
+
+code_change(_OldVsn, State, _Extra) ->
+	{ok, State}.
+
+register_servers(SubjectTable, Pids) ->
+	[register_server(SubjectTable, Pid) || Pid <- Pids].
+
+register_server(SubjectTable, Pid) ->
+	try
+		{subject, Subject} = gen_server:call(Pid, get_subject),
+		ets:insert(SubjectTable, {Subject, Pid})
+	catch
+		_:_ -> ok
+	end.
+
+deregister_servers(SubjectTable, Pids) ->
+	[deregister_server(SubjectTable, Pid) || Pid <- Pids].
+
+deregister_server(SubjectTable, Pid) ->
+	ets:match_delete(SubjectTable, {'_', Pid}).

server/src/subject_server.erl

@@ -0,0 +1,39 @@
+% Copyright (c) Camden Dixie O'Brien
+% SPDX-License-Identifier: AGPL-3.0-only
+
+-module(subject_server).
+-behaviour(gen_server).
+
+-export([start_link/1]).
+-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
+		 terminate/2, code_change/3]).
+
+start_link(Subject) ->
+	gen_server:start_link(?MODULE, Subject, []).
+
+init(Subject) ->
+	pg:join(study_system_server, subject_servers, self()),
+	{ok, #{subject => Subject}}.
+
+handle_call(get_subject, _From, State = #{subject := Subject}) ->
+	{reply, {subject, Subject}, State};
+handle_call(_Request, _From, State) ->
+	{reply, ok, State}.
+
+handle_cast(_Msg, State) ->
+	{noreply, State}.
+
+handle_info({new_session, Type, Timestamp, Minutes},
+			State = #{subject := Subject}) ->
+	io:format(
+	  "Received new ~p session: type ~p, timestamp ~p, minutes ~p~n",
+	  [Subject, Type, Timestamp, Minutes]),
+	{noreply, State};
+handle_info(_Info, State) ->
+	{noreply, State}.
+
+terminate(_Reason, _State) ->
+	ok.
+
+code_change(_OldVsn, State, _Extra) ->
+	{ok, State}.

server/src/subject_sup.erl

@@ -0,0 +1,25 @@
+% Copyright (c) Camden Dixie O'Brien
+% SPDX-License-Identifier: AGPL-3.0-only
+
+-module(subject_sup).
+-behaviour(supervisor).
+
+-export([start_link/0, init/1, start_subject/1]).
+
+start_link() ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+init([]) ->
+	SupFlags = #{strategy => simple_one_for_one,
+				 intensity => 5,
+				 period => 10},
+	ChildSpec = #{id => subject_server,
+				  start => {subject_server, start_link, []},
+				  restart => permanent,
+				  shutdown => 5000,
+				  type => worker,
+				  modules => [subject_server]},
+	{ok, {SupFlags, [ChildSpec]}}.
+
+start_subject(Subject) ->
+	supervisor:start_child(?MODULE, [Subject]).