Use COUNT member in enums

The client is doing it itself now anyway.

client/src/activities_view.vala

@@ -1,130 +1,140 @@
 namespace StudySystemClient {
-	private struct Activity {
-		public string subject;
-		public ActivityType type;
-	}
+	public class ActivitiesView : ListView<ActivityCard> {
+		private const uint REFRESH_PERIOD_MS = 30000;
 
-	enum ActivityType {
-		EXERCISES,
-		READING;
+		private Client client;
+		private Updater updater;
+		private Refresher refresher;
+		private bool pending_sort;
 
-		public string to_string() {
-			switch (this) {
-			case EXERCISES:
-				return "Exercises";
-			case READING:
-				return "Reading";
-			default:
-				return "Invalid activity type";
+		public ActivitiesView(Client client)  {
+			base();
+			add_css_class("card-container");
+			this.client = client;
+			updater = new Updater(this, client);
+			refresher = new Refresher(updater, REFRESH_PERIOD_MS);
+			pending_sort = false;
+			this.map.connect(() => {
+					updater.refresh.begin();
+					refresher.start();
+				});
+		}
+
+		internal IterableBox.Iterator<Type, ActivityCard> iterator() {
+			return container.iterator();
+		}
+
+		internal void new_card(Activity activity) {
+			var card = new ActivityCard(activity);
+			card.session_logged.connect(log_session);
+			card.log_closed.connect(handle_pending_sort);
+			container.append(card);
+		}
+
+		internal void remove_card(ActivityCard card) {
+			container.remove(card);
+		}
+
+		internal void sort() {
+			if (log_in_progress())
+				pending_sort = true;
+			else
+				container.sort(compare_cards);
+		}
+
+		private async void log_session(string subject, ActivityType type,
+									   int minutes) {
+			try {
+				yield client.log_session(subject, type, minutes);
+				yield updater.refresh();
+			} catch (ClientError e) {
+				stderr.printf("Error logging session: %s\n", e.message);
 			}
 		}
-	}
 
-	public class ActivitiesView : Gtk.Box {
-		public ActivitiesView()  {
-			margin_top = margin_bottom = margin_start = margin_end = 0;
+		private void handle_pending_sort() {
+			if (pending_sort) {
+				container.sort(compare_cards);
+				pending_sort = false;
+			}
+		}
 
-			var scrolled_window = new Gtk.ScrolledWindow();
-			scrolled_window.hscrollbar_policy = Gtk.PolicyType.NEVER;
-			scrolled_window.vexpand = true;
+		private bool log_in_progress() {
+			foreach (var card in container) {
+				if (card.logging)
+					return true;
+			}
+			return false;
+		}
 
-			var card_container = new Gtk.FlowBox();
-			card_container.homogeneous = true;
-			card_container.min_children_per_line = 1;
-			card_container.max_children_per_line = 1;
-			card_container.selection_mode = Gtk.SelectionMode.NONE;
-			card_container.valign = Gtk.Align.START;
-			scrolled_window.add_css_class("card-container");
-
-			var activities = new Activity[] {
-				{ "Linguistics", ActivityType.EXERCISES },
-				{ "Cybernetics", ActivityType.EXERCISES },
-				{ "Linguistics", ActivityType.READING },
-				{ "Physics", ActivityType.READING },
-				{ "Cybernetics", ActivityType.READING },
-				{ "Physics", ActivityType.EXERCISES },
-			};
-			foreach (var activity in activities)
-				card_container.append(new ActivityCard(activity));
-
-			scrolled_window.set_child(card_container);
-			this.append(scrolled_window);
+		private static int compare_cards(ActivityCard card1,
+										 ActivityCard card2) {
+			if (card1.activity.priority < card2.activity.priority)
+				return -1;
+			else if (card1.activity.priority > card2.activity.priority)
+				return 1;
+			else
+				return 0;
 		}
 	}
 
-	private class ActivityCard : Gtk.Frame {
-		public ActivityCard(Activity activity) {
-			add_css_class("card");
+	private class Updater : IRefreshable {
+		private weak ActivitiesView target;
+		private Client client;
 
-			var content = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 12);
-
-			var text = new Gtk.Box(Gtk.Orientation.VERTICAL, 6);
-			text.hexpand = true;
-
-			var subject = new Gtk.Label(activity.subject);
-			subject.halign = Gtk.Align.START;
-			subject.add_css_class("activity-subject");
-			text.append(subject);
-
-			var type = new Gtk.Label(activity.type.to_string());
-			type.halign = Gtk.Align.START;
-			text.append(type);
-
-			content.append(text);
-
-			var button
-				= new Gtk.Button.from_icon_name("appointment-new-symbolic");
-			button.vexpand = false;
-			button.valign = Gtk.Align.CENTER;
-			button.set_tooltip_text("Log session");
-			button.add_css_class("log-session-button");
-			content.append(button);
-
-			set_child(content);
-
-			var log_session_popover = new LogSessionPopover();
-			log_session_popover.set_parent(button);
-			button.clicked.connect(() => log_session_popover.popup());
-		}
-	}
-
-	private class LogSessionPopover : Gtk.Popover {
-		private const int DEFAULT_LENGTH = 30;
-
-		private Gtk.SpinButton input;
-
-		public LogSessionPopover() {
-			var content = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 6);
-
-			var label = new Gtk.Label("Minutes");
-			label.halign = Gtk.Align.START;
-			content.append(label);
-
-			var adjustment
-				= new Gtk.Adjustment(DEFAULT_LENGTH, 10, 480, 10, 10, 0);
-			input = new Gtk.SpinButton(adjustment, 1, 0);
-			input.numeric = true;
-			content.append(input);
-
-			var button = new Gtk.Button.from_icon_name("emblem-ok-symbolic");
-			button.halign = Gtk.Align.END;
-			button.set_tooltip_text("Submit");
-			button.add_css_class("suggested-action");
-			button.clicked.connect(submit);
-			content.append(button);
-
-			set_child(content);
-
-			closed.connect(reset);
+		public Updater(ActivitiesView target, Client client) {
+			this.target = target;
+			this.client = client;
 		}
 
-		private void submit() {
-			reset();
-			popdown();
+		public async void refresh() {
+			if (!client.connected || target == null)
+				return;
+			try {
+				var activities = yield client.list_activities();
+				apply_update(activities);
+				target.sort();
+			} catch (ClientError e) {
+				stderr.printf("Error refreshing activities: %s\n",
+							  e.message);
+			}
 		}
 
-		private void reset() {
-			input.value = DEFAULT_LENGTH;
+		private void apply_update(Array<Activity> activities) {
+			update_existing(activities);
+			for (uint i = 0; i < activities.length; ++i)
+				target.new_card(activities.index(i));
+		}
+
+		private void update_existing(Array<Activity> activities) {
+			var to_remove = new List<ActivityCard>();
+			foreach (var card in target) {
+				if (!update_card(card, activities))
+					to_remove.append(card);
+			}
+			foreach (var card in to_remove)
+				target.remove_card(card);
+		}
+
+		private bool update_card(ActivityCard card,
+								 Array<Activity> activities) {
+			var activity_index = find_activity(card, activities);
+			if (activity_index == null)
+				return false;
+			var priority = activities.index(activity_index).priority;
+			card.update_priority(priority);
+			activities._remove_index_fast(activity_index);
+			return true;
+		}
+
+		private static uint? find_activity(ActivityCard card,
+										   Array<Activity> activities) {
+			for (uint i = 0; i < activities.length; ++i) {
+				if (activities.index(i).subject == card.activity.subject
+					&& activities.index(i).type == card.activity.type)
+					return i;
+			}
+			return null;
 		}
 	}
 }

client/src/activity.vala

@@ -0,0 +1,25 @@
+namespace StudySystemClient {
+	public struct Activity {
+		public string subject;
+		public ActivityType type;
+		public double priority;
+	}
+
+	public enum ActivityType {
+		READING = 0,
+		EXERCISES = 1,
+
+		COUNT;
+
+		public string to_string() {
+			switch (this) {
+			case EXERCISES:
+				return "Exercises";
+			case READING:
+				return "Reading";
+			default:
+				return "Invalid activity type";
+			}
+		}
+	}
+}

client/src/activity_card.vala

@@ -0,0 +1,122 @@
+namespace StudySystemClient {
+	public class ActivityCard : Gtk.Frame {
+		public signal void session_logged(string subject, ActivityType type,
+										  int minutes);
+		public signal void log_closed();
+
+		public Activity activity { get; private set; }
+		public bool logging { get; private set; }
+
+		private Gtk.Label priority_label;
+
+		public ActivityCard(Activity activity) {
+			hexpand = true;
+			add_css_class("card");
+
+			this.activity = activity;
+			logging = false;
+
+			var subject = new Gtk.Label(activity.subject);
+			subject.halign = Gtk.Align.START;
+			subject.add_css_class("activity-subject");
+
+			var type = new Gtk.Label(activity.type.to_string());
+			type.add_css_class("activity-type");
+			var separator = new Gtk.Label("·");
+			separator.add_css_class("activity-priority");
+
+			priority_label = new Gtk.Label(priority_text(activity.priority));
+			priority_label.add_css_class("activity-priority");
+
+			var details = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 6);
+			details.append(type);
+			details.append(separator);
+			details.append(priority_label);
+
+			var text = new Gtk.Box(Gtk.Orientation.VERTICAL, 6);
+			text.hexpand = true;
+			text.append(subject);
+			text.append(details);
+
+			var content = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 12);
+			content.append(text);
+
+			var button
+				= new Gtk.Button.from_icon_name("appointment-new-symbolic");
+			button.vexpand = false;
+			button.valign = Gtk.Align.CENTER;
+			button.set_tooltip_text("Log session");
+			button.add_css_class("log-session-button");
+			content.append(button);
+
+			set_child(content);
+
+			var log_session_popover = new LogSessionPopover();
+			log_session_popover.set_parent(button);
+			log_session_popover.closed.connect(() => {
+					logging = false;
+					log_closed();
+				});
+			log_session_popover.session_logged.connect((minutes) => {
+					session_logged(activity.subject, activity.type, minutes);
+				});
+
+			button.clicked.connect(() => {
+					logging = true;
+					log_session_popover.popup();
+				});
+		}
+
+		public void update_priority(double new_priority) {
+			activity = { activity.subject, activity.type, new_priority };
+			priority_label.set_text(priority_text(new_priority));
+		}
+
+		private static string priority_text(double priority) {
+			return "%0.2f".printf(priority);
+		}
+	}
+
+	private class LogSessionPopover : Gtk.Popover {
+		public signal void session_logged(int minutes);
+
+		private const int DEFAULT_LENGTH = 30;
+
+		private Gtk.SpinButton input;
+
+		public LogSessionPopover() {
+			var content = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 6);
+
+			var label = new Gtk.Label("Minutes");
+			label.halign = Gtk.Align.START;
+			content.append(label);
+
+			var adjustment
+				= new Gtk.Adjustment(DEFAULT_LENGTH, 10, 480, 10, 10, 0);
+			input = new Gtk.SpinButton(adjustment, 1, 0);
+			input.numeric = true;
+			content.append(input);
+
+			var button = new Gtk.Button.from_icon_name("emblem-ok-symbolic");
+			button.halign = Gtk.Align.END;
+			button.set_tooltip_text("Submit");
+			button.add_css_class("suggested-action");
+			button.clicked.connect(submit);
+			content.append(button);
+
+			set_child(content);
+
+			closed.connect(reset);
+		}
+
+		private void submit() {
+			session_logged((int)input.value);
+			reset();
+			popdown();
+		}
+
+		private void reset() {
+			input.value = DEFAULT_LENGTH;
+		}
+	}
+}

client/src/client.vala

@@ -0,0 +1,68 @@
+namespace StudySystemClient {
+	public errordomain ClientError {
+		ERROR_RESPONSE,
+		UNEXPECTED_RESPONSE,
+	}
+
+	public class Client {
+		public signal void connection_status(bool connected);
+
+		public bool connected { get { return connection.connected; } }
+
+		private Connection connection;
+
+		public Client(string cert_dir) throws Error {
+			connection = new Connection(cert_dir, (connected) => {
+					connection_status(connected);
+				});
+		}
+
+		public async void ping() throws ClientError {
+			var response = yield connection.send(new Request.Ping());
+			if (response is Response.Ack) {
+				return;
+			} else if (response is Response.Error) {
+				throw new ClientError.ERROR_RESPONSE(
+					"Error response to Ping: %s",
+					response.value.to_string());
+			} else {
+				throw new ClientError.UNEXPECTED_RESPONSE(
+					"Unexpected response to Ping");
+			}
+		}
+
+		public async Array<Activity> list_activities()
+				throws ClientError {
+			var request = new Request.ListActivities();
+			var response = yield connection.send(request);
+			if (response is Response.Activities) {
+				return response.value;
+			} else if (response is Response.Error) {
+				throw new ClientError.ERROR_RESPONSE(
+					"Error response to ListActivities: %s",
+					response.value.to_string());
+			} else {
+				throw new ClientError.UNEXPECTED_RESPONSE(
+					"Unexpected response to ListActivities");
+			}
+		}
+
+		public async void log_session(string subject, ActivityType type,
+									  int minutes) throws ClientError {
+			var timestamp = new DateTime.now_utc().to_unix();
+			var request
+				= new Request.LogSession(subject, type, timestamp, minutes);
+			var response = yield connection.send(request);
+			if (response is Response.Ack) {
+				return;
+			} else if (response is Response.Error) {
+				throw new ClientError.ERROR_RESPONSE(
+					"Error response to LogSession: %s",
+					response.value.to_string());
+			} else {
+				throw new ClientError.UNEXPECTED_RESPONSE(
+					"Unexpected response to LogSession");
+			}
+		}
+	}
+}

client/src/connection.vala

@@ -1,221 +1,122 @@
 namespace StudySystemClient {
 	public class Connection {
-		public signal void received(uint8[] msg);
+		public delegate void StatusCallback(bool connected);
 
+		public bool connected { get; private set; }
+
+		private StatusCallback status_callback;
 		private SessionManager session_manager;
+		private TransactionManager transaction_manager;
 		private Worker worker;
 
-		public Connection(string cert_dir) throws Error {
+		public Connection(string cert_dir,
+						  owned StatusCallback status_callback)
+		throws Error {
 			var loopback = new InetAddress.loopback(SocketFamily.IPV6);
 			var session_factory
 				= new SessionFactory(loopback, 12888, cert_dir);
+			this.status_callback = (owned) status_callback;
 			session_manager = new SessionManager(
-				session_factory, (msg) => {
-					var msg_copy = new uint8[msg.length];
-					Memory.copy(msg_copy, msg, msg.length);
-					Idle.add(() => {
-							received(msg_copy);
-							return false;
-						}, GLib.Priority.DEFAULT_IDLE);
-				});
+				session_factory, (msg) => receive(msg),
+				(connected) => update_status(connected));
+			transaction_manager = new TransactionManager();
 			worker = new Worker(session_manager);
+			connected = true;
 		}
 
-		public void send(owned uint8[] msg) {
-			session_manager.send(msg);
+		public async Response.Body? send(Request.Body body) {
+			var transaction_id = transaction_manager.register(send.callback);
+			var request = new Request.Request(transaction_id, body);
+			session_manager.send(request.encode());
+			yield;
+			return transaction_manager.get_result(transaction_id);
+		}
+
+		private void receive(owned uint8[] msg) {
+			Response.Response response;
+			try {
+				response = new Response.Response.from_bytes(msg);
+			} catch (Response.DecodeError e) {
+				stderr.printf("Invalid response from server: %s", e.message);
+				return;
+			}
+			Idle.add(() => {
+					transaction_manager.resolve(response);
+					return false;
+				}, GLib.Priority.DEFAULT_IDLE);
+		}
+
+		private void update_status(bool connected) {
+			Idle.add(() => {
+					if (connected != this.connected) {
+						this.connected = connected;
+						status_callback(connected);
+					}
+					return false;
+				}, GLib.Priority.DEFAULT_IDLE);
 		}
 	}
 
-	private class Worker {
-		private uint TASK_PERIOD_MS = 10;
+	private class Continuation {
+		private SourceFunc callback;
+
+		public Continuation(owned SourceFunc callback) {
+			this.callback = (owned) callback;
+		}
+
+		public void resume() {
+			callback();
+		}
+	}
+
+	private class TransactionManager {
+		private uint16 next_transaction_id;
+		private HashTable<uint16, Continuation> pending;
+		private HashTable<uint16, Response.Body> results;
+
+		public TransactionManager() {
+			next_transaction_id = 0;
+			pending = new HashTable<uint16, Continuation>(null, null);
+			results = new HashTable<uint16, Response.Body>(null, null);
+		}
+
+		public uint16 register(owned SourceFunc callback) {
+			var transaction_id = next_transaction_id++;
+			pending.insert(transaction_id,
+						   new Continuation((owned) callback));
+			return transaction_id;
+		}
+
+		public void resolve(Response.Response response) {
+			var transaction_id = (uint16)response.transaction_id;
+			var continuation = pending.lookup(transaction_id);
+			if (continuation == null) {
+				stderr.printf("Response for non-pending transaction %d\n",
+							  transaction_id);
+				return;
+			}
+			results.insert(transaction_id, response.body);
+			continuation.resume();
+		}
+
+		public Response.Body? get_result(uint16 transaction_id) {
+			return results.lookup(transaction_id);
+		}
+	}
+
+	private class Worker : Periodic {
+		private const uint TASK_PERIOD_MS = 10;
 
 		private SessionManager session_manager;
-		private bool exit;
-		private Thread<void> thread;
 
 		public Worker(SessionManager session_manager) {
+			base(TASK_PERIOD_MS);
 			this.session_manager = session_manager;
-			exit = false;
-			thread = new Thread<void>("connection_worker", body);
+			start();
 		}
 
-		~Worker() {
-			exit = true;
-			thread.join();
-		}
-
-		private void body() {
-			while (!exit) {
-				session_manager.task();
-				Thread.usleep(1000 * TASK_PERIOD_MS);
-			}
-		}
-
-	}
-
-	private class SessionManager {
-		public delegate void ReceiveCallback(uint8[] msg);
-
-		private const uint INIT_RECONNECT_WAIT_MS = 500;
-		private const uint MAX_RECONNECT_WAIT_MS = 60000;
-		private const double RECONNECT_BACKOFF = 1.6;
-
-		private SessionFactory session_factory;
-		private ReceiveCallback receive_callback;
-		private Session? session;
-		private AsyncQueue<OutgoingMessage> queue;
-		private uint reconnect_wait_ms;
-
-		public SessionManager(SessionFactory session_factory,
-							  owned ReceiveCallback receive_callback) {
-			this.session_factory = session_factory;
-			this.receive_callback = (owned) receive_callback;
-			this.session = null;
-			queue = new AsyncQueue<OutgoingMessage>();
-			reconnect_wait_ms = INIT_RECONNECT_WAIT_MS;
-		}
-
-		public void send(uint8[] msg) {
-			queue.push(new OutgoingMessage(msg));
-		}
-
-		public void task() {
-			if (session != null) {
-				var failed_msg = session.task(queue);
-				if (failed_msg != null)
-					handle_failed_msg(failed_msg);
-			} else {
-				try_start_session();
-			}
-		}
-
-		private void handle_failed_msg(OutgoingMessage msg) {
-			msg.has_failed();
-			if (msg.should_retry())
-				queue.push(msg);
-			session = null;
-		}
-
-		private void try_start_session() {
-			try {
-				session = session_factory.start_session();
-				session.received.connect(
-					(msg) => receive_callback(msg));
-				reconnect_wait_ms = INIT_RECONNECT_WAIT_MS;
-			} catch (Error _) {
-				Thread.usleep(1000 * reconnect_wait_ms);
-				update_reconnect_wait();
-			}
-		}
-
-		private void update_reconnect_wait() {
-			var new_wait = RECONNECT_BACKOFF * reconnect_wait_ms;
-			if (new_wait < MAX_RECONNECT_WAIT_MS)
-				reconnect_wait_ms = (uint)new_wait;
-			else
-				reconnect_wait_ms = MAX_RECONNECT_WAIT_MS;
-		}
-	}
-
-	private class SessionFactory {
-		private const string CA_FILENAME = "/ca.pem";
-		private const string CERT_FILENAME = "/client.pem";
-		private const uint TIMEOUT_S = 1;
-
-		private InetSocketAddress host;
-		private TlsCertificate cert;
-		private TlsDatabase ca_db;
-
-		public SessionFactory(InetAddress host_addr, uint16 host_port,
-							  string cert_dir) throws Error {
-			host = new InetSocketAddress(host_addr, host_port);
-			var cert_path = cert_dir + CERT_FILENAME;
-			cert = new TlsCertificate.from_file(cert_path);
-			var ca_path = cert_dir + CA_FILENAME;
-			var db_type = TlsBackend.get_default().get_file_database_type();
-			ca_db = Object.new(db_type, "anchors", ca_path) as TlsDatabase;
-		}
-
-		public Session start_session() throws Error {
-			var plain_client = new SocketClient();
-			plain_client.set_timeout(TIMEOUT_S);
-			var plain_connection = plain_client.connect(host);
-			var connection = TlsClientConnection.new(plain_connection, host);
-			connection.set_database(ca_db);
-			connection.set_certificate(cert);
-			connection.handshake();
-			return new Session(connection);
-		}
-	}
-
-	private class Session {
-		public signal void received(uint8[] msg);
-
-		private const uint MAX_BATCH_SIZE = 10;
-		private const uint MAX_MSG_LEN = 1024;
-
-		private TlsClientConnection connection;
-
-		public Session(TlsClientConnection connection) {
-			this.connection = connection;
-		}
-
-		public OutgoingMessage? task(AsyncQueue<OutgoingMessage> queue) {
-			for (int i = 0; i < MAX_BATCH_SIZE; ++i) {
-				if (queue.length() == 0)
-					break;
-				var msg = queue.pop();
-				var success = true;
-				success &= send(msg);
-				success &= receive();
-				if (!success)
-					return msg;
-			}
-			return null;
-		}
-
-		private bool send(OutgoingMessage msg) {
-			try {
-				size_t written;
-				connection.output_stream.write_all(msg.content, out written);
-				return true;
-			} catch (IOError _) {
-				return false;
-			}
-		}
-
-		private bool receive() {
-			try {
-				var buffer = new uint8[MAX_MSG_LEN];
-				var len = connection.input_stream.read(buffer);
-				if (len <= 0)
-					return false;
-				received(buffer[0:len]);
-				return true;
-			} catch (IOError _) {
-				return false;
-			}
-		}
-	}
-
-	private class OutgoingMessage {
-		public uint8[] content { get; private set; }
-
-		private const uint MAX_FAIL_COUNT = 4;
-
-		private uint fail_count;
-
-		public OutgoingMessage(owned uint8[] content) {
-			this.content = (owned)content;
-			fail_count = 0;
-		}
-
-		public void has_failed() {
-			++fail_count;
-		}
-
-		public bool should_retry() {
-			return fail_count < MAX_FAIL_COUNT;
+		protected override void task() {
+			session_manager.task();
 		}
 	}
 }

client/src/der.vala

@@ -71,8 +71,8 @@ namespace StudySystemClient.Der {
 	}
 
 	public abstract class Datum {
-		internal uint8 type;
-		internal uint8[] content;
+		protected uint8 type;
+		protected uint8[] content;
 
 		public uint8[] encode() {
 			var buffer = new ByteArray();

client/src/iterable_box.vala

@@ -0,0 +1,52 @@
+namespace StudySystemClient {
+	public class IterableBox<T> : Gtk.Box {
+		private List<T> elements;
+
+		public IterableBox(Gtk.Orientation orientation, int spacing) {
+			this.orientation = orientation;
+			this.spacing = spacing;
+			elements = new List<T>();
+		}
+
+		public new void append(T element) {
+			elements.append(element);
+			base.append(element as Gtk.Widget);
+		}
+
+		public new void remove(T element) {
+			elements.remove(element);
+			base.remove(element as Gtk.Widget);
+		}
+
+		public Iterator<Type, T> iterator() {
+			return new Iterator<Type, T>(elements);
+		}
+
+		public void sort(CompareDataFunc<T> comparison) {
+			elements.sort_with_data(comparison);
+			foreach (var element in elements)
+				reorder_child_after(element as Gtk.Widget, null);
+		}
+
+		public class Iterator<Type, T> {
+			private unowned List<T> head;
+			private unowned T value;
+
+			public Iterator(List<T> elements) {
+				head = elements;
+			}
+
+			public bool next() {
+				if (head.is_empty())
+					return false;
+				value = head.data;
+				head = head.next;
+				return true;
+			}
+
+			public unowned T get() {
+				return value;
+			}
+		}
+	}
+}

client/src/list_view.vala

@@ -0,0 +1,20 @@
+namespace StudySystemClient {
+	public class ListView<T> : Gtk.Box {
+		protected IterableBox<T> container;
+
+		public ListView() {
+			hexpand = vexpand = true;
+			margin_top = margin_bottom = margin_start = margin_end = 0;
+
+			container = new IterableBox<T>(Gtk.Orientation.VERTICAL, 6);
+			container.valign = Gtk.Align.START;
+
+			var scrolled_window = new Gtk.ScrolledWindow();
+			scrolled_window.hscrollbar_policy = Gtk.PolicyType.NEVER;
+			scrolled_window.hexpand = scrolled_window.vexpand = true;
+			scrolled_window.set_child(container);
+
+			append(scrolled_window);
+		}
+	}
+}

client/src/main.vala

@@ -14,8 +14,8 @@ namespace StudySystemClient {
 					css_provider,
 					Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION);
 
-				var connection = new Connection(Config.CERT_DIR);
-				var main_window = new MainWindow(this, connection);
+				var client = new Client(Config.CERT_DIR);
+				var main_window = new MainWindow(this, client);
 				main_window.present();
 			} catch (Error e) {
 				stderr.printf("Failed to initialize: %s\n", e.message);

client/src/main_window.vala

@@ -1,23 +1,49 @@
 namespace StudySystemClient {
 	public class MainWindow : Gtk.ApplicationWindow {
-		private Connection connection;
-
-		public MainWindow(Gtk.Application app, Connection connection) {
+		public MainWindow(Gtk.Application app, Client client) {
 			Object(application: app);
 
 			default_width = 360;
 			default_height = 580;
 
-			this.connection = connection;
-
 			var header_bar = new Gtk.HeaderBar();
 			var title = new Gtk.Label("Study System Client");
 			title.add_css_class("title");
 			header_bar.title_widget = title;
 			set_titlebar(header_bar);
 
-			var activities_view = new ActivitiesView();
-			set_child(activities_view);
+			var connection_indicator = new ConnectionIndicator(client);
+			var activities_view = new ActivitiesView(client);
+
+			var content = new Gtk.Box(Gtk.Orientation.VERTICAL, 0);
+			content.append(connection_indicator);
+			content.append(activities_view);
+
+			set_child(content);
+		}
+	}
+
+	private class ConnectionIndicator : Gtk.Box {
+		public ConnectionIndicator(Client client) {
+			var icon
+				= new Gtk.Image.from_icon_name("network-offline-symbolic");
+			var label = new Gtk.Label("Disconnected");
+
+			var content = new Gtk.Box(Gtk.Orientation.HORIZONTAL, 8);
+			content.margin_top = content.margin_bottom
+				= content.margin_start = content.margin_end = 12;
+			content.hexpand = true;
+			content.halign = Gtk.Align.CENTER;
+			content.append(icon);
+			content.append(label);
+
+			var revealer = new Gtk.Revealer();
+			revealer.set_child(content);
+			append(revealer);
+
+			client.connection_status.connect((connected) => {
+					revealer.reveal_child = !connected;
+				});
 		}
 	}
 }

client/src/meson.build

@@ -11,9 +11,19 @@ lib = library(
   'study-system-client',
   sources: files(
     'activities_view.vala',
+    'activity.vala',
+    'activity_card.vala',
+    'client.vala',
     'connection.vala',
     'der.vala',
+    'iterable_box.vala',
+    'list_view.vala',
     'main_window.vala',
+    'periodic.vala',
+    'refresher.vala',
+    'request.vala',
+    'response.vala',
+    'session_manager.vala',
   ) + resources,
   dependencies: [gtk_dep],
   vala_vapi: 'study-system-client.vapi',

client/src/periodic.vala

@@ -0,0 +1,35 @@
+namespace StudySystemClient {
+	public abstract class Periodic {
+		private uint period_ms;
+		private bool exit;
+		private Thread<void> thread;
+
+		protected Periodic(uint period_ms) {
+			this.period_ms = period_ms;
+			exit = true;
+		}
+
+		~Periodic() {
+			if (!exit) {
+				exit = true;
+				thread.join();
+			}
+		}
+
+		protected abstract void task();
+
+		public void start() {
+			if (exit) {
+				exit = false;
+				thread = new Thread<void>("Periodic task", body);
+			}
+		}
+
+		private void body() {
+			while (!exit) {
+				task();
+				Thread.usleep(1000 * period_ms);
+			}
+		}
+	}
+}

client/src/refresher.vala

@@ -0,0 +1,23 @@
+namespace StudySystemClient {
+	public interface IRefreshable {
+		public abstract async void refresh();
+	}
+
+	private class Refresher : Periodic {
+		private weak IRefreshable target;
+
+		public Refresher(IRefreshable target, uint period_ms) {
+			base(period_ms);
+			this.target = target;
+		}
+
+		protected override void task() {
+			if (target != null) {
+				Idle.add(() => {
+						target.refresh.begin();
+						return false;
+					});
+			}
+		}
+	}
+}

client/src/request.vala

@@ -0,0 +1,54 @@
+namespace StudySystemClient.Request {
+	public class Request {
+		private Der.Datum datum;
+
+		public Request(uint16 transaction_id, Body body) {
+			datum = new Der.Sequence(
+				{ new Der.Integer(transaction_id), body.datum });
+		}
+
+		public uint8[] encode() {
+			return datum.encode();
+		}
+	}
+
+	public abstract class Body {
+		protected enum Tag {
+			PING = 0,
+			LIST_ACTIVITIES = 1,
+			LOG_SESSION = 2,
+		}
+
+		internal Der.Datum datum;
+
+		protected Body(Tag tag, Der.Datum datum) {
+			this.datum = new Der.Choice(tag, datum);
+		}
+	}
+
+	public class Ping : Body {
+		public Ping() {
+			base(Tag.PING, new Der.Null());
+		}
+	}
+
+	public class ListActivities : Body {
+		public ListActivities() {
+			base(Tag.LIST_ACTIVITIES, new Der.Null());
+		}
+	}
+
+	public class LogSession : Body {
+		public LogSession(string subject, ActivityType type,
+						  int64 timestamp, int minutes)
+		{
+			var fields = new Der.Datum[] {
+				new Der.Utf8String(subject),
+				new Der.Enumerated((int)type),
+				new Der.Integer(timestamp),
+				new Der.Integer(minutes),
+			};
+			base(Tag.LOG_SESSION, new Der.Sequence(fields));
+		}
+	}
+}

client/src/response.vala

@@ -0,0 +1,176 @@
+namespace StudySystemClient.Response {
+	public class Response {
+		public int transaction_id { get; private set; }
+		public Body body { get; private set; }
+
+		public Response.from_bytes(uint8[] bytes) throws DecodeError {
+			Der.Sequence sequence;
+			try {
+				sequence = Der.decode(bytes) as Der.Sequence;
+			} catch (Der.DecodeError e) {
+				throw new DecodeError.INVALID_RESPONSE(
+					"Response was not valid DER: " + e.message);
+			}
+			if (sequence == null) {
+				throw new DecodeError.INVALID_RESPONSE(
+					"Response was not a SEQUENCE");
+			}
+			if (sequence.value.length < 2) {
+				throw new DecodeError.INVALID_RESPONSE(
+					"Too few fields in Response: %u (expected 2)",
+					sequence.value.length);
+			}
+			var id_datum = sequence.value[0] as Der.Integer;
+			if (id_datum == null) {
+				throw new DecodeError.INVALID_RESPONSE(
+					"Response transactionId was not an INTEGER");
+			}
+			transaction_id = (int)id_datum.value;
+			body = Body.from_datum(sequence.value[1]);
+		}
+	}
+
+	public errordomain DecodeError {
+		INVALID_BODY,
+		INVALID_RESPONSE,
+		NOT_IMPLEMENTED,
+	}
+
+	public abstract class Body {
+		protected enum Tag {
+			ERROR = 0,
+			ACK = 1,
+			ACTIVITIES = 2,
+		}
+
+		internal static Body from_datum(Der.Datum datum) throws DecodeError {
+			var choice = datum as Der.Choice;
+			if (choice == null) {
+				throw new DecodeError.INVALID_BODY(
+					"ResponseBody was not a CHOICE");
+			}
+			switch (choice.id) {
+			case Tag.ERROR:
+				return new Error.from_datum(choice.value);
+			case Tag.ACK:
+				return new Ack.from_datum(choice.value);
+			case Tag.ACTIVITIES:
+				return new Activities.from_datum(choice.value);
+			default:
+				throw new DecodeError.INVALID_BODY(
+					"Invalid ResponseBody tag");
+			}
+		}
+	}
+
+	public class Error : Body {
+		public enum Value {
+			INVALID_REQUEST = 0,
+			INVALID_ARGUMENTS = 1,
+			SERVER_ERROR = 2,
+
+			COUNT;
+
+			public string to_string() {
+				switch (this) {
+				case INVALID_REQUEST:
+					return "Invalid request";
+				case INVALID_ARGUMENTS:
+					return "Invalid arguments";
+				case SERVER_ERROR:
+					return "Server error";
+				default:
+					return "Unknown error";
+				}
+			}
+		}
+
+		public Value value { get; private set; }
+
+		internal Error.from_datum(Der.Datum datum) throws DecodeError {
+			var enumerated = datum as Der.Enumerated;
+			if (enumerated == null) {
+				throw new DecodeError.INVALID_BODY(
+					"Error was not an ENUMERATED");
+			}
+			if (enumerated.value < 0 || enumerated.value >= Value.COUNT) {
+				throw new DecodeError.INVALID_BODY(
+					"Error type was not in range 0..$(Value.COUNT)");
+			}
+			value = (Value)enumerated.value;
+		}
+	}
+
+	public class Ack : Body {
+		internal Ack.from_datum(Der.Datum datum) throws DecodeError {
+			var @null = datum as Der.Null;
+			if (@null == null) {
+				throw new DecodeError.INVALID_BODY("Ack was not NULL");
+			}
+		}
+	}
+
+	public class Activities : Body {
+		public Array<Activity> value { get; private set; }
+
+		internal Activities.from_datum(Der.Datum datum) throws DecodeError {
+			value = new Array<Activity>();
+			if (datum is Der.Sequence) {
+				foreach (var activity_datum in datum.value)
+					value.append_val(activity_from_datum(activity_datum));
+			} else {
+				throw new DecodeError.INVALID_BODY(
+					"Activities was not a SEQUENCE");
+			}
+		}
+
+		private static Activity activity_from_datum(Der.Datum datum)
+			throws DecodeError {
+			if (datum is Der.Sequence) {
+				var fields = datum.value;
+				if (fields.length < 3) {
+					throw new DecodeError.INVALID_BODY(
+						"Too few fields in Activity: %u (expected 3)",
+						fields.length);
+				}
+				var subject = get_string("Activity.subject", fields[0]);
+				var activity_type
+					= get_activity_type("Activity.type", fields[1]);
+				var priority_int = get_int("Activity.priority", fields[2]);
+				var priority = (double)priority_int / 100.0;
+				return { subject, activity_type, priority };
+			} else {
+				throw new DecodeError.INVALID_BODY(
+					"Activity was not a SEQUENCE");
+			}
+		}
+
+		private static int get_int(string name, Der.Datum datum)
+			throws DecodeError {
+			if (datum is Der.Integer)
+				return (int)datum.value;
+			throw new DecodeError.INVALID_BODY(@"$name was not an INTEGER");
+		}
+
+		private static string get_string(string name, Der.Datum datum)
+			throws DecodeError {
+			if (datum is Der.Utf8String)
+				return datum.value;
+			throw new DecodeError.INVALID_BODY(
+				@"$name was not a UTF8String");
+		}
+
+		private static ActivityType get_activity_type(
+			string name, Der.Datum datum) throws DecodeError {
+			if (datum is Der.Enumerated) {
+				var value = datum.value;
+				if (0 <= value < ActivityType.COUNT)
+					return (ActivityType)value;
+				throw new DecodeError.INVALID_BODY(
+					"Invalid value for ActivityType: %lld", value);
+			}
+			throw new DecodeError.INVALID_BODY(
+				@"$name was not an ENUMERATED");
+		}
+	}
+}

client/src/session_manager.vala

@@ -0,0 +1,173 @@
+namespace StudySystemClient {
+	public class SessionManager {
+		public delegate void ReceiveCallback(owned uint8[] msg);
+
+		private const uint INIT_RECONNECT_WAIT_MS = 500;
+		private const uint MAX_RECONNECT_WAIT_MS = 30000;
+		private const double RECONNECT_BACKOFF = 1.6;
+
+		private SessionFactory session_factory;
+		private ReceiveCallback receive_callback;
+		private Connection.StatusCallback status_callback;
+		private Session? session;
+		private AsyncQueue<OutgoingMessage> queue;
+		private uint reconnect_wait_ms;
+
+		public SessionManager(
+			SessionFactory session_factory,
+			owned ReceiveCallback receive_callback,
+			owned Connection.StatusCallback status_callback) {
+			this.session_factory = session_factory;
+			this.receive_callback = (owned) receive_callback;
+			this.status_callback = (owned) status_callback;
+			this.session = null;
+			queue = new AsyncQueue<OutgoingMessage>();
+			reconnect_wait_ms = INIT_RECONNECT_WAIT_MS;
+		}
+
+		public void send(uint8[] msg) {
+			queue.push(new OutgoingMessage(msg));
+		}
+
+		public void task() {
+			if (session != null) {
+				var failed_msg = session.task(queue);
+				if (failed_msg != null)
+					handle_failed_msg(failed_msg);
+			} else {
+				try_start_session();
+			}
+		}
+
+		private void handle_failed_msg(OutgoingMessage msg) {
+			msg.has_failed();
+			if (msg.should_retry())
+				queue.push(msg);
+			session = null;
+			status_callback(false);
+		}
+
+		private void try_start_session() {
+			try {
+				session = session_factory.start_session();
+				session.received.connect((msg) => receive_callback(msg));
+				reconnect_wait_ms = INIT_RECONNECT_WAIT_MS;
+				status_callback(true);
+			} catch (Error _) {
+				status_callback(false);
+				Thread.usleep(1000 * reconnect_wait_ms);
+				update_reconnect_wait();
+			}
+		}
+
+		private void update_reconnect_wait() {
+			var new_wait = RECONNECT_BACKOFF * reconnect_wait_ms;
+			if (new_wait < MAX_RECONNECT_WAIT_MS)
+				reconnect_wait_ms = (uint)new_wait;
+			else
+				reconnect_wait_ms = MAX_RECONNECT_WAIT_MS;
+		}
+	}
+
+	public class SessionFactory {
+		private const string CA_FILENAME = "/ca.pem";
+		private const string CERT_FILENAME = "/client.pem";
+		private const uint TIMEOUT_S = 2;
+
+		private InetSocketAddress host;
+		private TlsCertificate cert;
+		private TlsDatabase ca_db;
+
+		public SessionFactory(InetAddress host_addr, uint16 host_port,
+							  string cert_dir) throws Error {
+			host = new InetSocketAddress(host_addr, host_port);
+			var cert_path = cert_dir + CERT_FILENAME;
+			cert = new TlsCertificate.from_file(cert_path);
+			var ca_path = cert_dir + CA_FILENAME;
+			var db_type = TlsBackend.get_default().get_file_database_type();
+			ca_db = Object.new(db_type, "anchors", ca_path) as TlsDatabase;
+		}
+
+		internal Session start_session() throws Error {
+			var plain_client = new SocketClient();
+			plain_client.set_timeout(TIMEOUT_S);
+			var plain_connection = plain_client.connect(host);
+			var connection = TlsClientConnection.new(plain_connection, host);
+			connection.set_database(ca_db);
+			connection.set_certificate(cert);
+			connection.handshake();
+			return new Session(connection);
+		}
+	}
+
+	private class Session {
+		public signal void received(uint8[] msg);
+
+		private const uint MAX_BATCH_SIZE = 10;
+		private const uint MAX_MSG_LEN = 1024;
+
+		private TlsClientConnection connection;
+
+		public Session(TlsClientConnection connection) {
+			this.connection = connection;
+		}
+
+		public OutgoingMessage? task(AsyncQueue<OutgoingMessage> queue) {
+			for (int i = 0; i < MAX_BATCH_SIZE; ++i) {
+				if (queue.length() == 0)
+					break;
+				var msg = queue.pop();
+				var success = true;
+				success &= send(msg);
+				success &= receive();
+				if (!success)
+					return msg;
+			}
+			return null;
+		}
+
+		private bool send(OutgoingMessage msg) {
+			try {
+				size_t written;
+				connection.output_stream.write_all(msg.content, out written);
+				return true;
+			} catch (IOError _) {
+				return false;
+			}
+		}
+
+		private bool receive() {
+			try {
+				var buffer = new uint8[MAX_MSG_LEN];
+				var len = connection.input_stream.read(buffer);
+				if (len <= 0)
+					return false;
+				received(buffer[0:len]);
+				return true;
+			} catch (IOError _) {
+				return false;
+			}
+		}
+	}
+
+	private class OutgoingMessage {
+		public uint8[] content { get; private set; }
+
+		private const uint MAX_FAIL_COUNT = 4;
+
+		private uint fail_count;
+
+		public OutgoingMessage(owned uint8[] content) {
+			this.content = (owned)content;
+			fail_count = 0;
+		}
+
+		public void has_failed() {
+			++fail_count;
+		}
+
+		public bool should_retry() {
+			return fail_count < MAX_FAIL_COUNT;
+		}
+	}
+}

client/styles.css

@@ -1,11 +1,11 @@
 .card-container {
-	background-color: mix(@theme_base_color, @theme_bg_color, 0.7);
+	background-color: color-mix(in oklab, @theme_base_color,
+								@theme_bg_color 60%);
 	padding: 6px;
 }
 
 .card {
-	border: 1px solid alpha(@theme_fg_color, 0.2);
-	box-shadow: 0 1px 2px alpha(black, 0.15);
+	box-shadow: 0 1px 2px rgba(0, 0, 0, 0.15);
 	background-color: @theme_bg_color;
 	padding: 12px 16px;
 }
@@ -14,6 +14,10 @@
 	font-weight: bold;
 }
 
+.activity-priority {
+	color: color-mix(in oklab, @theme_fg_color 60%, @theme_bg_color);
+}
+
 /*
  * The visual center (i.e. the center of the clock) of the
  * "appointment-new-symbolic" icon is slightly displaced from the

server/.gitignore

@@ -1,3 +1,4 @@
 _build/*
 *.beam
 src/StudySystemProtocol.erl
+include/*

server/asn1/StudySystemProtocol.asn1

@@ -1,11 +1,49 @@
 StudySystemProtocol DEFINITIONS EXPLICIT TAGS ::= BEGIN
 
-Request ::= CHOICE {
-	foo [0] NULL
+ActivityType ::= ENUMERATED {
+	reading(0),
+	exercises(1)
 }
 
-Response ::= CHOICE {
-	msg [0] UTF8String
+Session ::= SEQUENCE {
+	subject UTF8String,
+	type ActivityType,
+	timestamp INTEGER,
+	minutes INTEGER
+}
+
+RequestBody ::= CHOICE {
+	ping [0] NULL,
+	listActivities [1] NULL,
+	logSession [2] Session
+}
+
+Request ::= SEQUENCE {
+	transactionId INTEGER,
+	body RequestBody
+}
+
+Activity ::= SEQUENCE {
+	subject UTF8String,
+	type ActivityType,
+	priority INTEGER
+}
+
+Error ::= ENUMERATED {
+	invalidRequest(0),
+	invalidArguments(1),
+	serverError(2)
+}
+
+ResponseBody ::= CHOICE {
+	error [0] Error,
+	ack [1] NULL,
+	activities [2] SEQUENCE OF Activity
+}
+
+Response ::= SEQUENCE {
+	transactionId INTEGER,
+	body ResponseBody
 }
 
 END

server/src/session_server.erl

@@ -12,8 +12,10 @@ start_link(Socket) ->
 	gen_server:start_link(?MODULE, Socket, []).
 
 init(Socket) ->
+	ok = ssl:controlling_process(Socket, self()),
 	ok = ssl:setopts(Socket, [{active, true}]),
-	{ok, #{socket => Socket}}.
+	process_flag(trap_exit, true),
+	{ok, #{socket => Socket, transactions => #{}}}.
 
 handle_call(_Request, _From, State) ->
 	{reply, ok, State}.
@@ -21,17 +23,26 @@ handle_call(_Request, _From, State) ->
 handle_cast(_Msg, State) ->
 	{noreply, State}.
 
-handle_info({ssl, Socket, Data}, State) ->
+handle_info({ssl, Socket, Data}, State = #{transactions := Transactions}) ->
 	case 'StudySystemProtocol':decode('Request', Data) of
-		{ok, {foo, _}} ->
-			{ok, Encoded}
-				= 'StudySystemProtocol':encode('Response', {msg, "Foo"}),
-			ok = ssl:send(Socket, Encoded);
-		Result ->
-			io:format("Invalid message: ~p~n", [Result]),
-			ok
-	end,
-	{noreply, State};
+		{ok, {'Request', TransactionId, RequestBody}} ->
+			Pid = spawn_link(fun() -> handle_request(RequestBody) end),
+			NewTransactions = maps:put(Pid, TransactionId, Transactions),
+			{noreply, State#{transactions := NewTransactions}};
+		{error, {asn1, _Reason}} ->
+			send(Socket, -1, {error, invalidRequest}),
+			{noreply, State}
+	end;
+handle_info({'EXIT', Pid, Reason},
+			State = #{socket := Socket, transactions := Transactions})
+  when is_map_key(Pid, Transactions) ->
+	TransactionId = maps:get(Pid, Transactions),
+	Response = case Reason of
+				   {response, Value} -> Value;
+				   _ -> {error, serverError}
+			   end,
+	send(Socket, TransactionId, Response),
+	{noreply, State#{transactions := maps:remove(Pid, Transactions)}};
 handle_info({ssl_closed, _Socket}, State) ->
     {stop, normal, State};
 handle_info({ssl_error, _Socket, _Reason}, State) ->
@@ -44,3 +55,30 @@ terminate(_Reason, #{socket := Socket}) ->
 
 code_change(_OldVsn, State, _Extra) ->
 	{ok, State}.
+
+handle_request(Request) ->
+	timer:kill_after(500),
+	exit({response, map_request(Request)}).
+
+map_request({ping, 'NULL'}) ->
+	{ack, 'NULL'};
+map_request({listActivities, 'NULL'}) ->
+	{activities, Activities} = subject_router:get_activities(),
+	{activities,
+	 [{'Activity', Subject, Type, round(Priority * 100)}
+	  || {Subject, Type, Priority} <- Activities]};
+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 -> {ack, 'NULL'};
+		{error, _Error} -> {error, invalidArguments}
+	end;
+map_request(_) ->
+	{error, invalidArguments}.
+
+send(Socket, TransactionId, Response) ->
+	{ok, Encoded} = 'StudySystemProtocol':encode(
+					  'Response',
+					  {'Response', TransactionId, Response}),
+	ok = ssl:send(Socket, Encoded).

server/src/session_sup.erl

@@ -11,8 +11,8 @@ start_link() ->
 
 init([]) ->
 	SupFlags = #{strategy => simple_one_for_one,
-				 intensity => 10,
-				 period => 1},
+				 intensity => 5,
+				 period => 10},
 	ChildSpec = #{id => session_server,
 				  start => {session_server, start_link, []},
 				  restart => temporary,

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 +1,86 @@
+% 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, get_activities/0]).
+-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}).
+
+get_activities() ->
+	gen_server:call(?MODULE, get_activities).
+
+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}] ->
+			{reply,
+			 subject_server:log_session(Pid, Type, Timestamp, Minutes),
+			 State};
+		[] ->
+			{reply, {error, invalid_subject}, State}
+	end;
+handle_call(get_activities, _From,
+			State = #{subject_table := SubjectTable}) ->
+	Pids = lists:flatten(ets:match(SubjectTable, {'_', '$1'})),
+	Activities = lists:flatmap(
+				   fun(Pid) -> subject_server:get_activities(Pid) end,
+				   Pids),
+	{reply, {activities, Activities}, State};
+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} = subject_server:get_subject(Pid),
+		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 +1,60 @@
+% Copyright (c) Camden Dixie O'Brien
+% SPDX-License-Identifier: AGPL-3.0-only
+
+-module(subject_server).
+-behaviour(gen_server).
+
+-export([start_link/1, get_subject/1, get_activities/1, log_session/4]).
+-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, []).
+
+get_subject(Pid) ->
+	gen_server:call(Pid, get_subject).
+
+get_activities(Pid) ->
+	gen_server:call(Pid, get_activities).
+
+log_session(Pid, Type, Timestamp, Minutes) ->
+	gen_server:call(Pid, {log_session, {Type, Timestamp, Minutes}}).
+
+init(Subject) ->
+	pg:join(study_system_server, subject_servers, self()),
+	{ok, #{subject => Subject,
+		   priorities => #{reading => rand:uniform(),
+						   exercises => rand:uniform()}}}.
+
+handle_call(get_subject, _From, State = #{subject := Subject}) ->
+	{reply, {subject, Subject}, State};
+handle_call(get_activities, _From,
+			State = #{subject := Subject,
+					  priorities := #{reading := ReadingPriority,
+									  exercises := ExercisesPriority}}) ->
+	Reading = {Subject, reading, ReadingPriority},
+	Exercises = {Subject, exercises, ExercisesPriority},
+	{reply, [Reading, Exercises], State};
+handle_call({log_session, {Type, Timestamp, Minutes}}, _From,
+			State = #{subject := Subject, priorities := Priorities}) ->
+	case Priorities of
+		#{Type := Priority} ->
+			UpdatedPriorities = Priorities#{Type := Priority * 0.667},
+			{reply, ok, State#{priorities := UpdatedPriorities}};
+		_ ->
+			{reply, {error, invalid_type}, State}
+	end;
+handle_call(_Request, _From, State) ->
+	{reply, ok, State}.
+
+handle_cast(_Msg, State) ->
+	{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]).

server/src/tcp_server.erl

@@ -41,8 +41,7 @@ handle_info(accept, State = #state{socket = Socket}) ->
 handle_info({handshake, TlsSocket}, State) ->
 	case ssl:handshake(TlsSocket, 5000) of
 		{ok, ClientSocket} ->
-			{ok, Pid} = session_sup:start_session(ClientSocket),
-			ok = ssl:controlling_process(ClientSocket, Pid);
+			{ok, _Pid} = session_sup:start_session(ClientSocket);
 		{error, _Reason} ->
 			ok
 	end,