Add error message support and reporting on all commands.

12 files changed, 600 insertions, 623 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index d70301c..c8a6560 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -31,6 +31,8 @@ muniacli_SOURCES = \
 
 EXTRA_DIST = \
 	connectionhandler.h \
+	errorcodes.h \
+	exceptions.h \
 	http.h \
 	message.h \
 	messageparser.h \
diff --git a/src/errorcodes.h b/src/errorcodes.h
new file mode 100644
index 0000000..e305441
--- /dev/null
+++ b/src/errorcodes.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set et sw=2 ts=2: */
+/***************************************************************************
+ *            errorcodes.h
+ *
+ *  Fri Jul  3 13:19:18 CEST 2020
+ *  Copyright 2020 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Munia.
+ *
+ *  Munia is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Munia is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Munia; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#pragma once
+
+enum class ErrorCode
+{
+	Ok                     =  0,
+	LoginFailed            =  1,
+	Unauthorized           =  2,
+	MissingParent          =  4, // create
+	NoSuchId               =  6, // create  remove
+	IdAlreadyExists        =  7, // create
+	ProtectedNode          =  8, //         remove
+	NewParentIsSelf        =  9, // move
+	NewParentIsChildOfSelf = 10, // move
+	WrongNumberOfArguments = 11,
+	System                 = 41,
+	Unknown                = 42,
+};
diff --git a/src/exceptions.h b/src/exceptions.h
new file mode 100644
index 0000000..79f1113
--- /dev/null
+++ b/src/exceptions.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set et sw=2 ts=2: */
+/***************************************************************************
+ *            exceptions.h
+ *
+ *  Fri Jul  3 13:36:49 CEST 2020
+ *  Copyright 2020 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Munia.
+ *
+ *  Munia is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Munia is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Munia; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#pragma once
+
+#include "message.h"
+#include "errorcodes.h"
+
+namespace Error
+{
+
+struct MissingParent
+	: public ErrorMessage
+{
+	MissingParent()
+	{
+		code = ErrorCode::MissingParent;
+		msg = "Parent node does not exist.";
+	}
+};
+
+struct NoSuchId
+	: public ErrorMessage
+{
+	NoSuchId()
+	{
+		code = ErrorCode::NoSuchId;
+		msg = "Node does not exist.";
+	}
+};
+
+struct IdAlreadyExists
+	: public ErrorMessage
+{
+	IdAlreadyExists()
+	{
+		code = ErrorCode::IdAlreadyExists;
+		msg = "Id already exists.";
+	}
+};
+
+struct ProtectedNode
+	: public ErrorMessage
+{
+	ProtectedNode()
+	{
+		code = ErrorCode::ProtectedNode;
+		msg = "Node is protected.";
+	}
+};
+
+struct NewParentIsSelf
+	: public ErrorMessage
+{
+	NewParentIsSelf()
+	{
+		code = ErrorCode::NewParentIsSelf;
+		msg = "New parent is the node itself.";
+	}
+};
+struct NewParentIsChildOfSelf
+	: public ErrorMessage
+{
+	NewParentIsChildOfSelf()
+	{
+		code = ErrorCode::NewParentIsChildOfSelf;
+		msg = "New parent is a child of node itself.";
+	}
+};
+
+struct System
+	: public ErrorMessage
+{
+	System(const char* message)
+	{
+		code = ErrorCode::System;
+		msg = "Unknown error occurred: ";
+		msg += message;
+	}
+};
+
+} // ::Error
diff --git a/src/message.h b/src/message.h
index 3a6afdc..8d2d12f 100644
--- a/src/message.h
+++ b/src/message.h
@@ -32,6 +32,7 @@
 #include <vector>
 
 #include "node.h"
+#include "errorcodes.h"
 
 enum class cmd
 {
@@ -99,6 +100,13 @@ struct update_t
 	std::string value;
 };
 
+struct ErrorMessage
+{
+	ErrorCode code;
+	std::string msg;
+	struct lws* wsi;
+};
+
 struct message_t
 {
 	cmd_t cmd;
@@ -111,6 +119,7 @@ struct message_t
 	remove_t remove;
 	move_t move;
 	update_t update;
+	ErrorMessage error;
 
 	NodeIdList nodes;
 
diff --git a/src/messagehandler.cc b/src/messagehandler.cc
index 9a00e46..d20c963 100644
--- a/src/messagehandler.cc
+++ b/src/messagehandler.cc
@@ -34,6 +34,8 @@
 
 #include "messageparser.h"
 
+#include "errorcodes.h"
+
 MessageList handle_msg(MessageList msgList, clientid_t wsi)
 {
 
@@ -47,11 +49,19 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 		if(m.cmd == cmd::login)
 		{
 			connection_handler.login(wsi, m.login.user, m.login.password);
+			if(!connection_handler.authenticated(wsi))
+			{
+				outmsgs.push_back(create_msg_error(ErrorCode::LoginFailed,
+				                                   "Bad username or password.", wsi));
+				continue;
+			}
 		}
 
 		// If client is not authenticated; do not continue beyond this point...
 		if(!connection_handler.authenticated(wsi))
 		{
+			outmsgs.push_back(create_msg_error(ErrorCode::Unauthorized,
+			                                   "Not authorized.", wsi));
 			continue;
 		}
 
@@ -59,12 +69,19 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 		{
 		case cmd::login:
 			// Already handled, before this switch ... case
+			INFO(messagehandler, "Handling login command\n");
 			break;
 
 		case cmd::logout:
+			INFO(messagehandler, "Handling logout command\n");
 			connection_handler.logout(wsi);
 			break;
 
+		case cmd::create_with_attributes:
+			// Never sent to the server
+			INFO(messagehandler, "Handling create_with_attributes command\n");
+			break;
+
 		case cmd::create:
 			{
 				INFO(messagehandler, "Handling create command\n");
@@ -74,9 +91,15 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 					                                  m.create.insertbeforeid);
 					outmsgs.push_back(m);
 				}
-				catch (std::exception& e)
+				catch (const ErrorMessage& e)
 				{
-					DEBUG(messagehandler, "Error creating node\n");
+					// Set client id (wsi) and forward upstream
+					outmsgs.push_back(create_msg_error(e, wsi));
+				}
+				catch (...)
+				{
+					outmsgs.push_back(create_msg_error(ErrorCode::Unknown,
+					                                   "Unknown create error", wsi));
 				}
 			}
 			break;
@@ -99,9 +122,15 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 						id++;
 					}
 				}
-				catch (std::exception& e)
+				catch (const ErrorMessage& e)
+				{
+					// Set client id (wsi) and forward upstream
+					outmsgs.push_back(create_msg_error(e, wsi));
+				}
+				catch (...)
 				{
-					DEBUG(messagehandler, "Error remove node\n");
+					outmsgs.push_back(create_msg_error(ErrorCode::Unknown,
+					                                   "Unknown remove error", wsi));
 				}
 			}
 			break;
@@ -113,7 +142,8 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 				{
 					node_t removenode = node_manager.node(m.move.id);
 					NodeIdListPair tilpair =
-						node_manager.moveNode(m.move.id, m.move.parentid, m.move.insertbeforeid);
+						node_manager.moveNode(m.move.id, m.move.parentid,
+						                      m.move.insertbeforeid);
 					node_t createnode = node_manager.node(m.move.id);
 
 					message_t removemsg = create_msg_remove(removenode);
@@ -143,24 +173,27 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 					outmsgs.push_back(removemsg);
 					outmsgs.push_back(createmsg);
 				}
-				catch (std::exception& e)
+				catch (const ErrorMessage& e)
 				{
-					DEBUG(messagehandler, "Error moving node\n");
+					// Set client id (wsi) and forward upstream
+					outmsgs.push_back(create_msg_error(e, wsi));
+				}
+				catch (...)
+				{
+					outmsgs.push_back(create_msg_error(ErrorCode::Unknown,
+					                                   "Unknown move error", wsi));
 				}
 			}
 			break;
 
 		case cmd::subscribe:
-			{
-				//connection_handler.subscribe(wsi, m.subscribe.id);
-				outmsgs.push_back(m);
-			}
+			INFO(messagehandler, "Handling subscribe command\n");
+			outmsgs.push_back(m);
 			break;
 
 		case cmd::unsubscribe:
-			//connection_handler.unsubscribe(wsi, m.subscribe.id);
+			INFO(messagehandler, "Handling unsubscribe command\n");
 			outmsgs.push_back(m);
-			DEBUG(handler, "unsubscribe: %d\n", (int)m.unsubscribe.id);
 			break;
 
 		case cmd::update:
@@ -173,24 +206,24 @@ MessageList handle_msg(MessageList msgList, clientid_t wsi)
 					                                  m.update.value);
 					outmsgs.push_back(m);
 				}
-				catch (std::exception& e)
+				catch (const ErrorMessage& e)
 				{
-					DEBUG(messagehandler, "Error updating node\n");
+					// Set client id (wsi) and forward upstream
+					outmsgs.push_back(create_msg_error(e, wsi));
+				}
+				catch (...)
+				{
+					outmsgs.push_back(create_msg_error(ErrorCode::Unknown,
+					                                   "Unknown update error", wsi));
 				}
 			}
 			break;
 
 		case cmd::error:
-			ERR(messagehandler, "An error occurred.\n");
-			break;
-
-		default:
-			WARN(messagehandler, "!!! Unknown command %d\n", m.cmd);
+			INFO(messagehandler, "Handling error command\n");
+			outmsgs.push_back(m); // Just forward the error message
 			break;
 		}
-		node_manager.tree.toStdOut();
-		DEBUG(messagehandler, "%d affected nodes registered\n",
-		      (int)m.nodes.size());
 	}
 
 	return outmsgs;
diff --git a/src/messageparser.cc b/src/messageparser.cc
index 7393c5c..b0a2a6f 100644
--- a/src/messageparser.cc
+++ b/src/messageparser.cc
@@ -30,6 +30,7 @@
 #include <list>
 #include <vector>
 #include <map>
+#include <cassert>
 
 #include <hugin.hpp>
 
@@ -156,7 +157,8 @@ static nodeid_t getId(std::map<std::string, nodeid_t> &sym, std::string token)
 
 inline static void create_msg_list(MsgTokensList& msgTokensList,
                                    MessageList& msgList,
-                                   bool clientmode)
+                                   bool clientmode,
+                                   struct lws* wsi)
 {
 	size_t origin = 0;
 	if(clientmode)
@@ -174,6 +176,8 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 		//malformed msg
 		if(t.size() < origin+1)
 		{
+			msgList.push_back(create_msg_error(ErrorCode::Unknown,
+			                                   "malformed message", wsi));
 			continue;
 		}
 
@@ -192,7 +196,13 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 		else if(t[origin] == "remove") m.cmd = cmd::remove;
 		else if(t[origin] == "move") m.cmd = cmd::move;
 		else if(t[origin] == "update") m.cmd = cmd::update;
-		else m.cmd = cmd::error;
+		else if(t[origin] == "error") m.cmd = cmd::error;
+		else
+		{
+			msgList.push_back(create_msg_error(ErrorCode::Unknown,
+			                                   "unknown command", wsi));
+			continue;
+		}
 
 		switch(m.cmd)
 		{
@@ -200,7 +210,9 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 			{
 				if(t.size() != origin+1+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.subscribe.id = getId(sym, t[origin+1]);
@@ -211,7 +223,9 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 			{
 				if(t.size() != origin+1+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.unsubscribe.id = getId(sym, t[origin+1]);
@@ -223,7 +237,9 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 			{
 				if(t.size() != origin+1+2)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.login.user = t[origin+1];
@@ -235,23 +251,27 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 		case cmd::logout:
 			if(t.size() != origin+1)
 			{
-				DEBUG(msgparser, "Wrong number of parameters\n");
+				msgList.push_back(
+					create_msg_error(ErrorCode::WrongNumberOfArguments,
+					                 "Wrong number of arguments.", wsi));
 				continue;
 			}
 			break;
 
+		case cmd::create_with_attributes:
+			// Never sent to the server
+			break;
+
 		case cmd::create:
 			{
-				if(!clientmode && t.size() != origin+1+2+1)
+				if(t.size() != origin+1+2+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
-					continue;
-				}
-				if(clientmode && t.size() != origin+1+2+1)
-				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
+
 				if(clientmode)
 				{
 					m.create.id = getId(sym, t[origin+1]);
@@ -264,23 +284,29 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 					m.create.parentid = getId(sym, t[origin+2]);
 					m.create.insertbeforeid = getId(sym, t[origin+3]);
 				}
-				break;
 			}
+			break;
+
 		case cmd::remove:
 			{
 				if(t.size() != origin+1+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.remove.id = getId(sym, t[origin+1]);
 			}
 			break;
+
 		case cmd::move:
 			{
 				if(t.size() != origin+2+1+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.move.id = getId(sym, t[origin+1]);
@@ -288,11 +314,14 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 				m.move.insertbeforeid = getId(sym, t[origin+3]);
 			}
 			break;
+
 		case cmd::update:
 			{
 				if(t.size() != origin+3+1)
 				{
-					DEBUG(msgparser, "Wrong number of parameters\n");
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
 					continue;
 				}
 				m.update.id = getId(sym, t[origin+1]);
@@ -300,14 +329,27 @@ inline static void create_msg_list(MsgTokensList& msgTokensList,
 				m.update.value = t[origin+3];
 			}
 			break;
-		default:
+
+		case cmd::error:
+			{
+				if(t.size() != origin+2+1)
+				{
+					msgList.push_back(
+						create_msg_error(ErrorCode::WrongNumberOfArguments,
+						                 "Wrong number of arguments.", wsi));
+					continue;
+				}
+				m.error.code = static_cast<ErrorCode>(atoi(t[origin+1].data()));
+				m.error.msg = t[origin+2];
+			}
 			break;
 		};
+
 		msgList.push_back(m);
 	}
 }
 
-MessageList parse_msg(std::string data)
+MessageList parse_msg(std::string data, struct lws* wsi)
 {
 	DEBUG(msgparser, "Parsing: '%s'\n", data.c_str());
 
@@ -315,19 +357,19 @@ MessageList parse_msg(std::string data)
 	parse_into_msg_tokens(data, msgTokensList);
 
 	MessageList msgList;
-	create_msg_list(msgTokensList, msgList, false);
+	create_msg_list(msgTokensList, msgList, false, wsi);
 
 	return msgList;
 }
 
-MessageList parse_msg_client(std::string data)
+MessageList parse_msg_client(std::string data, struct lws* wsi)
 {
 	DEBUG(msgparser, "Parsing: '%s'\n", data.c_str());
 	MsgTokensList msgTokensList;
 	parse_into_msg_tokens(data, msgTokensList);
 
 	MessageList msgList;
-	create_msg_list(msgTokensList, msgList, true);
+	create_msg_list(msgTokensList, msgList, true, wsi);
 
 	return msgList;
 }
@@ -392,7 +434,18 @@ std::vector<std::string> msg_tostring(message_t m)
 			m.update.attribute + "\" \"" + m.update.value + "\";";
 		msgs.push_back(msg);
 		break;
-	default:
+	case cmd::error:
+		msg = "error " +
+			std::to_string(static_cast<int>(m.error.code)) + " \"" +
+			m.error.msg + "\";";
+		msgs.push_back(msg);
+		break;
+	case cmd::login:
+	case cmd::logout:
+	case cmd::subscribe:
+	case cmd::unsubscribe:
+		assert(false);
+		// The server never sends these messages so no need to serialise them.
 		break;
 	}
 
@@ -444,3 +497,23 @@ message_t create_msg_move(nodeid_t id, nodeid_t to, nodeid_t insertbeforeid)
 	m.move.insertbeforeid = insertbeforeid;
 	return m;
 }
+
+message_t create_msg_error(ErrorCode code, const std::string &msg,
+                           struct lws* wsi)
+{
+	message_t m;
+	m.cmd = cmd::error;
+	m.error.wsi = wsi;
+	m.error.code = code;
+	m.error.msg = msg;
+	return m;
+}
+
+message_t create_msg_error(const ErrorMessage &error, struct lws* wsi)
+{
+	message_t m;
+	m.cmd = cmd::error;
+	m.error = error;
+	m.error.wsi = wsi;
+	return m;
+}
diff --git a/src/messageparser.h b/src/messageparser.h
index 218f3a8..030c77b 100644
--- a/src/messageparser.h
+++ b/src/messageparser.h
@@ -27,13 +27,13 @@
  */
 #pragma once
 
-#include "message.h"
-
 #include <string>
 #include <vector>
 
-MessageList parse_msg(std::string msg);
-MessageList parse_msg_client(std::string msg);
+#include "message.h"
+
+MessageList parse_msg(std::string msg, struct lws* wsi);
+MessageList parse_msg_client(std::string msg, struct lws* wsi);
 
 //message_t create_msg(cmd::cmd_t type, node_t node);
 
@@ -52,3 +52,15 @@ message_t create_msg_create_with_attributes(node_t node,
 message_t create_msg_update(node_t node, const std::string &attr);
 message_t create_msg_remove(node_t node);
 message_t create_msg_move(nodeid_t id, nodeid_t to, nodeid_t insertbeforeid);
+
+//! Create new error message.
+//! \param code is the ErrorCode for this error message.
+//! \param msg is the error in textural form for easy presentation on the
+//!  clients.
+//! \param wsi is the client id that the error relates to (usually the one
+//!  that sent the command resulting in the error)
+message_t create_msg_error(ErrorCode code, const std::string &msg,
+                           struct lws* wsi);
+
+//! Convenience function.
+message_t create_msg_error(const ErrorMessage &error, struct lws* wsi);
diff --git a/src/munia_proto.cc b/src/munia_proto.cc
index 0508f9f..f0ec5be 100644
--- a/src/munia_proto.cc
+++ b/src/munia_proto.cc
@@ -98,8 +98,6 @@ int callback_lws_node(struct lws *wsi,
                       enum lws_callback_reasons reason,
                       void *user, void *in, size_t len)
 {
-	node_manager.tree.toStdOut();
-
 	DEBUG(proto, "Callback on %p\n", wsi);
 
 	switch (reason)
@@ -119,7 +117,8 @@ int callback_lws_node(struct lws *wsi,
 			// the position of the remove msg.
 			//
 			msgqueue_t::iterator i = msgqueue[wsi].begin();
-			while(i != msgqueue[wsi].end()) {
+			while(i != msgqueue[wsi].end())
+			{
 				message_t &msg = *i;
 				if(msg.cmd == cmd::remove)
 				{
@@ -168,10 +167,21 @@ int callback_lws_node(struct lws *wsi,
 					{
 						msgstr += " ";
 					}
-					auto msgs = msg_tostring(msg);
-					for(const auto& msg_string : msgs)
+					if(msg.cmd == cmd::error)
+					{
+						auto msgs = msg_tostring(msg);
+						for(const auto& msg_string : msgs)
+						{
+							msgstr += msg_string;
+						}
+					}
+					else
 					{
-						msgstr += std::to_string(msg.tid) + " " + msg_string;
+						auto msgs = msg_tostring(msg);
+						for(const auto& msg_string : msgs)
+						{
+							msgstr += std::to_string(msg.tid) + " " + msg_string;
+						}
 					}
 				}
 
@@ -216,7 +226,7 @@ int callback_lws_node(struct lws *wsi,
 			std::string data;
 			data.append((char*)in, len);
 
-			MessageList mlst = parse_msg(data);
+			MessageList mlst = parse_msg(data, wsi);
 			DEBUG(proto, "Handling %d incoming message\n", (int)mlst.size());
 			MessageList omsgs = handle_msg(mlst, wsi);
 			DEBUG(proto, "Handling %d outgoing messages\n", (int)omsgs.size());
@@ -224,21 +234,31 @@ int callback_lws_node(struct lws *wsi,
 			MessageList::iterator omi = omsgs.begin();
 			while(omi != omsgs.end())
 			{
-				DEBUG(proto, "Message\n");
+				DEBUG(proto, "Message %d\n", (int)omi->cmd);
 				if(omi->cmd == cmd::subscribe)
 				{
-					connection_handler.subscribe(wsi, omi->subscribe.id);
 					NodeIdList ids;
 					try
 					{
 						ids = node_manager.subNodes(omi->subscribe.id);
+						connection_handler.subscribe(wsi, omi->subscribe.id);
+					}
+					catch (const ErrorMessage& e)
+					{
+						// Set client id (wsi) and forward upstream
+						msgqueue[wsi].push_back(create_msg_error(e, wsi));
+						omi++;
+						continue;
 					}
-					catch(...)
+					catch (...)
 					{
-						DEBUG(proto, "No such node %d\n", (int)omi->subscribe.id);
+						msgqueue[wsi].push_back(
+							create_msg_error(ErrorCode::Unknown,
+							                 "Unknown subscribe error", wsi));
 						omi++;
 						continue;
 					}
+
 					NodeIdList::iterator id = ids.begin();
 					while(id != ids.end())
 					{
@@ -282,12 +302,22 @@ int callback_lws_node(struct lws *wsi,
 					{
 						ids = node_manager.subNodes(omi->unsubscribe.id);
 					}
-					catch(...)
+					catch (const ErrorMessage& e)
+					{
+						// Set client id (wsi) and forward upstream
+						msgqueue[wsi].push_back(create_msg_error(e, wsi));
+						omi++;
+						continue;
+					}
+					catch (...)
 					{
-						DEBUG(proto, "No such node %d\n", (int)omi->unsubscribe.id);
+						msgqueue[wsi].push_back(
+							create_msg_error(ErrorCode::Unknown,
+							                 "Unknown subscribe error", wsi));
 						omi++;
 						continue;
 					}
+
 					NodeIdList::reverse_iterator id = ids.rbegin();
 					while(id != ids.rend())
 					{
@@ -302,6 +332,10 @@ int callback_lws_node(struct lws *wsi,
 					}
 
 				}
+				else if(omi->cmd == cmd::error)
+				{
+					msgqueue[omi->error.wsi].push_back(*omi);
+				}
 				else
 				{
 					DEBUG(proto, "%d nodes affected by command\n",
diff --git a/src/nodemanager.cc b/src/nodemanager.cc
index e94c798..e10b64d 100644
--- a/src/nodemanager.cc
+++ b/src/nodemanager.cc
@@ -27,10 +27,10 @@
  */
 #include "nodemanager.h"
 
-#include <stdio.h>
-
 #include "hugin.hpp"
 
+#include "exceptions.h"
+
 // Global NodeManager object.
 NodeManager node_manager;
 
@@ -41,21 +41,15 @@ NodeManager node_manager;
 #define PROJECTS_ID 4
 #define FIRST_NODE_ID 10
 
-static bool isProtected(nodeid_t id)
-{
-	return id < FIRST_NODE_ID;
-}
-
 NodeManager::NodeManager()
 {
-	idCount = FIRST_NODE_ID;
 }
 
 NodeManager::~NodeManager()
 {
 }
 
-void NodeManager::init(std::string filename)
+void NodeManager::init(const std::string& filename)
 {
 	DEBUG(nodemgr, "Reading nodes from file: %s\n", filename.c_str());
 	file = filename;
@@ -103,182 +97,93 @@ void NodeManager::init(std::string filename)
 	tree.toStdOut();
 }
 
-node_t NodeManager::node(nodeid_t t)
-{
-	return tree.data(t);
-}
-
-nodeid_t NodeManager::createId()
-{
-	return tree.createId();
-}
-
-bool NodeManager::hasId(nodeid_t id)
+NodeIdList NodeManager::createNode(nodeid_t parentid, nodeid_t id,
+                                   nodeid_t insertbeforeid)
 {
-	return tree.hasId(id);
-}
-
-NodeIdListPair NodeManager::moveNode(nodeid_t id, nodeid_t to, nodeid_t beforeId)
-	throw (std::exception)
-{
-	if(isProtected(id))
-	{
-		return NodeIdListPair();
-	}
-
-	if(id == to)
-	{
-		throw std::exception(); // Node and new parent are the same node.
-	}
-
-	//node_t t = tree.data(id);
-
-	// Make sure the new parent exists. This will throw an exception if it doesn't
-	//node_t t_ = tree.data(to);
-
-	//t.parentid = to;
-
-	//NodeIdList tilremove = tree.remove(id);
-	NodeIdList tilremove;
-	tilremove.push_back(id);
-	NodeIdList ancestors = tree.ancestorList(id);
-	tilremove.insert(tilremove.end(), ancestors.begin(), ancestors.end());
-
-	//  NodeIdList tilcreate = tree.insertAsChild(to, id, t);
-	NodeIdList tilcreate;
-	tilcreate.push_back(to);
-	ancestors = tree.ancestorList(to);
-	tilcreate.insert(tilcreate.end(), ancestors.begin(), ancestors.end());
-
-	tree.move(id, to, beforeId);
+	NodeIdList affectedNodes;
 
-	NodeIdListPair tilpair;
-	tilpair.first = tilremove;
-	tilpair.second = tilcreate;
+	node_t t;
+	t.attributes["title"] = "";
+	t.id = id;
 
+	affectedNodes = tree.insertAsChild(parentid, id, t, insertbeforeid);
 	flushNodes();
 
-	return tilpair;
+	return affectedNodes;
 }
 
-NodeIdList NodeManager::removeNode(nodeid_t id)
-	throw (std::exception)
+NodeIdList NodeManager::updateNode(nodeid_t id, const std::string &name,
+                                   const std::string &value)
 {
 	if(isProtected(id))
 	{
-		return NodeIdList();
+		throw Error::ProtectedNode();
 	}
 
 	NodeIdList affectedNodes;
 
-	if(tree.bfs(id).size() > 1)
-	{
-		throw std::exception();
-	}
-
-	try
-	{
-		affectedNodes = tree.remove(id);
-	}
-	catch(std::exception& e)
-	{
-		throw e;
-	}
+	affectedNodes = tree.updateData(id, name, value);
 
 	flushNodes();
 
 	return affectedNodes;
 }
 
-NodeIdList NodeManager::updateNode(nodeid_t id, const std::string &name,
-                                   const std::string &value)
-	throw (std::exception)
+NodeIdList NodeManager::removeNode(nodeid_t id)
 {
 	if(isProtected(id))
 	{
-		return NodeIdList();
+		throw Error::ProtectedNode();
 	}
 
 	NodeIdList affectedNodes;
-
-	try
-	{
-		affectedNodes = tree.updateData(id, name, value);
-	}
-	catch(std::exception& e)
-	{
-		throw e;
-	}
-
+	affectedNodes = tree.remove(id);
 	flushNodes();
 
 	return affectedNodes;
 }
 
-NodeIdList NodeManager::createNode(nodeid_t parentid, nodeid_t id, nodeid_t insertbeforeid)
-	throw (std::exception)
+NodeIdListPair NodeManager::moveNode(nodeid_t id, nodeid_t to,
+                                     nodeid_t beforeId)
 {
-	if(hasId(id))
+	if(isProtected(id))
 	{
-		// Id alerady in tree, ignore
-		return {};
+		throw Error::ProtectedNode();
 	}
 
-	NodeIdList affectedNodes;
+	NodeIdList tilremove;
+	tilremove.push_back(id);
+	NodeIdList ancestors = tree.ancestorList(id);
+	tilremove.insert(tilremove.end(), ancestors.begin(), ancestors.end());
 
-	node_t t;
-	t.attributes["title"] = "";
-	t.id = id;
+	NodeIdList tilcreate;
+	tilcreate.push_back(to);
+	ancestors = tree.ancestorList(to);
+	tilcreate.insert(tilcreate.end(), ancestors.begin(), ancestors.end());
 
-	try
-	{
-		affectedNodes = tree.insertAsChild(parentid, id, t, insertbeforeid);
-	}
-	catch(std::exception& e)
-	{
-		throw e;
-	}
+	tree.move(id, to, beforeId); // TODO: Use node list pair from return value
 
 	flushNodes();
 
-	return affectedNodes;
+	return {tilremove, tilcreate};
 }
 
 NodeIdList NodeManager::subNodes(nodeid_t t)
-	throw (std::exception)
 {
 	NodeIdList affectedNodes;
-
-	try
-	{
-		affectedNodes = tree.bfs(t);
-	}
-	catch(std::exception& e)
-	{
-		throw e;
-	}
-
+	affectedNodes = tree.bfs(t);
 	return affectedNodes;
 }
 
-//NodeIdList NodeManager::ancestorList(nodeid_t id)
-//	throw (std::exception)
-//{
-//	NodeIdList ancestors;
-//
-//	try
-//	{
-//		ancestors = tree.ancestorList(id);
-//		goto finish;
-//	}
-//	catch(std::exception& e)
-//	{
-//		throw e;
-//	}
-//
-//finish:
-//	return ancestors;
-//}
+node_t NodeManager::node(nodeid_t t)
+{
+	return tree.data(t);
+}
+
+nodeid_t NodeManager::createId()
+{
+	return tree.createId();
+}
 
 void NodeManager::flushNodes()
 {
@@ -292,122 +197,12 @@ void NodeManager::flushNodes()
 	fclose(fp);
 }
 
-#if 0
-NodeList nodelist;
-
-node_t create_node(std::string title, std::string desc)
-{
-	node_t t;
-	t.parent_id = current_id_count();
-	t.attributes["title"] = title;
-	t.desc = desc;
-	t.id = id_count; id_count++;
-
-	return t;
-}
-
-NodeList load_nodelist_from_file(std::string file)
-{
-	NodeList list;
-
-	// create MuniaDb class which handles nodes, db-flush and db-init.
-
-	return list;
-}
-
-bool save_nodelist_to_file(NodeList list, std::string file)
-{
-	FILE* fp;
-
-	if(! (fp = fopen(file.c_str(), "w")))
-	{
-		return false;
-	}
-
-	if(!fprintf(fp, "<nodelist>\n"))
-	{
-		fclose(fp);
-		return false;
-	}
-
-	NodeList::iterator it;
-	for(it = nodelist.begin(); it != nodelist.end(); it++)
-	{
-		node_t t = *it;
-		int r = 1;
-
-		//printf("Flushing node %d\n", t.id);
-		r |= fprintf(fp, "  <node id=\"%d\" parent_id=\"%d\">\n", t.id, t.parent_id);
-		r |= fprintf(fp, "    <title>%s</title>\n", xml_encode(t.attributes["title"]).c_str());
-		r |= fprintf(fp, "    <desc>%s</desc>\n", xml_encode(t.attributes["description"]).c_str());
-		r |= fprintf(fp, "  </node>)\n");
-
-		if(!r)
-		{
-			fclose(fp);
-			return false;
-		}
-	}
-
-	if(!fprintf(fp, "</nodelist>\n"))
-	{
-		fclose(fp);
-		return false;
-	}
-
-	fclose(fp);
-	return true;
-}
-
-static void delete_node(node_t t, NodeList& graveyard);
-
-static void delete_children(node_t t, NodeList& graveyard)
-{
-	NodeList::iterator it;
-	for(it = nodelist.begin(); it != nodelist.end(); it++)
-	{
-		if(it->parent_id == t.id) {
-			delete_node(*it, graveyard);
-		}
-	}
-}
-
-static void delete_node(node_t t, NodeList& graveyard)
+bool NodeManager::hasId(nodeid_t id)
 {
-	NodeList::iterator it;
-	for(it = nodelist.begin(); it != nodelist.end(); it++)
-	{
-		if(it->id == t.id)
-		{
-			break;
-		}
-	}
-
-	if(it != nodelist.end())
-	{
-		graveyard.push_back(*it);
-		delete_children(*it, graveyard);
-	}
+	return tree.hasId(id);
 }
 
-void delete_node(int id, NodeList& graveyard)
+bool NodeManager::isProtected(nodeid_t id) const
 {
-	node_t t;
-	t.id = id;
-	delete_node(t, graveyard);
-
-	for(NodeList::iterator it = graveyard.begin();
-	    it != graveyard.end(); it++)
-	{
-		for(NodeList::iterator it_tl = nodelist.begin();
-		    it_tl != nodelist.end(); it_tl++)
-		{
-			if(it_tl->id == it->id)
-			{
-				nodelist.erase(it_tl);
-				break;
-			}
-		}
-	}
+	return id < FIRST_NODE_ID;
 }
-#endif
diff --git a/src/nodemanager.h b/src/nodemanager.h
index 85b7955..8909eb1 100644
--- a/src/nodemanager.h
+++ b/src/nodemanager.h
@@ -27,10 +27,8 @@
  */
 #pragma once
 
-#include <list>
 #include <string>
-#include <stdio.h>
-#include <exception>
+#include <utility>
 
 #include "node.h"
 #include "nodetree.h"
@@ -43,173 +41,31 @@ public:
 	NodeManager();
 	~NodeManager();
 
-	void init(std::string filename);
+	void init(const std::string& filename);
 
-	NodeIdList createNode(nodeid_t parentid, nodeid_t id, nodeid_t insertbeforeid) throw (std::exception);
-	NodeIdList updateNode(nodeid_t id, const std::string &name,
-	                      const std::string &value) throw (std::exception);
-	NodeIdList removeNode(nodeid_t id) throw (std::exception);
+	NodeIdList createNode(nodeid_t parentid, nodeid_t id,
+	                      nodeid_t insertbeforeid);
 
-	NodeIdListPair moveNode(nodeid_t id, nodeid_t newParent, nodeid_t beforeId) throw (std::exception);
+	NodeIdList updateNode(nodeid_t id, const std::string& name,
+	                      const std::string& value);
 
-	NodeIdList subNodes(nodeid_t) throw (std::exception);
+	NodeIdList removeNode(nodeid_t id);
 
-	NodeTree tree;
+	NodeIdListPair moveNode(nodeid_t id, nodeid_t newParent, nodeid_t beforeId);
 
-	node_t node(nodeid_t t);
+	NodeIdList subNodes(nodeid_t id);
 
-	void flushNodes();
+	node_t node(nodeid_t t);
 
 	nodeid_t createId();
-	bool hasId(nodeid_t id);
 
 private:
-	//  NodeIdList ancestorList(nodeid_t node);
-	nodeid_t idCount;
-	node_t nextNode();
+	void flushNodes();
+	bool hasId(nodeid_t id);
+	bool isProtected(nodeid_t id) const;
 
 	std::string file;
+	NodeTree tree;
 };
 
-#ifndef FOOBAR
 extern NodeManager node_manager;
-#endif
-
-
-#if 0
-
-/*
-Node:
-  id
-  subnodes
-//  tags
-  title
-  description
-//  primary_assignment
-//  secondary_assignment
-
-
-Protocol:
-
-Server -> client:
- update [id] [title] [description];
- move [id] [x] [y];
- add [id] [title] [description] [x] [y];
- del [id]
-
-Client -> server:
- update [id] [title] [description];
- move [id] [x] [y];
- add [title] [description] [x] [y];
- del [id]
-
-title and description are " encapsulated utf-8 string with " escaped with a backslash.
-x and y are integers as strings
-id are an integer as a string
- */
-
-/*
-typedef struct {
-  int x, y;
-  int id;
-  std::string title;
-  std::string desc;
-} node_t;
-*/
-/*
-protocol:
-  add_node title description parent_id
-  del_node id
-  update_node id title description
-  move_node id parent
-  copy_node id parent
-*/
-
-
-
-//typedef std::list<node_t> NodeList;
-
-class CompareByParentid
-{
-public:
-	bool operator()(const node_t &a, const node_t &b) const
-	{
-		return a.parent_id < b.parent_id;
-	}
-};
-
-class NodeList
-	: public std::list<node_t>
-{
-public:
-	NodeList() {}
-	~NodeList(){}
-
-	void insert(node_t t)
-	{
-		if(t.id == t.parent_id)
-		{
-			return;
-		}
-		printf("inserting node %d with parent %d\n", t.id, t.parent_id);
-
-		if(t.parent_id == -1)
-		{
-			std::list<node_t>::push_front(t);
-			return;
-		}
-
-		std::list<node_t>::iterator it;
-		for(it = begin(); it != end(); ++it)
-		{
-			printf("\tcomparing %d and %d\n", t.parent_id, it->id);
-			if(t.parent_id == it->id)
-			{
-				break;
-			}
-		}
-		assert(it != end());
-
-		std::list<node_t>::insert(++it, t);
-
-		//std::list<node_t>::push_back(t);
-		//std::list<node_t>::sort(CompareByParentid());
-	}
-
-	void move(node_t t)
-	{
-		std::list<node_t>::iterator it;
-		for(it = begin(); it != end(); it++)
-		{
-			if(t.id == it->id)
-			{
-				break;
-			}
-		}
-		assert(it != end());
-		//if(it != end())
-		//{
-		std::list<node_t>::erase(it);
-		//}
-		insert(t);
-	}
-
-	void push_back(node_t t)
-	{
-		insert(t);
-	}
-
-private:
-	std::list<node_t> list;
-};
-
-
-extern NodeList nodelist;
-
-//typedef std::priority_queue<node_t, std::vector<node_t>, CompareByParentid> NodeList;
-
-node_t create_node(std::string title, std::string desc, /*int x, int y*/ int parent_id);
-
-NodeList load_nodelist_from_file(std::string file);
-bool save_nodelist_to_file(NodeList t, std::string file);
-#endif/*0*/
diff --git a/src/nodetree.cc b/src/nodetree.cc
index a2499ea..f0877ff 100644
--- a/src/nodetree.cc
+++ b/src/nodetree.cc
@@ -34,6 +34,7 @@
 #include "hugin.hpp"
 
 #include "xml_encode_decode.h"
+#include "exceptions.h"
 
 #define ROOT_PARENT_ID -1
 
@@ -75,22 +76,14 @@ std::string Node::toXML(std::string prefix)
 static void concatNodeIdLists(NodeIdList& pre, NodeIdList& post)
 {
 	pre.insert(pre.end(), post.begin(), post.end());
-	//for(NodeIdList::iterator it = post.begin();
-	//it != post.end(); it++)
-	//{
-	//  pre.push_back(
-	//}
 }
 
 NodeTree::NodeTree()
 {
-	root = NULL;
-	nextid = 10;
 }
 
 NodeTree::~NodeTree()
 {
-	// cleanup tree
 }
 
 nodeid_t NodeTree::createId()
@@ -106,7 +99,7 @@ nodeid_t NodeTree::createId()
 	return nodeid;
 }
 
-bool NodeTree::hasId(nodeid_t nodeid)
+bool NodeTree::hasId(nodeid_t nodeid) const
 {
 	return id2node.find(nodeid) != id2node.end();
 }
@@ -115,11 +108,15 @@ static nodeid_t rootid = -1;
 
 NodeIdList NodeTree::insertAsChild(nodeid_t parentid, nodeid_t id,
                                    node_t data, nodeid_t insertBeforeId)
-	throw (std::exception)
 {
 	NodeIdList affectedNodes;
 
-	// Initialize
+	if(parentid == id)
+	{
+		throw Error::NewParentIsSelf(); // Node and new parent are the same node.
+	}
+
+	// Initialized?
 	if(!root)
 	{
 		rootid = id;
@@ -130,62 +127,46 @@ NodeIdList NodeTree::insertAsChild(nodeid_t parentid, nodeid_t id,
 	}
 	else
 	{
-		try
+		if(!hasId(parentid))
 		{
-			Node* parent = id2node.at(parentid);
-			Node* child = createNode(id);
-			//DEBUG(nodetree, "!!!!!!!id in insert: %d\n", data.id);
-			child->data = data;
-			insertChild(parent, child, insertBeforeId);
-
-			//affectedNodes.push_back(parentid);
-			affectedNodes.push_back(id);
-			NodeIdList ancestors = ancestorList(id);
-			concatNodeIdLists(affectedNodes, ancestors);
-		}
-		catch(std::exception& e)
-		{
-			throw e;
+			throw Error::MissingParent();
 		}
+
+		Node* parent = id2node.at(parentid);
+		Node* child = createNode(id);
+
+		child->data = data;
+		insertChild(parent, child, insertBeforeId);
+		affectedNodes.push_back(id);
+
+		NodeIdList ancestors = ancestorList(id);
+		concatNodeIdLists(affectedNodes, ancestors);
 	}
 
-	//DEBUG(nodetree, "Child %d added to %d, affecting %d nodes\n",
-	//      id, parentid, affectedNodes.size());
 	return affectedNodes;
 }
 
 NodeIdList NodeTree::remove(nodeid_t id)
-	throw (std::exception)
 {
+	if(!hasId(id))
+	{
+		throw Error::NoSuchId();
+	}
+
 	NodeIdList affectedNodes;
 	affectedNodes.push_back(id);
 	NodeIdList ancestors = ancestorList(id);
 	concatNodeIdLists(affectedNodes, ancestors);
 
-	//DEBUG(nodetree, "Removing %d\n", id);
-	//DEBUG(nodetree, "!!!!!affected nodes %d\n", affectedNodes.size());
-
-	Node* node = id2node[id];
-
-	//DEBUG(nodetree, "node: %p, id %d, parent %p\n", node, node->data.id, node->parent);
+	Node* node = id2node.at(id);
 
-	//DEBUG(nodetree, "!!!!!size %d\n", node->parent->children.size());
 	node->parent->children.remove(node);
-	for(NodeList::iterator it = node->parent->children.begin();
-	    it != node->parent->children.end();
-	    it++)
-	{
-		//DEBUG(nodetree, "%p\n", *it);
-	}
-	//DEBUG(nodetree, "!!!!!size %d\n", node->parent->children.size());
 
 	NodeIdList idlist = bfs(id);
 	NodeIdList::reverse_iterator it = idlist.rbegin();
 	while(it != idlist.rend())
 	{
 		node_t node = data(*it);
-		//Node* n = id2node[node.id];
-		//delete(n);
 		it++;
 	}
 
@@ -208,112 +189,114 @@ static bool findNode(Node *needle, Node *haystack)
 }
 
 NodeIdList NodeTree::move(nodeid_t id, nodeid_t toid, nodeid_t beforeId)
-	throw (std::exception)
 {
 	NodeIdList affectedNodes;
 
-	try
+	if(id == toid)
 	{
-		Node* child = id2node.at(id);
-		Node* newparent = id2node.at(toid);
+		throw Error::NewParentIsSelf(); // Node and new parent are the same node.
+	}
 
-		// Test if new parent is a child of the node itself...
-		if(findNode(newparent, child))
-		{
-			throw std::exception();
-		}
+	if(!hasId(id))
+	{
+		throw Error::NoSuchId();
+	}
 
-		if(!child->parent)
-		{
-			throw std::exception();
-		}
+	Node* child = id2node.at(id);
 
-		child->parent->children.remove(child);
-		bool inserted{false};
-		for(auto it = newparent->children.begin();
-		    it != newparent->children.end();
-		    ++it)
-		{
-			if((*it)->id == beforeId)
-			{
-				newparent->children.insert(it, child);
-				inserted = true;
-			}
-		}
-		if(!inserted)
-		{
-			// beforeId was not found in parent - inserting last instead.
-			newparent->children.push_back(child);
-		}
+	if(!hasId(toid))
+	{
+		throw Error::MissingParent();
+	}
 
-		child->parent = newparent;
+	Node* newparent = id2node.at(toid);
 
-		affectedNodes.push_back(id);
-		//    affectedNodes.push_back(child->parent->id);
-		NodeIdList ancestors = ancestorList(id);
-		concatNodeIdLists(affectedNodes, ancestors);
-		affectedNodes.push_back(toid);
-		ancestors = ancestorList(toid);
+	// Test if new parent is a child of the node itself...
+	if(findNode(newparent, child))
+	{
+		throw Error::NewParentIsChildOfSelf();
+	}
+
+	if(!child->parent)
+	{
+		throw Error::System("Node does not have a parent.");
+	}
+
+	child->parent->children.remove(child);
+	bool inserted{false};
+	for(auto it = newparent->children.begin();
+	    it != newparent->children.end();
+	    ++it)
+	{
+		if((*it)->id == beforeId)
+		{
+			newparent->children.insert(it, child);
+			inserted = true;
+		}
 	}
-	catch(std::exception& e)
+	if(!inserted)
 	{
-		throw e;
+		// beforeId was not found in parent - inserting last instead.
+		newparent->children.push_back(child);
 	}
 
+	child->parent = newparent;
+
+	affectedNodes.push_back(id);
+
+	NodeIdList ancestors = ancestorList(id);
+	concatNodeIdLists(affectedNodes, ancestors);
+	affectedNodes.push_back(toid);
+	ancestors = ancestorList(toid);
+
 	return affectedNodes;
 }
 
 NodeIdList NodeTree::updateData(nodeid_t id, const std::string &name,
                                 const std::string &value)
-  throw (std::exception)
 {
+	if(!hasId(id))
+	{
+		throw Error::NoSuchId();
+	}
+
 	NodeIdList affectedNodes;
 
-	try
-	{
-		Node* node = id2node.at(id);
-		node->data.attributes[name] = value;
+	Node* node = id2node.at(id);
+	node->data.attributes[name] = value;
 
-		affectedNodes.push_back(id);
-		NodeIdList ancestors = ancestorList(id);
-		concatNodeIdLists(affectedNodes, ancestors);
-	}
-	catch(std::exception& e)
-	{
-		throw e;
-	}
+	affectedNodes.push_back(id);
+	NodeIdList ancestors = ancestorList(id);
+	concatNodeIdLists(affectedNodes, ancestors);
 
 	return affectedNodes;
 }
 
 node_t NodeTree::data(nodeid_t id)
-	throw (std::exception)
 {
+	if(!hasId(id))
+	{
+		throw Error::NoSuchId();
+	}
+
 	node_t t;
 
-	try
+	Node* node = id2node.at(id);
+	node_t tmp = node->data;
+	t.id = node->id;
+	t.attributes = tmp.attributes;
+
+	if(node->parent)
 	{
-		Node* node = id2node.at(id);
-		node_t tmp = node->data;
-		t.id = node->id;
-		t.attributes = tmp.attributes;
-		//DEBUG(nodetree, "!!!!t.id and tmp.id in data: %d and %d\n", t.id, tmp.id);
-		if(node->parent)
-		{
-			t.parentid = node->parent->id;
-		}
-		else
-		{
-			if(t.id != rootid)
-			{
-				throw std::exception();
-			}
-			t.parentid = -1;
-		}
+		t.parentid = node->parent->id;
 	}
-	catch(std::exception& e)
+	else
 	{
-		throw e;
+		if(t.id != rootid)
+		{
+			throw Error::System("Node has no parent, but node is not root.");
+		}
+		t.parentid = -1;
 	}
 
 	return t;
@@ -321,8 +304,12 @@ node_t NodeTree::data(nodeid_t id)
 
 // bfs search from id in tree
 NodeIdList NodeTree::bfs(nodeid_t id)
-	throw (std::exception)
 {
+	if(!hasId(id))
+	{
+		throw Error::NoSuchId();
+	}
+
 	NodeIdList lst;
 	lst.push_back(id);
 
@@ -353,35 +340,36 @@ NodeIdList NodeTree::bfs(nodeid_t id)
 }
 
 NodeIdList NodeTree::ancestorList(nodeid_t id)
-	throw (std::exception)
 {
 	NodeIdList ancestors;
 
-	try
+	if(!hasId(id))
 	{
-		Node* current = id2node.at(id);
-		while(current->parent)
-		{
-			ancestors.push_back(current->parent->id);
-			current = current->parent;
-		}
+		throw Error::NoSuchId();
 	}
-	catch(std::exception& e)
+
+	Node* current = id2node.at(id);
+	auto origin = current;
+	while(current->parent)
 	{
-		throw e;
+		ancestors.push_back(current->parent->id);
+		current = current->parent;
+		if(current == origin)
+		{
+			throw Error::System("Cycle detected.");
+		}
 	}
 
-	//DEBUG(nodetree, "Collected %d ancestors to %u\n", ancestors.size(), id);
-	//for(NodeIdList::iterator it = ancestors.begin();
-	//    it != ancestors.end(); it++)
-	//{
-	//	DEBUG(nodetree, "\tancestor %u\n", *it);
-	//}
 	return ancestors;
 }
 
 Node* NodeTree::createNode(nodeid_t id)
 {
+	if(hasId(id))
+	{
+		throw Error::IdAlreadyExists();
+	}
+
 	Node* node = new Node();
 	node->parent = NULL;
 	node->id = id;
@@ -425,6 +413,7 @@ static void printNode(Node* node, std::string prefix)
 	{
 	  return;
 	}
+
 	node_t t = node->data;
 	DEBUG(nodetree, "%s- %u - %s (%p)\n", prefix.c_str(), (int)node->id,
 	      t.attributes["title"].c_str(), node);
@@ -444,12 +433,13 @@ void NodeTree::toStdOut()
 
 std::string NodeTree::toXML()
 {
-	Node *root = id2node.at(rootid);
-
 	std::string xml;
 	xml += "<?xml version='1.0' encoding='UTF-8'?>\n";
 	xml += "<nodetree nextid=\""+id2str(nextid)+"\">\n";
-	xml += root->toXML("  ");
+	if(root)
+	{
+		xml += root->toXML("  ");
+	}
 	xml += "</nodetree>";
 
 	return xml;
diff --git a/src/nodetree.h b/src/nodetree.h
index f2f4600..41f7272 100644
--- a/src/nodetree.h
+++ b/src/nodetree.h
@@ -29,7 +29,6 @@
 
 #include <list>
 #include <map>
-#include <exception>
 
 #include "node.h"
 
@@ -54,33 +53,57 @@ public:
 	~NodeTree();
 
 	nodeid_t createId();
-	bool hasId(nodeid_t nodeid);
+	bool hasId(nodeid_t nodeid) const;
 
+	//! May throw:
+	//! - Error::MissingParent if the parent node id does not exist in the tree.
+	//! - Error::NoSuchId if the ancestorList cannot be made from the supplied id.
+	//! - Error::IdAlreadyExists if the supplied id already exists in the tree.
+	//! - Error::NewParentIsSelf if id and parentid are the same.
 	NodeIdList insertAsChild(nodeid_t parentid, nodeid_t id, node_t data,
-	                         nodeid_t insertBeforeId) throw (std::exception);
-	NodeIdList remove(nodeid_t id) throw (std::exception);
-	NodeIdList move(nodeid_t id, nodeid_t newParentId,
-	                nodeid_t insertBeforeId) throw (std::exception);
+	                         nodeid_t insertBeforeId);
+
+	//! May throw:
+	//! - Error::NoSuchId if node id does not exist.
+	//! - Error::ProtectedNode if node is protected and cannot be removed.
+	NodeIdList remove(nodeid_t id);
+
+	//! May throw:
+	//! - Error::NewParentIsSelf if id and parentid are the same.
+	//! - Error::NoSuchId if node id does not exist.
+	//! - Error::MissingParent if new parent node does not exist.
+	//! - Error::ProtectedNode if node is protected and cannot be (re)moved.
+	NodeIdList move(nodeid_t id, nodeid_t newParentId, nodeid_t insertBeforeId);
+
+	//! May throw:
+	//! - Error::NoSuchId if node id does not exist.
 	NodeIdList updateData(nodeid_t id, const std::string &name,
-	                      const std::string &value) throw (std::exception);
-	node_t data(nodeid_t id) throw (std::exception);
+	                      const std::string &value);
 
-	NodeIdList bfs(nodeid_t id) throw (std::exception);
+	//! May throw:
+	//! - Error::NoSuchId if node id does not exist.
+	node_t data(nodeid_t id);
 
-	NodeIdList ancestorList(nodeid_t id) throw (std::exception);
+	//! May throw:
+	//! - Error::NoSuchId if node id does not exist.
+	NodeIdList bfs(nodeid_t id);
+
+	//! May throw:
+	//! - Error::NoSuchId if node id does not exist.
+	NodeIdList ancestorList(nodeid_t id);
 
 	void toStdOut();
 
 	std::string toXML();
-	void fromXML(const std::string& xml);
 
-	nodeid_t nextid;
+	void fromXML(const std::string& xml);
 
 private:
 	friend class XmlParser;
 	Node* createNode(nodeid_t id);
 	void insertChild(Node* parent, Node* child, nodeid_t insertBeforeId);
 
-	Node* root;
+	nodeid_t nextid{10};
+	Node* root{nullptr};
 	std::map<int, Node*> id2node;
 };