// SPDX-FileCopyrightText: 2012 Icinga GmbH <https://icinga.com>
// SPDX-License-Identifier: GPL-2.0-or-later

#include "db_ido_mysql/idomysqlconnection.hpp"
#include "db_ido_mysql/idomysqlconnection-ti.cpp"
#include "db_ido/dbtype.hpp"
#include "db_ido/dbvalue.hpp"
#include "base/logger.hpp"
#include "base/objectlock.hpp"
#include "base/convert.hpp"
#include "base/utility.hpp"
#include "base/perfdatavalue.hpp"
#include "base/application.hpp"
#include "base/configtype.hpp"
#include "base/exception.hpp"
#include "base/statsfunction.hpp"
#include "base/defer.hpp"
#include <utility>

using namespace icinga;

REGISTER_TYPE(IdoMysqlConnection);
REGISTER_STATSFUNCTION(IdoMysqlConnection, &IdoMysqlConnection::StatsFunc);

const char * IdoMysqlConnection::GetLatestSchemaVersion() const noexcept
{
	return "1.15.1";
}

const char * IdoMysqlConnection::GetCompatSchemaVersion() const noexcept
{
	return "1.14.3";
}

void IdoMysqlConnection::OnConfigLoaded()
{
	ObjectImpl<IdoMysqlConnection>::OnConfigLoaded();

	m_QueryQueue.SetName("IdoMysqlConnection, " + GetName());

	Library shimLibrary{"mysql_shim"};

	auto create_mysql_shim = shimLibrary.GetSymbolAddress<create_mysql_shim_ptr>("create_mysql_shim");

	m_Mysql.reset(create_mysql_shim());

	std::swap(m_Library, shimLibrary);
}

void IdoMysqlConnection::OnAllConfigLoaded()
{
	ObjectImpl<IdoMysqlConnection>::OnAllConfigLoaded();

	Log(LogWarning, "IdoMysqlConnection")
		<< "This feature is DEPRECATED and will be removed in v2.18.";
}

void IdoMysqlConnection::StatsFunc(const Dictionary::Ptr& status, const Array::Ptr& perfdata)
{
	DictionaryData nodes;

	for (const IdoMysqlConnection::Ptr& idomysqlconnection : ConfigType::GetObjectsByType<IdoMysqlConnection>()) {
		size_t queryQueueItems = idomysqlconnection->m_QueryQueue.GetLength();
		double queryQueueItemRate = idomysqlconnection->m_QueryQueue.GetTaskCount(60) / 60.0;

		nodes.emplace_back(idomysqlconnection->GetName(), new Dictionary({
			{ "version", idomysqlconnection->GetSchemaVersion() },
			{ "instance_name", idomysqlconnection->GetInstanceName() },
			{ "connected", idomysqlconnection->GetConnected() },
			{ "query_queue_items", queryQueueItems },
			{ "query_queue_item_rate", queryQueueItemRate }
		}));

		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_queries_rate", idomysqlconnection->GetQueryCount(60) / 60.0));
		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_queries_1min", idomysqlconnection->GetQueryCount(60)));
		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_queries_5mins", idomysqlconnection->GetQueryCount(5 * 60)));
		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_queries_15mins", idomysqlconnection->GetQueryCount(15 * 60)));
		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_query_queue_items", queryQueueItems));
		perfdata->Add(new PerfdataValue("idomysqlconnection_" + idomysqlconnection->GetName() + "_query_queue_item_rate", queryQueueItemRate));
	}

	status->Set("idomysqlconnection", new Dictionary(std::move(nodes)));
}

void IdoMysqlConnection::Resume()
{
	Log(LogInformation, "IdoMysqlConnection")
		<< "'" << GetName() << "' resumed.";

	SetConnected(false);

	m_QueryQueue.SetExceptionCallback([this](boost::exception_ptr exp) { ExceptionHandler(std::move(exp)); });

	/* Immediately try to connect on Resume() without timer. */
	m_QueryQueue.Enqueue([this]() { Reconnect(); }, PriorityImmediate);

	m_TxTimer = Timer::Create();
	m_TxTimer->SetInterval(1);
	m_TxTimer->OnTimerExpired.connect([this](const Timer * const&) { NewTransaction(); });
	m_TxTimer->Start();

	m_ReconnectTimer = Timer::Create();
	m_ReconnectTimer->SetInterval(10);
	m_ReconnectTimer->OnTimerExpired.connect([this](const Timer * const&){ ReconnectTimerHandler(); });
	m_ReconnectTimer->Start();

	/* Start with queries after connect. */
	DbConnection::Resume();

	ASSERT(m_Mysql->thread_safe());
}

void IdoMysqlConnection::Pause()
{
	Log(LogDebug, "IdoMysqlConnection")
		<< "Attempting to pause '" << GetName() << "'.";

	DbConnection::Pause();

	m_ReconnectTimer->Stop(true);
	m_TxTimer->Stop(true);

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Rescheduling disconnect task.";
#endif /* I2_DEBUG */

	Log(LogInformation, "IdoMysqlConnection")
		<< "'" << GetName() << "' paused.";

}

void IdoMysqlConnection::ExceptionHandler(boost::exception_ptr exp)
{
	Log(LogCritical, "IdoMysqlConnection", "Exception during database operation: Verify that your database is operational!");

	Log(LogDebug, "IdoMysqlConnection")
		<< "Exception during database operation: " << DiagnosticInformation(std::move(exp));

	if (GetConnected()) {
		m_Mysql->close(&m_Connection);

		SetConnected(false);
	}
}

void IdoMysqlConnection::AssertOnWorkQueue()
{
	ASSERT(m_QueryQueue.IsWorkerThread());
}

void IdoMysqlConnection::Disconnect()
{
	AssertOnWorkQueue();

	if (!GetConnected())
		return;

	Query("COMMIT");
	m_Mysql->close(&m_Connection);

	SetConnected(false);

	Log(LogInformation, "IdoMysqlConnection")
		<< "Disconnected from '" << GetName() << "' database '" << GetDatabase() << "'.";
}

void IdoMysqlConnection::NewTransaction()
{
	if (IsPaused() && GetPauseCalled())
		return;

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling new transaction and finishing async queries.";
#endif /* I2_DEBUG */

	m_QueryQueue.Enqueue([this]() { InternalNewTransaction(); }, PriorityHigh);
}

void IdoMysqlConnection::InternalNewTransaction()
{
	AssertOnWorkQueue();

	if (!GetConnected())
		return;

	IncreasePendingQueries(2);

	AsyncQuery("COMMIT");
	AsyncQuery("BEGIN");

	FinishAsyncQueries();
}

void IdoMysqlConnection::ReconnectTimerHandler()
{
#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling reconnect task.";
#endif /* I2_DEBUG */

	/* Only allow Reconnect events with high priority. */
	m_QueryQueue.Enqueue([this]() { Reconnect(); }, PriorityImmediate);
}

void IdoMysqlConnection::Reconnect()
{
	AssertOnWorkQueue();

	if (!IsActive())
		return;

	CONTEXT("Reconnecting to MySQL IDO database '" << GetName() << "'");

	double startTime = Utility::GetTime();

	SetShouldConnect(true);

	bool reconnect = false;

	/* Ensure to close old connections first. */
	if (GetConnected()) {
		/* Check if we're really still connected */
		if (m_Mysql->ping(&m_Connection) == 0)
			return;

		m_Mysql->close(&m_Connection);
		SetConnected(false);
		reconnect = true;
	}

	Log(LogDebug, "IdoMysqlConnection")
		<< "Reconnect: Clearing ID cache.";

	ClearIDCache();

	String ihost, isocket_path, iuser, ipasswd, idb;
	String isslKey, isslCert, isslCa, isslCaPath, isslCipher;
	const char *host, *socket_path, *user , *passwd, *db;
	const char *sslKey, *sslCert, *sslCa, *sslCaPath, *sslCipher;
	bool enableSsl;
	long port;

	ihost = GetHost();
	isocket_path = GetSocketPath();
	iuser = GetUser();
	ipasswd = GetPassword();
	idb = GetDatabase();

	enableSsl = GetEnableSsl();
	isslKey = GetSslKey();
	isslCert = GetSslCert();
	isslCa = GetSslCa();
	isslCaPath = GetSslCapath();
	isslCipher = GetSslCipher();

	host = (!ihost.IsEmpty()) ? ihost.CStr() : nullptr;
	port = GetPort();
	socket_path = (!isocket_path.IsEmpty()) ? isocket_path.CStr() : nullptr;
	user = (!iuser.IsEmpty()) ? iuser.CStr() : nullptr;
	passwd = (!ipasswd.IsEmpty()) ? ipasswd.CStr() : nullptr;
	db = (!idb.IsEmpty()) ? idb.CStr() : nullptr;

	sslKey = (!isslKey.IsEmpty()) ? isslKey.CStr() : nullptr;
	sslCert = (!isslCert.IsEmpty()) ? isslCert.CStr() : nullptr;
	sslCa = (!isslCa.IsEmpty()) ? isslCa.CStr() : nullptr;
	sslCaPath = (!isslCaPath.IsEmpty()) ? isslCaPath.CStr() : nullptr;
	sslCipher = (!isslCipher.IsEmpty()) ? isslCipher.CStr() : nullptr;

	/* connection */
	if (!m_Mysql->init(&m_Connection)) {
		Log(LogCritical, "IdoMysqlConnection")
			<< "mysql_init() failed: out of memory";

		BOOST_THROW_EXCEPTION(std::bad_alloc());
	}

	/* Read "latin1" (here, in the schema and in Icinga Web) as "bytes".
	   Icinga 2 and Icinga Web use byte-strings everywhere and every byte-string is a valid latin1 string.
	   This way the (actually mostly UTF-8) bytes are transferred end-to-end as-is. */
	m_Mysql->options(&m_Connection, MYSQL_SET_CHARSET_NAME, "latin1");

	if (enableSsl)
		m_Mysql->ssl_set(&m_Connection, sslKey, sslCert, sslCa, sslCaPath, sslCipher);

	if (!m_Mysql->real_connect(&m_Connection, host, user, passwd, db, port, socket_path, CLIENT_FOUND_ROWS | CLIENT_MULTI_STATEMENTS)) {
		Log(LogCritical, "IdoMysqlConnection")
			<< "Connection to database '" << db << "' with user '" << user << "' on '" << host << ":" << port
			<< "' " << (enableSsl ? "(SSL enabled) " : "") << "failed: \"" << m_Mysql->error(&m_Connection) << "\"";

		BOOST_THROW_EXCEPTION(std::runtime_error(m_Mysql->error(&m_Connection)));
	}

	Log(LogNotice, "IdoMysqlConnection")
		<< "Reconnect: '" << GetName() << "' is now connected to database '" << GetDatabase() << "'.";

	SetConnected(true);

	IdoMysqlResult result = Query("SELECT @@global.max_allowed_packet AS max_allowed_packet");

	Dictionary::Ptr row = FetchRow(result);

	if (row)
		m_MaxPacketSize = row->Get("max_allowed_packet");
	else
		m_MaxPacketSize = 64 * 1024;

	DiscardRows(result);

	String dbVersionName = "idoutils";
	result = Query("SELECT version FROM " + GetTablePrefix() + "dbversion WHERE name='" + Escape(dbVersionName) + "'");

	row = FetchRow(result);

	if (!row) {
		m_Mysql->close(&m_Connection);
		SetConnected(false);

		Log(LogCritical, "IdoMysqlConnection", "Schema does not provide any valid version! Verify your schema installation.");

		BOOST_THROW_EXCEPTION(std::runtime_error("Invalid schema."));
	}

	DiscardRows(result);

	String version = row->Get("version");

	SetSchemaVersion(version);

	if (Utility::CompareVersion(GetCompatSchemaVersion(), version) < 0) {
		m_Mysql->close(&m_Connection);
		SetConnected(false);

		Log(LogCritical, "IdoMysqlConnection")
			<< "Schema version '" << version << "' does not match the required version '"
			<< GetCompatSchemaVersion() << "' (or newer)! Please check the upgrade documentation at "
			<< "https://icinga.com/docs/icinga2/latest/doc/16-upgrading-icinga-2/#upgrading-mysql-db";

		BOOST_THROW_EXCEPTION(std::runtime_error("Schema version mismatch."));
	}

	String instanceName = GetInstanceName();

	result = Query("SELECT instance_id FROM " + GetTablePrefix() + "instances WHERE instance_name = '" + Escape(instanceName) + "'");
	row = FetchRow(result);

	if (!row) {
		Query("INSERT INTO " + GetTablePrefix() + "instances (instance_name, instance_description) VALUES ('" + Escape(instanceName) + "', '" + Escape(GetInstanceDescription()) + "')");
		m_InstanceID = GetLastInsertID();
	} else {
		m_InstanceID = DbReference(row->Get("instance_id"));
	}

	DiscardRows(result);

	Endpoint::Ptr my_endpoint = Endpoint::GetLocalEndpoint();

	/* we have an endpoint in a cluster setup, so decide if we can proceed here */
	if (my_endpoint && GetHAMode() == HARunOnce) {
		/* get the current endpoint writing to programstatus table */
		result = Query("SELECT UNIX_TIMESTAMP(status_update_time) AS status_update_time, endpoint_name FROM " +
			GetTablePrefix() + "programstatus WHERE instance_id = " + Convert::ToString(m_InstanceID));
		row = FetchRow(result);
		DiscardRows(result);

		String endpoint_name;

		if (row)
			endpoint_name = row->Get("endpoint_name");
		else
			Log(LogNotice, "IdoMysqlConnection", "Empty program status table");

		/* if we did not write into the database earlier, another instance is active */
		if (endpoint_name != my_endpoint->GetName()) {
			double status_update_time;

			if (row)
				status_update_time = row->Get("status_update_time");
			else
				status_update_time = 0;

			double now = Utility::GetTime();

			double status_update_age = now - status_update_time;
			double failoverTimeout = GetFailoverTimeout();

			if (status_update_age < failoverTimeout) {
				Log(LogInformation, "IdoMysqlConnection")
					<< "Last update by endpoint '" << endpoint_name << "' was "
					<< status_update_age << "s ago (< failover timeout of " << failoverTimeout << "s). Retrying.";

				m_Mysql->close(&m_Connection);
				SetConnected(false);
				SetShouldConnect(false);

				return;
			}

			/* activate the IDO only, if we're authoritative in this zone */
			if (IsPaused()) {
				Log(LogNotice, "IdoMysqlConnection")
					<< "Local endpoint '" << my_endpoint->GetName() << "' is not authoritative, bailing out.";

				m_Mysql->close(&m_Connection);
				SetConnected(false);

				return;
			}

			SetLastFailover(now);

			Log(LogInformation, "IdoMysqlConnection")
				<< "Last update by endpoint '" << endpoint_name << "' was "
				<< status_update_age << "s ago. Taking over '" << GetName() << "' in HA zone '" << Zone::GetLocalZone()->GetName() << "'.";
		}

		Log(LogNotice, "IdoMysqlConnection", "Enabling IDO connection in HA zone.");
	}

	Log(LogInformation, "IdoMysqlConnection")
		<< "MySQL IDO instance id: " << static_cast<long>(m_InstanceID) << " (schema version: '" + version + "')";

	/* set session time zone to utc */
	Query("SET SESSION TIME_ZONE='+00:00'");

	Query("SET SESSION SQL_MODE='NO_AUTO_VALUE_ON_ZERO'");

	Query("BEGIN");

	/* update programstatus table */
	UpdateProgramStatus();

	/* record connection */
	Query("INSERT INTO " + GetTablePrefix() + "conninfo " +
		"(instance_id, connect_time, last_checkin_time, agent_name, agent_version, connect_type, data_start_time) VALUES ("
		+ Convert::ToString(static_cast<long>(m_InstanceID)) + ", NOW(), NOW(), 'icinga2 db_ido_mysql', '" + Escape(Application::GetAppVersion())
		+ "', '" + (reconnect ? "RECONNECT" : "INITIAL") + "', NOW())");

	/* clear config tables for the initial config dump */
	PrepareDatabase();

	std::ostringstream q1buf;
	q1buf << "SELECT object_id, objecttype_id, name1, name2, is_active FROM " + GetTablePrefix() + "objects WHERE instance_id = " << static_cast<long>(m_InstanceID);
	result = Query(q1buf.str());

	std::vector<DbObject::Ptr> activeDbObjs;

	while ((row = FetchRow(result))) {
		DbType::Ptr dbtype = DbType::GetByID(row->Get("objecttype_id"));

		if (!dbtype)
			continue;

		DbObject::Ptr dbobj = dbtype->GetOrCreateObjectByName(row->Get("name1"), row->Get("name2"));
		SetObjectID(dbobj, DbReference(row->Get("object_id")));
		bool active = row->Get("is_active");
		SetObjectActive(dbobj, active);

		if (active)
			activeDbObjs.emplace_back(std::move(dbobj));
	}

	SetIDCacheValid(true);

	EnableActiveChangedHandler();

	for (const DbObject::Ptr& dbobj : activeDbObjs) {
		if (dbobj->GetObject())
			continue;

		Log(LogNotice, "IdoMysqlConnection")
			<< "Deactivate deleted object name1: '" << dbobj->GetName1()
			<< "' name2: '" << dbobj->GetName2() + "'.";
		DeactivateObject(dbobj);
	}

	UpdateAllObjects();

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling session table clear and finish connect task.";
#endif /* I2_DEBUG */

	m_QueryQueue.Enqueue([this]() { ClearTablesBySession(); }, PriorityNormal);

	m_QueryQueue.Enqueue([this, startTime]() { FinishConnect(startTime); }, PriorityNormal);
}

void IdoMysqlConnection::FinishConnect(double startTime)
{
	AssertOnWorkQueue();

	if (!GetConnected() || IsPaused())
		return;

	FinishAsyncQueries();

	Log(LogInformation, "IdoMysqlConnection")
		<< "Finished reconnecting to '" << GetName() << "' database '" << GetDatabase() << "' in "
		<< std::setw(2) << Utility::GetTime() - startTime << " second(s).";

	Query("COMMIT");
	Query("BEGIN");
}

void IdoMysqlConnection::ClearTablesBySession()
{
	/* delete all comments and downtimes without current session token */
	ClearTableBySession("comments");
	ClearTableBySession("scheduleddowntime");
}

void IdoMysqlConnection::ClearTableBySession(const String& table)
{
	Query("DELETE FROM " + GetTablePrefix() + table + " WHERE instance_id = " +
		Convert::ToString(static_cast<long>(m_InstanceID)) + " AND session_token <> " +
		Convert::ToString(GetSessionToken()));
}

void IdoMysqlConnection::AsyncQuery(const String& query, const std::function<void (const IdoMysqlResult&)>& callback)
{
	AssertOnWorkQueue();

	IdoAsyncQuery aq;
	aq.Query = query;
	/* XXX: Important: The callback must not immediately execute a query, but enqueue it!
	 * See https://github.com/Icinga/icinga2/issues/4603 for details.
	 */
	aq.Callback = callback;
	m_AsyncQueries.emplace_back(std::move(aq));
}

void IdoMysqlConnection::FinishAsyncQueries()
{
	std::vector<IdoAsyncQuery> queries;
	m_AsyncQueries.swap(queries);

	std::vector<IdoAsyncQuery>::size_type offset = 0;

	// This will be executed if there is a problem with executing the queries,
	// at which point this function throws an exception and the queries should
	// not be listed as still pending in the queue.
	Defer decreaseQueries ([this, &offset, &queries]() {
		auto lostQueries = queries.size() - offset;

		if (lostQueries > 0) {
			DecreasePendingQueries(lostQueries);
		}
	});

	while (offset < queries.size()) {
		std::ostringstream querybuf;

		std::vector<IdoAsyncQuery>::size_type count = 0;
		size_t num_bytes = 0;

		Defer decreaseQueries ([this, &offset, &count]() {
			offset += count;
			DecreasePendingQueries(count);
			m_UncommittedAsyncQueries += count;
		});

		for (std::vector<IdoAsyncQuery>::size_type i = offset; i < queries.size(); i++) {
			const IdoAsyncQuery& aq = queries[i];

			size_t size_query = aq.Query.GetLength() + 1;

			if (count > 0) {
				if (num_bytes + size_query > m_MaxPacketSize - 512)
					break;

				querybuf << ";";
			}

			IncreaseQueryCount();
			count++;

			Log(LogDebug, "IdoMysqlConnection")
				<< "Query: " << aq.Query;

			querybuf << aq.Query;
			num_bytes += size_query;
		}

		String query = querybuf.str();

		if (m_Mysql->query(&m_Connection, query.CStr()) != 0) {
			std::ostringstream msgbuf;
			String message = m_Mysql->error(&m_Connection);
			msgbuf << "Error \"" << message << "\" when executing query \"" << query << "\"";
			Log(LogCritical, "IdoMysqlConnection", msgbuf.str());

			BOOST_THROW_EXCEPTION(
				database_error()
				<< errinfo_message(m_Mysql->error(&m_Connection))
				<< errinfo_database_query(query)
			);
		}

		for (std::vector<IdoAsyncQuery>::size_type i = offset; i < offset + count; i++) {
			const IdoAsyncQuery& aq = queries[i];

			MYSQL_RES *result = m_Mysql->store_result(&m_Connection);

			m_AffectedRows = m_Mysql->affected_rows(&m_Connection);

			IdoMysqlResult iresult;

			if (!result) {
				if (m_Mysql->field_count(&m_Connection) > 0) {
					std::ostringstream msgbuf;
					String message = m_Mysql->error(&m_Connection);
					msgbuf << "Error \"" << message << "\" when executing query \"" << aq.Query << "\"";
					Log(LogCritical, "IdoMysqlConnection", msgbuf.str());

					BOOST_THROW_EXCEPTION(
						database_error()
						<< errinfo_message(m_Mysql->error(&m_Connection))
						<< errinfo_database_query(query)
					);
				}
			} else
				iresult = IdoMysqlResult(result, [this](MYSQL_RES* result) { m_Mysql->free_result(result); });

			if (aq.Callback)
				aq.Callback(iresult);

			if (m_Mysql->next_result(&m_Connection) > 0) {
				std::ostringstream msgbuf;
				String message = m_Mysql->error(&m_Connection);
				msgbuf << "Error \"" << message << "\" when executing query \"" << query << "\"";
				Log(LogCritical, "IdoMysqlConnection", msgbuf.str());

				BOOST_THROW_EXCEPTION(
					database_error()
					<< errinfo_message(m_Mysql->error(&m_Connection))
					<< errinfo_database_query(query)
				);
			}
		}
	}

	if (m_UncommittedAsyncQueries > 25000) {
		m_UncommittedAsyncQueries = 0;

		Query("COMMIT");
		Query("BEGIN");
	}
}

IdoMysqlResult IdoMysqlConnection::Query(const String& query)
{
	AssertOnWorkQueue();

	IncreasePendingQueries(1);
	Defer decreaseQueries ([this]() { DecreasePendingQueries(1); });

	/* finish all async queries to maintain the right order for queries */
	FinishAsyncQueries();

	Log(LogDebug, "IdoMysqlConnection")
		<< "Query: " << query;

	IncreaseQueryCount();

	if (m_Mysql->query(&m_Connection, query.CStr()) != 0) {
		std::ostringstream msgbuf;
		String message = m_Mysql->error(&m_Connection);
		msgbuf << "Error \"" << message << "\" when executing query \"" << query << "\"";
		Log(LogCritical, "IdoMysqlConnection", msgbuf.str());

		BOOST_THROW_EXCEPTION(
			database_error()
			<< errinfo_message(m_Mysql->error(&m_Connection))
			<< errinfo_database_query(query)
		);
	}

	MYSQL_RES *result = m_Mysql->store_result(&m_Connection);

	m_AffectedRows = m_Mysql->affected_rows(&m_Connection);

	if (!result) {
		if (m_Mysql->field_count(&m_Connection) > 0) {
			std::ostringstream msgbuf;
			String message = m_Mysql->error(&m_Connection);
			msgbuf << "Error \"" << message << "\" when executing query \"" << query << "\"";
			Log(LogCritical, "IdoMysqlConnection", msgbuf.str());

			BOOST_THROW_EXCEPTION(
				database_error()
				<< errinfo_message(m_Mysql->error(&m_Connection))
				<< errinfo_database_query(query)
			);
		}

		return IdoMysqlResult();
	}

	return IdoMysqlResult(result, [this](MYSQL_RES* result) { m_Mysql->free_result(result); });
}

DbReference IdoMysqlConnection::GetLastInsertID()
{
	AssertOnWorkQueue();

	return {static_cast<long>(m_Mysql->insert_id(&m_Connection))};
}

int IdoMysqlConnection::GetAffectedRows()
{
	AssertOnWorkQueue();

	return m_AffectedRows;
}

String IdoMysqlConnection::Escape(const String& s)
{
	AssertOnWorkQueue();

	String utf8s = Utility::ValidateUTF8(s);

	size_t length = utf8s.GetLength();
	auto *to = new char[utf8s.GetLength() * 2 + 1];

	m_Mysql->real_escape_string(&m_Connection, to, utf8s.CStr(), length);

	String result = String(to);

	delete [] to;

	return result;
}

Dictionary::Ptr IdoMysqlConnection::FetchRow(const IdoMysqlResult& result)
{
	AssertOnWorkQueue();

	MYSQL_ROW row;
	MYSQL_FIELD *field;
	unsigned long *lengths, i;

	row = m_Mysql->fetch_row(result.get());

	if (!row)
		return nullptr;

	lengths = m_Mysql->fetch_lengths(result.get());

	if (!lengths)
		return nullptr;

	Dictionary::Ptr dict = new Dictionary();

	m_Mysql->field_seek(result.get(), 0);
	for (field = m_Mysql->fetch_field(result.get()), i = 0; field; field = m_Mysql->fetch_field(result.get()), i++)
		dict->Set(field->name, String(row[i], row[i] + lengths[i]));

	return dict;
}

void IdoMysqlConnection::DiscardRows(const IdoMysqlResult& result)
{
	Dictionary::Ptr row;

	while ((row = FetchRow(result)))
		; /* empty loop body */
}

void IdoMysqlConnection::ActivateObject(const DbObject::Ptr& dbobj)
{
	if (IsPaused())
		return;

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling object activation task for '" << dbobj->GetName1() << "!" << dbobj->GetName2() << "'.";
#endif /* I2_DEBUG */

	m_QueryQueue.Enqueue([this, dbobj]() { InternalActivateObject(dbobj); }, PriorityNormal);
}

void IdoMysqlConnection::InternalActivateObject(const DbObject::Ptr& dbobj)
{
	AssertOnWorkQueue();

	if (IsPaused())
		return;

	if (!GetConnected())
		return;

	DbReference dbref = GetObjectID(dbobj);
	std::ostringstream qbuf;

	if (!dbref.IsValid()) {
		if (!dbobj->GetName2().IsEmpty()) {
			qbuf << "INSERT INTO " + GetTablePrefix() + "objects (instance_id, objecttype_id, name1, name2, is_active) VALUES ("
				<< static_cast<long>(m_InstanceID) << ", " << dbobj->GetType()->GetTypeID() << ", "
				<< "'" << Escape(dbobj->GetName1()) << "', '" << Escape(dbobj->GetName2()) << "', 1)";
		} else {
			qbuf << "INSERT INTO " + GetTablePrefix() + "objects (instance_id, objecttype_id, name1, is_active) VALUES ("
				<< static_cast<long>(m_InstanceID) << ", " << dbobj->GetType()->GetTypeID() << ", "
				<< "'" << Escape(dbobj->GetName1()) << "', 1)";
		}

		Query(qbuf.str());
		SetObjectID(dbobj, GetLastInsertID());
	} else {
		qbuf << "UPDATE " + GetTablePrefix() + "objects SET is_active = 1 WHERE object_id = " << static_cast<long>(dbref);
		IncreasePendingQueries(1);
		AsyncQuery(qbuf.str());
	}
}

void IdoMysqlConnection::DeactivateObject(const DbObject::Ptr& dbobj)
{
	if (IsPaused())
		return;

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling object deactivation task for '" << dbobj->GetName1() << "!" << dbobj->GetName2() << "'.";
#endif /* I2_DEBUG */

	m_QueryQueue.Enqueue([this, dbobj]() { InternalDeactivateObject(dbobj); }, PriorityNormal);
}

void IdoMysqlConnection::InternalDeactivateObject(const DbObject::Ptr& dbobj)
{
	AssertOnWorkQueue();

	if (IsPaused())
		return;

	if (!GetConnected())
		return;

	DbReference dbref = GetObjectID(dbobj);

	if (!dbref.IsValid())
		return;

	std::ostringstream qbuf;
	qbuf << "UPDATE " + GetTablePrefix() + "objects SET is_active = 0 WHERE object_id = " << static_cast<long>(dbref);
	IncreasePendingQueries(1);
	AsyncQuery(qbuf.str());

	/* Note that we're _NOT_ clearing the db refs via SetReference/SetConfigUpdate/SetStatusUpdate
	 * because the object is still in the database. */

	SetObjectActive(dbobj, false);
}

bool IdoMysqlConnection::FieldToEscapedString(const String& key, const Value& value, Value *result)
{
	if (key == "instance_id") {
		*result = static_cast<long>(m_InstanceID);
		return true;
	} else if (key == "session_token") {
		*result = GetSessionToken();
		return true;
	}

	Value rawvalue = DbValue::ExtractValue(value);

	if (rawvalue.GetType() == ValueEmpty) {
		*result = "NULL";
	} else if (rawvalue.IsObjectType<ConfigObject>()) {
		DbObject::Ptr dbobjcol = DbObject::GetOrCreateByObject(rawvalue);

		if (!dbobjcol) {
			*result = 0;
			return true;
		}

		if (!IsIDCacheValid())
			return false;

		DbReference dbrefcol;

		if (DbValue::IsObjectInsertID(value)) {
			dbrefcol = GetInsertID(dbobjcol);

			if (!dbrefcol.IsValid())
				return false;
		} else {
			dbrefcol = GetObjectID(dbobjcol);

			if (!dbrefcol.IsValid()) {
				InternalActivateObject(dbobjcol);

				dbrefcol = GetObjectID(dbobjcol);

				if (!dbrefcol.IsValid())
					return false;
			}
		}

		*result = static_cast<long>(dbrefcol);
	} else if (DbValue::IsTimestamp(value)) {
		// MySQL TIMESTAMP columns have the year-2038 problem, hence the upper limit below.
		// Also, they don't accept FROM_UNIXTIME(0): ERROR 1292 (22007): Incorrect datetime value: '1970-01-01 00:00:00'

		double ts = rawvalue;
		std::ostringstream msgbuf;
		msgbuf << "FROM_UNIXTIME(" << std::fixed << std::setprecision(0)
			<< std::fmin(std::fmax(ts, 1.0), 2147483647.0) << ")";
		*result = Value(msgbuf.str());
	} else if (DbValue::IsObjectInsertID(value)) {
		auto id = static_cast<long>(rawvalue);

		if (id <= 0)
			return false;

		*result = id;
		return true;
	} else {
		Value fvalue;

		if (rawvalue.IsBoolean())
			fvalue = Convert::ToLong(rawvalue);
		else
			fvalue = rawvalue;

		*result = "'" + Escape(fvalue) + "'";
	}

	return true;
}

void IdoMysqlConnection::ExecuteQuery(const DbQuery& query)
{
	if (IsPaused() && GetPauseCalled())
		return;

	ASSERT(query.Category != DbCatInvalid);

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling execute query task, type " << query.Type << ", table '" << query.Table << "'.";
#endif /* I2_DEBUG */

	IncreasePendingQueries(1);
	m_QueryQueue.Enqueue([this, query]() { InternalExecuteQuery(query, -1); }, query.Priority, true);
}

void IdoMysqlConnection::ExecuteMultipleQueries(const std::vector<DbQuery>& queries)
{
	if (IsPaused())
		return;

	if (queries.empty())
		return;

#ifdef I2_DEBUG /* I2_DEBUG */
	Log(LogDebug, "IdoMysqlConnection")
		<< "Scheduling multiple execute query task, type " << queries[0].Type << ", table '" << queries[0].Table << "'.";
#endif /* I2_DEBUG */

	IncreasePendingQueries(queries.size());
	m_QueryQueue.Enqueue([this, queries]() { InternalExecuteMultipleQueries(queries); }, queries[0].Priority, true);
}

bool IdoMysqlConnection::CanExecuteQuery(const DbQuery& query)
{
	if (query.Object && !IsIDCacheValid())
		return false;

	if (query.WhereCriteria) {
		ObjectLock olock(query.WhereCriteria);
		Value value;

		for (const Dictionary::Pair& kv : query.WhereCriteria) {
			if (!FieldToEscapedString(kv.first, kv.second, &value))
				return false;
		}
	}

	if (query.Fields) {
		ObjectLock olock(query.Fields);

		for (const Dictionary::Pair& kv : query.Fields) {
			Value value;

			if (!FieldToEscapedString(kv.first, kv.second, &value))
				return false;
		}
	}

	return true;
}

void IdoMysqlConnection::InternalExecuteMultipleQueries(const std::vector<DbQuery>& queries)
{
	AssertOnWorkQueue();

	if (IsPaused()) {
		DecreasePendingQueries(queries.size());
		return;
	}

	if (!GetConnected()) {
		DecreasePendingQueries(queries.size());
		return;
	}


	for (const DbQuery& query : queries) {
		ASSERT(query.Type == DbQueryNewTransaction || query.Category != DbCatInvalid);

		if (!CanExecuteQuery(query)) {

#ifdef I2_DEBUG /* I2_DEBUG */
			Log(LogDebug, "IdoMysqlConnection")
				<< "Scheduling multiple execute query task again: Cannot execute query now. Type '"
				<< query.Type << "', table '" << query.Table << "', queue size: '" << GetPendingQueryCount() << "'.";
#endif /* I2_DEBUG */

			m_QueryQueue.Enqueue([this, queries]() { InternalExecuteMultipleQueries(queries); }, query.Priority);
			return;
		}
	}

	for (const DbQuery& query : queries) {
		InternalExecuteQuery(query);
	}
}

void IdoMysqlConnection::InternalExecuteQuery(const DbQuery& query, int typeOverride)
{
	AssertOnWorkQueue();

	if (IsPaused() && GetPauseCalled()) {
		DecreasePendingQueries(1);
		return;
	}

	if (!GetConnected()) {
		DecreasePendingQueries(1);
		return;
	}

	if (query.Type == DbQueryNewTransaction) {
		DecreasePendingQueries(1);
		InternalNewTransaction();
		return;
	}

	/* check whether we're allowed to execute the query first */
	if (GetCategoryFilter() != DbCatEverything && (query.Category & GetCategoryFilter()) == 0) {
		DecreasePendingQueries(1);
		return;
	}

	if (query.Object && query.Object->GetObject()->GetExtension("agent_check").ToBool()) {
		DecreasePendingQueries(1);
		return;
	}

	/* check if there are missing object/insert ids and re-enqueue the query */
	if (!CanExecuteQuery(query)) {

#ifdef I2_DEBUG /* I2_DEBUG */
		Log(LogDebug, "IdoMysqlConnection")
			<< "Scheduling execute query task again: Cannot execute query now. Type '"
			<< typeOverride << "', table '" << query.Table << "', queue size: '" << GetPendingQueryCount() << "'.";
#endif /* I2_DEBUG */

		m_QueryQueue.Enqueue([this, query, typeOverride]() { InternalExecuteQuery(query, typeOverride); }, query.Priority);
		return;
	}

	std::ostringstream qbuf, where;
	int type;

	if (query.WhereCriteria) {
		where << " WHERE ";

		ObjectLock olock(query.WhereCriteria);
		Value value;
		bool first = true;

		for (const Dictionary::Pair& kv : query.WhereCriteria) {
			if (!FieldToEscapedString(kv.first, kv.second, &value)) {

#ifdef I2_DEBUG /* I2_DEBUG */
				Log(LogDebug, "IdoMysqlConnection")
					<< "Scheduling execute query task again: Cannot execute query now. Type '"
					<< typeOverride << "', table '" << query.Table << "', queue size: '" << GetPendingQueryCount() << "'.";
#endif /* I2_DEBUG */

				m_QueryQueue.Enqueue([this, query]() { InternalExecuteQuery(query, -1); }, query.Priority);
				return;
			}

			if (!first)
				where << " AND ";

			where << kv.first << " = " << value;

			if (first)
				first = false;
		}
	}

	type = (typeOverride != -1) ? typeOverride : query.Type;

	bool upsert = false;

	if ((type & DbQueryInsert) && (type & DbQueryUpdate)) {
		bool hasid = false;

		if (query.Object) {
			if (query.ConfigUpdate)
				hasid = GetConfigUpdate(query.Object);
			else if (query.StatusUpdate)
				hasid = GetStatusUpdate(query.Object);
		}

		if (!hasid)
			upsert = true;

		type = DbQueryUpdate;
	}

	if ((type & DbQueryInsert) && (type & DbQueryDelete)) {
		std::ostringstream qdel;
		qdel << "DELETE FROM " << GetTablePrefix() << query.Table << where.str();
		IncreasePendingQueries(1);
		AsyncQuery(qdel.str());

		type = DbQueryInsert;
	}

	switch (type) {
		case DbQueryInsert:
			qbuf << "INSERT INTO " << GetTablePrefix() << query.Table;
			break;
		case DbQueryUpdate:
			qbuf << "UPDATE " << GetTablePrefix() << query.Table << " SET";
			break;
		case DbQueryDelete:
			qbuf << "DELETE FROM " << GetTablePrefix() << query.Table;
			break;
		default:
			VERIFY(!"Invalid query type.");
	}

	if (type == DbQueryInsert || type == DbQueryUpdate) {
		std::ostringstream colbuf, valbuf;

		if (type == DbQueryUpdate && query.Fields->GetLength() == 0)
			return;

		ObjectLock olock(query.Fields);

		bool first = true;
		for (const Dictionary::Pair& kv : query.Fields) {
			Value value;

			if (!FieldToEscapedString(kv.first, kv.second, &value)) {

#ifdef I2_DEBUG /* I2_DEBUG */
				Log(LogDebug, "IdoMysqlConnection")
					<< "Scheduling execute query task again: Cannot extract required INSERT/UPDATE fields, key '"
					<< kv.first << "', val '" << kv.second << "', type " << typeOverride << ", table '" << query.Table << "'.";
#endif /* I2_DEBUG */

				m_QueryQueue.Enqueue([this, query]() { InternalExecuteQuery(query, -1); }, query.Priority);
				return;
			}

			if (type == DbQueryInsert) {
				if (!first) {
					colbuf << ", ";
					valbuf << ", ";
				}

				colbuf << kv.first;
				valbuf << value;
			} else {
				if (!first)
					qbuf << ", ";

				qbuf << " " << kv.first << " = " << value;
			}

			if (first)
				first = false;
		}

		if (type == DbQueryInsert)
			qbuf << " (" << colbuf.str() << ") VALUES (" << valbuf.str() << ")";
	}

	if (type != DbQueryInsert)
		qbuf << where.str();

	AsyncQuery(qbuf.str(), [this, query, type, upsert](const IdoMysqlResult&) { FinishExecuteQuery(query, type, upsert); });
}

void IdoMysqlConnection::FinishExecuteQuery(const DbQuery& query, int type, bool upsert)
{
	if (upsert && GetAffectedRows() == 0) {

#ifdef I2_DEBUG /* I2_DEBUG */
		Log(LogDebug, "IdoMysqlConnection")
			<< "Rescheduling DELETE/INSERT query: Upsert UPDATE did not affect rows, type " << type << ", table '" << query.Table << "'.";
#endif /* I2_DEBUG */

		IncreasePendingQueries(1);
		m_QueryQueue.Enqueue([this, query]() { InternalExecuteQuery(query, DbQueryDelete | DbQueryInsert); }, query.Priority);

		return;
	}

	if (type == DbQueryInsert && query.Object) {
		if (query.ConfigUpdate) {
			SetInsertID(query.Object, GetLastInsertID());
			SetConfigUpdate(query.Object, true);
		} else if (query.StatusUpdate)
			SetStatusUpdate(query.Object, true);
	}

	if (type == DbQueryInsert && query.Table == "notifications" && query.NotificationInsertID)
		query.NotificationInsertID->SetValue(static_cast<long>(GetLastInsertID()));
}

void IdoMysqlConnection::CleanUpExecuteQuery(const String& table, const String& time_column, double max_age)
{
	if (IsPaused())
		return;

#ifdef I2_DEBUG /* I2_DEBUG */
		Log(LogDebug, "IdoMysqlConnection")
			<< "Rescheduling cleanup query for table '" << table << "' and column '"
			<< time_column << "'. max_age is set to '" << max_age << "'.";
#endif /* I2_DEBUG */

	IncreasePendingQueries(1);
	m_QueryQueue.Enqueue([this, table, time_column, max_age]() { InternalCleanUpExecuteQuery(table, time_column, max_age); }, PriorityLow, true);
}

void IdoMysqlConnection::InternalCleanUpExecuteQuery(const String& table, const String& time_column, double max_age)
{
	AssertOnWorkQueue();

	if (IsPaused()) {
		DecreasePendingQueries(1);
		return;
	}

	if (!GetConnected()) {
		DecreasePendingQueries(1);
		return;
	}

	AsyncQuery("DELETE FROM " + GetTablePrefix() + table + " WHERE instance_id = " +
		Convert::ToString(static_cast<long>(m_InstanceID)) + " AND " + time_column +
		" < FROM_UNIXTIME(" + Convert::ToString(static_cast<long>(max_age)) + ")");
}

void IdoMysqlConnection::FillIDCache(const DbType::Ptr& type)
{
	String query = "SELECT " + type->GetIDColumn() + " AS object_id, " + type->GetTable() + "_id, config_hash FROM " + GetTablePrefix() + type->GetTable() + "s";
	IdoMysqlResult result = Query(query);

	Dictionary::Ptr row;

	while ((row = FetchRow(result))) {
		DbReference dbref(row->Get("object_id"));
		SetInsertID(type, dbref, DbReference(row->Get(type->GetTable() + "_id")));
		SetConfigHash(type, dbref, row->Get("config_hash"));
	}
}

int IdoMysqlConnection::GetPendingQueryCount() const
{
	return m_QueryQueue.GetLength();
}
