TeaSpeakLibrary/src/sql/mysql/MySQL.cpp

#include <memory>

#include "MySQL.h"
#include "src/log/LogUtils.h"
#include <pipes/misc/http.h>

#include <memory>
#include <utility>

#include <mysql/mysql.h>

#define CR_CONNECTION_ERROR     (2002)
#define CR_SERVER_GONE_ERROR    (2006)
#define CR_SERVER_LOST          (2013)

using namespace std;
using namespace sql;
using namespace sql::mysql;

//TODO: Cache statements in general any only reapply the values

MySQLManager::MySQLManager() : SqlManager(SqlType::TYPE_MYSQL) {}
MySQLManager::~MySQLManager() {}

//Property info: https://dev.mysql.com/doc/connector-j/5.1/en/connector-j-reference-configuration-properties.html
//mysql://[host][:port]/[database][?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]

#define MYSQL_PREFIX "mysql://"
inline result parse_url(const string& url, std::map<std::string, std::string>& connect_map) {
	string target_url;
	if(url.find(MYSQL_PREFIX) != 0)
		return {ERROR_MYSQL_INVLID_URL, "Missing mysql:// at begin"};

	auto index_parms = url.find('?');
	if(index_parms == string::npos) {
		target_url = "tcp://" + url.substr(strlen(MYSQL_PREFIX));
	} else {
		target_url = "tcp://" + url.substr(strlen(MYSQL_PREFIX), index_parms - strlen(MYSQL_PREFIX));
		auto parms = url.substr(index_parms + 1);
		size_t index = 0;
		do {
			auto idx = parms.find('&', index);
			auto element = parms.substr(index, idx - index);

			auto key_idx = element.find('=');
			auto key = element.substr(0, key_idx);
			auto value = element.substr(key_idx + 1);
			connect_map[key] = http::decode_url(value);
			logTrace(LOG_GENERAL, "Got mysql property {}. Value: {}", key, value);

			index = idx + 1;
		} while(index != 0);
	}

	//if(!connect_map["hostName"].get<const char*>() || strcmp(*connect_map["hostName"].get<const char*>(), ""))
	connect_map["hostName"] = target_url;
	logTrace(LOG_GENERAL, "Got mysql property {}. Value: {}", "hostName", target_url);
	return result::success;
}

//mysql://[host][:port]/[database][?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]
inline bool parse_mysql_data(const string& url, string& error, string& host, uint16_t& port, string& database, map<string, string>& properties) {
	size_t parse_index = 0;
	/* parse the scheme */
	{
		auto index = url.find("://", parse_index);
		if(index == -1 || url.substr(parse_index, index - parse_index) != "mysql") {
			error = "missing/invalid URL scheme";
			return false;
		}

		parse_index = index + 3;
		if(parse_index >= url.length()) {
			error = "unexpected EOL after scheme";
			return false;
		}
	}

	/* parse host[:port]*/
	{
		auto index = url.find('/', parse_index);
		if(index == -1) {
			error = "missing host/port";
			return false;
		}

		auto host_port = url.substr(parse_index, index - parse_index);

		auto port_index = host_port.find(':');
		if(port_index == -1) {
			host = host_port;
		} else {
			host = host_port.substr(0, port_index);
			auto port_str = host_port.substr(port_index + 1);
			try {
				port = stol(port_str);
			} catch(std::exception& ex) {
				error = "failed to parse port";
				return false;
			}
		}
		if(host.empty()) {
			error = "host is empty";
			return false;
		}

		parse_index = index + 1;
		if(parse_index >= url.length()) {
			error = "unexpected EOL after host/port";
			return false;
		}
	}

	/* the database */
	{
		auto index = url.find('?', parse_index);
		if(index == -1) {
			database = url.substr(parse_index);
			parse_index = url.length();
		} else {
			database = url.substr(parse_index, index - parse_index);
			parse_index = index + 1;
		}

		if(database.empty()) {
			error = "database is empty";
			return false;
		}
	}

	/* properties */
	string full_property, property_key, property_value;
	while(parse_index < url.length()){
		/* "read" the next property */
		{
			auto index = url.find('&', parse_index); /* next entry */
			if(index == -1) {
				full_property = url.substr(parse_index);
				parse_index = url.length();
			} else {
				full_property = url.substr(parse_index, index - parse_index);
				parse_index = index + 1;
			}
		}

		/* parse it */
		{
			auto index = full_property.find('=');
			if(index == -1) {
				error = "invalid property format (missing '=')";
				return false;
			}

			property_key = full_property.substr(0, index);
			property_value = full_property.substr(index + 1);
			if(property_key.empty() || property_value.empty()) {
				error = "invalid property key/value (empty)";
				return false;
			}

			properties[property_key] = http::decode_url(property_value);
		}
	}
	return true;
}

mysql::Connection::~Connection() {
	{
		lock_guard lock(this->used_lock);
		assert(!this->used);
	}

	if(this->handle) {
		mysql_close(this->handle);
		this->handle = nullptr;
	}
}

result MySQLManager::connect(const std::string &url) {
	this->disconnecting = false;
	string error;

	map<string, string> properties;
	string host, database;
	uint16_t port;

	if(!parse_mysql_data(url, error, host, port, database, properties)) {
		error = "URL parsing failed: " + error;
		return {ERROR_MYSQL_INVLID_URL, error};
	}

	size_t connections = 4;
	if(properties.count("connections") > 0) {
		try {
			connections = stol(properties["connections"]);
		} catch(std::exception& ex) {
			return {ERROR_MYSQL_INVLID_PROPERTIES, "could not parse connection count"};
		}
	}

	string username, password;
	if(properties.count("userName") > 0) username = properties["userName"];
	if(properties.count("username") > 0) username = properties["username"];
	if(username.empty()) return {ERROR_MYSQL_INVLID_PROPERTIES, "missing username property"};

	if(properties.count("password") > 0) password = properties["password"];
	if(password.empty()) return {ERROR_MYSQL_INVLID_PROPERTIES, "missing password property"};

	//debugMessage(LOG_GENERAL, R"([MYSQL] Starting {} connections to {}:{} with database "{}" as user "{}")", connections, host, port, database, username);

	for(size_t index = 0; index < connections; index++) {
		auto connection = make_shared<Connection>();
		connection->handle = mysql_init(nullptr);
		if(!connection->handle)
			return {-1, "failed to allocate connection " + to_string(index)};

		{
			my_bool reconnect = 1;
			mysql_options(connection->handle, MYSQL_OPT_RECONNECT, &reconnect);
		}

		auto result = mysql_real_connect(connection->handle, host.c_str(), username.c_str(), password.c_str(), database.c_str(), port, nullptr, 0); //CLIENT_MULTI_RESULTS | CLIENT_MULTI_STATEMENTS
		if(!result)
			return {-1, "failed to connect to server with connection " + to_string(index) + ": " + mysql_error(connection->handle)};

		connection->used = false;
		this->connections.push_back(connection);
	}
    return result::success;
}

bool MySQLManager::connected() {
	lock_guard<mutex> lock(this->connections_lock);
	return !this->connections.empty();
}

result MySQLManager::disconnect() {
	lock_guard<mutex> lock(this->connections_lock);
	this->disconnecting = true;

	this->connections.clear();
	this->connections_condition.notify_all();

	this->disconnecting = false;
	return result::success;
}

struct StatementGuard {
	MYSQL_STMT* stmt;

	~StatementGuard() {
		mysql_stmt_close(this->stmt);
	}
};

struct ResultGuard {
	MYSQL_RES* result;

	~ResultGuard() {
		mysql_free_result(this->result);
	}
};

template <typename T>
struct FreeGuard {
	T* ptr;

	~FreeGuard() {
		if(this->ptr) ::free(this->ptr);
	}
};

template <typename T>
struct DeleteAGuard {
	T* ptr;

	~DeleteAGuard() {
		delete[] this->ptr;
	}
};

std::shared_ptr<CommandData> MySQLManager::allocateCommandData() {
	return make_shared<MySQLCommand>();
}

std::shared_ptr<CommandData> MySQLManager::copyCommandData(std::shared_ptr<CommandData> ptr) {
	auto _new = this->allocateCommandData();
	_new->handle = ptr->handle;
	_new->lock = ptr->lock;
	_new->sql_command = ptr->sql_command;
	_new->variables = ptr->variables;

	auto __new = static_pointer_cast<MySQLCommand>(_new);
	auto __ptr = static_pointer_cast<MySQLCommand>(ptr);
	//__new->stmt = __ptr->stmt;
	return __new;
}

namespace sql::mysql {
		bool evaluate_sql_query(string& sql, const std::vector<variable>& vars, std::vector<variable>& result) {
			char quote = 0;
			for(int index = 0; index < sql.length(); index++) {
				if(sql[index] == '\'' || sql[index] == '"' || sql[index] == '`') {
					if(quote > 0) {
						if(quote == sql[index]) quote = 0;
					} else {
						quote = sql[index];
					}
					continue;
				}
				if(quote > 0) continue;
				if(sql[index] != ':') continue;

				auto index_end = sql.find_first_not_of("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_", index + 1);
				if(index_end == string::npos) index_end = sql.length();

				string key = sql.substr(index, index_end - index);
				//Now we can replace it with a ?
				sql.replace(index, index_end - index, "?", 1);

				bool insert = false;
				for(const auto& e : vars)
					if(e.key() == key) {
						result.push_back(e);
						insert = true;
						break;
					}
				if(!insert)
					result.emplace_back();
			}
			return true;
		}

		struct BindMemory { };

		/* memory must be freed via ::free! */
		bool create_bind(BindMemory*& memory, const std::vector<variable>& variables) {
			size_t required_bytes = sizeof(MYSQL_BIND) * variables.size();

			/* first lets calculate the required memory */
			{
				for(auto& variable : variables) {
					switch (variable.type()) {
						case VARTYPE_NULL:
							break;
						case VARTYPE_BOOLEAN:
							required_bytes += sizeof(bool);
							break;
						case VARTYPE_INT:
							required_bytes += sizeof(int32_t);
							break;
						case VARTYPE_LONG:
							required_bytes += sizeof(int64_t);
							break;
						case VARTYPE_DOUBLE:
							required_bytes += sizeof(double);
							break;
						case VARTYPE_FLOAT:
							required_bytes += sizeof(float);
							break;
						case VARTYPE_TEXT:
							//TODO: Use a direct pointer to the variable's value instead of copying it
							required_bytes += sizeof(unsigned long*) + variable.value().length();
							break;
						default:
							return false; /* unknown variable type */
					}
				}
			}
			if(!required_bytes) {
				memory = nullptr;
				return true;
			}

			//logTrace(LOG_GENERAL, "[MYSQL] Allocated {} bytes for parameters", required_bytes);
			memory = (BindMemory*) malloc(required_bytes);
			if(!memory)
				return false;

			memset(memory, 0, required_bytes);
			/* lets fill the values */
			{
				size_t memory_index = variables.size() * sizeof(MYSQL_BIND);
				auto bind_ptr = (MYSQL_BIND*) memory;
				auto payload_ptr = (char*) memory + sizeof(MYSQL_BIND) * variables.size();

				for(size_t index = 0; index < variables.size(); index++) {
					bind_ptr->buffer = payload_ptr;

					auto& variable = variables[index];
					switch (variable.type()) {
						case VARTYPE_NULL:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_NULL;
							break;
						case VARTYPE_BOOLEAN:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_TINY;
							bind_ptr->buffer_length = sizeof(bool);
							*(bool*) payload_ptr = variable.as<bool>();
							break;
						case VARTYPE_INT:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_LONG;
							bind_ptr->buffer_length = sizeof(int32_t);
							*(int32_t*) payload_ptr = variable.as<int32_t>();
							break;
						case VARTYPE_LONG:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_LONGLONG;
							bind_ptr->buffer_length = sizeof(int64_t);
							*(int64_t*) payload_ptr = variable.as<int64_t>();
							break;
						case VARTYPE_DOUBLE:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_DOUBLE;
							bind_ptr->buffer_length = sizeof(double);
							*(double*) payload_ptr = variable.as<double>();
							break;
						case VARTYPE_FLOAT:
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_FLOAT;
							bind_ptr->buffer_length = sizeof(float);
							*(float*) payload_ptr = variable.as<float>();
							break;
						case VARTYPE_TEXT: {
							auto value = variable.value();

							//TODO: Use a direct pointer to the variable's value instead of copying it
							//May use a string object allocated on the memory_ptr? (Special deinit needed then!)
							bind_ptr->buffer_type = enum_field_types::MYSQL_TYPE_STRING;
							bind_ptr->buffer_length = value.length();

							bind_ptr->length = (unsigned long*) payload_ptr;
							*bind_ptr->length = bind_ptr->buffer_length;

							payload_ptr += sizeof(unsigned long*);
							memory_index += sizeof(unsigned long*);

							memcpy(payload_ptr, value.data(), value.length());
							bind_ptr->buffer = payload_ptr;
							break;
						}
						default:
							return false; /* unknown variable type */
					}

					payload_ptr += bind_ptr->buffer_length;
					bind_ptr++;
					assert(memory_index <= required_bytes);
				}
			}

			return true;
		}

		struct ResultBindDescriptor {
			size_t primitive_size = 0;

			void(*destroy)(char*& /* primitive ptr */) = nullptr;
			bool(*create)(const MYSQL_FIELD& /* field */, MYSQL_BIND& /* bind */, char*& /* primitive ptr */) = nullptr;

			bool(*get_as_string)(MYSQL_BIND& /* bind */, std::string& /* result */) = nullptr;
		};

		/* memory to primitive string */
		template <typename T>
		bool m2ps(MYSQL_BIND& bind, string& str) {
			if(bind.error_value || (bind.error && *bind.error)) return false;
			str = std::to_string(*(T*) bind.buffer);
			return true;
		}

		template <size_t size>
		void _do_destroy_primitive(char*& primitive_ptr) {
			primitive_ptr += size;
		}

		template <uint8_t type, size_t size>
		bool _do_bind_primitive(const MYSQL_FIELD&, MYSQL_BIND& bind, char*& primitive_ptr) {
			bind.buffer = (void*) primitive_ptr;
			bind.buffer_length = size;
			bind.buffer_type = (enum_field_types) type;
			primitive_ptr += size;
			return true;
		}

		#define CREATE_PRIMATIVE_BIND_DESCRIPTOR(mysql_type, c_type, size) \
			case mysql_type:\
				static ResultBindDescriptor _ ##mysql_type = {\
						size,\
						_do_destroy_primitive<size>,\
						_do_bind_primitive<mysql_type, size>,\
						m2ps<c_type>\
				};\
				return &_ ##mysql_type;

		const ResultBindDescriptor* get_bind_descriptor(enum_field_types type) {
			switch (type) {
				case MYSQL_TYPE_NULL:
					static ResultBindDescriptor _null = {
							/* primitive_size */    0,
							/* destroy */           _do_destroy_primitive<0>,
							/* create */            _do_bind_primitive<MYSQL_TYPE_NULL, 0>,
							/* get_as_string */     [](MYSQL_BIND&, string& str) { str.clear(); return true; }
					};
					return &_null;
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_TINY, int8_t, 1);
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_SHORT, int16_t, 2);
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_INT24, int32_t, 4);
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_LONG, int32_t, 4);
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_LONGLONG, int64_t, 8);
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_DOUBLE, double, sizeof(double));
				CREATE_PRIMATIVE_BIND_DESCRIPTOR(MYSQL_TYPE_FLOAT, float, sizeof(float));
				case MYSQL_TYPE_VAR_STRING:
				case MYSQL_TYPE_STRING:
				case MYSQL_TYPE_BLOB:
					static ResultBindDescriptor _string = {
							/* primitive_size */    sizeof(void*) + sizeof(unsigned long*), /* we store the allocated buffer in the primitive types buffer and the length */
							/* destroy */           [](char*& primitive) { ::free(*(void**) primitive); primitive += sizeof(void*); primitive += sizeof(unsigned long*); },
							/* create */            [](const MYSQL_FIELD& field, MYSQL_BIND& bind, char*& primitive) {
								bind.buffer_length = field.max_length > 0 ? field.max_length : min(field.length, 5UL * 1024UL * 1024UL);
								bind.buffer = malloc(bind.buffer_length);
								bind.buffer_type = MYSQL_TYPE_BLOB;

								*(void**) primitive = bind.buffer;
								primitive += sizeof(void*);

								bind.length = (unsigned long*) primitive;
								primitive += sizeof(unsigned long*);

								return bind.buffer != nullptr;
							},
							/* get_as_string */     [](MYSQL_BIND& bind, std::string& result) {
								auto length = bind.length ? *bind.length : bind.length_value;
								result.reserve(length);
								result.assign((const char*) bind.buffer, length);
								return true;
							}
					};
					return &_string;
				default:
					return nullptr;
			}
		}

		#undef CREATE_PRIMATIVE_BIND_DESCRIPTOR

		struct ResultBind {
			size_t field_count = 0;
			BindMemory* memory = nullptr;
			const ResultBindDescriptor** descriptors = nullptr;

			~ResultBind() {
				if(memory) {
					auto memory_ptr = (char*) this->memory + (sizeof(MYSQL_BIND) * field_count);

					for(size_t index = 0; index < this->field_count; index++)
						this->descriptors[index]->destroy(memory_ptr);

					::free(memory);
				}
				delete[] descriptors;
			}

			ResultBind(const ResultBind&) = delete;
			ResultBind(ResultBind&&) = default;

			inline bool get_as_string(size_t column, string& result) {
				if(!descriptors) return false;

				auto& bind_ptr = *(MYSQL_BIND*) ((char*) this->memory + sizeof(MYSQL_BIND) * column);
				return this->descriptors[column]->get_as_string(bind_ptr, result);
			}

			inline bool get_as_string(string* results) {
				if(!descriptors) return false;

				auto bind_ptr = (MYSQL_BIND*) this->memory;
				for(int index = 0; index <  this->field_count; index++)
					if(!this->descriptors[index]->get_as_string(*bind_ptr, results[index]))
						return false;
					else
						bind_ptr++;
				return true;
			}
		};

		bool create_result_bind(size_t field_count, MYSQL_FIELD* fields, ResultBind& result) {
			size_t required_bytes = sizeof(MYSQL_BIND) * field_count;

			assert(!result.field_count);
			assert(!result.descriptors);
			assert(!result.memory);
			result.descriptors = new const ResultBindDescriptor*[field_count];
			result.field_count = field_count;

			for(size_t index = 0; index < field_count; index++) {
				result.descriptors[index] = get_bind_descriptor(fields[index].type);
				if(!result.descriptors[index]) return false;

				required_bytes += result.descriptors[index]->primitive_size;
			}

			if(!required_bytes) {
				result.memory = nullptr;
				return true;
			}

			logTrace(LOG_GENERAL, "[MYSQL] Allocated {} bytes for response", required_bytes);
			result.memory = (BindMemory*) malloc(required_bytes);
			if(!result.memory)
				return false;

			memset(result.memory, 0, required_bytes);
			auto memory_ptr = (char*) result.memory + (sizeof(MYSQL_BIND) * field_count);
			auto bind_ptr = (MYSQL_BIND*) result.memory;
			for(size_t index = 0; index < field_count; index++) {
				if(!result.descriptors[index]->create(fields[index], *bind_ptr, memory_ptr)) return false;
				bind_ptr->buffer_type = fields[index].type;
				bind_ptr++;
			}
			assert(memory_ptr == ((char*) result.memory + required_bytes)); /* Overflow check */
			return true;
		}
	}

AcquiredConnection::AcquiredConnection(MySQLManager* owner, const std::shared_ptr<sql::mysql::Connection> &connection) : owner(owner), connection(connection) { }
AcquiredConnection::~AcquiredConnection() {
	{
		lock_guard lock{this->connection->used_lock};
		this->connection->used = false;
	}

	{
		lock_guard lock(this->owner->connections_lock);
		this->owner->connections_condition.notify_one();
	}
}
std::unique_ptr<AcquiredConnection> MySQLManager::next_connection() {
	unique_ptr<AcquiredConnection> result;
	{
		unique_lock connections_lock(this->connections_lock);

		while(!result) {
			size_t available_connections = 0;
			for(const auto& connection : this->connections) {
				available_connections++;

				{
					lock_guard use_lock(connection->used_lock);
					if(connection->used) continue;
						connection->used = true;
				}

				result = std::make_unique<AcquiredConnection>(this, connection);
				break;
			}

			if(!result) {
				if(available_connections == 0) {
					if(this->listener_disconnected)
						this->listener_disconnected(false);
					this->disconnect();
					return nullptr;
				}

				this->connections_condition.wait(connections_lock); /* wait for the next connection */
			}
		}
	}
    //TODO: Test if the connection hasn't been used for a longer while if so use mysql_ping() to verify the connection

    return result;
}

void MySQLManager::connection_closed(const std::shared_ptr<sql::mysql::Connection> &connection) {
	bool call_disconnect = false;
	{
		unique_lock connections_lock(this->connections_lock);
		auto index = find(this->connections.begin(), this->connections.end(), connection);
		if(index == this->connections.end()) return;

		this->connections.erase(index);
		call_disconnect = this->connections.empty();
	}

	auto dl = this->listener_disconnected;
	if(call_disconnect && dl)
		dl(this->disconnecting);
}

result MySQLManager::executeCommand(std::shared_ptr<CommandData> _ptr) {
	auto ptr = static_pointer_cast<MySQLCommand>(_ptr);
	if(!ptr) { return {-1, "invalid command handle"}; }

	std::lock_guard<threads::Mutex> lock(ptr->lock);
	auto command = ptr->sql_command;

	auto variables = ptr->variables;
	vector<variable> mapped_variables;
	if(!sql::mysql::evaluate_sql_query(command, variables, mapped_variables)) return {ptr->sql_command, -1, "Could not map sqlite vars to mysql!"};

	FreeGuard<BindMemory> bind_parameter_memory{nullptr};
	if(!sql::mysql::create_bind(bind_parameter_memory.ptr, mapped_variables)) return {ptr->sql_command, -1, "Failed to allocate bind memory!"};

	ResultBind bind_result_data{0, nullptr, nullptr};

	auto connection = this->next_connection();
	if(!connection) return {ptr->sql_command, -1, "Could not get a valid connection!"};

	StatementGuard stmt_guard{mysql_stmt_init(connection->connection->handle)};
	if(!stmt_guard.stmt)
		return {ptr->sql_command, -1, "failed to allocate statement"};

	if(mysql_stmt_prepare(stmt_guard.stmt, command.c_str(), command.length())) {
		auto errc = mysql_stmt_errno(stmt_guard.stmt);
		if(errc == CR_SERVER_GONE_ERROR || errc == CR_SERVER_LOST || errc == CR_CONNECTION_ERROR)
			this->connection_closed(connection->connection);

		return {ptr->sql_command, -1, "failed to prepare statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	}

	/* validate all parameters */
	auto parameter_count = mysql_stmt_param_count(stmt_guard.stmt);
	if(parameter_count != mapped_variables.size())
		return {ptr->sql_command, -1, "invalid parameter count. Statement contains " + to_string(parameter_count) + " parameters but only " + to_string(mapped_variables.size()) + " are given."};

	if(bind_parameter_memory.ptr) {
		if(mysql_stmt_bind_param(stmt_guard.stmt, (MYSQL_BIND*) bind_parameter_memory.ptr))
			return {ptr->sql_command, -1, "failed to bind parameters to statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	} else if(parameter_count > 0)
		return {ptr->sql_command, -1, "invalid parameter count. Statement contains " + to_string(parameter_count) + " parameters but only " + to_string(mapped_variables.size()) + " are given (bind nullptr)."};


	if(mysql_stmt_execute(stmt_guard.stmt)) {
		auto errc = mysql_stmt_errno(stmt_guard.stmt);
		if(errc == CR_SERVER_GONE_ERROR || errc == CR_SERVER_LOST || errc == CR_CONNECTION_ERROR)
			this->connection_closed(connection->connection);

		return {ptr->sql_command, -1, "failed to execute query statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	}

	return result::success;
}

result MySQLManager::queryCommand(shared_ptr<CommandData> _ptr, const QueryCallback &fn) {
	auto ptr = static_pointer_cast<MySQLCommand>(_ptr);
	if(!ptr) { return {-1, "invalid command handle"}; }

	std::lock_guard<threads::Mutex> lock(ptr->lock);
	auto command = ptr->sql_command;

	auto variables = ptr->variables;
	vector<variable> mapped_variables;
	if(!sql::mysql::evaluate_sql_query(command, variables, mapped_variables)) return {ptr->sql_command, -1, "Could not map sqlite vars to mysql!"};

	FreeGuard<BindMemory> bind_parameter_memory{nullptr};
	if(!sql::mysql::create_bind(bind_parameter_memory.ptr, mapped_variables)) return {ptr->sql_command, -1, "Failed to allocate bind memory!"};

	ResultBind bind_result_data{0, nullptr, nullptr};

	auto connection = this->next_connection();
	if(!connection) return {ptr->sql_command, -1, "Could not get a valid connection!"};

	StatementGuard stmt_guard{mysql_stmt_init(connection->connection->handle)};
	if(!stmt_guard.stmt)
		return {ptr->sql_command, -1, "failed to allocate statement"};

	if(mysql_stmt_prepare(stmt_guard.stmt, command.c_str(), command.length())) {
		auto errc = mysql_stmt_errno(stmt_guard.stmt);
		if(errc == CR_SERVER_GONE_ERROR || errc == CR_SERVER_LOST || errc == CR_CONNECTION_ERROR)
			this->connection_closed(connection->connection);

		return {ptr->sql_command, -1, "failed to prepare statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	}

	/* validate all parameters */
	{
		auto parameter_count = mysql_stmt_param_count(stmt_guard.stmt);
		if(parameter_count != mapped_variables.size())
			return {ptr->sql_command, -1, "invalid parameter count. Statement contains " + to_string(parameter_count) + " parameters but only " + to_string(mapped_variables.size()) + " are given."};
	}

	if(bind_parameter_memory.ptr) {
		if(mysql_stmt_bind_param(stmt_guard.stmt, (MYSQL_BIND*) bind_parameter_memory.ptr))
			return {ptr->sql_command, -1, "failed to bind parameters to statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	}

	if(mysql_stmt_execute(stmt_guard.stmt)) {
		auto errc = mysql_stmt_errno(stmt_guard.stmt);
		if(errc == CR_SERVER_GONE_ERROR || errc == CR_SERVER_LOST || errc == CR_CONNECTION_ERROR)
			this->connection_closed(connection->connection);

		return {ptr->sql_command, -1, "failed to execute query statement: " + string(mysql_stmt_error(stmt_guard.stmt))};
	}

	//if(mysql_stmt_store_result(stmt_guard.stmt))
	//	return {ptr->sql_command, -1, "failed to store query result: " + string(mysql_stmt_error(stmt_guard.stmt))};

	ResultGuard result_guard{mysql_stmt_result_metadata(stmt_guard.stmt)};
	if(!result_guard.result)
		return {ptr->sql_command, -1, "failed to query result metadata: " + string(mysql_stmt_error(stmt_guard.stmt))};


	auto field_count = mysql_num_fields(result_guard.result);
	DeleteAGuard<string> field_names{new string[field_count]};
	DeleteAGuard<string> field_values{new string[field_count]};

	{
		auto field_meta = mysql_fetch_fields(result_guard.result);
		if(!field_meta && field_count > 0)
			return {ptr->sql_command, -1, "failed to fetch field meta"};

		if(!sql::mysql::create_result_bind(field_count, field_meta, bind_result_data))
			return {ptr->sql_command, -1, "failed to allocate result buffer"};

		if(mysql_stmt_bind_result(stmt_guard.stmt, (MYSQL_BIND*) bind_result_data.memory))
			return {ptr->sql_command, -1, "failed to bind response buffer to statement: " + string(mysql_stmt_error(stmt_guard.stmt))};

		for(size_t index = 0; index < field_count; index++) {
			field_names.ptr[index] = field_meta[index].name; // field_meta cant be null because it has been checked above
			//cout << field_names.ptr[index] << " - " << field_meta[index].max_length << endl;
		}
	}

	bool user_quit = false;
	int stmt_code, row_id = 0;
	while(!(stmt_code = mysql_stmt_fetch(stmt_guard.stmt))) {
		bind_result_data.get_as_string(field_values.ptr);

		if(fn(field_count, field_values.ptr, field_names.ptr) != 0) {
			user_quit = true;
			break;
		}

		row_id++;
	}

	if(!user_quit) {
		if(stmt_code == 1) {
			auto errc = mysql_stmt_errno(stmt_guard.stmt);
			if(errc == CR_SERVER_GONE_ERROR || errc == CR_SERVER_LOST || errc == CR_CONNECTION_ERROR)
				this->connection_closed(connection->connection);

			return {ptr->sql_command, -1, "failed to fetch response row " + to_string(row_id) + ": " + string(mysql_stmt_error(stmt_guard.stmt))};
		} else if(stmt_code == MYSQL_NO_DATA)
			;
		else if(stmt_code == MYSQL_DATA_TRUNCATED)
			return {ptr->sql_command, -1, "response data has been truncated"};
	}
	return result::success;
}