//================================================================================
// Name        : SensorGroupTemplate.h
// Author      : Micha Mueller
// Copyright   : Leibniz Supercomputing Centre
// Description : Interface template for sensor group functionality.
//================================================================================

//================================================================================
// This file is part of DCDB (DataCenter DataBase)
// Copyright (C) 2018-2019 Leibniz Supercomputing Centre
//
// This program 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.
//
// This program 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 this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
//================================================================================

#ifndef SENSORGROUPTEMPLATE_H_
#define SENSORGROUPTEMPLATE_H_

#include "SensorGroupInterface.h"
#include "EntityInterface.h"

#include "timestamp.h"

#include <vector>
#include <memory>

/**
 * @brief Interface template for sensor group implementations with entities.
 *
 * @details There is a partial template specialization for E = nullptr_t, i.e.
 *          for groups without entities, see SensorGroupTemplate<S, nullptr_t>.
 *          Common code has to be duplicated and maintained twice here and in
 *          the SensorGroupTemplate<S, nullptr_t>. However, having two templates
 *          for cases with and without entities greatly reduces code duplication
 *          in derived plugin sensor groups.
 *
 * @ingroup pusherplugins
 */
template <class S, class E = nullptr_t>
class SensorGroupTemplate : public SensorGroupInterface {
	//the template shall only be instantiated for classes which derive from SensorBase and EntityInterface respectively
	static_assert(std::is_base_of<SensorBase, S>::value, "S must derive from SensorBase!");
	static_assert(std::is_base_of<EntityInterface, E>::value, "E must derive from EntityInterface!");

protected:
	using S_Ptr = std::shared_ptr<S>;

public:
	SensorGroupTemplate(const std::string groupName) :
		SensorGroupInterface(groupName),
		_entity(nullptr) {}

	SensorGroupTemplate(const SensorGroupTemplate& other) :
		SensorGroupInterface(other),
		_entity(other._entity) {

		for(auto s : other._sensors) {
			S_Ptr sensor = std::make_shared<S>(*s);
			_sensors.push_back(sensor);
			_baseSensors.push_back(sensor);
		}
	}

	virtual ~SensorGroupTemplate() {
	    if(_keepRunning) {
	        stop();
	    }

		_sensors.clear();
		_baseSensors.clear();
	}

	SensorGroupTemplate& operator=(const SensorGroupTemplate& other) {
		SensorGroupInterface::operator=(other);
		_sensors.clear();
		_baseSensors.clear();

		for(auto s : other._sensors) {
			S_Ptr sensor = std::make_shared<S>(*s);
			_sensors.push_back(sensor);
			_baseSensors.push_back(sensor);
		}

		_entity = other._entity;

		return *this;
	}

	void setEntity(E* entity) { _entity = entity; }
	E* const getEntity() const { return _entity; }

	/**
	 * @brief Initialize the sensor group.
	 *
	 * @details This method must not be overwritten. See execOnInit() if custom
	 *          actions are required during initialization. Initializes
	 *          associated sensors and entity.
	 *
	 * @param io IO service to initialize the timer with.
	 */
    virtual void init(boost::asio::io_service& io) final override {
        if(!_entity) {
            LOG(error) << "No entity set for group " << _groupName << "! Cannot initialize group";
            return;
        }

        SensorGroupInterface::init(io);

        for(auto s : _sensors) {
            s->initSensor(_interval);
        }

        _entity->init(io);

        this->execOnInit();
    }

    /**
     * @brief Start the sensor group (i.e. start collecting data).
     *
     * @details This method must not be overwritten. See execOnStart() if custom
     *          actions are required during startup.
     */
    virtual void start() final override {
        if (_keepRunning) {
            //we have been started already
            LOG(info) << "Sensorgroup " << _groupName << " already running.";
            return;
        }

        if (!this->execOnStart()) {
            LOG(error) << "Sensorgroup " << _groupName << ": Startup failed.";
            return;
        }

        if (_entity) {
            _keepRunning = true;
            _pendingTasks++;
            _timer->async_wait(_entity->getStrand()->wrap(std::bind(&SensorGroupTemplate::readAsync, this)));
            LOG(info) << "Sensorgroup " << _groupName << " started.";
        } else {
            LOG(error) << "No entity set for group " << _groupName << "! Cannot start polling.";
        }
    }

    /**
     * @brief Stop the sensor group (i.e. stop collecting data).
     *
     * @details This method must not be overwritten. See execOnStop() if custom
     *          actions are required during shutdown.
     */
    virtual void stop() final override {
        if (!_keepRunning) {
            LOG(info) << "Sensorgroup " << _groupName << " already stopped.";
            return;
        }

        _keepRunning = false;
        //cancel any outstanding readAsync()
        _timer->cancel();
        wait();

        this->execOnStop();
        LOG(info) << "Sensorgroup " << _groupName << " stopped.";
    }

    /**
     * @brief Add a sensor to this group.
     *
     * @details Not intended to be overwritten.
     *
     * @param s Shared pointer to the sensor.
     */
	virtual void pushBackSensor(SBasePtr s) final override {
		//check if dynamic cast returns nullptr
		if (S_Ptr dSensor = std::dynamic_pointer_cast<S>(s)) {
			_sensors.push_back(dSensor);
			_baseSensors.push_back(s);
		} else {
			LOG(warning) << "Group " << _groupName << ": Type mismatch when storing sensor! Sensor omitted";
		}
	}

	/**
     * @brief Retrieve all sensors of this group.
     *
     * @details Not intended to be overwritten.
     *
     * @return A std::vector with shared pointers to all associated sensors.
     */
	virtual std::vector<SBasePtr>& getSensors() final override { return _baseSensors; }

	/**
     * @brief Print SensorGroup configuration.
     *
     * @details Always call %SensorGroupTemplate::printConfig() to print
     *          complete configuration of a sensor group. This method takes
     *          care of calling SensorGroupInterface::printConfig() and
     *          derived %printConfig() methods in correct order.
     *
     * @param ll Log severity level to be used from logger.
     */
	virtual void printConfig(LOG_LEVEL ll) final override {
	    //print common base attributes
	    SensorGroupInterface::printConfig(ll);

	    //print plugin specific group attributes
	    this->printGroupConfig(ll);

        if (_entity) {
            LOG_VAR(ll) << "            Entity " << _entity->getName();
        } else {
            LOG_VAR(ll) << "            No entity set!";
        }

	    //print associated sensors
        LOG_VAR(ll) << "            Sensors:";
        for(auto s : _sensors) {
            s->SensorBase::printConfig(ll, lg);
            s->printConfig(ll, lg);
        }
	}

protected:

	/**
     * @brief Asynchronous callback if _timer expires.
     *
     * @details Issues a read() and sets the timer again if _keepRunning is true.
     *          Not intended to be overwritten.
     */
	void readAsync() final override {
	    this->read();
	    if (_timer && _keepRunning) {
	        _timer->expires_at(timestamp2ptime(nextReadingTime()));
	        _pendingTasks++;
	        _timer->async_wait(_entity->getStrand()->wrap(std::bind(&SensorGroupTemplate::readAsync, this)));
	    }
	    _pendingTasks--;
	}

	//TODO move common logic to interface
	///@name Can be overwritten
	///@{
	/**
     * @brief Implement plugin specific actions to initialize a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions for initialization, this should be implemented here.
     *          %execOnInit() is appropriately called by this template during
     *          init().
     */
	virtual void execOnInit() { /* do nothing if not overwritten */ }

    /**
     * @brief Implement plugin specific actions to start a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions to start polling data (e.g. open a file descriptor),
     *          this should be implemented here. %execOnStart() is appropriately
     *          called by this template during start().
     *
     * @return True on success, false otherwise.
     */
    virtual bool execOnStart() { return true; }

    /**
     * @brief Implement plugin specific actions to stop a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions to stop polling data (e.g. close a file descriptor),
     *          this should be implemented here. %execOnStop() is appropriately
     *          called by this template during stop().
     */
    virtual void execOnStop() { /* do nothing if not overwritten */ }
    ///@}

	std::vector<S_Ptr>    _sensors; ///< Sensors associated with this group
	std::vector<SBasePtr> _baseSensors; ///< Maintain vector with SensorBase pointers for fast getSensors() implementation
	E*                    _entity; ///< Entity this group is associated to
};


////////////////////////////////////////////////////////////////////////////////
// Partial template specialization for E = nullptr_t
////////////////////////////////////////////////////////////////////////////////


/**
 * @brief Interface partial template specialization for sensor group
 *        implementations without entities.
 *
 * @details There is a general template for groups with entities, see
 *          SensorGroupTemplate. Common code has to be duplicated and maintained
 *          twice here and in SensorGroupTemplate. However, having two templates
 *          for cases with and without entities greatly reduces code duplication
 *          in derived plugin sensor groups.
 *
 * @ingroup pusherplugins
 */
template <class S>
class SensorGroupTemplate<S, nullptr_t> : public SensorGroupInterface {
    //the template shall only be instantiated for classes which derive from SensorBase
    static_assert(std::is_base_of<SensorBase, S>::value, "S must derive from SensorBase!");

protected:
    using S_Ptr = std::shared_ptr<S>;

public:
    SensorGroupTemplate(const std::string groupName) :
        SensorGroupInterface(groupName){}

    SensorGroupTemplate(const SensorGroupTemplate& other) :
        SensorGroupInterface(other){

        for(auto s : other._sensors) {
            S_Ptr sensor = std::make_shared<S>(*s);
            _sensors.push_back(sensor);
            _baseSensors.push_back(sensor);
        }
    }

    virtual ~SensorGroupTemplate() {
        if(_keepRunning) {
            stop();
        }

        _sensors.clear();
        _baseSensors.clear();
    }

    SensorGroupTemplate& operator=(const SensorGroupTemplate& other) {
        SensorGroupInterface::operator=(other);
        _sensors.clear();
        _baseSensors.clear();

        for(auto s : other._sensors) {
            S_Ptr sensor = std::make_shared<S>(*s);
            _sensors.push_back(sensor);
            _baseSensors.push_back(sensor);
        }

        return *this;
    }

    /**
     * @brief Initialize the sensor group.
     *
     * @details This method must not be overwritten. See execOnInit() if custom
     *          actions are required during initialization. Initializes
     *          associated sensors and entity.
     *
     * @param io IO service to initialize the timer with.
     */
    virtual void init(boost::asio::io_service& io) final override {
        SensorGroupInterface::init(io);

        for(auto s : _sensors) {
            s->initSensor(_interval);
        }

        this->execOnInit();
    }

    /**
     * @brief Start the sensor group (i.e. start collecting data).
     *
     * @details This method must not be overwritten. See execOnStart() if custom
     *          actions are required during startup.
     */
    virtual void start() final override {
        if (_keepRunning) {
            //we have been started already
            LOG(info) << "Sensorgroup " << _groupName << " already running.";
            return;
        }

        if (!this->execOnStart()) {
            LOG(error) << "Sensorgroup " << _groupName << ": Startup failed.";
            return;
        }

        _keepRunning = true;
        _pendingTasks++;
        _timer->async_wait(std::bind(&SensorGroupTemplate::readAsync, this));
        LOG(info) << "Sensorgroup " << _groupName << " started.";
    }

    /**
     * @brief Stop the sensor group (i.e. stop collecting data).
     *
     * @details This method must not be overwritten. See execOnStop() if custom
     *          actions are required during shutdown.
     */
    virtual void stop() final override {
        if (!_keepRunning) {
            LOG(info) << "Sensorgroup " << _groupName << " already stopped.";
            return;
        }

        _keepRunning = false;
        //cancel any outstanding readAsync()
        _timer->cancel();
        wait();

        this->execOnStop();
        LOG(info) << "Sensorgroup " << _groupName << " stopped.";
    }

    /**
     * @brief Add a sensor to this group.
     *
     * @details Not intended to be overwritten.
     *
     * @param s Shared pointer to the sensor.
     */
    virtual void pushBackSensor(SBasePtr s) final override {
        //check if dynamic cast returns nullptr
        if (S_Ptr dSensor = std::dynamic_pointer_cast<S>(s)) {
            _sensors.push_back(dSensor);
            _baseSensors.push_back(s);
        } else {
            LOG(warning) << "Group " << _groupName << ": Type mismatch when storing sensor! Sensor omitted";
        }
    }

    /**
     * @brief Retrieve all sensors of this group.
     *
     * @details Not intended to be overwritten.
     *
     * @return A std::vector with shared pointers to all associated sensors.
     */
    virtual std::vector<SBasePtr>& getSensors() final override { return _baseSensors; }

    /**
     * @brief Print SensorGroup configuration.
     *
     * @details Always call %SensorGroupTemplate::printConfig() to print
     *          complete configuration of a sensor group. This method takes
     *          care of calling SensorGroupInterface::printConfig() and
     *          derived %printConfig() methods in correct order.
     *
     * @param ll Log severity level to be used from logger.
     */
    virtual void printConfig(LOG_LEVEL ll) final override {
        //print common base attributes
        SensorGroupInterface::printConfig(ll);

        //print plugin specific group attributes
        this->printGroupConfig(ll);

        //print associated sensors
        LOG_VAR(ll) << "            Sensors:";
        for(auto s : _sensors) {
            s->SensorBase::printConfig(ll, lg);
            s->printConfig(ll, lg);
        }
    }

protected:

    /**
     * @brief Asynchronous callback if _timer expires.
     *
     * @details Issues a read() and sets the timer again if _keepRunning is true.
     *          Not intended to be overwritten.
     */
    void readAsync() final override {
        this->read();
        if (_timer && _keepRunning) {
            _timer->expires_at(timestamp2ptime(nextReadingTime()));
            _pendingTasks++;
            _timer->async_wait(std::bind(&SensorGroupTemplate::readAsync, this));
        }
        _pendingTasks--;
    }

    ///@name Can be overwritten
    ///@{
    /**
     * @brief Implement plugin specific actions to initialize a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions for initialization, this should be implemented here.
     *          %initGroup() is appropriately called by this template during
     *          init().
     */
    virtual void execOnInit() { /* do nothing if not overwritten */ }

    /**
     * @brief Implement plugin specific actions to start a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions to start polling data (e.g. open a file descriptor),
     *          this should be implemented here. %startGroup() is appropriately
     *          called by this template during start().
     *
     * @return True on success, false otherwise.
     */
    virtual bool execOnStart() { return true; }

    /**
     * @brief Implement plugin specific actions to stop a group here.
     *
     * @details If a derived class (i.e. a plugin group) requires further custom
     *          actions to stop polling data (e.g. close a file descriptor),
     *          this should be implemented here. %stopGroup() is appropriately
     *          called by this template during stop().
     */
    virtual void execOnStop() { /* do nothing if not overwritten */ }
    ///@}

    std::vector<S_Ptr>    _sensors; ///< Sensors associated with this group
    std::vector<SBasePtr> _baseSensors; ///< Maintain vector with SensorBase pointers for fast getSensors() implementation
};

#endif /* SENSORGROUPTEMPLATE_H_ */