/*
    Scan Tailor - Interactive post-processing tool for scanned pages.
    Copyright (C)  Joseph Artsimovich <joseph.artsimovich@gmail.com>

    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 3 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, see <http://www.gnu.org/licenses/>.
*/

#ifndef SPFIT_LINEAR_FORCE_BALANCER_H_
#define SPFIT_LINEAR_FORCE_BALANCER_H_

namespace spfit
{

/**
 * \brief Implements one possible strategy of choosing the internal / external force ratio.
 *
 * The strategy is starting with some value and linearly changing it (usually decreasing)
*  over time.
 */
class LinearForceBalancer
{
    // Member-wise copying is OK.
public:
    /**
     * Sets both the current and the target ratio, so that it doesn't change over time.
     */
    LinearForceBalancer(double internal_external_ratio);

    double currentRatio() const
    {
        return m_currentRatio;
    }

    void setCurrentRatio(double internal_external_ratio);

    double targetRatio() const
    {
        return m_targetRatio;
    }

    void setTargetRatio(double internal_external_ratio);

    /**
     * Sets the number of iterations after which the internal / external force
     * ratio reaches its target value.  This method doesn't change the
     * current ratio.
     */
    void setIterationsToTarget(int iterations);

    double calcInternalForceWeight(double internal_force, double external_force) const;

    /**
     * Returns the current internal / external force ratio, then moves
     * it towards its target value.  After it reaches its target value,
     * further nextIteration() calls will keep returning the same value.
     */
    void nextIteration();
private:
    void recalcRateOfChange();

    double m_currentRatio;
    double m_targetRatio;
    double m_rateOfChange;
    int m_iterationsToTarget;
};

} // namespace spfit

#endif
