/*  -*-c++-*- 
 *  Copyright (C) 2008 Cedric Pinson <cedric.pinson@plopbyte.net>
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library 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 
 * OpenSceneGraph Public License for more details.
*/


#ifndef OSGANIMATION_TARGET_H
#define OSGANIMATION_TARGET_H

#include <vector>
#include <osg/Quat>
#include <osg/Vec3>
#include <osg/Vec2>
#include <osg/Vec4>
#include <osg/Referenced>
#include <osgAnimation/Export>

namespace osgAnimation 
{

    class Channel;

    class OSGANIMATION_EXPORT Target : public osg::Referenced
    {
    public:
            
        Target();
        virtual ~Target() {}
        void reset() { _weight = 0; _priorityWeight = 0; }
        int getCount() const { return referenceCount(); }
        float getWeight() const { return _weight; }
    protected:
        float _weight;
        float _priorityWeight;
        int _lastPriority;
    };


    template <class T>
    class TemplateTarget : public Target
    {
    public:
            
        TemplateTarget() : _target() {}
        TemplateTarget(const T& v) { setValue(v); }
        TemplateTarget(const TemplateTarget& v) { setValue(v.getValue()); }

        inline void lerp(float t, const T& a, const T& b);

        /**
         *  The priority is used to detect a change of priority
         *  It's important to update animation target in priority
         *  order. eg:
         *  all animation with priority 1
         *  all animation with priority 0
         *  all animation with priority -1
         *  ...
         */
        void update(float weight, const T& val, int priority)
        {
            if (_weight || _priorityWeight)
            {
                if (_lastPriority != priority)
                {
                    // change in priority
                    // add to weight with the same previous priority cumulated weight
                    _weight += _priorityWeight * (1.0 - _weight);
                    _priorityWeight = 0;
                    _lastPriority = priority;
                }

                _priorityWeight += weight;
                float t = (1.0 - _weight) * weight / _priorityWeight;
                lerp(t, _target, val);
            }
            else
            {
                _priorityWeight = weight;
                _lastPriority = priority;
                _target = val;
            }
        }
        const T& getValue() const { return _target; }

        void setValue(const T& value) { _target = value; }

    protected:

        T _target;
    };

    template <class T>
    inline void TemplateTarget<T>::lerp(float t, const T& a, const T& b)
    {
        _target = a * (1.0f - t) + b * t;
    }

    template <>
    inline void TemplateTarget<osg::Quat>::lerp(float t, const osg::Quat& a, const osg::Quat& b)
    {
        if (a.asVec4() * b.asVec4() < 0.0)
        {
            _target = a * (1.0f - t) + b * -t;
        }
        else
        {
            _target = a * (1.0f - t) + b * t;
        }

        osg::Quat::value_type len2 = _target.length2();
        if ( len2 != 1.0 && len2 != 0.0) 
            _target *= 1.0/sqrt(len2);
    }

    typedef TemplateTarget<osg::Quat> QuatTarget;
    typedef TemplateTarget<osg::Vec3> Vec3Target;
    typedef TemplateTarget<osg::Vec4> Vec4Target;
    typedef TemplateTarget<osg::Vec2> Vec2Target;
    typedef TemplateTarget<float> FloatTarget;
    typedef TemplateTarget<double> DoubleTarget;
  
}

#endif