/*
---------------------------------------------------------------------------
Open Asset Import Library (assimp)
---------------------------------------------------------------------------

Copyright (c) 2006-2019, assimp team

All rights reserved.

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  following disclaimer.

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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*/

#include "assimp_view.h"

#include <tuple>

using namespace AssimpView;

// ------------------------------------------------------------------------------------------------
// Constructor on a given animation.
AnimEvaluator::AnimEvaluator( const aiAnimation* pAnim)
{
    mAnim = pAnim;
    mLastTime = 0.0;
    mLastPositions.resize( pAnim->mNumChannels, std::make_tuple( 0, 0, 0));
}

// ------------------------------------------------------------------------------------------------
// Evaluates the animation tracks for a given time stamp.
void AnimEvaluator::Evaluate( double pTime)
{
    // extract ticks per second. Assume default value if not given
    double ticksPerSecond = mAnim->mTicksPerSecond != 0.0 ? mAnim->mTicksPerSecond : 25.0;
    // every following time calculation happens in ticks
    pTime *= ticksPerSecond;

    // map into anim's duration
    double time = 0.0f;
    if( mAnim->mDuration > 0.0)
        time = fmod( pTime, mAnim->mDuration);

    if( mTransforms.size() != mAnim->mNumChannels)
        mTransforms.resize( mAnim->mNumChannels);

    // calculate the transformations for each animation channel
    for( unsigned int a = 0; a < mAnim->mNumChannels; a++)
    {
        const aiNodeAnim* channel = mAnim->mChannels[a];

        // ******** Position *****
        aiVector3D presentPosition( 0, 0, 0);
        if( channel->mNumPositionKeys > 0)
        {
            // Look for present frame number. Search from last position if time is after the last time, else from beginning
            // Should be much quicker than always looking from start for the average use case.
            unsigned int frame = (time >= mLastTime) ? std::get<0>(mLastPositions[a]) : 0;
            while( frame < channel->mNumPositionKeys - 1)
            {
                if( time < channel->mPositionKeys[frame+1].mTime)
                    break;
                frame++;
            }

            // interpolate between this frame's value and next frame's value
            unsigned int nextFrame = (frame + 1) % channel->mNumPositionKeys;
            const aiVectorKey& key = channel->mPositionKeys[frame];
            const aiVectorKey& nextKey = channel->mPositionKeys[nextFrame];
            double diffTime = nextKey.mTime - key.mTime;
            if( diffTime < 0.0)
                diffTime += mAnim->mDuration;
            if( diffTime > 0)
            {
                float factor = float( (time - key.mTime) / diffTime);
                presentPosition = key.mValue + (nextKey.mValue - key.mValue) * factor;
            } else
            {
                presentPosition = key.mValue;
            }

            std::get<0>(mLastPositions[a]) = frame;
        }

        // ******** Rotation *********
        aiQuaternion presentRotation( 1, 0, 0, 0);
        if( channel->mNumRotationKeys > 0)
        {
            unsigned int frame = (time >= mLastTime) ? std::get<1>(mLastPositions[a]) : 0;
            while( frame < channel->mNumRotationKeys - 1)
            {
                if( time < channel->mRotationKeys[frame+1].mTime)
                    break;
                frame++;
            }

            // interpolate between this frame's value and next frame's value
            unsigned int nextFrame = (frame + 1) % channel->mNumRotationKeys;
            const aiQuatKey& key = channel->mRotationKeys[frame];
            const aiQuatKey& nextKey = channel->mRotationKeys[nextFrame];
            double diffTime = nextKey.mTime - key.mTime;
            if( diffTime < 0.0)
                diffTime += mAnim->mDuration;
            if( diffTime > 0)
            {
                float factor = float( (time - key.mTime) / diffTime);
                aiQuaternion::Interpolate( presentRotation, key.mValue, nextKey.mValue, factor);
            } else
            {
                presentRotation = key.mValue;
            }

            std::get<1>(mLastPositions[a]) = frame;
        }

        // ******** Scaling **********
        aiVector3D presentScaling( 1, 1, 1);
        if( channel->mNumScalingKeys > 0)
        {
            unsigned int frame = (time >= mLastTime) ? std::get<2>(mLastPositions[a]) : 0;
            while( frame < channel->mNumScalingKeys - 1)
            {
                if( time < channel->mScalingKeys[frame+1].mTime)
                    break;
                frame++;
            }

            // TODO: (thom) interpolation maybe? This time maybe even logarithmic, not linear
            presentScaling = channel->mScalingKeys[frame].mValue;
            std::get<2>(mLastPositions[a]) = frame;
        }

        // build a transformation matrix from it
        aiMatrix4x4& mat = mTransforms[a];
        mat = aiMatrix4x4( presentRotation.GetMatrix());
        mat.a1 *= presentScaling.x; mat.b1 *= presentScaling.x; mat.c1 *= presentScaling.x;
        mat.a2 *= presentScaling.y; mat.b2 *= presentScaling.y; mat.c2 *= presentScaling.y;
        mat.a3 *= presentScaling.z; mat.b3 *= presentScaling.z; mat.c3 *= presentScaling.z;
        mat.a4 = presentPosition.x; mat.b4 = presentPosition.y; mat.c4 = presentPosition.z;
        //mat.Transpose();
    }

    mLastTime = time;
}