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

Copyright (c) 2006-2024, assimp team

All rights reserved.

Redistribution and use of this software in source and binary forms,
with or without modification, are permitted provided that the following
conditions are met:

* Redistributions of source code must retain the above
  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
  copyright notice, this list of conditions and the
  following disclaimer in the documentation and/or other
  materials provided with the distribution.

* Neither the name of the assimp team, nor the names of its
  contributors may be used to endorse or promote products
  derived from this software without specific prior
  written permission of the assimp team.

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,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
---------------------------------------------------------------------------
*/

/** @file SceneAnimator.cpp
 *  @brief Implementation of the utility class SceneAnimator
 */

#include "assimp_view.h"

using namespace AssimpView;

const aiMatrix4x4 IdentityMatrix;

// ------------------------------------------------------------------------------------------------
// Constructor for a given scene.
SceneAnimator::SceneAnimator(const aiScene *pScene, size_t pAnimIndex) :
        mScene(pScene),
        mCurrentAnimIndex(-1),
        mAnimEvaluator(nullptr),
        mRootNode(nullptr) {
    // build the nodes-for-bones table
    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
        const aiMesh *mesh = pScene->mMeshes[i];
        for (unsigned int n = 0; n < mesh->mNumBones; ++n) {
            const aiBone *bone = mesh->mBones[n];

            mBoneNodesByName[bone->mName.data] = pScene->mRootNode->FindNode(bone->mName);
        }
    }

    // changing the current animation also creates the node tree for this animation
    SetAnimIndex(pAnimIndex);
}

// ------------------------------------------------------------------------------------------------
// Destructor
SceneAnimator::~SceneAnimator() {
    delete mRootNode;
    delete mAnimEvaluator;
}

// ------------------------------------------------------------------------------------------------
// Sets the animation to use for playback.
void SceneAnimator::SetAnimIndex(size_t pAnimIndex) {
    // no change
    if (pAnimIndex == static_cast<unsigned int>(mCurrentAnimIndex)) {
        return;
    }

    // kill data of the previous anim
    delete mRootNode;
    mRootNode = nullptr;
    delete mAnimEvaluator;
    mAnimEvaluator = nullptr;
    mNodesByName.clear();

    mCurrentAnimIndex = static_cast<int>(pAnimIndex);

    // create the internal node tree. Do this even in case of invalid animation index
    // so that the transformation matrices are properly set up to mimic the current scene
    mRootNode = CreateNodeTree(mScene->mRootNode, nullptr);

    // invalid anim index
    if (static_cast<unsigned int>(mCurrentAnimIndex) >= mScene->mNumAnimations) {
        return;
    }

    // create an evaluator for this animation
    mAnimEvaluator = new AnimEvaluator(mScene->mAnimations[mCurrentAnimIndex]);
}

// ------------------------------------------------------------------------------------------------
// Calculates the node transformations for the scene.
void SceneAnimator::Calculate(double pTime) {
    // invalid anim
    if (!mAnimEvaluator) {
        return;
    }

    // calculate current local transformations
    mAnimEvaluator->Evaluate(pTime);

    // and update all node transformations with the results
    UpdateTransforms(mRootNode, mAnimEvaluator->GetTransformations());
}

// ------------------------------------------------------------------------------------------------
// Retrieves the most recent local transformation matrix for the given node.
const aiMatrix4x4 &SceneAnimator::GetLocalTransform(const aiNode *node) const {
    NodeMap::const_iterator it = mNodesByName.find(node);
    if (it == mNodesByName.end()) {
        return IdentityMatrix;
    }

    return it->second->mLocalTransform;
}

// ------------------------------------------------------------------------------------------------
// Retrieves the most recent global transformation matrix for the given node.
const aiMatrix4x4 &SceneAnimator::GetGlobalTransform(const aiNode *node) const {
    NodeMap::const_iterator it = mNodesByName.find(node);
    if (it == mNodesByName.end()) {
        return IdentityMatrix;
    }

    return it->second->mGlobalTransform;
}

// ------------------------------------------------------------------------------------------------
// Calculates the bone matrices for the given mesh.
const std::vector<aiMatrix4x4> &SceneAnimator::GetBoneMatrices(const aiNode *pNode, size_t pMeshIndex /* = 0 */) {
    ai_assert(pMeshIndex < pNode->mNumMeshes);
    size_t meshIndex = pNode->mMeshes[pMeshIndex];
    ai_assert(meshIndex < mScene->mNumMeshes);
    const aiMesh *mesh = mScene->mMeshes[meshIndex];

    // resize array and initialize it with identity matrices
    mTransforms.resize(mesh->mNumBones, aiMatrix4x4());

    // calculate the mesh's inverse global transform
    aiMatrix4x4 globalInverseMeshTransform = GetGlobalTransform(pNode);
    globalInverseMeshTransform.Inverse();

    // Bone matrices transform from mesh coordinates in bind pose to mesh coordinates in skinned pose
    // Therefore the formula is offsetMatrix * currentGlobalTransform * inverseCurrentMeshTransform
    for (size_t a = 0; a < mesh->mNumBones; ++a) {
        const aiBone *bone = mesh->mBones[a];
        const aiMatrix4x4 &currentGlobalTransform = GetGlobalTransform(mBoneNodesByName[bone->mName.data]);
        mTransforms[a] = globalInverseMeshTransform * currentGlobalTransform * bone->mOffsetMatrix;
    }

    // and return the result
    return mTransforms;
}

// ------------------------------------------------------------------------------------------------
// Recursively creates an internal node structure matching the current scene and animation.
SceneAnimNode *SceneAnimator::CreateNodeTree(aiNode *pNode, SceneAnimNode *pParent) {
    // create a node
    SceneAnimNode *internalNode = new SceneAnimNode(pNode->mName.data);
    internalNode->mParent = pParent;
    mNodesByName[pNode] = internalNode;

    // copy its transformation
    internalNode->mLocalTransform = pNode->mTransformation;
    CalculateGlobalTransform(internalNode);

    // find the index of the animation track affecting this node, if any
    if (static_cast<unsigned int>(mCurrentAnimIndex) < mScene->mNumAnimations) {
        internalNode->mChannelIndex = -1;
        const aiAnimation *currentAnim = mScene->mAnimations[mCurrentAnimIndex];
        for (unsigned int a = 0; a < currentAnim->mNumChannels; a++) {
            if (currentAnim->mChannels[a]->mNodeName.data == internalNode->mName) {
                internalNode->mChannelIndex = a;
                break;
            }
        }
    }

    // continue for all child nodes and assign the created internal nodes as our children
    for (unsigned int a = 0; a < pNode->mNumChildren; ++a) {
        SceneAnimNode *childNode = CreateNodeTree(pNode->mChildren[a], internalNode);
        internalNode->mChildren.push_back(childNode);
    }

    return internalNode;
}

// ------------------------------------------------------------------------------------------------
// Recursively updates the internal node transformations from the given matrix array
void SceneAnimator::UpdateTransforms(SceneAnimNode *pNode, const std::vector<aiMatrix4x4> &pTransforms) {
    // update node local transform
    if (pNode->mChannelIndex != -1) {
        ai_assert(static_cast<unsigned int>(pNode->mChannelIndex) < pTransforms.size());
        pNode->mLocalTransform = pTransforms[pNode->mChannelIndex];
    }

    // update global transform as well
    CalculateGlobalTransform(pNode);

    // continue for all children
    for (std::vector<SceneAnimNode *>::iterator it = pNode->mChildren.begin(); it != pNode->mChildren.end(); ++it) {
        UpdateTransforms(*it, pTransforms);
    }
}

// ------------------------------------------------------------------------------------------------
// Calculates the global transformation matrix for the given internal node
void SceneAnimator::CalculateGlobalTransform(SceneAnimNode *pInternalNode) {
    // concatenate all parent transforms to get the global transform for this node
    pInternalNode->mGlobalTransform = pInternalNode->mLocalTransform;
    SceneAnimNode *node = pInternalNode->mParent;
    while (node) {
        pInternalNode->mGlobalTransform = node->mLocalTransform * pInternalNode->mGlobalTransform;
        node = node->mParent;
    }
}