/** Implementation of the BVH loader */
/*
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*/

#ifndef ASSIMP_BUILD_NO_BVH_IMPORTER

#include "BVHLoader.h"
#include <assimp/SkeletonMeshBuilder.h>
#include <assimp/TinyFormatter.h>
#include <assimp/fast_atof.h>
#include <assimp/importerdesc.h>
#include <assimp/scene.h>
#include <assimp/IOSystem.hpp>
#include <assimp/Importer.hpp>
#include <map>
#include <memory>

namespace Assimp {

using namespace Assimp::Formatter;

static constexpr aiImporterDesc desc = {
    "BVH Importer (MoCap)",
    "",
    "",
    "",
    aiImporterFlags_SupportTextFlavour,
    0,
    0,
    0,
    0,
    "bvh"
};

// ------------------------------------------------------------------------------------------------
// Aborts the file reading with an exception
template <typename... T>
AI_WONT_RETURN void BVHLoader::ThrowException(T &&...args) {
    throw DeadlyImportError(mFileName, ":", mLine, " - ", args...);
}

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
BVHLoader::BVHLoader() :
        mLine(),
        mAnimTickDuration(),
        mAnimNumFrames(),
        noSkeletonMesh() {}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
BVHLoader::~BVHLoader() = default;

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool BVHLoader::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool /*checkSig*/) const {
    static const char *tokens[] = { "HIERARCHY" };
    return SearchFileHeaderForToken(pIOHandler, pFile, tokens, AI_COUNT_OF(tokens));
}

// ------------------------------------------------------------------------------------------------
void BVHLoader::SetupProperties(const Importer *pImp) {
    noSkeletonMesh = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_NO_SKELETON_MESHES, 0) != 0;
}

// ------------------------------------------------------------------------------------------------
// Loader meta information
const aiImporterDesc *BVHLoader::GetInfo() const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void BVHLoader::InternReadFile(const std::string &pFile, aiScene *pScene, IOSystem *pIOHandler) {
    mFileName = pFile;

    // read file into memory
    std::unique_ptr<IOStream> file(pIOHandler->Open(pFile));
    if (file == nullptr) {
        throw DeadlyImportError("Failed to open file ", pFile, ".");
    }

    size_t fileSize = file->FileSize();
    if (fileSize == 0) {
        throw DeadlyImportError("File is too small.");
    }

    mBuffer.resize(fileSize);
    file->Read(&mBuffer.front(), 1, fileSize);

    // start reading
    mReader = mBuffer.begin();
    mLine = 1;
    ReadStructure(pScene);

    if (!noSkeletonMesh) {
        // build a dummy mesh for the skeleton so that we see something at least
        SkeletonMeshBuilder meshBuilder(pScene);
    }

    // construct an animation from all the motion data we read
    CreateAnimation(pScene);
}

// ------------------------------------------------------------------------------------------------
// Reads the file
void BVHLoader::ReadStructure(aiScene *pScene) {
    // first comes hierarchy
    std::string header = GetNextToken();
    if (header != "HIERARCHY")
        ThrowException("Expected header string \"HIERARCHY\".");
    ReadHierarchy(pScene);

    // then comes the motion data
    std::string motion = GetNextToken();
    if (motion != "MOTION")
        ThrowException("Expected beginning of motion data \"MOTION\".");
    ReadMotion(pScene);
}

// ------------------------------------------------------------------------------------------------
// Reads the hierarchy
void BVHLoader::ReadHierarchy(aiScene *pScene) {
    std::string root = GetNextToken();
    if (root != "ROOT")
        ThrowException("Expected root node \"ROOT\".");

    // Go read the hierarchy from here
    pScene->mRootNode = ReadNode();
}

// ------------------------------------------------------------------------------------------------
// Reads a node and recursively its children and returns the created node;
aiNode *BVHLoader::ReadNode() {
    // first token is name
    std::string nodeName = GetNextToken();
    if (nodeName.empty() || nodeName == "{")
        ThrowException("Expected node name, but found \"", nodeName, "\".");

    // then an opening brace should follow
    std::string openBrace = GetNextToken();
    if (openBrace != "{")
        ThrowException("Expected opening brace \"{\", but found \"", openBrace, "\".");

    // Create a node
    aiNode *node = new aiNode(nodeName);
    std::vector<aiNode *> childNodes;

    // and create an bone entry for it
    mNodes.emplace_back(node);
    Node &internNode = mNodes.back();

    // now read the node's contents
    std::string siteToken;
    while (true) {
        std::string token = GetNextToken();

        // node offset to parent node
        if (token == "OFFSET")
            ReadNodeOffset(node);
        else if (token == "CHANNELS")
            ReadNodeChannels(internNode);
        else if (token == "JOINT") {
            // child node follows
            aiNode *child = ReadNode();
            child->mParent = node;
            childNodes.push_back(child);
        } else if (token == "End") {
            // The real symbol is "End Site". Second part comes in a separate token
            siteToken.clear();
            siteToken = GetNextToken();
            if (siteToken != "Site")
                ThrowException("Expected \"End Site\" keyword, but found \"", token, " ", siteToken, "\".");

            aiNode *child = ReadEndSite(nodeName);
            child->mParent = node;
            childNodes.push_back(child);
        } else if (token == "}") {
            // we're done with that part of the hierarchy
            break;
        } else {
            // everything else is a parse error
            ThrowException("Unknown keyword \"", token, "\".");
        }
    }

    // add the child nodes if there are any
    if (childNodes.size() > 0) {
        node->mNumChildren = static_cast<unsigned int>(childNodes.size());
        node->mChildren = new aiNode *[node->mNumChildren];
        std::copy(childNodes.begin(), childNodes.end(), node->mChildren);
    }

    // and return the sub-hierarchy we built here
    return node;
}

// ------------------------------------------------------------------------------------------------
// Reads an end node and returns the created node.
aiNode *BVHLoader::ReadEndSite(const std::string &pParentName) {
    // check opening brace
    std::string openBrace = GetNextToken();
    if (openBrace != "{")
        ThrowException("Expected opening brace \"{\", but found \"", openBrace, "\".");

    // Create a node
    aiNode *node = new aiNode("EndSite_" + pParentName);

    // now read the node's contents. Only possible entry is "OFFSET"
    std::string token;
    while (true) {
        token.clear();
        token = GetNextToken();

        // end node's offset
        if (token == "OFFSET") {
            ReadNodeOffset(node);
        } else if (token == "}") {
            // we're done with the end node
            break;
        } else {
            // everything else is a parse error
            ThrowException("Unknown keyword \"", token, "\".");
        }
    }

    // and return the sub-hierarchy we built here
    return node;
}
// ------------------------------------------------------------------------------------------------
// Reads a node offset for the given node
void BVHLoader::ReadNodeOffset(aiNode *pNode) {
    // Offset consists of three floats to read
    aiVector3D offset;
    offset.x = GetNextTokenAsFloat();
    offset.y = GetNextTokenAsFloat();
    offset.z = GetNextTokenAsFloat();

    // build a transformation matrix from it
    pNode->mTransformation = aiMatrix4x4(1.0f, 0.0f, 0.0f, offset.x,
            0.0f, 1.0f, 0.0f, offset.y,
            0.0f, 0.0f, 1.0f, offset.z,
            0.0f, 0.0f, 0.0f, 1.0f);
}

// ------------------------------------------------------------------------------------------------
// Reads the animation channels for the given node
void BVHLoader::ReadNodeChannels(BVHLoader::Node &pNode) {
    // number of channels. Use the float reader because we're lazy
    float numChannelsFloat = GetNextTokenAsFloat();
    unsigned int numChannels = (unsigned int)numChannelsFloat;

    for (unsigned int a = 0; a < numChannels; a++) {
        std::string channelToken = GetNextToken();

        if (channelToken == "Xposition")
            pNode.mChannels.push_back(Channel_PositionX);
        else if (channelToken == "Yposition")
            pNode.mChannels.push_back(Channel_PositionY);
        else if (channelToken == "Zposition")
            pNode.mChannels.push_back(Channel_PositionZ);
        else if (channelToken == "Xrotation")
            pNode.mChannels.push_back(Channel_RotationX);
        else if (channelToken == "Yrotation")
            pNode.mChannels.push_back(Channel_RotationY);
        else if (channelToken == "Zrotation")
            pNode.mChannels.push_back(Channel_RotationZ);
        else
            ThrowException("Invalid channel specifier \"", channelToken, "\".");
    }
}

// ------------------------------------------------------------------------------------------------
// Reads the motion data
void BVHLoader::ReadMotion(aiScene * /*pScene*/) {
    // Read number of frames
    std::string tokenFrames = GetNextToken();
    if (tokenFrames != "Frames:")
        ThrowException("Expected frame count \"Frames:\", but found \"", tokenFrames, "\".");

    float numFramesFloat = GetNextTokenAsFloat();
    mAnimNumFrames = (unsigned int)numFramesFloat;

    // Read frame duration
    std::string tokenDuration1 = GetNextToken();
    std::string tokenDuration2 = GetNextToken();
    if (tokenDuration1 != "Frame" || tokenDuration2 != "Time:")
        ThrowException("Expected frame duration \"Frame Time:\", but found \"", tokenDuration1, " ", tokenDuration2, "\".");

    mAnimTickDuration = GetNextTokenAsFloat();

    // resize value vectors for each node
    for (std::vector<Node>::iterator it = mNodes.begin(); it != mNodes.end(); ++it)
        it->mChannelValues.reserve(it->mChannels.size() * mAnimNumFrames);

    // now read all the data and store it in the corresponding node's value vector
    for (unsigned int frame = 0; frame < mAnimNumFrames; ++frame) {
        // on each line read the values for all nodes
        for (std::vector<Node>::iterator it = mNodes.begin(); it != mNodes.end(); ++it) {
            // get as many values as the node has channels
            for (unsigned int c = 0; c < it->mChannels.size(); ++c)
                it->mChannelValues.push_back(GetNextTokenAsFloat());
        }

        // after one frame worth of values for all nodes there should be a newline, but we better don't rely on it
    }
}

// ------------------------------------------------------------------------------------------------
// Retrieves the next token
std::string BVHLoader::GetNextToken() {
    // skip any preceding whitespace
    while (mReader != mBuffer.end()) {
        if (!isspace((unsigned char)*mReader))
            break;

        // count lines
        if (*mReader == '\n')
            mLine++;

        ++mReader;
    }

    // collect all chars till the next whitespace. BVH is easy in respect to that.
    std::string token;
    while (mReader != mBuffer.end()) {
        if (isspace((unsigned char)*mReader))
            break;

        token.push_back(*mReader);
        ++mReader;

        // little extra logic to make sure braces are counted correctly
        if (token == "{" || token == "}")
            break;
    }

    // empty token means end of file, which is just fine
    return token;
}

// ------------------------------------------------------------------------------------------------
// Reads the next token as a float
float BVHLoader::GetNextTokenAsFloat() {
    std::string token = GetNextToken();
    if (token.empty())
        ThrowException("Unexpected end of file while trying to read a float");

    // check if the float is valid by testing if the atof() function consumed every char of the token
    const char *ctoken = token.c_str();
    float result = 0.0f;
    ctoken = fast_atoreal_move<float>(ctoken, result);

    if (ctoken != token.c_str() + token.length())
        ThrowException("Expected a floating point number, but found \"", token, "\".");

    return result;
}

// ------------------------------------------------------------------------------------------------
// Constructs an animation for the motion data and stores it in the given scene
void BVHLoader::CreateAnimation(aiScene *pScene) {
    // create the animation
    pScene->mNumAnimations = 1;
    pScene->mAnimations = new aiAnimation *[1];
    aiAnimation *anim = new aiAnimation;
    pScene->mAnimations[0] = anim;

    // put down the basic parameters
    anim->mName.Set("Motion");
    anim->mTicksPerSecond = 1.0 / double(mAnimTickDuration);
    anim->mDuration = double(mAnimNumFrames - 1);

    // now generate the tracks for all nodes
    anim->mNumChannels = static_cast<unsigned int>(mNodes.size());
    anim->mChannels = new aiNodeAnim *[anim->mNumChannels];

    // FIX: set the array elements to nullptr to ensure proper deletion if an exception is thrown
    for (unsigned int i = 0; i < anim->mNumChannels; ++i)
        anim->mChannels[i] = nullptr;

    for (unsigned int a = 0; a < anim->mNumChannels; a++) {
        const Node &node = mNodes[a];
        const std::string nodeName = std::string(node.mNode->mName.data);
        aiNodeAnim *nodeAnim = new aiNodeAnim;
        anim->mChannels[a] = nodeAnim;
        nodeAnim->mNodeName.Set(nodeName);
        std::map<BVHLoader::ChannelType, int> channelMap;

        // Build map of channels
        for (unsigned int channel = 0; channel < node.mChannels.size(); ++channel) {
            channelMap[node.mChannels[channel]] = channel;
        }

        // translational part, if given
        if (node.mChannels.size() == 6) {
            nodeAnim->mNumPositionKeys = mAnimNumFrames;
            nodeAnim->mPositionKeys = new aiVectorKey[mAnimNumFrames];
            aiVectorKey *poskey = nodeAnim->mPositionKeys;
            for (unsigned int fr = 0; fr < mAnimNumFrames; ++fr) {
                poskey->mTime = double(fr);

                // Now compute all translations
                for (BVHLoader::ChannelType channel = Channel_PositionX; channel <= Channel_PositionZ; channel = (BVHLoader::ChannelType)(channel + 1)) {
                    // Find channel in node
                    std::map<BVHLoader::ChannelType, int>::iterator mapIter = channelMap.find(channel);

                    if (mapIter == channelMap.end())
                        throw DeadlyImportError("Missing position channel in node ", nodeName);
                    else {
                        int channelIdx = mapIter->second;
                        switch (channel) {
                        case Channel_PositionX:
                            poskey->mValue.x = node.mChannelValues[fr * node.mChannels.size() + channelIdx];
                            break;
                        case Channel_PositionY:
                            poskey->mValue.y = node.mChannelValues[fr * node.mChannels.size() + channelIdx];
                            break;
                        case Channel_PositionZ:
                            poskey->mValue.z = node.mChannelValues[fr * node.mChannels.size() + channelIdx];
                            break;

                        default:
                            break;
                        }
                    }
                }
                ++poskey;
            }
        } else {
            // if no translation part is given, put a default sequence
            aiVector3D nodePos(node.mNode->mTransformation.a4, node.mNode->mTransformation.b4, node.mNode->mTransformation.c4);
            nodeAnim->mNumPositionKeys = 1;
            nodeAnim->mPositionKeys = new aiVectorKey[1];
            nodeAnim->mPositionKeys[0].mTime = 0.0;
            nodeAnim->mPositionKeys[0].mValue = nodePos;
        }

        // rotation part. Always present. First find value offsets
        {

            // Then create the number of rotation keys
            nodeAnim->mNumRotationKeys = mAnimNumFrames;
            nodeAnim->mRotationKeys = new aiQuatKey[mAnimNumFrames];
            aiQuatKey *rotkey = nodeAnim->mRotationKeys;
            for (unsigned int fr = 0; fr < mAnimNumFrames; ++fr) {
                aiMatrix4x4 temp;
                aiMatrix3x3 rotMatrix;
                for (unsigned int channelIdx = 0; channelIdx < node.mChannels.size(); ++channelIdx) {
                    switch (node.mChannels[channelIdx]) {
                    case Channel_RotationX: {
                        const float angle = node.mChannelValues[fr * node.mChannels.size() + channelIdx] * float(AI_MATH_PI) / 180.0f;
                        aiMatrix4x4::RotationX(angle, temp);
                        rotMatrix *= aiMatrix3x3(temp);
                    } break;
                    case Channel_RotationY: {
                        const float angle = node.mChannelValues[fr * node.mChannels.size() + channelIdx] * float(AI_MATH_PI) / 180.0f;
                        aiMatrix4x4::RotationY(angle, temp);
                        rotMatrix *= aiMatrix3x3(temp);
                    } break;
                    case Channel_RotationZ: {
                        const float angle = node.mChannelValues[fr * node.mChannels.size() + channelIdx] * float(AI_MATH_PI) / 180.0f;
                        aiMatrix4x4::RotationZ(angle, temp);
                        rotMatrix *= aiMatrix3x3(temp);
                    } break;
                    default:
                        break;
                    }
                }
                rotkey->mTime = double(fr);
                rotkey->mValue = aiQuaternion(rotMatrix);
                ++rotkey;
            }
        }

        // scaling part. Always just a default track
        {
            nodeAnim->mNumScalingKeys = 1;
            nodeAnim->mScalingKeys = new aiVectorKey[1];
            nodeAnim->mScalingKeys[0].mTime = 0.0;
            nodeAnim->mScalingKeys[0].mValue.Set(1.0f, 1.0f, 1.0f);
        }
    }
}

} // namespace Assimp

#endif // !! ASSIMP_BUILD_NO_BVH_IMPORTER