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

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*/
#include "ArmaturePopulate.h"

#include <assimp/BaseImporter.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/postprocess.h>
#include <assimp/scene.h>

namespace Assimp {

static bool IsBoneNode(const aiString &bone_name, std::vector<aiBone *> &bones) {
    for (aiBone *bone : bones) {
        if (bone->mName == bone_name) {
            return true;
        }
    }

    return false;
}

bool ArmaturePopulate::IsActive(unsigned int pFlags) const {
    return (pFlags & aiProcess_PopulateArmatureData) != 0;
}

void ArmaturePopulate::SetupProperties(const Importer *) {
    // do nothing
}

void ArmaturePopulate::Execute(aiScene *out) {

    // Now convert all bone positions to the correct mOffsetMatrix
    std::vector<aiBone *> bones;
    std::vector<aiNode *> nodes;
    std::map<aiBone *, aiNode *> bone_stack;
    BuildBoneList(out->mRootNode, out->mRootNode, out, bones);
    BuildNodeList(out->mRootNode, nodes);

    BuildBoneStack(out->mRootNode, out, bones, bone_stack, nodes);

    ASSIMP_LOG_DEBUG("Bone stack size: ", bone_stack.size());

    for (std::pair<aiBone *, aiNode *> kvp : bone_stack) {
        aiBone *bone = kvp.first;
        aiNode *bone_node = kvp.second;
        ASSIMP_LOG_VERBOSE_DEBUG("active node lookup: ", bone->mName.C_Str());
        
        // lcl transform grab - done in generate_nodes :)
        aiNode *armature = GetArmatureRoot(bone_node, bones);

        ai_assert(armature);

#ifndef ASSIMP_BUILD_NO_ARMATUREPOPULATE_PROCESS
        // set up bone armature id
        bone->mArmature = armature;

        // set this bone node to be referenced properly
        ai_assert(bone_node);
        bone->mNode = bone_node;
#endif
    }
}


// Reprocess all nodes to calculate bone transforms properly based on the REAL
// mOffsetMatrix not the local.
// Before this would use mesh transforms which is wrong for bone transforms
// Before this would work for simple character skeletons but not complex meshes
// with multiple origins
// Source: sketch fab log cutter fbx
void ArmaturePopulate::BuildBoneList(aiNode *current_node,
                                     const aiNode *root_node,
                                     const aiScene *scene,
                                     std::vector<aiBone *> &bones) {
    ai_assert(scene);
    for (unsigned int nodeId = 0; nodeId < current_node->mNumChildren; ++nodeId) {
        aiNode *child = current_node->mChildren[nodeId];
        ai_assert(child);

        // check for bones
        for (unsigned int meshId = 0; meshId < child->mNumMeshes; ++meshId) {
            ai_assert(child->mMeshes);
            unsigned int mesh_index = child->mMeshes[meshId];
            aiMesh *mesh = scene->mMeshes[mesh_index];
            ai_assert(mesh);

            for (unsigned int boneId = 0; boneId < mesh->mNumBones; ++boneId) {
                aiBone *bone = mesh->mBones[boneId];
                ai_assert(nullptr != bone);

                // duplicate mehes exist with the same bones sometimes :)
                // so this must be detected
                if (std::find(bones.begin(), bones.end(), bone) == bones.end()) {
                    // add the element once
                    bones.emplace_back(bone);
                }
            }

            // find mesh and get bones
            // then do recursive lookup for bones in root node hierarchy
        }

        BuildBoneList(child, root_node, scene, bones);
    }
}

// Prepare flat node list which can be used for non recursive lookups later
void ArmaturePopulate::BuildNodeList(const aiNode *current_node,
                                     std::vector<aiNode *> &nodes) {
    ai_assert(nullptr != current_node);

    for (unsigned int nodeId = 0; nodeId < current_node->mNumChildren; ++nodeId) {
        aiNode *child = current_node->mChildren[nodeId];
        ai_assert(child);

        if (child->mNumMeshes == 0) {
            nodes.emplace_back(child);
        }

        BuildNodeList(child, nodes);
  }
}

// A bone stack allows us to have multiple armatures, with the same bone names
// A bone stack allows us also to retrieve bones true transform even with
// duplicate names :)
void ArmaturePopulate::BuildBoneStack(const aiNode *root_node,
                                      const aiScene*,
                                      const std::vector<aiBone *> &bones,
                                      std::map<aiBone *, aiNode *> &bone_stack,
                                  std::vector<aiNode *> &node_stack) {
    if (node_stack.empty()) {
        return;
    }
    ai_assert(nullptr != root_node);

    for (aiBone *bone : bones) {
        ai_assert(bone);
        aiNode *node = GetNodeFromStack(bone->mName, node_stack);
        if (node == nullptr) {
            node_stack.clear();
            BuildNodeList(root_node, node_stack);
            ASSIMP_LOG_VERBOSE_DEBUG("Resetting bone stack: nullptr element ", bone->mName.C_Str());

            node = GetNodeFromStack(bone->mName, node_stack);

            if (nullptr == node) {
                ASSIMP_LOG_ERROR("serious import issue node for bone was not detected");
                continue;
            }
        }

        ASSIMP_LOG_VERBOSE_DEBUG("Successfully added bone[", bone->mName.C_Str(), "] to stack and bone node is: ", node->mName.C_Str());

        bone_stack.insert(std::pair<aiBone *, aiNode *>(bone, node));
    }
}

// Returns the armature root node
// This is required to be detected for a bone initially, it will recurse up
// until it cannot find another bone and return the node No known failure
// points. (yet)
aiNode *ArmaturePopulate::GetArmatureRoot(aiNode *bone_node, std::vector<aiBone *> &bone_list) {
    while (nullptr != bone_node) {
        if (!IsBoneNode(bone_node->mName, bone_list)) {
            ASSIMP_LOG_VERBOSE_DEBUG("GetArmatureRoot() Found valid armature: ", bone_node->mName.C_Str());
            return bone_node;
        }

        bone_node = bone_node->mParent;
    }

    ASSIMP_LOG_ERROR("GetArmatureRoot() can't find armature!");

    return nullptr;
}

// Pop this node by name from the stack if found
// Used in multiple armature situations with duplicate node / bone names
// Known flaw: cannot have nodes with bone names, will be fixed in later release
// (serious to be fixed) Known flaw: nodes which have more than one bone could
// be prematurely dropped from stack
aiNode *ArmaturePopulate::GetNodeFromStack(const aiString &node_name,
                                           std::vector<aiNode *> &nodes) {
    std::vector<aiNode *>::iterator iter;
    aiNode *found = nullptr;
    for (iter = nodes.begin(); iter < nodes.end(); ++iter) {
        aiNode *element = *iter;
        ai_assert(nullptr != element);
        // node valid and node name matches
        if (element->mName == node_name) {
            found = element;
            break;
        }
    }

    if (found != nullptr) {
        ASSIMP_LOG_INFO("Removed node from stack: ", found->mName.C_Str());
        // now pop the element from the node list
        nodes.erase(iter);

        return found;
    }

    // unique names can cause this problem
    ASSIMP_LOG_ERROR("[Serious] GetNodeFromStack() can't find node from stack!");

    return nullptr;
}

} // Namespace Assimp
