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/** @file Implementation of the IrrMesh importer class */

#ifndef ASSIMP_BUILD_NO_IRRMESH_IMPORTER

#include "IRRMeshLoader.h"
#include <assimp/ParsingUtils.h>
#include <assimp/fast_atof.h>
#include <assimp/importerdesc.h>
#include <assimp/material.h>
#include <assimp/mesh.h>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>
#include <memory>

using namespace Assimp;

static constexpr aiImporterDesc desc = {
    "Irrlicht Mesh Reader",
    "",
    "",
    "http://irrlicht.sourceforge.net/",
    aiImporterFlags_SupportTextFlavour,
    0,
    0,
    0,
    0,
    "xml irrmesh"
};

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool IRRMeshImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool /*checkSig*/) const {
    /* NOTE: A simple check for the file extension is not enough
     * here. Irrmesh and irr are easy, but xml is too generic
     * and could be collada, too. So we need to open the file and
     * search for typical tokens.
     */
    static const char *tokens[] = { "irrmesh" };
    return SearchFileHeaderForToken(pIOHandler, pFile, tokens, AI_COUNT_OF(tokens));
}

// ------------------------------------------------------------------------------------------------
// Get a list of all file extensions which are handled by this class
const aiImporterDesc *IRRMeshImporter::GetInfo() const {
    return &desc;
}

static void releaseMaterial(aiMaterial **mat) {
    if (*mat != nullptr) {
        delete *mat;
        *mat = nullptr;
    }
}

static void releaseMesh(aiMesh **mesh) {
    if (*mesh != nullptr) {
        delete *mesh;
        *mesh = nullptr;
    }
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void IRRMeshImporter::InternReadFile(const std::string &pFile,
        aiScene *pScene, IOSystem *pIOHandler) {
    std::unique_ptr<IOStream> file(pIOHandler->Open(pFile));

    // Check whether we can read from the file
    if (file == nullptr) {
        throw DeadlyImportError("Failed to open IRRMESH file ", pFile);
    }

    // Construct the irrXML parser
    XmlParser parser;
    if (!parser.parse(file.get())) {
        throw DeadlyImportError("XML parse error while loading IRRMESH file ", pFile);
    }
    XmlNode root = parser.getRootNode();

    // final data
    std::vector<aiMaterial *> materials;
    std::vector<aiMesh *> meshes;
    materials.reserve(5);
    meshes.reserve(5);

    // temporary data - current mesh buffer
    // TODO move all these to inside loop
    aiMaterial *curMat = nullptr;
    aiMesh *curMesh = nullptr;
    unsigned int curMatFlags = 0;

    std::vector<aiVector3D> curVertices, curNormals, curTangents, curBitangents;
    std::vector<aiColor4D> curColors;
    std::vector<aiVector3D> curUVs, curUV2s;

    // some temporary variables
    // textMeaning is a 15 year old variable, that could've been an enum
    // int textMeaning = 0; // 0=none? 1=vertices 2=indices
    // int vertexFormat = 0; // 0 = normal; 1 = 2 tcoords, 2 = tangents
    bool useColors = false;

    // irrmesh files have a top level <mesh> owning multiple <buffer> nodes.
    // Each <buffer> contains <material>, <vertices>, and <indices>
    // <material> tags here directly owns the material data specs
    // <vertices> are a vertex per line, contains position, UV1 coords, maybe UV2, normal, tangent, bitangent
    // <boundingbox> is ignored, I think assimp recalculates those?

    // Parse the XML file
    pugi::xml_node const &meshNode = root.child("mesh");
    for (pugi::xml_node bufferNode : meshNode.children()) {
        if (ASSIMP_stricmp(bufferNode.name(), "buffer")) {
            // Might be a useless warning
            ASSIMP_LOG_WARN("IRRMESH: Ignoring non buffer node <", bufferNode.name(), "> in mesh declaration");
            continue;
        }

        curMat = nullptr;
        curMesh = nullptr;

        curVertices.clear();
        curColors.clear();
        curNormals.clear();
        curUV2s.clear();
        curUVs.clear();
        curTangents.clear();
        curBitangents.clear();

        // TODO ensure all three nodes are present and populated
        // before allocating everything

        // Get first material node
        pugi::xml_node materialNode = bufferNode.child("material");
        if (materialNode) {
            curMat = ParseMaterial(materialNode, curMatFlags);
            // Warn if there's more materials
            if (materialNode.next_sibling("material")) {
                ASSIMP_LOG_WARN("IRRMESH: Only one material description per buffer, please");
            }
        } else {
            ASSIMP_LOG_ERROR("IRRMESH: Buffer must contain one material");
            continue;
        }

        // Get first vertices node
        pugi::xml_node verticesNode = bufferNode.child("vertices");
        if (verticesNode) {
            pugi::xml_attribute vertexCountAttrib = verticesNode.attribute("vertexCount");
            int vertexCount = vertexCountAttrib.as_int();
            if (vertexCount == 0) {
                // This is possible ... remove the mesh from the list and skip further reading
                ASSIMP_LOG_WARN("IRRMESH: Found mesh with zero vertices");
                releaseMaterial(&curMat);
                continue; // Bail out early
            };

            curVertices.reserve(vertexCount);
            curNormals.reserve(vertexCount);
            curColors.reserve(vertexCount);
            curUVs.reserve(vertexCount);

            VertexFormat vertexFormat;
            // Determine the file format
            pugi::xml_attribute typeAttrib = verticesNode.attribute("type");
            if (!ASSIMP_stricmp("2tcoords", typeAttrib.value())) {
                curUV2s.reserve(vertexCount);
                vertexFormat = VertexFormat::t2coord;
                if (curMatFlags & AI_IRRMESH_EXTRA_2ND_TEXTURE) {
                    // *********************************************************
                    // We have a second texture! So use this UV channel
                    // for it. The 2nd texture can be either a normal
                    // texture (solid_2layer or lightmap_xxx) or a normal
                    // map (normal_..., parallax_...)
                    // *********************************************************
                    int idx = 1;
                    aiMaterial *mat = (aiMaterial *)curMat;

                    if (curMatFlags & AI_IRRMESH_MAT_lightmap) {
                        mat->AddProperty(&idx, 1, AI_MATKEY_UVWSRC_LIGHTMAP(0));
                    } else if (curMatFlags & AI_IRRMESH_MAT_normalmap_solid) {
                        mat->AddProperty(&idx, 1, AI_MATKEY_UVWSRC_NORMALS(0));
                    } else if (curMatFlags & AI_IRRMESH_MAT_solid_2layer) {
                        mat->AddProperty(&idx, 1, AI_MATKEY_UVWSRC_DIFFUSE(1));
                    }
                }
            } else if (!ASSIMP_stricmp("tangents", typeAttrib.value())) {
                curTangents.reserve(vertexCount);
                curBitangents.reserve(vertexCount);
                vertexFormat = VertexFormat::tangent;
            } else if (!ASSIMP_stricmp("standard", typeAttrib.value())) {
                vertexFormat = VertexFormat::standard;
            } else {
                // Unsupported format, discard whole buffer/mesh
                // Assuming we have a correct material, then release it
                // We don't have a correct mesh for sure here
                releaseMaterial(&curMat);
                ASSIMP_LOG_ERROR("IRRMESH: Unknown vertex format");
                continue; // Skip rest of buffer
            };

            // We know what format buffer is, collect numbers
            std::string v = verticesNode.text().get();
            const char *end = v.c_str() + v.size();
            ParseBufferVertices(v.c_str(), end, vertexFormat,
                    curVertices, curNormals,
                    curTangents, curBitangents,
                    curUVs, curUV2s, curColors, useColors);
        }

        // Get indices
        // At this point we have some vertices and a valid material
        // Collect indices and create aiMesh at the same time
        pugi::xml_node indicesNode = bufferNode.child("indices");
        if (indicesNode) {
            // start a new mesh
            curMesh = new aiMesh();

            // allocate storage for all faces
            pugi::xml_attribute attr = indicesNode.attribute("indexCount");
            curMesh->mNumVertices = attr.as_int();
            if (!curMesh->mNumVertices) {
                // This is possible ... remove the mesh from the list and skip further reading
                ASSIMP_LOG_WARN("IRRMESH: Found mesh with zero indices");

                // mesh - away
                releaseMesh(&curMesh);

                // material - away
                releaseMaterial(&curMat);
                continue; // Go to next buffer
            }

            if (curMesh->mNumVertices % 3) {
                ASSIMP_LOG_WARN("IRRMESH: Number if indices isn't divisible by 3");
            }

            curMesh->mNumFaces = curMesh->mNumVertices / 3;
            curMesh->mFaces = new aiFace[curMesh->mNumFaces];

            // setup some members
            curMesh->mMaterialIndex = (unsigned int)materials.size();
            curMesh->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;

            // allocate storage for all vertices
            curMesh->mVertices = new aiVector3D[curMesh->mNumVertices];

            if (curNormals.size() == curVertices.size()) {
                curMesh->mNormals = new aiVector3D[curMesh->mNumVertices];
            }
            if (curTangents.size() == curVertices.size()) {
                curMesh->mTangents = new aiVector3D[curMesh->mNumVertices];
            }
            if (curBitangents.size() == curVertices.size()) {
                curMesh->mBitangents = new aiVector3D[curMesh->mNumVertices];
            }
            if (curColors.size() == curVertices.size() && useColors) {
                curMesh->mColors[0] = new aiColor4D[curMesh->mNumVertices];
            }
            if (curUVs.size() == curVertices.size()) {
                curMesh->mTextureCoords[0] = new aiVector3D[curMesh->mNumVertices];
            }
            if (curUV2s.size() == curVertices.size()) {
                curMesh->mTextureCoords[1] = new aiVector3D[curMesh->mNumVertices];
            }

            // read indices
            aiFace *curFace = curMesh->mFaces;
            aiFace *const faceEnd = curMesh->mFaces + curMesh->mNumFaces;

            aiVector3D *pcV = curMesh->mVertices;
            aiVector3D *pcN = curMesh->mNormals;
            aiVector3D *pcT = curMesh->mTangents;
            aiVector3D *pcB = curMesh->mBitangents;
            aiColor4D *pcC0 = curMesh->mColors[0];
            aiVector3D *pcT0 = curMesh->mTextureCoords[0];
            aiVector3D *pcT1 = curMesh->mTextureCoords[1];

            unsigned int curIdx = 0;
            unsigned int total = 0;

            // NOTE this might explode for UTF-16 and wchars
            const char *sz = indicesNode.text().get();
            const char *end = sz + std::strlen(sz);
            
            // For each index loop over aiMesh faces
            while (SkipSpacesAndLineEnd(&sz, end)) {
                if (curFace >= faceEnd) {
                    ASSIMP_LOG_ERROR("IRRMESH: Too many indices");
                    break;
                }
                // if new face
                if (!curIdx) {
                    curFace->mNumIndices = 3;
                    curFace->mIndices = new unsigned int[3];
                }

                // Read index base 10
                // function advances the pointer
                unsigned int idx = strtoul10(sz, &sz);
                if (idx >= curVertices.size()) {
                    ASSIMP_LOG_ERROR("IRRMESH: Index out of range");
                    idx = 0;
                }

                // make up our own indices?
                curFace->mIndices[curIdx] = total++;

                // Copy over data to aiMesh
                *pcV++ = curVertices[idx];
                if (pcN)
                    *pcN++ = curNormals[idx];
                if (pcT)
                    *pcT++ = curTangents[idx];
                if (pcB)
                    *pcB++ = curBitangents[idx];
                if (pcC0)
                    *pcC0++ = curColors[idx];
                if (pcT0)
                    *pcT0++ = curUVs[idx];
                if (pcT1)
                    *pcT1++ = curUV2s[idx];

                // start new face
                if (++curIdx == 3) {
                    ++curFace;
                    curIdx = 0;
                }
            }
            // We should be at the end of mFaces
            if (curFace != faceEnd) {
                ASSIMP_LOG_ERROR("IRRMESH: Not enough indices");
            }
        }

        // Finish processing the mesh - do some small material workarounds
        if (curMatFlags & AI_IRRMESH_MAT_trans_vertex_alpha && !useColors) {
            // Take the opacity value of the current material
            // from the common vertex color alpha
            aiMaterial *mat = (aiMaterial *)curMat;
            mat->AddProperty(&curColors[0].a, 1, AI_MATKEY_OPACITY);
        }
        
        // end of previous buffer. A material and a mesh should be there
        if (!curMat || !curMesh) {
            ASSIMP_LOG_ERROR("IRRMESH: A buffer must contain a mesh and a material");
            releaseMaterial(&curMat);
            releaseMesh(&curMesh);
        } else {
            materials.push_back(curMat);
            meshes.push_back(curMesh);
        }
    }

    // If one is empty then so is the other
    if (materials.empty() || meshes.empty()) {
        throw DeadlyImportError("IRRMESH: Unable to read a mesh from this file");
    }

    // now generate the output scene
    pScene->mNumMeshes = (unsigned int)meshes.size();
    pScene->mMeshes = new aiMesh *[pScene->mNumMeshes];
    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
        pScene->mMeshes[i] = meshes[i];

        // clean this value ...
        pScene->mMeshes[i]->mNumUVComponents[3] = 0;
    }

    pScene->mNumMaterials = (unsigned int)materials.size();
    pScene->mMaterials = new aiMaterial *[pScene->mNumMaterials];
    ::memcpy(pScene->mMaterials, &materials[0], sizeof(void *) * pScene->mNumMaterials);

    pScene->mRootNode = new aiNode();
    pScene->mRootNode->mName.Set("<IRRMesh>");
    pScene->mRootNode->mNumMeshes = pScene->mNumMeshes;
    pScene->mRootNode->mMeshes = new unsigned int[pScene->mNumMeshes];

    for (unsigned int i = 0; i < pScene->mNumMeshes; ++i) {
        pScene->mRootNode->mMeshes[i] = i;
    };
}

void IRRMeshImporter::ParseBufferVertices(const char *sz, const char *end, VertexFormat vertexFormat,
        std::vector<aiVector3D> &vertices, std::vector<aiVector3D> &normals,
        std::vector<aiVector3D> &tangents, std::vector<aiVector3D> &bitangents,
        std::vector<aiVector3D> &UVs, std::vector<aiVector3D> &UV2s,
        std::vector<aiColor4D> &colors, bool &useColors) {
    // read vertices
    do {
        SkipSpacesAndLineEnd(&sz, end);
        aiVector3D temp;
        aiColor4D c;

        // Read the vertex position
        sz = fast_atoreal_move<float>(sz, (float &)temp.x);
        SkipSpaces(&sz, end);

        sz = fast_atoreal_move<float>(sz, (float &)temp.y);
        SkipSpaces(&sz, end);

        sz = fast_atoreal_move<float>(sz, (float &)temp.z);
        SkipSpaces(&sz, end);
        vertices.push_back(temp);

        // Read the vertex normals
        sz = fast_atoreal_move<float>(sz, (float &)temp.x);
        SkipSpaces(&sz, end);

        sz = fast_atoreal_move<float>(sz, (float &)temp.y);
        SkipSpaces(&sz, end);

        sz = fast_atoreal_move<float>(sz, (float &)temp.z);
        SkipSpaces(&sz, end);
        normals.push_back(temp);

        // read the vertex colors
        uint32_t clr = strtoul16(sz, &sz);
        ColorFromARGBPacked(clr, c);

        // If we're pushing more than one distinct color
        if (!colors.empty() && c != *(colors.end() - 1))
            useColors = true;

        colors.push_back(c);
        SkipSpaces(&sz, end);

        // read the first UV coordinate set
        sz = fast_atoreal_move<float>(sz, (float &)temp.x);
        SkipSpaces(&sz, end);

        sz = fast_atoreal_move<float>(sz, (float &)temp.y);
        SkipSpaces(&sz, end);
        temp.z = 0.f;
        temp.y = 1.f - temp.y; // DX to OGL
        UVs.push_back(temp);

        // NOTE these correspond to specific S3DVertex* structs in irr sourcecode
        // So by definition, all buffers have either UV2 or tangents or neither
        // read the (optional) second UV coordinate set
        if (vertexFormat == VertexFormat::t2coord) {
            sz = fast_atoreal_move<float>(sz, (float &)temp.x);
            SkipSpaces(&sz, end);

            sz = fast_atoreal_move<float>(sz, (float &)temp.y);
            temp.y = 1.f - temp.y; // DX to OGL
            UV2s.push_back(temp);
        }
        // read optional tangent and bitangent vectors
        else if (vertexFormat == VertexFormat::tangent) {
            // tangents
            sz = fast_atoreal_move<float>(sz, (float &)temp.x);
            SkipSpaces(&sz, end);

            sz = fast_atoreal_move<float>(sz, (float &)temp.z);
            SkipSpaces(&sz, end);

            sz = fast_atoreal_move<float>(sz, (float &)temp.y);
            SkipSpaces(&sz, end);
            temp.y *= -1.0f;
            tangents.push_back(temp);

            // bitangents
            sz = fast_atoreal_move<float>(sz, (float &)temp.x);
            SkipSpaces(&sz, end);

            sz = fast_atoreal_move<float>(sz, (float &)temp.z);
            SkipSpaces(&sz, end);

            sz = fast_atoreal_move<float>(sz, (float &)temp.y);
            SkipSpaces(&sz, end);
            temp.y *= -1.0f;
            bitangents.push_back(temp);
        }
    } while (SkipLine(&sz, end));
    // IMPORTANT: We assume that each vertex is specified in one
    // line. So we can skip the rest of the line - unknown vertex
    // elements are ignored.
}

#endif // !! ASSIMP_BUILD_NO_IRRMESH_IMPORTER
