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

#ifndef ASSIMP_BUILD_NO_TERRAGEN_IMPORTER

#include "TerragenLoader.h"

#include <assimp/StreamReader.h>

#include <assimp/importerdesc.h>

#include <assimp/scene.h>

#include <assimp/DefaultLogger.hpp>

#include <assimp/IOSystem.hpp>

#include <assimp/Importer.hpp>

namespace Assimp {

static constexpr aiImporterDesc desc = {

    "Terragen Heightmap Importer",

    "",

    "",

    "http://www.planetside.co.uk/",

    aiImporterFlags_SupportBinaryFlavour,

    0,

    0,

    0,

    0,

    "ter"

};

// ------------------------------------------------------------------------------------------------

// Constructor to be privately used by Importer

TerragenImporter::TerragenImporter() :

        configComputeUVs(false) {

    // empty

}

// ------------------------------------------------------------------------------------------------

// Returns whether the class can handle the format of the given file.

bool TerragenImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool /*checkSig*/) const {

    static const char *tokens[] = { "terragen" };

    return SearchFileHeaderForToken(pIOHandler, pFile, tokens, AI_COUNT_OF(tokens));

}

// ------------------------------------------------------------------------------------------------

// Build a string of all file extensions supported

const aiImporterDesc *TerragenImporter::GetInfo() const {

    return &desc;

}

// ------------------------------------------------------------------------------------------------

// Setup import properties

void TerragenImporter::SetupProperties(const Importer *pImp) {

    // AI_CONFIG_IMPORT_TER_MAKE_UVS

    configComputeUVs = (0 != pImp->GetPropertyInteger(AI_CONFIG_IMPORT_TER_MAKE_UVS, 0));

}

// ------------------------------------------------------------------------------------------------

// Imports the given file into the given scene structure.

void TerragenImporter::InternReadFile(const std::string &pFile,

        aiScene *pScene, IOSystem *pIOHandler) {

    IOStream *file = pIOHandler->Open(pFile, "rb");

    // Check whether we can read from the file

    if (file == nullptr)

        throw DeadlyImportError("Failed to open TERRAGEN TERRAIN file ", pFile, ".");

    // Construct a stream reader to read all data in the correct endianness

    StreamReaderLE reader(file);

    if (reader.GetRemainingSize() < 16)

        throw DeadlyImportError("TER: file is too small");

    // Check for the existence of the two magic strings 'TERRAGEN' and 'TERRAIN '

    if (::strncmp((const char *)reader.GetPtr(), AI_TERR_BASE_STRING, 8))

        throw DeadlyImportError("TER: Magic string \'TERRAGEN\' not found");

    if (::strncmp((const char *)reader.GetPtr() + 8, AI_TERR_TERRAIN_STRING, 8))

        throw DeadlyImportError("TER: Magic string \'TERRAIN\' not found");

    unsigned int x = 0, y = 0, mode = 0;

    aiNode *root = pScene->mRootNode = new aiNode();

    root->mName.Set("<TERRAGEN.TERRAIN>");

    // Default scaling is 30

    root->mTransformation.a1 = root->mTransformation.b2 = root->mTransformation.c3 = 30.f;

    // Now read all chunks until we're finished or an EOF marker is encountered

    reader.IncPtr(16);

    while (reader.GetRemainingSize() >= 4) {

        const char *head = (const char *)reader.GetPtr();

        reader.IncPtr(4);

        // EOF, break in every case

        if (!::strncmp(head, AI_TERR_EOF_STRING, 4))

            break;

        // Number of x-data points

        if (!::strncmp(head, AI_TERR_CHUNK_XPTS, 4)) {

            x = (uint16_t)reader.GetI2();

        }

        // Number of y-data points

        else if (!::strncmp(head, AI_TERR_CHUNK_YPTS, 4)) {

            y = (uint16_t)reader.GetI2();

        }

        // Squared terrains width-1.

        else if (!::strncmp(head, AI_TERR_CHUNK_SIZE, 4)) {

            x = y = (uint16_t)reader.GetI2() + 1;

        }

        // terrain scaling

        else if (!::strncmp(head, AI_TERR_CHUNK_SCAL, 4)) {

            root->mTransformation.a1 = reader.GetF4();

            root->mTransformation.b2 = reader.GetF4();

            root->mTransformation.c3 = reader.GetF4();

        }

        // mapping == 1: earth radius

        else if (!::strncmp(head, AI_TERR_CHUNK_CRAD, 4)) {

            reader.GetF4();

        }

        // mapping mode

        else if (!::strncmp(head, AI_TERR_CHUNK_CRVM, 4)) {

            mode = reader.GetI1();

            if (0 != mode)

                ASSIMP_LOG_ERROR("TER: Unsupported mapping mode, a flat terrain is returned");

        }

        // actual terrain data

        else if (!::strncmp(head, AI_TERR_CHUNK_ALTW, 4)) {

            float hscale = (float)reader.GetI2() / 65536;

            float bheight = (float)reader.GetI2();

            if (!hscale) hscale = 1;

            // Ensure we have enough data

            if (reader.GetRemainingSize() < x * y * 2)

                throw DeadlyImportError("TER: ALTW chunk is too small");

            if (x <= 1 || y <= 1)

                throw DeadlyImportError("TER: Invalid terrain size");

            // Allocate the output mesh

            pScene->mMeshes = new aiMesh *[pScene->mNumMeshes = 1];

            aiMesh *m = pScene->mMeshes[0] = new aiMesh();

            // We return quads

            aiFace *f = m->mFaces = new aiFace[m->mNumFaces = (x - 1) * (y - 1)];

            aiVector3D *pv = m->mVertices = new aiVector3D[m->mNumVertices = m->mNumFaces * 4];

            aiVector3D *uv(nullptr);

            float step_y(0.0f), step_x(0.0f);

            if (configComputeUVs) {

                uv = m->mTextureCoords[0] = new aiVector3D[m->mNumVertices];

                step_y = 1.f / y;

                step_x = 1.f / x;

            }

            const int16_t *data = (const int16_t *)reader.GetPtr();

            for (unsigned int yy = 0, t = 0; yy < y - 1; ++yy) {

                for (unsigned int xx = 0; xx < x - 1; ++xx, ++f) {

                    // make verts

                    const float fy = (float)yy, fx = (float)xx;

                    unsigned tmp, tmp2;

                    *pv++ = aiVector3D(fx, fy, (float)data[(tmp2 = x * yy) + xx] * hscale + bheight);

                    *pv++ = aiVector3D(fx, fy + 1, (float)data[(tmp = x * (yy + 1)) + xx] * hscale + bheight);

                    *pv++ = aiVector3D(fx + 1, fy + 1, (float)data[tmp + xx + 1] * hscale + bheight);

                    *pv++ = aiVector3D(fx + 1, fy, (float)data[tmp2 + xx + 1] * hscale + bheight);

                    // also make texture coordinates, if necessary

                    if (configComputeUVs) {

                        *uv++ = aiVector3D(step_x * xx, step_y * yy, 0.f);

                        *uv++ = aiVector3D(step_x * xx, step_y * (yy + 1), 0.f);

                        *uv++ = aiVector3D(step_x * (xx + 1), step_y * (yy + 1), 0.f);

                        *uv++ = aiVector3D(step_x * (xx + 1), step_y * yy, 0.f);

                    }

                    // make indices

                    f->mIndices = new unsigned int[f->mNumIndices = 4];

                    for (unsigned int i = 0; i < 4; ++i) {

                        f->mIndices[i] = t;

                        t++;

                    }

                }

            }

            // Add the mesh to the root node

            root->mMeshes = new unsigned int[root->mNumMeshes = 1];

            root->mMeshes[0] = 0;

        }

        // Get to the next chunk (4 byte aligned)

        unsigned dtt = reader.GetCurrentPos() & 0x3;

        if (dtt) {

            reader.IncPtr(4 - dtt);

        }

    }

    // Check whether we have a mesh now

    if (pScene->mNumMeshes != 1)

        throw DeadlyImportError("TER: Unable to load terrain");

    // Set the AI_SCENE_FLAGS_TERRAIN bit

    pScene->mFlags |= AI_SCENE_FLAGS_TERRAIN;

}

} // namespace Assimp

#endif // !! ASSIMP_BUILD_NO_TERRAGEN_IMPORTER