/*
   Copyright (C) 2018, Unvanquished Developers
   All Rights Reserved.

   This file is part of NetRadiant.

   NetRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   NetRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with NetRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */


#include "crn_rgba.h"

#include <string.h>

#include <memory>


#include "ddslib.h"
#include "crn_decomp.h"

int LittleLong(int l) {
#if GDEF_ARCH_ENDIAN_BIG
    std::reverse(reinterpret_cast<unsigned char *>( &l ), reinterpret_cast<unsigned char *>( &l ) + sizeof(int));
#endif
    return l;
}

// Sets `x` and `y` to the width and height of the input crn image. Returns false if there is an
// error reading the image.
extern "C" int GetCRNImageSize(const void *buffer, int length, int *x, int *y) {
    crnd::crn_texture_info ti;
    if(!crnd::crnd_get_texture_info(buffer, length, &ti) ||
      // Ensure we are not trying to load a cubemap (which has 6 faces...)
      (ti.m_faces != 1) ) {
        return false;
    }
    if (x) *x = ti.m_width;
    if (y) *y = ti.m_height;
    return true;
}

// Converts a .crn file to RGBA. Stores the pixels in outBuf. Use GetCRNImageSize to get the image
// size to determine how big outBuf should be. The function will return false if the image does not
// fit inside outBuf.
extern "C" int ConvertCRNtoRGBA(const void *buffer, int length, int outBufLen, void* outBuf) {
    crnd::crn_texture_info ti;
    if(!crnd::crnd_get_texture_info(buffer, length, &ti) ||
      // Ensure we are not trying to load a cubemap (which has 6 faces...)
      (ti.m_faces != 1) ) {
        return false;
    }

    // Sanity check mipmaps.
    if (ti.m_levels <= 0) {
        return false;
    }

    // The largest layer is always layer 0, so load that one.
    crnd::crn_level_info li;
    if (!crnd::crnd_get_level_info( buffer, length, 0, &li)) {
        return false;
    }

    // Ensure we can fit the final image in outBuf.
    if (outBufLen < ti.m_width * ti.m_height) {
        return false;
    }

    crnd::crnd_unpack_context ctx = crnd::crnd_unpack_begin(buffer, length);
    if (!ctx) {
        return false;
    }

    // Since the texture is compressed and the crunch library doesn't provide the code to convert the code
    // to RGBAImage, we'll need to convert it to DDS first and use the DDS decompression routines to get
    // the raw pixels (theoretically, we could refactor the DDS functions to be generalized, but for now,
    // this seems much more maintainable...). This code is cribbed from the example code in
    // the crunch repo: https://github.com/DaemonEngine/crunch/blob/master/example2/example2.cpp
    // Compute the face's width, height, number of DXT blocks per row/col, etc.
    // This is not a proper DDS conversion; it's only enough to get the ddslib decompressor to be happy.
    const crn_uint32 blocks_x = std::max(1U, (ti.m_width + 3) >> 2);
    const crn_uint32 blocks_y = std::max(1U, (ti.m_height + 3) >> 2);
    const crn_uint32 row_pitch = blocks_x * crnd::crnd_get_bytes_per_dxt_block(ti.m_format);
    const crn_uint32 total_face_size = row_pitch * blocks_y;
    const crn_uint32 ddsSize = sizeof(ddsBuffer_t) + total_face_size;
    std::unique_ptr<char> ddsBuffer(new char[ddsSize]);
    memset(ddsBuffer.get(), 0, ddsSize);


    ddsBuffer_t* dds = reinterpret_cast<ddsBuffer_t*>(ddsBuffer.get());

    memcpy(&dds->magic, "DDS ", sizeof(dds->magic));
    dds->size = LittleLong(124);  // Size of the DDS header.
    dds->height = LittleLong(ti.m_height);
    dds->width = LittleLong(ti.m_width);
    dds->mipMapCount = LittleLong(1);

    dds->pixelFormat.size = LittleLong(sizeof(ddsPixelFormat_t));

    crn_format fundamental_fmt = crnd::crnd_get_fundamental_dxt_format(ti.m_format);
    dds->pixelFormat.fourCC = LittleLong(crnd::crnd_crn_format_to_fourcc(fundamental_fmt));
    if (fundamental_fmt != ti.m_format) {
        // It's a funky swizzled DXTn format - write its FOURCC to RGBBitCount.
        dds->pixelFormat.rgbBitCount = LittleLong(crnd::crnd_crn_format_to_fourcc(ti.m_format));
    }
    char* imageArray[1];
    imageArray[0] = reinterpret_cast<char*>(&dds->data);
    if (!crnd::crnd_unpack_level(ctx, reinterpret_cast<void**>(&imageArray), total_face_size, row_pitch, 0)) {
        return false;
    }

    if (DDSDecompress(dds, reinterpret_cast<unsigned char*>(outBuf)) == -1) {
        return false;
    }
    return true;
}