/**
  @file GImage_png.cpp
  @author Morgan McGuire, http://graphics.cs.williams.edu
  @created 2002-05-27
  @edited  2009-04-20
 */
#include "G3D/platform.h"
#include "G3D/GImage.h"
#include "G3D/BinaryInput.h"
#include "G3D/BinaryOutput.h"
#include "G3D/Log.h"
#include <png.h>

namespace G3D {


//libpng required function signature
static void png_read_data(
    png_structp png_ptr,
    png_bytep data,
    png_size_t length) {


    debugAssert( png_ptr->io_ptr != NULL );
    debugAssert( length >= 0 );
    debugAssert( data != NULL );

    ((BinaryInput*)png_ptr->io_ptr)->readBytes(data, length);
}

//libpng required function signature
static void png_write_data(png_structp png_ptr,
    png_bytep data,
    png_size_t length) {

    debugAssert( png_ptr->io_ptr != NULL );
    debugAssert( data != NULL );

    ((BinaryOutput*)png_ptr->io_ptr)->writeBytes(data, length);
}

//libpng required function signature
static void png_flush_data(
    png_structp png_ptr) {
    (void)png_ptr;
    //Do nothing.
}

//libpng required function signature
static void png_error(
    png_structp png_ptr,
    png_const_charp error_msg) {
    
    (void)png_ptr;
    debugAssert( error_msg != NULL );
    throw GImage::Error(error_msg, "PNG"); 
}


//libpng required function signature
void png_warning(
    png_structp png_ptr,
    png_const_charp warning_msg) {

    (void)png_ptr;
    debugAssert( warning_msg != NULL );
    Log::common()->println(warning_msg);
}


void GImage::encodePNG(
    BinaryOutput&           out) const {

    if (! (m_channels == 1 || m_channels == 3 || m_channels == 4)) {
        throw GImage::Error(format("Illegal channels for PNG: %d", m_channels), out.getFilename());
    }
    if (m_width <= 0) {
        throw GImage::Error(format("Illegal width for PNG: %d", m_width), out.getFilename());
    }
    if (m_height <= 0) {
        throw GImage::Error(format("Illegal height for PNG: %d", m_height), out.getFilename());
    }

    // PNG library requires that the height * pointer size fit within an int
    if (png_uint_32(m_height) * png_sizeof(png_bytep) > PNG_UINT_32_MAX) {
        throw GImage::Error("Unsupported PNG height.", out.getFilename());
    }

    out.setEndian(G3D_LITTLE_ENDIAN);

    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, png_error, png_warning);
    if (! png_ptr) {
        throw GImage::Error("Unable to initialize PNG encoder.", out.getFilename());
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (! info_ptr) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
        throw GImage::Error("Unable to initialize PNG encoder.", out.getFilename());
    }

    //setup libpng write handler so can use BinaryOutput
    png_set_write_fn(png_ptr, (void*)&out, png_write_data, png_flush_data);
    png_color_8_struct sig_bit;

    switch (m_channels) {
    case 1:
        png_set_IHDR(png_ptr, info_ptr, m_width, m_height, 8, PNG_COLOR_TYPE_GRAY,
            PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
        sig_bit.red = 0;
        sig_bit.green = 0;
        sig_bit.blue = 0;
        sig_bit.alpha = 0;
        sig_bit.gray = 8;
        break;

    case 3:
        png_set_IHDR(png_ptr, info_ptr, m_width, m_height, 8, PNG_COLOR_TYPE_RGB,
            PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

        sig_bit.red = 8;
        sig_bit.green = 8;
        sig_bit.blue = 8;
        sig_bit.alpha = 0;
        sig_bit.gray = 0;
        break;

    case 4:
        png_set_IHDR(png_ptr, info_ptr, m_width, m_height, 8, PNG_COLOR_TYPE_RGBA,
            PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
        sig_bit.red = 8;
        sig_bit.green = 8;
        sig_bit.blue = 8;
        sig_bit.alpha = 8;
        sig_bit.gray = 0;
        break;

    default:
        png_destroy_write_struct(&png_ptr, &info_ptr);
        throw GImage::Error("Unsupported number of channels for PNG.", out.getFilename());
    }


    png_set_sBIT(png_ptr, info_ptr, &sig_bit);

    //write the png header
    png_write_info(png_ptr, info_ptr);

    png_bytepp row_pointers = new png_bytep[m_height];

    for (int i=0; i < m_height; ++i) {
        row_pointers[i] = (png_bytep)&m_byte[m_width * m_channels * i];
    }

    png_write_image(png_ptr, row_pointers);

    png_write_end(png_ptr, info_ptr);

    delete[] row_pointers;

    png_destroy_write_struct(&png_ptr, &info_ptr);
}


void GImage::decodePNG(
    BinaryInput&        input) {

    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, png_error, png_warning);
    if (png_ptr == NULL) {
        throw GImage::Error("Unable to initialize PNG decoder.", input.getFilename());
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (info_ptr == NULL) {
        png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
        throw GImage::Error("Unable to initialize PNG decoder.", input.getFilename());
    }

    png_infop end_info = png_create_info_struct(png_ptr);
    if (end_info == NULL) {
        png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
        throw GImage::Error("Unable to initialize PNG decoder.", input.getFilename());
    }

    // now that the libpng structures are setup, change the error handlers and read routines
    // to use G3D functions so that BinaryInput can be used.

    png_set_read_fn(png_ptr, (png_voidp)&input, png_read_data);
    
    // read in sequentially so that three copies of the file are not in memory at once
    png_read_info(png_ptr, info_ptr);

    png_uint_32 png_width, png_height;
    int bit_depth, color_type, interlace_type;
    // this will validate the data it extracts from info_ptr
    png_get_IHDR(png_ptr, info_ptr, &png_width, &png_height, &bit_depth, &color_type,
       &interlace_type, NULL, NULL);

    if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
        png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
        throw GImage::Error("Unsupported PNG color type - PNG_COLOR_TYPE_GRAY_ALPHA.", input.getFilename());
    }

    m_width  = static_cast<uint32>(png_width);
    m_height = static_cast<uint32>(png_height);

    //swap bytes of 16 bit files to least significant byte first
    png_set_swap(png_ptr);

    png_set_strip_16(png_ptr);

    //Expand paletted colors into true RGB triplets
    if (color_type == PNG_COLOR_TYPE_PALETTE) {
        png_set_palette_to_rgb(png_ptr);
    }

    //Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel
    if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
        png_set_expand(png_ptr);
    }

    //Expand paletted or RGB images with transparency to full alpha channels
    //so the data will be available as RGBA quartets.
    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
        png_set_tRNS_to_alpha(png_ptr);
    }

    // Fix sub-8 bit_depth to 8bit
    if (bit_depth < 8) {
        png_set_packing(png_ptr);
    }

    if ((color_type == PNG_COLOR_TYPE_RGBA) ||
        ((color_type == PNG_COLOR_TYPE_PALETTE) && (png_ptr->num_trans > 0)) ) {

        m_channels = 4;
        m_byte = (uint8*)m_memMan->alloc(m_width * m_height * 4);

    } else if ((color_type == PNG_COLOR_TYPE_RGB) || 
               (color_type == PNG_COLOR_TYPE_PALETTE)) {

        m_channels = 3;
        m_byte = (uint8*)System::malloc(m_width * m_height * 3);

    } else if (color_type == PNG_COLOR_TYPE_GRAY) {

        m_channels = 1;

        // Round up to the nearest 8 rows to avoid a bug in the PNG decoder
        int h = iCeil(m_height / 8) * 8;
        int sz = m_width * h;
        m_byte = (uint8*)m_memMan->alloc(sz);

    } else {
        throw GImage::Error("Unsupported PNG bit-depth or type.", input.getFilename());
    }

    //since we are reading row by row, required to handle interlacing
    uint32 number_passes = png_set_interlace_handling(png_ptr);

    png_read_update_info(png_ptr, info_ptr);

    for (uint32 pass = 0; pass < number_passes; ++pass) {
        for (uint32 y = 0; y < (uint32)m_height; ++y) {
            png_bytep rowPointer = &m_byte[m_width * m_channels * y]; 
            png_read_rows(png_ptr, &rowPointer, NULL, 1);
        }
    }

//    png_read_image(png_ptr, &_byte);
    png_read_end(png_ptr, info_ptr);

    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
}

}