#include "png.h"

#include <iostream>
#include <GL/glew.h>
#include "../graphics/Texture.h"

#ifndef _WIN32
#define LIBPNG
#endif

#ifdef LIBPNG
#include <png.h>

int _png_load(const char* file, int* width, int* height){
    FILE *f;
    int is_png, bit_depth, color_type, row_bytes;
    png_infop info_ptr, end_info;
    png_uint_32 t_width, t_height;
    png_byte header[8], *image_data;
    png_bytepp row_pointers;
    png_structp png_ptr;
    GLuint texture;
    int alpha;

    if ( !( f = fopen(file, "r" ) ) ) {
        return 0;
    }
    fread( header, 1, 8, f );
    is_png = !png_sig_cmp( header, 0, 8 );
    if ( !is_png ) {
        fclose( f );
        return 0;
    }
    png_ptr = png_create_read_struct( PNG_LIBPNG_VER_STRING, NULL,
        NULL, NULL );
    if ( !png_ptr ) {
        fclose( f );
        return 0;
    }
    info_ptr = png_create_info_struct( png_ptr );
    if ( !info_ptr ) {
        png_destroy_read_struct( &png_ptr, (png_infopp) NULL,
            (png_infopp) NULL );
        fclose( f );
        return 0;
    }
    end_info = png_create_info_struct( png_ptr );
    if ( !end_info ) {
        png_destroy_read_struct( &png_ptr, (png_infopp) NULL,
            (png_infopp) NULL );
        fclose( f );
        return 0;
    }
    if ( setjmp( png_jmpbuf( png_ptr ) ) ) {
        png_destroy_read_struct( &png_ptr, &info_ptr, &end_info );
        fclose( f );
        return 0;
    }
    png_init_io( png_ptr, f );
    png_set_sig_bytes( png_ptr, 8 );
    png_read_info( png_ptr, info_ptr );
    png_get_IHDR( png_ptr, info_ptr, &t_width, &t_height, &bit_depth,
        &color_type, NULL, NULL, NULL );
    *width = t_width;
    *height = t_height;
    png_read_update_info( png_ptr, info_ptr );
    row_bytes = png_get_rowbytes( png_ptr, info_ptr );
    image_data = (png_bytep) malloc( row_bytes * t_height * sizeof(png_byte) );
    if ( !image_data ) {
        png_destroy_read_struct( &png_ptr, &info_ptr, &end_info );
        fclose( f );
        return 0;
    }
    row_pointers = (png_bytepp) malloc( t_height * sizeof(png_bytep) );
    if ( !row_pointers ) {
        png_destroy_read_struct( &png_ptr, &info_ptr, &end_info );
        free( image_data );
        fclose( f );
        return 0;
    }
    for (unsigned int i = 0; i < t_height; ++i ) {
        row_pointers[t_height - 1 - i] = image_data + i * row_bytes;
    }
    png_read_image( png_ptr, row_pointers );
    switch ( png_get_color_type( png_ptr, info_ptr ) ) {
        case PNG_COLOR_TYPE_RGBA:
            alpha = GL_RGBA;
            break;
        case PNG_COLOR_TYPE_RGB:
            alpha = GL_RGB;
            break;
        default:
            printf( "Color type %d not supported!\n",
                png_get_color_type( png_ptr, info_ptr ) );
            png_destroy_read_struct( &png_ptr, &info_ptr, &end_info );
            return 0;
    }
    // configure second post-processing framebuffer

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, t_width, t_height, 0,
        alpha, GL_UNSIGNED_BYTE, (GLvoid *) image_data);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 3);
    glGenerateMipmap(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);

    png_destroy_read_struct( &png_ptr, &info_ptr, &end_info );
    free( image_data );
    free( row_pointers );
    fclose( f );
    return texture;
}
#else
#include <spng.h>
#include <stdio.h>
#include <inttypes.h>

int _png_load(const char* file, int* pwidth, int* pheight){
	int r = 0;
	FILE *png;
	char *pngbuf = nullptr;
	spng_ctx *ctx = nullptr;
	unsigned char *out = nullptr;

	png = fopen(file, "rb");
	if (png == nullptr){
		std::cerr << "could not to open file " << file << std::endl;
		return 0;
	}

	fseek(png, 0, SEEK_END);
	long siz_pngbuf = ftell(png);
	rewind(png);
	if(siz_pngbuf < 1) {
		std::cerr << "could not to read file " << file << std::endl;
		return 0;
	}
	pngbuf = new char[siz_pngbuf];
	if(fread(pngbuf, siz_pngbuf, 1, png) != 1){
		std::cerr << "fread() failed" << std::endl;
		return 0;
	}
	ctx = spng_ctx_new(0);
	if (ctx == nullptr){
		std::cerr << "spng_ctx_new() failed" << std::endl;
		return 0;
	}
	r = spng_set_crc_action(ctx, SPNG_CRC_USE, SPNG_CRC_USE);
	if (r){
		std::cerr << "spng_set_crc_action() error: " << spng_strerror(r) << std::endl;
		return 0;
	}
	r = spng_set_png_buffer(ctx, pngbuf, siz_pngbuf);
	if (r){
		std::cerr << "spng_set_png_buffer() error: " << spng_strerror(r) << std::endl;
		return 0;
	}

	spng_ihdr ihdr;
	r = spng_get_ihdr(ctx, &ihdr);
	if (r){
		std::cerr << "spng_get_ihdr() error: " << spng_strerror(r) << std::endl;
		return 0;
	}

	char *clr_type_str;
	if(ihdr.color_type == SPNG_COLOR_TYPE_GRAYSCALE)
		clr_type_str = "grayscale";
	else if(ihdr.color_type == SPNG_COLOR_TYPE_TRUECOLOR)
		clr_type_str = "truecolor";
	else if(ihdr.color_type == SPNG_COLOR_TYPE_INDEXED)
		clr_type_str = "indexed color";
	else if(ihdr.color_type == SPNG_COLOR_TYPE_GRAYSCALE_ALPHA)
		clr_type_str = "grayscale with alpha";
	else
		clr_type_str = "truecolor with alpha";

	size_t out_size;
	r = spng_decoded_image_size(ctx, SPNG_FMT_RGBA8, &out_size);
	if (r){
		std::cerr << "spng_decoded_image_size() error: " << spng_strerror(r) << std::endl;
		return 0;
	}
	out = new unsigned char[out_size];
	r = spng_decode_image(ctx, out, out_size, SPNG_FMT_RGBA8, 0);
	if (r){
		std::cerr << "spng_decode_image() error: " << spng_strerror(r) << std::endl;
		return 0;
	}

	unsigned char* flipped = new unsigned char[out_size];

	for (size_t i = 0; i < ihdr.height; i+=1){
		size_t rowsize = ihdr.width*4;
		for (size_t j = 0; j < rowsize; j++){
			flipped[(ihdr.height-i-1)*rowsize+j] = out[i*rowsize+j];
		}
	}
	delete[] out;

    unsigned int texture;
    int alpha = GL_RGBA;

    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ihdr.width, ihdr.height, 0,
        alpha, GL_UNSIGNED_BYTE, (GLvoid *) flipped);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glBindTexture(GL_TEXTURE_2D, 0);

    pwidth[0] = ihdr.width;
    pheight[0] = ihdr.height;

	spng_ctx_free(ctx);
	delete[] pngbuf;

    return texture;
}

#endif

Texture* png::load_texture(std::string filename){
	int width, height;
	GLuint texture = _png_load(filename.c_str(), &width, &height);
	if (texture == 0){
		std::cerr << "Could not load texture " << filename << std::endl;
		return nullptr;
	}
	return new Texture(texture, width, height);
}