/*******************************************************************************

 Copyright (c) 2009, Charles McGarvey
 All rights reserved.
 
 Redistribution   and   use  in  source  and  binary  forms,  with  or  without
 modification, are permitted provided that the following conditions are met:
 
   * Redistributions  of  source  code  must retain the above copyright notice,
     this list of conditions and the following disclaimer.
   * Redistributions  in binary form must reproduce the above copyright notice,
     this  list of conditions and the following disclaimer in the documentation
     and/or other materials provided with the distribution.
 
 THIS  SOFTWARE  IS  PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 AND  ANY  EXPRESS  OR  IMPLIED  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED.  IN  NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 FOR  ANY  DIRECT,  INDIRECT,  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 DAMAGES  (INCLUDING,  BUT  NOT  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 SERVICES;  LOSS  OF  USE,  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 CAUSED  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR  TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*******************************************************************************/

#include <stdexcept>
#include <cstdlib>

#include <boost/bind.hpp>

#include <SDL/SDL.h>
#include <SDL/SDL_image.h>

#include "dispatcher.hh"
#include "opengl.hh"

#include "texture.hh"


namespace dc {


class texture_impl
{
	void unloadFromGL()
	{
		if (object)
		{
			glDeleteTextures(1, &object);
			object = 0;
		}
	}

	void contextRecreated(const notification& note)
	{
		unloadFromGL();
		uploadToGL();
	}

public:
	texture_impl(const std::string& filePath, bool keepInMemory)
		: object(0), imageData(0), imagePath(filePath), keepData(keepInMemory)
	{
		dispatcher::instance().addHandler("video.context_recreated",
				boost::bind(&texture_impl::contextRecreated, this, _1),
				this);
	}

	~texture_impl()
	{
		dispatcher::instance().removeHandler(this);

		if (imageData)
		{
			SDL_FreeSurface(imageData);
		}
		unloadFromGL();
	}


	static int powerOfTwo(int input)
	{
		int value = 1;

		while (value < input)
		{
			value <<= 1;
		}
		return value;
	}

	// Adapted from some public domain code.  This code is common enough that it
	// really should be included in SDL_image...
	static SDL_Surface* prepareImageForGL(SDL_Surface* surface)
	{
		/* Use the surface width and height expanded to powers of 2 */
		int w = powerOfTwo(surface->w);
		int h = powerOfTwo(surface->h);

		SDL_Surface* image = SDL_CreateRGBSurface
		(
			SDL_SWSURFACE,
			w, h,
			32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
			0x000000FF, 
			0x0000FF00, 
			0x00FF0000, 
			0xFF000000
#else
			0xFF000000,
			0x00FF0000, 
			0x0000FF00, 
			0x000000FF
#endif
		);

		if (!image)
		{
			return 0;
		}

		// Save the alpha blending attributes.
		Uint32 savedFlags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
		Uint8  savedAlpha = surface->format->alpha;
		if (savedFlags & SDL_SRCALPHA)
		{
			SDL_SetAlpha(surface, 0, 0);
		}

		SDL_Rect srcArea, destArea;
		/* Copy the surface into the GL texture image */
		srcArea.x = 0; destArea.x = 0;
		/* Copy it in at the bottom, because we're going to flip
		   this image upside-down in a moment
		*/
		srcArea.y = 0; destArea.y = h - surface->h;
		srcArea.w = surface->w;
		srcArea.h = surface->h;
		SDL_BlitSurface(surface, &srcArea, image, &destArea);

		/* Restore the alpha blending attributes */
		if (savedFlags & SDL_SRCALPHA)
		{
			SDL_SetAlpha(surface, savedFlags, savedAlpha);
		}

		/* Turn the image upside-down, because OpenGL textures
		   start at the bottom-left, instead of the top-left
		*/
		Uint8 line[image->pitch];

		/* These two make the following more readable */
		Uint8 *pixels = static_cast<Uint8*>(image->pixels);
		Uint16 pitch = image->pitch;
		int ybegin = 0;
		int yend = image->h - 1;

		// TODO: consider if this lock is legal/appropriate
		if (SDL_MUSTLOCK(image)) { SDL_LockSurface(image); }
		while (ybegin < yend)
		{
			memcpy(line, pixels + pitch*ybegin, pitch);
			memcpy(pixels + pitch*ybegin, pixels + pitch*yend, pitch);
			memcpy(pixels + pitch*yend, line, pitch);
			ybegin++;
			yend--;
		}
		if (SDL_MUSTLOCK(image)) { SDL_UnlockSurface(image); }

		return image;
	}


	void loadImageData()
	{
		SDL_Surface* surface;

		surface = IMG_Load(imagePath.c_str());

		if (!surface)
		{
			throw std::runtime_error("could not load image data from file");
		}

		imageData = prepareImageForGL(surface);
		SDL_FreeSurface(surface);

		if (!imageData)
		{
			throw std::runtime_error("error in preparing image data for GL");
		}

		if (imageData->format->BytesPerPixel == 3)
		{
			mode = GL_RGB;
		}
		else if (imageData->format->BytesPerPixel == 4)
		{
			mode = GL_RGBA;
		}
		else
		{
			SDL_FreeSurface(imageData);
			throw std::runtime_error("image must be 24 or 32 bpp");
		}

		width = imageData->w;
		height = imageData->h;
	}


	void uploadToGL()
	{
		if (object)
		{
			// Already loaded.
			return;
		}

		if (!imageData)
		{
			loadImageData();
		}

		glGenTextures(1, &object);

		glBindTexture(GL_TEXTURE_2D, object);

		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			mode,
			imageData->w,
			imageData->h,
			0,
			mode,
			GL_UNSIGNED_BYTE,
			imageData->pixels
		);

		// These default filters can be changed later...
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

		if (!keepData)
		{
			SDL_FreeSurface(imageData);
			imageData = 0;
		}
	}


	unsigned width;
	unsigned height;
	int mode;
	GLuint object;

	std::string imagePath;
	bool keepData;
	SDL_Surface* imageData;
};


texture::texture(const std::string& filePath, bool keepInMemory)
	: impl(new texture_impl(filePath, keepInMemory)) {}


const std::string& texture::filePath()
{
	return impl->imagePath;
}


void texture::bind()
{
	glBindTexture(GL_TEXTURE_2D, object());
}

GLuint texture::object()
{
	if (!impl->object)
	{
		impl->uploadToGL();
	}

	return impl->object;
}


unsigned texture::width()
{
	return impl->width;
}

unsigned texture::height()
{
	return impl->height;
}



} // namespace dc