#include "heightmap.h"

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "debug.h"
#include "compiler.h"


Heightmap::Heightmap(const char* fileName, float scaling, int displaylistResolution, int vertexResolution)
{
	this->scaleFactor = scaling;
	this->setName(fileName);
	
	this->import(fileName, displaylistResolution, vertexResolution);
	
	this->finalize();
}

Heightmap::~Heightmap ()
{
}

bool Heightmap::import (const char* fileName, int displaylistResolution, int vertexResolution)
{
	PRINTF(4)("preparing to read in file: %s\n", fileName);
	
	// using SDL-image to load the bitmap
	this->bitmap = IMG_Load(fileName);

	// how many pixels wide is a display list?
	int pixPerDLSide = displaylistResolution * vertexResolution;

	int howManyListsWide = bitmap->w / pixPerDLSide + 1;
	int howManyListsHigh = bitmap->h / pixPerDLSide + 1;
	
	// calculated pixel dimensions of one display list. usually equals pixPerDLSide, but at the end of the picture
	// this needs to be shorter, that we do not make a segfault
	int width = pixPerDLSide;
	int height = pixPerDLSide;
	
	for (int i=0; i<howManyListsWide; i++)
	{
		for (int j=0; j<howManyListsHigh; j++)
		{
			// catch out of image access in x-direction
			if ( (j+1)*pixPerDLSide - 1 >= bitmap->w )	width = bitmap->w - j*pixPerDLSide;
			else										width = pixPerDLSide;
			// y-direction
			if ( (i+1)*pixPerDLSide - 1 >= bitmap->h )	height = bitmap->h - i*pixPerDLSide;
			else										height = pixPerDLSide;
			
			this->readIntoGroup(j*pixPerDLSide,i*pixPerDLSide,width,height,vertexResolution);
		}
	}
	
	return true;
}

void Heightmap::readIntoGroup(int left, int top,int width, int height, int vertexResolution)
{
	//this->newGroup();
	
	for (int z=top; z < top+height; z++)
	{
		for (int x=left; x < left+width; x++)
		{
			this->addVertex(x,this->getHeightAt(x,z),z);
		}
	}
}

float Heightmap::getHeightAt(int x, int z)
{
	Uint8 index;
	SDL_Color color;
	
	SDL_LockSurface(bitmap);
	
	index = *((Uint8*)bitmap->pixels + z * bitmap->pitch + x * bitmap->format->BytesPerPixel);
	color = bitmap->format->palette->colors[index];
	
	SDL_UnlockSurface(bitmap);
	
	// return the red component, because in a grayscale pic, r,g and b are all the same value
	return (GLint)color.r;
}