/*
 *	touch.c
 *	written by Holmes Futrell
 *	use however you want
 */

#include "SDL.h"
#include "math.h"
#include "common.h"

#define BRUSH_SIZE 32			/* width and height of the brush */
#define PIXELS_PER_ITERATION 5  /* number of pixels between brush blots when forming a line */ 

static SDL_TextureID brushID=0; /* texture for the brush */

/*
	draws a line from (startx, starty) to (startx + dx, starty + dy)
	this is accomplished by drawing several blots spaced PIXELS_PER_ITERATION apart
*/
void drawLine(float startx, float starty, float dx, float dy) {

	float distance = sqrt(dx*dx+dy*dy);						/* length of line segment (pythagoras) */
	int iterations = distance / PIXELS_PER_ITERATION + 1;	/* number of brush sprites to draw for the line */
	float dx_prime = dx / iterations;						/* x-shift per iteration */
	float dy_prime = dy / iterations;						/* y-shift per iteration */
	SDL_Rect dstRect;										/* rect to draw brush sprite into */
	
	dstRect.w = BRUSH_SIZE;
	dstRect.h = BRUSH_SIZE;
	
	/* setup x and y for the location of the first sprite */
	float x = startx - BRUSH_SIZE / 2.0f;
	float y = starty - BRUSH_SIZE / 2.0f;		
	
	int i;
	/* draw a series of blots to form the line */
	for (i=0; i<iterations; i++) {
		dstRect.x = x;
		dstRect.y = y;
		/* shift x and y for next sprite location */
		x += dx_prime;
		y += dy_prime;
		/* draw brush blot */
		SDL_RenderCopy(brushID, NULL, &dstRect);
	}
}

/*
	loads the brush texture
*/
void initializeTexture() {
	SDL_Surface *bmp_surface;
	bmp_surface = SDL_LoadBMP("stroke.bmp");
	if (bmp_surface == NULL) {
		fatalError("could not load stroke.bmp");
	}
	brushID = SDL_CreateTextureFromSurface(SDL_PIXELFORMAT_ABGR8888, bmp_surface);
	SDL_FreeSurface(bmp_surface);
	if (brushID == 0) {
		fatalError("could not create brush texture");
	}
	/* additive blending -- laying strokes on top of eachother makes them brighter */
	SDL_SetTextureBlendMode(brushID, SDL_TEXTUREBLENDMODE_ADD);
	/* set brush color (red) */
	SDL_SetTextureColorMod(brushID, 255, 100, 100);
}

int main(int argc, char *argv[]) {
	
	int x, y, dx, dy;		/* mouse location	   */
	Uint8 state;			/* mouse (touch) state */
	SDL_Event event;
	SDL_WindowID windowID;	/* main window */
	int done;				/* does user want to quit? */
	
	/* initialize SDL */
	if (SDL_Init(SDL_INIT_VIDEO) < 0) {
		fatalError("Could not initialize SDL");
	}
	
	/* create main window and renderer */
	windowID = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,\
								SDL_WINDOW_OPENGL|SDL_WINDOW_SHOWN|SDL_WINDOW_BORDERLESS);
	SDL_CreateRenderer(windowID, 0, 0);		
	
	/*load brush texture */
	initializeTexture();
	
	/* fill canvass initially with all black */
	SDL_RenderFill(0, 0, 0, 255, NULL);
	SDL_RenderPresent();
		
	done = 0;
	while (!done && SDL_WaitEvent(&event)) {
		switch (event.type) {
			case SDL_QUIT:
				done = 1;
				break;
			case SDL_MOUSEMOTION:
				SDL_SelectMouse(event.motion.which);  /* select 'mouse' (touch) that moved */
				state = SDL_GetMouseState(&x, &y);	  /* get its location */
				SDL_GetRelativeMouseState(&dx, &dy);  /* find how much the mouse moved */
				if (state & SDL_BUTTON_LMASK) {		  /* is the mouse (touch) down? */
					drawLine(x - dx, y - dy, dx, dy); /* draw line segment */
					SDL_RenderPresent();
				}
				break;
		}
	}
	
	/* cleanup */
	SDL_DestroyTexture(brushID);
	SDL_Quit();
	
	return 0;
}