//-------------------------------------------------------------------
//	2dimwalk.cpp
//
//	This program enhances our 'randwalk.cpp' demo by showing a
//	two-dimensional walk, with barriers above and below, where
//	a molecule can move left or right, and up or down, or else
//	can remain stationary in either or both of the dimensions. 
//
//		to compile:  $ g++ 2dimewalk.cpp -o 2dimwalk
//		to execute:  $ ./2dimwalk
//
//	programmer: ALLAN CRUSE
//	written on: 25 JAN 2011
//-------------------------------------------------------------------

#include <stdio.h>	// for printf() 
#include <stdlib.h>	// for random()
#include <unistd.h>	// for usleep()  
#include <time.h>	// for time()

int main( int argc, char **argv )
{
	// prepare a blank screen
	printf( "\e[H\e[J" );	// clear the screen
	printf( "\e[?25l" ); 	// hide the cursor
	fflush( stdout );

	// draw the horizontal barriers
	printf( "\e[12;0H" );
	for (int k = 0; k < 80; k++) printf( "-" );
	printf( "\e[18;0H" );
	for (int k = 0; k < 80; k++) printf( "-" );
	fflush( stdout );

	// seed the random number generator
	srandom( time( 0 ) );

	// initialize the simulation
	int	row = 15, col = 40;
	printf( "\e[%d;%dH%c", row, col, 'o' ); fflush( stdout );

	// exhibit the two-dimensional random walk
	for (int i = 0; i < 100; i++)
		{
		usleep( 125000 );	// 125 milliseconds
		printf( "\e[%d;%dH%c", row, col, ' ' ); fflush( stdout );
		int	x = random() % 3;
		int	y = random() % 3;
		switch ( x )
			{
			case 0: ++col; break;
			case 1: --col; break;
			}
		switch ( y )
			{
			case 0: ++row; break;
			case 1: --row; break;
			}
		if ( row == 12 ) ++row;
		if ( row == 18 ) --row;
		if ( col == 1 ) ++col;
		if ( col == 79 ) --col;
		printf( "\e[%d;%dH%c", row, col, 'o' ); fflush( stdout );
		}

	// prepare the cursor for program exit
	printf( "\e[24;0H" );	// move cursor to bottom of screen
	printf( "\e[?25h" );	// show the cursor
	fflush( stdout );	
}