// Etch-a-Sketch
// by Trevor Shannon
//
// based on Graph 
// by David A. Mellis

import processing.serial.*;

Serial port;
String buff = "";
String buff1 = "";
String buff2 = "";
int index = 0;
int NEWLINE = 10;

// Store the last 256 values received so we can graph them.
int[] valuesx = new int[256];
int[] valuesy = new int[256];

void setup()
{
  size(512, 512);
  
  port = new Serial(this, "COM9", 9600);  
  
  // If you know the name of the port used by the Arduino board, you
  // can specify it directly like this.
  //port = new Serial(this, "COM1", 9600);
  

}

void draw()
{
  background(0);
  stroke(0);
  
  // Graph the stored values by drawing a lines between them.
  for (int i = 0; i < 255; i++){
    stroke(i);
    line(512 - valuesx[i], 512 - valuesy[i], 512-valuesx[i + 1], 512 - valuesy[i + 1]);
  }
  while (port.available() > 0)
    serialEvent(port.read());
}

void serialEvent(int serial)
{
  if (serial != NEWLINE) {
    // Store all the characters on the line.
    buff += char(serial);
  } 
  else {
    // The end of each line is marked by two characters, a carriage
    // return and a newline.  We're here because we've gotten a newline,
    // but we still need to strip off the carriage return.
    buff = buff.substring(0, buff.length()-1);
    index = buff.indexOf(",");
    buff1 = buff.substring(0, index);
    buff2 = buff.substring(index+1, buff.length());
    
    // Parse the String into an integer.  We divide by 4 because
    // analog inputs go from 0 to 1023 while colors in Processing
    // only go from 0 to 255.
    int x = Integer.parseInt(buff1)/2;
    int y = Integer.parseInt(buff2)/2;

    // Clear the value of "buff"
    buff = "";
    
    // Shift over the existing values to make room for the new one.
    for (int i = 0; i < 255; i++)
    {
      valuesx[i] = valuesx[i + 1];
      valuesy[i] = valuesy[i + 1];
    }
    
    // Add the received value to the array.
    valuesx[255] = x;
    valuesy[255] = y;
  }
}