#include <HID.h>// include the library
int swipe = 0;//slide
boolean left = false;
boolean right = false;
int maxD = 5;//(in cm) maximum distance from ultrasonic at which the obstruction will be considered a gesture
long int lastTouch = -1;
int resetAfter = 1000;//ms
int afterslideDelay = 500;//
int slideleft_Begin = -1;
int slideNone = 0;
int slideright_Begin =1;
//Declaring the connected pins
int lLed = 7;
int rLed = 6;
const int lEcho = 2;
const int lTrig = 3;
const int rEcho = 4;
const int rTrig = 5;
void setup(){
pinMode(lLed,OUTPUT);
pinMode(rLed,OUTPUT);
pinMode(rEcho,INPUT);
pinMode(rTrig,OUTPUT);
pinMode(lEcho,INPUT);
pinMode(lTrig,OUTPUT);
Serial.begin(9600);
// Sends a clean report to the host. This is important because
// the 16u2 of the Uno/Mega is not turned off while programming
// so you want to start with a clean report to avoid strange bugs after reset.

pressRawKeyboard(0, 0);
}
//get distance
//echo is input, trigger is output
unsigned long measureD(int input, int output){
digitalWrite(output, HIGH);
delayMicroseconds(10);
digitalWrite(output, LOW);
long range= pulseIn(input, HIGH);
int distance= range / 29 / 2;// to get distance in cm
return distance;
}
//
boolean act (int input, int output, int led){
int d = measureD(input,output);
boolean pinActivated = false;
if (d < maxD){
  digitalWrite(led,HIGH);
  pinActivated = true;
}
else{
  digitalWrite(led,LOW);
  pinActivated = false;
}
return pinActivated;
}
void slideNow(char directn){
if ('R' == directn)
{
  // press the right rrow key
  //Serial.println("F");
  pressRawKeyboard(0,RAW_KEYBOARD_RIGHT_ARROW); //modifiers + key
  pressRawKeyboard(0, 0); // release! Important
}
if ('L' == directn)
{
  //press the left arrow key
  //Serial.println("B"); for debug
  pressRawKeyboard(0,RAW_KEYBOARD_LEFT_ARROW); // //modifiers + key
  pressRawKeyboard(0, 0); // release! Important

}
delay(afterslideDelay);
swipe = slideNone;
}
void pressRawKeyboard(uint8_t modifiers, uint8_t key){
uint8_t keys[8] = {
modifiers, 0, key, 0, 0, 0, 0, 0 }; //modifiers, reserved, key[0]
HID_SendReport(HID_REPORTID_KeyboardReport, keys, sizeof(keys));
}
void loop(){
left = act(lEcho,lTrig,lLed);
right = act(rEcho,rTrig,rLed);
if (left || right){
  lastTouch = millis();
}
if (millis() - lastTouch > resetAfter){
  swipe = 0;
  //serial.println(@reset slide& timer);
}
if (swipe >= slideNone){
  if ((left)&&(!right)){
    swipe = slideright_Begin;
}
  if ((right)&&(swipe == slideright_Begin)){
    slideNow('R');
}
}
if (swipe <= slideNone ){
  if ((right)&&(!left)){
    swipe = slideleft_Begin;
}
  if ((left) && (swipe == slideleft_Begin)){
    slideNow('L');
}
}
delay(50);
}