#include <TimerOne.h>

/*
 *  upper nibble hold the button state
 *  lower nibble hold the counter value
 */
volatile uint8_t var = 0;

/*
 *   button pressed logic  0
 *   buuton released logic 1
 */
#define BUTTON_SET       0
#define BUTTON_RESET     1

#define b1  2
#define b2  3
#define b3  4
#define b4  5

#define B1_STATE_POS   0x10
#define B2_STATE_POS   0x20
#define B3_STATE_POS   0x40
#define B4_STATE_POS   0x80

const uint16_t t1_load = 0; 
const uint16_t t1_comp = 249; 
#define  DEBOUNCE_TIME  6   // for 100 ms 


/*
 *  Timer Initialization Function (mocked)
 *  initialize timer on periodic base to call its ISR after every 10ms
 */


void init_timer()
{
  //Reset Time1 Control Register A to its defualt value
TCCR1A = 0; 

/* Set prescaler of 256, 
NOTE: FIrst 3 bits of TCCR1B need to be 100 for 256 prescaler*/
TCCR1B &= ~(1 << CS12); //Set Bit 2
TCCR1B |= (1 << CS11); // Clear Bit 1
TCCR1B |= (1 << CS10);  // Clear Bit 0 

// Reset Timer1 and Set Compare Value 
TCNT1 = t1_load; // Reset Timer 1
OCR1A = t1_comp; // Set Compare Value of 31250 (Output Compare Register)

// Enable Timer1 compare Interrupt 
TIMSK1 = (1 << OCIE1A); 

// Enable Global Interrupts, NOTE: Enabled by defualt
sei(); 
// Timer1.initialize(10000); // Set the timer period to 10000 microseconds (10ms)
// Timer1.attachInterrupt(timerCallback);
}


/*
* start the timer 
*/
void timer_start()
{
	
}

/*
 * stop the timer
 */
void timer_stop()
{
	
}

bool state = 0;

void timerCallback() {
  // Your code to run every 10ms
  
   digitalWrite(13, state);
  state = !state;
  btn_loop();
}

ISR(TIMER1_COMPA_vect){

   
 // switch_loop();
  //TCNT1 = t1_load; // Reset Timer1 to 0.
  digitalWrite(13, state);
  state = !state;
  btn_loop();
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
pinMode(2, INPUT_PULLUP);
pinMode(3, INPUT_PULLUP);
pinMode(4, INPUT_PULLUP);
pinMode(5, INPUT_PULLUP);
pinMode(13, OUTPUT);
init_timer();
}

void loop() {
  Key_check();
}


/*
bool digitalRead(uint8_t pin)
{
	// return 0 when pressd
	// return 1 when released
}
*/

/*
 *  Check if any of key pressed with debounce time of 100ms
 */
void btn_loop()
{

  if((digitalRead(b1)== BUTTON_SET) && (var >> 4 == 0x0))
  {
    if((var & 0x0F) < DEBOUNCE_TIME)
    {
      var += 1; 
    }else
    {      
      var |= B1_STATE_POS;  
    }
  }
  else if((digitalRead(b2)== BUTTON_SET) && (var >> 4 == 0))
  {
    if((var & 0x0F) < DEBOUNCE_TIME)
    {
      var += 1; 
    }else
    {
      var |= B2_STATE_POS; 
    }
  }
  else if((digitalRead(b3)== BUTTON_SET) && (var >> 4 == 0))
  {
    if((var & 0x0F) < DEBOUNCE_TIME)
    {
      var += 1; 
    }else
    {
      var |= B3_STATE_POS;
    }
  }
  else if((digitalRead(b4)== BUTTON_SET) && (var >> 4 == 0))
  {
    if((var & 0x0F) < DEBOUNCE_TIME)
    {
      var += 1; 
    }else
    {  
      var |= B4_STATE_POS;   
    }
  }
  else if(var >> 4 != 0)
  {
    if((var & 0x0f) < 0x0f)
        var += 1;
  }else        
  {
    var &= 0xF0;
  }
}



void print_press_type(uint8_t var)
{
    if((var & 0x0f) >6 && (var & 0x0f) < 12)
    {
      Serial.println("short pressed");
    }else if((var & 0x0f) > 12 && (var & 0x0f) < 16)
    {
      Serial.println("long pressed");
    }else
    {
      Serial.println("pressed");
    }
}

/*
 *  Function to check which key pressed 
 *  this function will reset the key state after the button is released
*/
void Key_check()
{ 
  if((var & B1_STATE_POS) == B1_STATE_POS && digitalRead(b1))  /* check if btn was pressed for 100ms and now released*/
  {
    Serial.println("1");
    print_press_type(var);
    var &= ~(B1_STATE_POS);
    var &= ~(0x0F); 
  }
  if((var & B2_STATE_POS) == B2_STATE_POS && digitalRead(b2)) /* check if btn was pressed for 100ms and now released*/
  {
     Serial.println("2");
    print_press_type(var);
   
    var &= ~(B2_STATE_POS);
    var &= ~(0x0F); 
  }
  if((var & B3_STATE_POS) == B3_STATE_POS && digitalRead(b3)) /* check if btn was pressed for 100ms and now released*/
  {
    Serial.println("3");
    print_press_type(var);  
    var &= ~(B3_STATE_POS);
    var &= ~(0x0F); 
  }

  if((var & B4_STATE_POS) == B4_STATE_POS  && digitalRead(b4)) /* check if btn was pressed for 100ms and now released*/
  {
    Serial.println("4");
    print_press_type(var);
    var &= ~(B4_STATE_POS);
    var &= ~(0x0F); 
  }
}