#include <LiquidCrystal_I2C.h>

//shift register control signals
#define data_pin 11
#define latch_pin 12
#define clock_pin 13

// simulate parking sensors using pushbuttons
#define park4_pb 4
#define park3_pb 5
#define park2_pb 6
#define park1_pb 7

// initial status of parking lots - empty is false, full is true
bool p4status=false;
bool p3status=false;
bool p2status=false;
bool p1status=false;

// storage place for pushbuttons values  for each parking slot
int value_park4=1;
int value_park3 =1;
int value_park2=1;
int value_park1 =1;

// storage for available space
int space =0;

// variable to store binary weightage for each parking
int p1,p2,p3,p4,p;

// array that store parking display led that need to be shifted out
byte display[]={0xAA,0xA9,0xA6,0xA5,0x9A,0x99,0x96,0x95,0x6A,0x69,0x66,0x65,0x5A,0x59,0x56,0x55};

// create an instance on liquid crystal object
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup()
{
  // all shift register control signals are output
  pinMode(data_pin, OUTPUT);
  pinMode(latch_pin, OUTPUT);
  pinMode(clock_pin, OUTPUT);

  //all parking sensors are input
  pinMode(park4_pb, INPUT);
  pinMode(park3_pb, INPUT);
  pinMode(park2_pb, INPUT);
  pinMode(park1_pb, INPUT);

  lcd.init(); // initialize the lcd
  lcd.backlight(); // Turn on backlight
}

void loop()
{ 
  // read parking sensor values and store in respective variable
  value_park4 = digitalRead(park4_pb);
  value_park3 = digitalRead(park3_pb);
  value_park2 = digitalRead(park2_pb);
  value_park1 = digitalRead(park1_pb);
  delay(200); // delay to avoid debouncing

// parking sensors are active low; when full the logic is 0
  if(value_park4==0)  // if park 4 is full
  {
    p4status=!p4status; // change the status from false to true 
    (p4status==true)? p4=1 :p4 =0;   // if park 4 status is full, then assign weight 1
  }

  if(value_park3==0)
  {
    p3status=!p3status;
    (p3status==true)? p3=2 : p3 =0;
  }

  if(value_park2==0)
  {
    p2status=!p2status;
    (p2status==true)? p2=4 : p2 =0;
  }

  if(value_park1==0)
  {
    p1status=!p1status;
    (p1status==true)? p1=8 : p1 =0;
  }

//add all the weightage to determine the data that need to send to shift register
int p=p4+p3+p2+p1;

// call the function that send data to shift register and turn on related led
display_led(p);
 
}

void display_led( int p)
{
      for ( int i=0;i<16;i++)
      {
       if( i==p)
       {
         // send data to shift register and shift out parallelly
        digitalWrite(latch_pin, LOW); // Output low level to latchPin
        shiftOut(data_pin, clock_pin, MSBFIRST, display[i]); // Send serial data to 74HC595
        digitalWrite(latch_pin, HIGH); 

        // display available space based on p value
        if (p==0)
         { 
          lcd.setCursor(4,0);
          lcd.print("AVAILABLE");
          lcd.setCursor(4,1);
          lcd.print("4 SPACES");
         }
        else if (p==1 || p==2|| p==4||p==8)
        {
          lcd.setCursor(4,0);
          lcd.print("AVAILABLE");
          lcd.setCursor(4,1);
          lcd.print("3 SPACES");
        }
        else if (p==3 || p==5|| p==6||p==9||p==10||p==12)
        {
          lcd.setCursor(4,0);
          lcd.print("AVAILABLE");
          lcd.setCursor(4,1);
          lcd.print("2 SPACES");

        }
        else if (p==7 || p==11|| p==13||p==14)
        {
          lcd.setCursor(4,0);
          lcd.print("AVAILABLE");
          lcd.setCursor(4,1);
          lcd.print("1 SPACES");
        }
        else
        {
          lcd.setCursor(4,0);
          lcd.print("AVAILABLE");
          lcd.setCursor(4,1);
          lcd.print("0 SPACE");
        }
       }
      }
}