#include <SevSegShift.h>

// Pin definitions for shift register
#define SHIFT_PIN_SHCP 7   // Clock pin - SHCP/SH_CP
#define SHIFT_PIN_STCP 4   // Latch pin - STCP/ST_CP
#define SHIFT_PIN_DS 8     // Data pin - DS

// Pin definitions for ultrasonic sensor
#define TRIG_PIN 12
#define ECHO_PIN 11

// Pin definitions for LEDs and buzzer
#define RED_LED 5
#define YELLOW_LED 6
#define GREEN_LED 3
#define BUZZER 2

// Digit pins connected to Arduino
const int digit1 = A0;
const int digit2 = A1;
const int digit3 = A2;
const int digit4 = A3;

// Define segment pins (mapped through shift register)
const byte numDigits = 4;
const byte digitPins[] = {digit1, digit2, digit3, digit4};
const byte numSegmentPins = 8; // 7 segments + decimal point
const byte segmentPins[] = {0, 1, 2, 3, 4, 5, 6, 7}; // Pins on shift register

// Initialize SevSegShift
SevSegShift sevseg(SHIFT_PIN_DS, SHIFT_PIN_SHCP, SHIFT_PIN_STCP, 1, true); // 1 shift register, common anode display

// Variables
int distance = 0;
unsigned long lastMeasurement = 0;
const unsigned long MEASUREMENT_INTERVAL = 100; // Measure every 100ms

// Beep timing variables
unsigned long lastBeepTime = 0;
const unsigned long BEEP_ON_TIME = 100;    // Beep for 100ms
const unsigned long BEEP_OFF_TIME = 900;   // Silent for 900ms
boolean isBeeping = false;

void setup() {
  // Initialize display
  sevseg.begin(COMMON_ANODE, numDigits, digitPins, segmentPins, true, false, false, false);
  sevseg.setBrightness(90);

  // Initialize sensor pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  
  // Initialize LED and buzzer pins
  pinMode(RED_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(BUZZER, OUTPUT);
  
  // Initially turn off all LEDs and buzzer
  digitalWrite(RED_LED, LOW);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(BUZZER, LOW);
}

void loop() {
  unsigned long currentTime = millis();
  
  // Update distance measurement periodically
  if (currentTime - lastMeasurement >= MEASUREMENT_INTERVAL) {
    distance = measureDistance();
    lastMeasurement = currentTime;
    updateWarnings();
  }
  
  // Must be called frequently to maintain display
  sevseg.refreshDisplay();
}

int measureDistance() {
  // Clear trigger pin
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  
  // Send 10μs pulse
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  
  // Measure the response
  long duration = pulseIn(ECHO_PIN, HIGH);
  
  // Calculate distance in cm and ensure it's within valid range
  int dist = duration * 0.034 / 2;
  return constrain(dist, 0, 9999); // Ensure distance fits on display
}

void updateWarnings() {
  // Reset all indicators
  digitalWrite(RED_LED, LOW);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(GREEN_LED, LOW);
  
  unsigned long currentTime = millis();

  if (distance <= 10) {
    // Danger zone - continuous beep and red light
    digitalWrite(RED_LED, HIGH);
    tone(BUZZER, 1000);
    isBeeping = true;
  }
  else if (distance > 10 && distance <= 30) {
    // Warning zone - yellow light and short beeps
    digitalWrite(YELLOW_LED, HIGH);
    
    // Manage beeping timing
    if (!isBeeping && currentTime - lastBeepTime >= BEEP_OFF_TIME) {
      // Start a new beep
      tone(BUZZER, 500);
      isBeeping = true;
      lastBeepTime = currentTime;
    }
    else if (isBeeping && currentTime - lastBeepTime >= BEEP_ON_TIME) {
      // End the beep
      noTone(BUZZER);
      isBeeping = false;
      lastBeepTime = currentTime;
    }
  }
  else {
    // Safe zone - green light, no beep
    digitalWrite(GREEN_LED, HIGH);
    noTone(BUZZER);
    isBeeping = false;
  }

  // Update display
  sevseg.setNumber(distance +1);
}