#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
#include <IRremote.h>

// --- PIN CONFIGURATION ---
const int PIN_RED    = 12;
const int PIN_YELLOW = 11;
const int PIN_GREEN  = 10;
const int PIN_BLUE   = 6; 
const int PIN_BUZZER = 5;  // Siren

const int PIN_TRIG   = 9;
const int PIN_ECHO   = 8;
const int PIN_SWITCH = 4;  // Signal Switch
const int PIN_IR     = 7;

// --- OBJECTS ---
LiquidCrystal_I2C lcd(0x27, 16, 2);

// --- VARIABLES ---
enum TrafficMode { AUTO, FORCE_RED, FORCE_GREEN };
TrafficMode currentMode = AUTO;

bool wasActivePreviously = false; 

// Timing Variables
unsigned long lastTrafficChange = 0;
unsigned long lastSirenChange = 0;
int autoState = 0; 
int sirenState = LOW; // Beep State

// Durations
const int GREEN_DURATION = 1000;
const int YELLOW_DURATION = 500;
const int RED_DURATION = 1000;

void setup() {
  pinMode(PIN_RED, OUTPUT);
  pinMode(PIN_YELLOW, OUTPUT);
  pinMode(PIN_GREEN, OUTPUT);
  pinMode(PIN_BLUE, OUTPUT);
  pinMode(PIN_BUZZER, OUTPUT);
  pinMode(PIN_TRIG, OUTPUT);
  pinMode(PIN_ECHO, INPUT);
  pinMode(PIN_SWITCH, INPUT);

  lcd.init();
  lcd.backlight();
  lcd.print("System Ready");
  delay(1000);
  lcd.clear();

  IrReceiver.begin(PIN_IR, ENABLE_LED_FEEDBACK);
  Serial.begin(9600);
}

void loop() {
  // 1. READ SENSORS
  long distance = readDistance();
  bool signalActive = (digitalRead(PIN_SWITCH) == HIGH); 
  bool ambulanceClose = (distance < 100);
  
  // 2. CHECK STATUS
  bool systemActive = (signalActive && ambulanceClose);

  // 3. HANDLE RESET (Connection/Disconnection)
  if (systemActive != wasActivePreviously) {
    if (systemActive) {
      // CONNECTED: Blue Light ON, but SILENT waiting for command
      digitalWrite(PIN_BLUE, HIGH);
      currentMode = AUTO; 
      updateLCD("AMBULANCE MODE", "Waiting Cmd...");
      IrReceiver.resume();
    } else {
      // DISCONNECTED: Everything OFF
      digitalWrite(PIN_BLUE, LOW);
      digitalWrite(PIN_BUZZER, LOW); 
      currentMode = AUTO;
      updateLCD("NORMAL TRAFFIC", "Auto Cycle");
    }
    wasActivePreviously = systemActive;
  }

  // 4. ACTIVE BEHAVIOR
  if (systemActive) {
    // Check Remote
    if (IrReceiver.decode()) {
      int command = IrReceiver.decodedIRData.command;
      
      if (command == 48) { // Button 1 -> STOP
        currentMode = FORCE_RED;
        updateLCD("AMBULANCE MODE", "CMD: STOP (RED)");
      }
      else if (command == 24) { // Button 2 -> GO
        currentMode = FORCE_GREEN;
        updateLCD("AMBULANCE MODE", "CMD: GO (GREEN)");
      }
      else if (command == 122) { // Button 3 -> RESUME
        currentMode = AUTO;
        updateLCD("AMBULANCE MODE", "CMD: RESUME");
      }
      IrReceiver.resume();
    }
  } 

  // 5. CONTROL OUTPUTS (Lights & Buzzer)
  
  // LOGIC: Only sound buzzer if we are FORCING the lights
  if (currentMode == FORCE_RED || currentMode == FORCE_GREEN) {
    runSafeSiren(); // Beep!
    
    if (currentMode == FORCE_RED) setLights(HIGH, LOW, LOW);
    else setLights(LOW, LOW, HIGH);
  } 
  else {
    // Mode is AUTO (Silent)
    digitalWrite(PIN_BUZZER, LOW); // Silence the buzzer
    runAutoCycle();
  }
}

// --- HELPER FUNCTIONS ---

// Safe digital beep that won't crash the remote
void runSafeSiren() {
  unsigned long currentMillis = millis();
  
  // Toggle sound ON/OFF every 300ms
  if (currentMillis - lastSirenChange >= 300) {
    lastSirenChange = currentMillis;
    
    if (sirenState == LOW) {
      sirenState = HIGH;
      analogWrite(PIN_BUZZER, 127); // PWM ON (Creates a tone ~980Hz)
    } else {
      sirenState = LOW;
      analogWrite(PIN_BUZZER, 0);   // PWM OFF (Silence)
    }
  }
}

void updateLCD(String line1, String line2) {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print(line1);
  lcd.setCursor(0,1);
  lcd.print(line2);
}

void runAutoCycle() {
  unsigned long currentMillis = millis();
  
  switch (autoState) {
    case 0: // GREEN
      setLights(LOW, LOW, HIGH);
      if (currentMillis - lastTrafficChange >= GREEN_DURATION) {
        autoState = 1;
        lastTrafficChange = currentMillis;
      }
      break;
    case 1: // YELLOW
      setLights(LOW, HIGH, LOW);
      if (currentMillis - lastTrafficChange >= YELLOW_DURATION) {
        autoState = 2;
        lastTrafficChange = currentMillis;
      }
      break;
    case 2: // RED
      setLights(HIGH, LOW, LOW);
      if (currentMillis - lastTrafficChange >= RED_DURATION) {
        autoState = 0;
        lastTrafficChange = currentMillis;
      }
      break;
  }
}

void setLights(int r, int y, int g) {
  digitalWrite(PIN_RED, r);
  digitalWrite(PIN_YELLOW, y);
  digitalWrite(PIN_GREEN, g);
}

long readDistance() {
  digitalWrite(PIN_TRIG, LOW); delayMicroseconds(2);
  digitalWrite(PIN_TRIG, HIGH); delayMicroseconds(10);
  digitalWrite(PIN_TRIG, LOW);
  return pulseIn(PIN_ECHO, HIGH) * 0.034 / 2;
}