#include <LiquidCrystal.h>

// ---------------- Pin Configuration ----------------
#define BUTTON A0
#define SWITCH_PIN 2
#define TRIG 3
#define ECHO 4
#define BUZZER 5
#define LCD_VO 6
#define LCD_D7 7
#define LCD_D6 8
#define LCD_D5 9
#define LCD_D4 10
#define LCD_E 11
#define LCD_RS 12
#define LDR_DO 13

LiquidCrystal lcd(LCD_RS, LCD_E, LCD_D4, LCD_D5, LCD_D6, LCD_D7);

// ---------------- Constants ----------------
const bool SWITCH_ACTIVE_LOW = true;
const unsigned long muteDuration = 300000UL;     // 5 minutes
const unsigned long lcdUpdateInterval = 400;
const unsigned long preBeepDelay = 20000UL;      // 20 s before active
const unsigned long beepCycle = 4000UL;
const unsigned long beepPatternDuration = 1000UL;
const unsigned long debounceDelay = 250UL;
const unsigned long proximityPauseDist = 61;     // 2 ft
const unsigned long proximityReleaseDist = 65;   // hysteresis

// ---------------- State ----------------
bool isMuted = false;
bool systemActive = false;
bool belowThreshold = false;
bool lastButtonState = LOW;
bool lastSwitchState = HIGH;
bool proximityPaused = false;
bool buzzerOn = false;

unsigned long muteStartTime = 0;
unsigned long thresholdStartTime = 0;
unsigned long beepStartTime = 0;
unsigned long lastLCDUpdate = 0;
unsigned long lastButtonPressTime = 0;
unsigned long lastBeepCycle = 0;
unsigned long lastBeepAction = 0;

// ---------------- Setup ----------------
void setup() {
  pinMode(BUTTON, INPUT);
  pinMode(SWITCH_PIN, INPUT_PULLUP);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(BUZZER, OUTPUT);
  pinMode(LDR_DO, INPUT);
  pinMode(LCD_VO, OUTPUT);

  analogWrite(LCD_VO, 50); // set contrast

  delay(800);
  lcd.begin(16, 2);
  lcd.clear();
  lcd.print("System Starting...");
  delay(1500);
  lcd.clear();

  Serial.begin(9600);
  resetSystem();
}

// ---------------- Loop ----------------
void loop() {
  unsigned long now = millis();
  analogWrite(LCD_VO, 50);  // keep contrast constant

  bool buttonState = digitalRead(BUTTON);
  bool switchState = (SWITCH_ACTIVE_LOW) ? !digitalRead(SWITCH_PIN) : digitalRead(SWITCH_PIN);
  bool ldrDark = (digitalRead(LDR_DO) == LOW);  // *** FIXED: LOW = dark ***
  float distance = getDistanceCM();

  // ---- Handle switch toggle ----
  if (switchState != lastSwitchState) {
    lastSwitchState = switchState;
    resetSystem();
    lcd.clear();
    delay(400);
  }

  // ---- SWITCH OFF = Calibration Mode ----
  if (!switchState) {
    noTone(BUZZER);
    showLCD(now, "Calibration Mode", "Wait...");
    return;
  }

  // ---- Mute Button Logic ----
  if (buttonState != lastButtonState && (now - lastButtonPressTime > debounceDelay)) {
    lastButtonPressTime = now;
    lastButtonState = buttonState;

    if (buttonState == HIGH) {
      if (!isMuted) {
        isMuted = true;
        muteStartTime = now;
        noTone(BUZZER);
        lcd.clear();
        lcd.print("System paused");
        lcd.setCursor(0, 1);
        lcd.print("Mute:05m00s");
      } else {
        // Cancel mute
        isMuted = false;
        muteStartTime = 0;
        lcd.clear();
        lcd.print("Mute canceled");
        delay(1000);
        lcd.clear();
      }
    }
  }

  // ---- Mute Timer Expiration ----
  if (isMuted && (now - muteStartTime >= muteDuration)) {
    isMuted = false;
    muteStartTime = 0;
    lcd.clear();
    lcd.print("Mute ended");
    delay(1000);
    lcd.clear();
  }

  // ---- Proximity Pause ----
  if (distance <= proximityPauseDist) {
    proximityPaused = true;
  } else if (distance > proximityReleaseDist) {
    proximityPaused = false;
  }

  // ---- LDR Darkness Detection ----
  if (ldrDark) {
    if (!belowThreshold) {
      belowThreshold = true;
      thresholdStartTime = now;
    }
    if (!systemActive && (now - thresholdStartTime >= preBeepDelay)) {
      systemActive = true;
      beepStartTime = now;
    }
  } else {
    belowThreshold = false;
    systemActive = false;
    thresholdStartTime = 0;
    beepStartTime = 0;
    stopBuzzer();
  }

  // ---- Build LCD Text ----
  String topText;
  String bottomText = " ";

  if (isMuted) {
    topText = "System paused";
    unsigned long elapsed = now - muteStartTime;
    unsigned long remaining = (elapsed < muteDuration) ? (muteDuration - elapsed) : 0;
    unsigned int m = remaining / 60000;
    unsigned int s = (remaining % 60000) / 1000;
    char buffer[17];
    sprintf(buffer, "Mute:%02dm%02ds", m, s);
    bottomText = String(buffer);
    stopBuzzer();
  }
  else if (proximityPaused) {
    topText = "System paused";
    char buffer[17];
    sprintf(buffer, "Obj:%3.0fcm", distance);
    bottomText = String(buffer);
    stopBuzzer();
  }
  else if (systemActive) {
    topText = "System active";
    unsigned long activeTime = now - beepStartTime;
    unsigned int m = activeTime / 60000;
    unsigned int s = (activeTime % 60000) / 1000;
    char buffer[17];
    sprintf(buffer, "Active:%02d:%02d", m, s);
    bottomText = String(buffer);

    handleBuzzer(now);
  }
  else if (belowThreshold) {
    topText = "System ready";
    unsigned long elapsed = now - thresholdStartTime;
    unsigned long remain = (elapsed < preBeepDelay) ? (preBeepDelay - elapsed) / 1000 : 0;
    char buffer[17];
    sprintf(buffer, "Start in:%02lds", remain);
    bottomText = String(buffer);
    stopBuzzer();
  }
  else {
    topText = "System ready";
    char buffer[17];
    float feet = distance / 30.48;
    sprintf(buffer, "LDR:%d  %4.1fft", digitalRead(LDR_DO), feet);
    bottomText = String(buffer);
    stopBuzzer();
  }

  showLCD(now, topText, bottomText);
}

// ---------------- Distance Measurement ----------------
float getDistanceCM() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  long duration = pulseIn(ECHO, HIGH, 30000);
  if (duration == 0) return 999;
  return duration * 0.0343 / 2.0;
}

// ---------------- LCD Update ----------------
void showLCD(unsigned long now, String top, String bottom) {
  if (now - lastLCDUpdate < lcdUpdateInterval) return;
  lastLCDUpdate = now;

  lcd.setCursor(0, 0);
  lcd.print(top);
  for (int i = top.length(); i < 16; i++) lcd.print(" ");

  lcd.setCursor(0, 1);
  lcd.print(bottom);
  for (int i = bottom.length(); i < 16; i++) lcd.print(" ");
}

// ---------------- Buzzer Control ----------------
void handleBuzzer(unsigned long now) {
  if (now - lastBeepCycle >= beepCycle) {
    lastBeepCycle = now;
    lastBeepAction = now;
  }

  if (now - lastBeepAction < beepPatternDuration) {
    if (!buzzerOn) {
      tone(BUZZER, 4000);  // loud 4 kHz tone
      buzzerOn = true;
    }
  } else {
    stopBuzzer();
  }
}

void stopBuzzer() {
  if (buzzerOn) {
    noTone(BUZZER);
    buzzerOn = false;
  }
}

// ---------------- Reset ----------------
void resetSystem() {
  stopBuzzer();
  isMuted = false;
  systemActive = false;
  belowThreshold = false;
  thresholdStartTime = 0;
  beepStartTime = 0;
  muteStartTime = 0;
  lastBeepCycle = 0;
  lastBeepAction = 0;
  proximityPaused = false;
  lcd.clear();
}