#include <Wire.h>
#include <Adafruit_BMP085.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <LiquidCrystal_I2C.h>
#include <ESP32Servo.h>

// --- PIN DEFINITIONS ---
#define POT_PIN      34
#define BUTTON_PIN   35
#define SERVO_PIN    32
#define BUZZER_PIN   25
#define ONE_WIRE_BUS 23
#define LED_RED      12
#define LED_GREEN    14
#define LED_BLUE     27

// --- SYSTEM CONSTANTS ---
const float TANK_MAX_L = 10.0;       // 10L cylinder
const float REF_PRESSURE = 1013.25;  // hPa at "Full"
const float CRITICAL_PCT = 20.0;     // Alarm threshold
const float MAX_FLOW_LPM = 20.0;     // Max LPM at full potentiometer

// --- OBJECTS ---
Adafruit_BMP085 bmp;
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
LiquidCrystal_I2C lcd(0x27, 16, 2);
Servo flowServo;

// --- DYNAMIC STATE ---
float currentGasLiters = 10.0;       // Starts full
unsigned long lastTick = 0;
int lcdPage = 0;
bool isMuted = false;

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);
  
  lcd.init();
  lcd.backlight();
  sensors.begin();
  bmp.begin();
  flowServo.attach(SERVO_PIN);

  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LED_RED, OUTPUT);
  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_BLUE, OUTPUT);

  // Initial LED Test Sequence (Visual Confirmation)
  digitalWrite(LED_RED, HIGH); delay(200); digitalWrite(LED_RED, LOW);
  digitalWrite(LED_BLUE, HIGH); delay(200); digitalWrite(LED_BLUE, LOW);
  digitalWrite(LED_GREEN, HIGH); delay(200); digitalWrite(LED_GREEN, LOW);

  lastTick = millis();
}

void loop() {
  unsigned long now = millis();
  float dt = (now - lastTick) / 1000.0; // Delta time in seconds
  lastTick = now;

  // 1. INPUT SENSING
  sensors.requestTemperatures();
  float tempC = sensors.getTempCByIndex(0);
  int potVal = analogRead(POT_PIN);
  
  // 2. FLOW DYNAMICS
  // Map pot to 0-20 LPM
  float flowLPM = (potVal / 4095.0) * MAX_FLOW_LPM;
  int servoPos = map(potVal, 0, 4095, 0, 180);
  flowServo.write(servoPos);

  // 3. REAL-TIME CYLINDER DEPLETION
  // Gas used in this loop: (Liters/Min / 60) * seconds passed
  float litersConsumed = (flowLPM / 60.0) * dt;
  currentGasLiters -= litersConsumed;
  
  // 4. PRESSURE & TEMPERATURE COMPENSATION
  // Calculate "Effective Pressure" based on remaining gas and temperature
  // P = (nRT) / V. If Temp increases, pressure increases.
  float tempK = tempC + 273.15;
  float calculatedPressure = (currentGasLiters * REF_PRESSURE * tempK) / (TANK_MAX_L * 293.15);
  
  // Ensure we don't go below zero or above 100%
  currentGasLiters = constrain(currentGasLiters, 0, TANK_MAX_L);
  float volPercent = (currentGasLiters / TANK_MAX_L) * 100.0;

  // 5. TIME TO EMPTY (TTE)
  float tteMinutes = (flowLPM > 0.1) ? (currentGasLiters / flowLPM) : 0;
  float tteHours = tteMinutes / 60.0;

  // 6. LED LOGIC & ALARMS
  updateVisuals(volPercent, flowLPM, potVal);

  // 7. USER INTERFACE
  if (digitalRead(BUTTON_PIN) == LOW) {
    delay(50); 
    if (volPercent < CRITICAL_PCT) isMuted = true;
    else { lcdPage = !lcdPage; lcd.clear(); }
    while(digitalRead(BUTTON_PIN) == LOW);
  }

  refreshLCD(calculatedPressure, tempC, flowLPM, currentGasLiters, volPercent, tteHours);
}

void updateVisuals(float pct, float flow, int pot) {
  static int lastPot = 0;
  
  // --- BLUE LED: "Activity/Flow Adjustment" ---
  // Lights up if you are moving the knob
  if (abs(pot - lastPot) > 50) {
    digitalWrite(LED_BLUE, HIGH);
    lastPot = pot;
  } else {
    digitalWrite(LED_BLUE, LOW);
  }

  // --- RED/GREEN LED: "Status" ---
  if (pct < CRITICAL_PCT || flow > 15.0) {
    // ALERT STATE
    digitalWrite(LED_RED, HIGH);
    digitalWrite(LED_GREEN, LOW);
    
    if (!isMuted) {
      tone(BUZZER_PIN, 800, 100); // 800Hz beep
    } else {
      noTone(BUZZER_PIN);
    }
  } else {
    // HEALTHY STATE
    digitalWrite(LED_RED, LOW);
    digitalWrite(LED_GREEN, HIGH);
    noTone(BUZZER_PIN);
    isMuted = false; // Reset mute when safe
  }
}

void refreshLCD(float p, float t, float f, float v, float vp, float tte) {
  lcd.setCursor(0, 0);
  if (lcdPage == 0) {
    lcd.print("P:"); lcd.print(p,0); lcd.print("hPa ");
    lcd.print("T:"); lcd.print(t,1); lcd.print("C");
    lcd.setCursor(0, 1);
    lcd.print("FLOW:"); lcd.print(f, 1); lcd.print("LPM ");
    // Heartbeat indicator to show real-time processing
    lcd.print((millis() % 1000 < 500) ? "*" : " ");
  } else {
    lcd.print("VOL:"); lcd.print(vp, 1); lcd.print("% (");
    lcd.print(v, 1); lcd.print("L)");
    lcd.setCursor(0, 1);
    lcd.print("TTE:"); 
    if (f < 0.2) lcd.print("--- HRS   ");
    else { lcd.print(tte, 2); lcd.print(" HRS "); }
  }
}