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

// ===== LCD I2C =====
LiquidCrystal_I2C lcd(0x27, 20, 4);

// ===== PIN =====
#define PH_PIN     34
#define TDS_PIN    35
#define TURB_PIN   32
#define FLOW_PIN   33   // potentiometer
#define BUZZER_PIN 25

// ===== FLOW =====
float flowRate = 0;
float totalLiters = 0;

// Moving average
#define FLOW_AVG_COUNT 5
int flowBuffer[FLOW_AVG_COUNT] = {0};
int flowIndex = 0;

void setup() {
  Serial.begin(115200);

  pinMode(BUZZER_PIN, OUTPUT);

  lcd.init();
  lcd.backlight();

  lcd.setCursor(0,0);
  lcd.print("System Starting...");
  delay(2000);
  lcd.clear();
}

void loop() {

  // ===== READ SENSOR =====
  int phRaw   = analogRead(PH_PIN);
  int tdsRaw  = analogRead(TDS_PIN);
  int turbRaw = analogRead(TURB_PIN);
  int flowRaw = analogRead(FLOW_PIN);

  // ===== pH =====
  float voltagePH = phRaw * (3.3 / 4095.0);
  float pH = (voltagePH / 3.3) * 14.0;

  // ===== TDS =====
  float voltageTDS = tdsRaw * (3.3 / 4095.0);

  float tds = (133.42 * pow(voltageTDS, 3)
              - 255.86 * pow(voltageTDS, 2)
              + 857.39 * voltageTDS) * 0.5;

  if (tds < 0) tds = 0;
  if (tds > 1000) tds = 1000;

  // ===== TURBIDITY (LIMITED TO 500 NTU) =====
  float turbidity = map(turbRaw, 0, 4095, 0, 500);

  if (turbidity < 0) turbidity = 0;
  if (turbidity > 500) turbidity = 500;

  // ===== FLOW =====
  flowBuffer[flowIndex] = flowRaw;
  flowIndex = (flowIndex + 1) % FLOW_AVG_COUNT;

  long sum = 0;
  for (int i = 0; i < FLOW_AVG_COUNT; i++) sum += flowBuffer[i];

  int flowAvg = sum / FLOW_AVG_COUNT;

  flowRate = map(flowAvg, 0, 4095, 0, 1000) / 100.0;

  totalLiters += flowRate / 60.0;

  // ===== CONDITION =====
  String status;

  if (pH >= 6.5 && pH <= 8.5 && tds < 500 && turbidity < 5) {
    status = "SAFE";
    digitalWrite(BUZZER_PIN, LOW);
  } else {
    status = "UNSAFE";
    digitalWrite(BUZZER_PIN, HIGH);
  }

  // ===== SERIAL =====
  Serial.print("pH: "); Serial.print(pH, 2);
  Serial.print(" | TDS: "); Serial.print(tds, 0);
  Serial.print(" | NTU: "); Serial.print(turbidity, 0);
  Serial.print(" | Flow: "); Serial.print(flowRate, 2);
  Serial.print(" | Total: "); Serial.print(totalLiters, 2);
  Serial.print(" | "); Serial.println(status);

  // ===== LCD =====
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("pH:");
  lcd.print(pH, 2);

  lcd.setCursor(10, 0);
  lcd.print("TDS:");
  lcd.print((int)tds);

  lcd.setCursor(0, 1);
  lcd.print("NTU:");
  lcd.print((int)turbidity);
  lcd.print("/500");

  lcd.setCursor(10, 1);
  lcd.print(status);

  lcd.setCursor(0, 2);
  lcd.print("Flow:");
  lcd.print(flowRate, 1);
  lcd.print("L/m");

  lcd.setCursor(0, 3);
  lcd.print("Vol:");
  lcd.print(totalLiters, 2);
  lcd.print("L");

  delay(1000);
}