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

// Initialize LCD: Address 0x27, 16 columns, 2 rows
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Pin assignments
const int startStopPin = A1;  // START/STOP
const int cirkulPin = 2;      // Output 2
const int dozirPin = 3;       // Output 3
const int alarmPin = 4;       // Output 4
const int phMeterPin = A0;    // PH Meter Input

// Constants
const int maxMinutes = 99;    // Max counter in minutes
const int p1Countdown = 45;   // Countdown for P1
const float phDropThreshold = 0.5; // PH drop requirement in 15 minutes
const float phMin = 1.0;      // PH threshold for stopping P2
const unsigned long checkInterval = 15 * 60 * 1000; // 15 minutes in milliseconds
const unsigned long blinkInterval = 2000; // 2 seconds for blinking alarm

// Variables
bool programRunning = false;  // Program running state
bool programPaused = false;   // Pause state
bool phError = false;         // PH error state
unsigned long lastCheckTime = 0; // Last time PH drop was checked
unsigned long lastBlinkTime = 0; // Last time alarm blinked
unsigned long programStartTime = 0; // Program start time
unsigned long countdownStartTime = 0; // Countdown start time
int currentPhase = 0;         // Program phase (0 = P1+P2, 1 = P1, 2 = Finished)
float lastPhValue = 7.0;      // Last recorded PH value
int elapsedP1Minutes = 0;     // Elapsed minutes counter for P1
int elapsedP2Minutes = 0;     // Elapsed minutes counter for P2

void setup() {
  lcd.begin(16, 2);
  lcd.backlight();

  pinMode(startStopPin, INPUT_PULLUP);
  pinMode(cirkulPin, OUTPUT);
  pinMode(dozirPin, OUTPUT);
  pinMode(alarmPin, OUTPUT);

  // Initial states
  digitalWrite(cirkulPin, LOW);
  digitalWrite(dozirPin, LOW);
  digitalWrite(alarmPin, LOW);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("P1: 00 P2: 00");
  lcd.setCursor(0, 1);
  lcd.print("PH: --.-");
}

void loop() {
  // Check for START/STOP button press
  if (digitalRead(startStopPin) == LOW) {
    delay(300); // Debounce
    programRunning = !programRunning;

    if (programRunning) {
      programPaused = false;
      if (currentPhase == 0) {
        programStartTime = millis();
        countdownStartTime = millis();
        elapsedP1Minutes = 0;
        elapsedP2Minutes = 0;
      }
    }
  }

  // Handle program phases
  if (programRunning && !programPaused) {
    handleProgram();
  } else if (phError) {
    handlePhError();
  }
}

void handleProgram() {
  float phValue = readPH();

  // Phase 0: P1+P2 running
  if (currentPhase == 0) {
    unsigned long currentTime = millis();
    elapsedP1Minutes = (currentTime - programStartTime) / 60000; // P1 time
    elapsedP2Minutes = (currentTime - programStartTime) / 60000; // P2 time

    if (elapsedP1Minutes >= maxMinutes) elapsedP1Minutes = maxMinutes;
    if (elapsedP2Minutes >= maxMinutes) elapsedP2Minutes = maxMinutes;

    lcd.setCursor(0, 0);
    lcd.print("P1: ");
    lcd.print(elapsedP1Minutes);
    lcd.print(" P2: ");
    lcd.print(elapsedP2Minutes);

    lcd.setCursor(0, 1);
    lcd.print("PH: ");
    lcd.print(phValue, 1); // Display PH value with one decimal place

    digitalWrite(cirkulPin, HIGH); // Output 2 ON
    digitalWrite(dozirPin, HIGH); // Output 3 ON

    // Check PH value
    if (phValue < phMin) {
      currentPhase = 1;
      countdownStartTime = millis();
    }

    // Check PH drop
    if (millis() - lastCheckTime >= checkInterval) {
      if (lastPhValue - phValue < phDropThreshold) {
        triggerPhError();
      }
      lastCheckTime = millis();
      lastPhValue = phValue;
    }
  }

  // Phase 1: P1 running (45 min countdown)
  else if (currentPhase == 1) {
    unsigned long currentTime = millis();
    int countdown = p1Countdown - ((currentTime - countdownStartTime) / 60000);

    if (countdown <= 0) {
      countdown = 0;
      currentPhase = 2; // Move to finished phase
    }

    lcd.setCursor(0, 0);
    lcd.print("P1: ");
    lcd.print(countdown);
    lcd.print(" P2: --");

    lcd.setCursor(0, 1);
    lcd.print("PH: ");
    lcd.print(phValue, 1); // Display PH value with one decimal place

    digitalWrite(cirkulPin, HIGH); // Output 2 ON
    digitalWrite(dozirPin, LOW);  // Output 3 OFF
  }

  // Phase 2: Finished
  else if (currentPhase == 2) {
    lcd.setCursor(0, 0);
    lcd.print("P1: 00 P2: 00");

    lcd.setCursor(0, 1);
    lcd.print("PH: ");
    lcd.print(phValue, 1); // Display PH value with one decimal place

    digitalWrite(cirkulPin, LOW); // Output 2 OFF
    digitalWrite(dozirPin, LOW); // Output 3 OFF
    programRunning = false;      // Stop program
  }
}

void handlePhError() {
  unsigned long currentTime = millis();
  lcd.setCursor(0, 0);
  lcd.print("PH ERROR!       ");

  // Blink alarm
  if (currentTime - lastBlinkTime >= blinkInterval) {
    bool alarmState = digitalRead(alarmPin);
    digitalWrite(alarmPin, !alarmState); // Toggle alarm state
    lastBlinkTime = currentTime;
  }

  lcd.setCursor(0, 1);
  lcd.print("PH: ");
  lcd.print(readPH(), 1); // Display PH value with one decimal place

  if (digitalRead(startStopPin) == LOW) {
    delay(300); // Debounce
    phError = false;
    programRunning = true;
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("P1: 00 P2: 00");
  }
}

void triggerPhError() {
  digitalWrite(cirkulPin, LOW); // Stop outputs
  digitalWrite(dozirPin, LOW);
  phError = true;
  programRunning = false;
}

float readPH() {
  int sensorValue = analogRead(phMeterPin);
  float voltage = sensorValue * (5.0 / 1023.0); // Convert to voltage
  return map(voltage, 2.75, 0.78, 0, 14); // Map to PH range
}