/*
 * Auto-Refillable Psychrometer Controller
 * Designed for Arduino Uno R3
 *
 * Hardware:
 * - Arduino Uno R3
 * - 5V IR Water Sensor (Top - Wetting Sock Tank) on A0
 * - 5V IR Water Sensor (Bottom - Reservoir) on A1
 * - 3-32V DC-DC Solid State Relay on D8 (controlling 12V pump)
 */

#define PIN_TOP_SENSOR A0
#define PIN_BOTTOM_SENSOR A1
#define PIN_RELAY 8
#define PIN_LED 13 // Use Uno's built-in LED

// Uncomment the next line to use a 10-sec delay for testing instead of 1 hour
#define TEST_MODE

#ifdef TEST_MODE
const unsigned long CONFIRMATION_DELAY_MS = 10000UL; // 10 seconds
#else
const unsigned long CONFIRMATION_DELAY_MS = 3600000UL; // 1 hour
#endif

const float VOLTAGE_THRESHOLD = 2.5;
// Voltage > 2.5V means NO WATER (sensor exposed to air)
// Voltage < 2.5V means WATER DETECTED (sensor submerged)

unsigned long emptyStartTime = 0;
unsigned long pumpStartTime = 0;
bool isCountingDown = false;
bool isPumping = false;
bool isDoubleFillWaiting = false;
unsigned long fillStopTime = 0;
bool hasDoneDoubleFill = false;

void setup() {
  Serial.begin(9600);
  pinMode(PIN_RELAY, OUTPUT);
  pinMode(PIN_LED, OUTPUT);
  digitalWrite(PIN_RELAY, LOW); // Ensure pump is OFF on startup
  Serial.println("Psychrometer Controller Initialized.");
}

float getVoltage(int pin) {
  int adcValue = analogRead(pin);
  return (adcValue * 5.0) / 1023.0;
}

void loop() {
  float topVoltage = getVoltage(PIN_TOP_SENSOR);
  float bottomVoltage = getVoltage(PIN_BOTTOM_SENSOR);

  bool topNoWater = (topVoltage > VOLTAGE_THRESHOLD);
  bool bottomNoWater = (bottomVoltage > VOLTAGE_THRESHOLD);

  // Safety Interlock: If reservoir is empty, stop everything.
  if (bottomNoWater) {
    if (isPumping) {
      Serial.println("WARNING: Reservoir empty! Stopping pump.");
      digitalWrite(PIN_RELAY, LOW);
      isPumping = false;

      unsigned long fillDuration = millis() - pumpStartTime;
      Serial.print("EVENT: FILL_HALTED (Reservoir empty) | Duration: ");
      Serial.print(fillDuration / 1000.0, 1);
      Serial.println(" s");
    }
    // Also reset countdown so we don't start immediately if reservoir gets
    // refilled but sock is still empty
    if (isCountingDown) {
      Serial.println("Reservoir empty. Pausing/Resetting timer.");
      isCountingDown = false;
    }
    isDoubleFillWaiting = false;
  } else {
    // --- Normal Operation ---

    // 1. Check if top tank is full while pumping
    if (isPumping) {
      if (!topNoWater) { // Top sensor < 2.0V (water detected)
        Serial.println("Top tank filled! Stopping pump.");
        digitalWrite(PIN_RELAY, LOW);
        isPumping = false;

        unsigned long fillDuration = millis() - pumpStartTime;
        Serial.print("EVENT: FILL_COMPLETE | Duration: ");
        Serial.print(fillDuration / 1000.0, 1);
        Serial.println(" s");

        isCountingDown = false; // Reset state

        if (!hasDoneDoubleFill) {
          isDoubleFillWaiting = true;
          fillStopTime = millis();
          Serial.println(
              "Waiting 5s to see if water settles (double fill check)...");
        } else {
          hasDoneDoubleFill = false; // Cycle complete
        }
      }
    } else if (isDoubleFillWaiting) {
      if (topNoWater) {
        Serial.println(
            "Water settled and sensor is dry! Starting double fill.");
        digitalWrite(PIN_RELAY, HIGH);
        isPumping = true;
        pumpStartTime = millis();
        isDoubleFillWaiting = false;
        hasDoneDoubleFill = true;
      } else {
        if (millis() - fillStopTime >= 5000) {
          Serial.println("Water level stable. Fill cycle complete.");
          isDoubleFillWaiting = false;
          hasDoneDoubleFill = false; // Cycle complete
        }
      }
    }
    // 2. Wait for top tank to be empty for the confirmation period
    else {
      if (topNoWater) {
        if (!isCountingDown) {
          Serial.println(
              "Top tank empty detected. Starting confirmation timer...");
          isCountingDown = true;
          emptyStartTime = millis();
        } else {
          unsigned long elapsedTime = millis() - emptyStartTime;
          if (elapsedTime >= CONFIRMATION_DELAY_MS) {
            Serial.println("Timer finished! Starting pump.");
            digitalWrite(PIN_RELAY, HIGH);
            isPumping = true;
            pumpStartTime = millis();
            isCountingDown = false;
          }
        }
      }
      // 3. Reset countdown if water sloshes or is detected again before timer
      // finishes
      else {
        if (isCountingDown) {
          Serial.println(
              "Water detected before timer finished! Resetting timer.");
          isCountingDown = false;
        }
      }
    }
  }

  // --- LED Status Indicator Logic ---
  unsigned long currentMillis = millis();
  bool ledState = false;

  if (bottomNoWater) {
    // Constant ON with short OFF flash every 5s = water reservoir empty
    int cycle = currentMillis % 5000;
    ledState = (cycle > 100);
  } else if (isPumping) {
    // Quicker steady flash (like a broken turn signal) = filling
    // Pattern: 200ms ON, 200ms OFF
    int cycle = currentMillis % 400;
    ledState = (cycle < 200);
  } else if (isCountingDown) {
    // Steady flashing (like a turn signal) = pending filling
    // Pattern: 500ms ON, 500ms OFF
    int cycle = currentMillis % 1000;
    ledState = (cycle < 500);
  } else {
    // Short flash every 5s = good
    int cycle = currentMillis % 5000;
    ledState = (cycle < 100);
  }

  digitalWrite(PIN_LED, ledState ? HIGH : LOW);

  // Debug output every 5 seconds
  static unsigned long lastDebugTime = 0;
  if (millis() - lastDebugTime >= 5000) {
    lastDebugTime = millis();
    Serial.print("Top (Sock): ");
    Serial.print(topVoltage);
    Serial.print("V | ");
    Serial.print("Bottom (Res): ");
    Serial.print(bottomVoltage);
    Serial.print("V | ");
    if (bottomNoWater) {
      Serial.println("Status: HALTED (Reservoir Empty)");
    } else if (isPumping) {
      Serial.println("Status: PUMPING");
    } else if (isDoubleFillWaiting) {
      unsigned long elapsed = millis() - fillStopTime;
      unsigned long remain = (elapsed < 5000) ? (5000 - elapsed) / 1000 : 0;
      Serial.print("Status: DOUBLE FILL WAIT (");
      Serial.print(remain);
      Serial.println("s left)");
    } else if (isCountingDown) {
      unsigned long elapsed = millis() - emptyStartTime;
      unsigned long remain = (elapsed < CONFIRMATION_DELAY_MS)
                                 ? (CONFIRMATION_DELAY_MS - elapsed) / 1000
                                 : 0;
      Serial.print("Status: WAITING (");
      Serial.print(remain);
      Serial.println("s left)");
    } else {
      Serial.println("Status: IDLE");
    }
  }

  delay(100);
}