//==============================================================================
const int LDR_DIGITAL_PIN = 34;  // Digital output from LDR module (DO pin)
const int SWITCH_PIN      = 23;  // Manual override switch (active LOW)
const int RELAY_PIN       = 4;   // SSR control pin

const unsigned long ON_DELAY  = 1UL * 1000UL;  // Brightness hold time before turning ON
const unsigned long OFF_DELAY = 1UL * 1000UL;  // Darkness hold time before turning OFF

unsigned long brightStartTime = 0;
unsigned long darkStartTime   = 0;

bool relayState = false;
bool prev_state = false;
bool prev_ovr = false;
//==============================================================================
void setup() {
  Serial.begin(115200);
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(SWITCH_PIN, INPUT_PULLUP);
  pinMode(LDR_DIGITAL_PIN, INPUT);
  digitalWrite(RELAY_PIN, LOW);
  Serial.println("System Initialized");
}
//==============================================================================
void loop() {
  bool ovr = !digitalRead(SWITCH_PIN);         // Manual override active?
  bool isBright = digitalRead(LDR_DIGITAL_PIN) == LOW;  // LOW = bright (depends on module)

  // Manual override status change
  if (ovr != prev_ovr) {
    Serial.print("Manual switch turned ");
    Serial.println(ovr ? "ON" : "OFF");
    prev_ovr = ovr;

    // Reset timers when override ends
    if (!ovr) {
      brightStartTime = 0;
      darkStartTime = 0;
      relayState = false;  // Force relay OFF immediately
      Serial.println("Manual override ended — relay OFF");
    }
  }

  // Hysteresis logic
  if (ovr) {
    relayState = true;
    brightStartTime = 0;
    darkStartTime = 0;
  } else if (!relayState) {
    // Relay is OFF, wait for sustained brightness
    if (isBright) {
      if (brightStartTime == 0) brightStartTime = millis();
      else if (millis() - brightStartTime >= ON_DELAY) {
        relayState = true;
        brightStartTime = 0;
        Serial.println("Sustained brightness — relay ON");
      }
    } else {
      brightStartTime = 0;
    }
  } else {
    // Relay is ON, wait for sustained darkness
    if (!isBright) {
      if (darkStartTime == 0) darkStartTime = millis();
      else if (millis() - darkStartTime >= OFF_DELAY) {
        relayState = false;
        darkStartTime = 0;
        Serial.println("Sustained darkness — relay OFF");
      }
    } else {
      darkStartTime = 0;
    }
  }

  // Print relay status changes
  if (relayState != prev_state) {
    if (ovr) {
      Serial.println("Relay manually turned ON");
    } else if (relayState) {
      Serial.println("Relay activated due to sustained brightness");
    } else {
      Serial.println("Relay deactivated due to sustained darkness");
    }
    prev_state = relayState;
  }

  digitalWrite(RELAY_PIN, relayState);  // Final relay control
  delay(20);  // Smooth polling loop
}
//==============================================================================