#include <Adafruit_NeoPixel.h>

#define LED_PIN               6    // Pin where your WS2812B LED strip is connected
#define NUM_LEDS              96   // Total number of LEDs in the strip (16 LEDs per stair * 6 stairs)
#define LEDS_PER_STAIR        16   // Number of LEDs per stair
#define TRIG_PIN_BOTTOM       9    // Trigger pin for the bottom HC-SR04
#define ECHO_PIN_BOTTOM       10   // Echo pin for the bottom HC-SR04
#define TRIG_PIN_TOP          7    // Trigger pin for the top HC-SR04
#define ECHO_PIN_TOP          8    // Echo pin for the top HC-SR04
#define SOUND_SPEED           0.034  // Speed of sound in cm/us
#define MAX_DISTANCE          100    // Maximum distance to detect motion (in cm)
#define STAIR_DELAY           200    // Delay between each stair lighting up (in ms)
#define FADE_SPEED            20     // Speed of the fill effect (in ms)
#define HOLD_TIME             5000  // Time to keep the lights on before fading out (in ms)

Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);

unsigned long illuminationStartTime = 0;
bool isIlluminated = false;
bool motionDetected = false;
enum Direction {UP, DOWN};
Direction motionDirection;

void setup() {
  pinMode(TRIG_PIN_BOTTOM, OUTPUT);
  pinMode(ECHO_PIN_BOTTOM, INPUT);
  pinMode(TRIG_PIN_TOP, OUTPUT);
  pinMode(ECHO_PIN_TOP, INPUT);
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
  Serial.begin(9600);
}

void loop() {
  detectMotion();

  if (motionDetected && !isIlluminated) {
    if (motionDirection == UP) {
      illuminateStairs(UP);
    } else if (motionDirection == DOWN) {
      illuminateStairs(DOWN);
    }
    illuminationStartTime = millis();
    isIlluminated = true;
    motionDetected = false;
  }

  if (isIlluminated) {
    // Reset timer if motion is detected again during illumination or hold time
    if (detectMotionDuringIllumination()) {
      illuminationStartTime = millis();
    }
    // Check if hold time has elapsed to start fade out
    if (millis() - illuminationStartTime >= HOLD_TIME) {
      if (motionDirection == UP) {
        fadeOutStairs(DOWN);
      } else if (motionDirection == DOWN) {
        fadeOutStairs(UP);
      }
      isIlluminated = false;
    }
  }

  delay(50); // Small delay to prevent excessive CPU usage
}

void detectMotion() {
  float distanceBottom = measureDistance(TRIG_PIN_BOTTOM, ECHO_PIN_BOTTOM);
  float distanceTop = measureDistance(TRIG_PIN_TOP, ECHO_PIN_TOP);

  if (distanceBottom > 0 && distanceBottom < MAX_DISTANCE) {
    motionDetected = true;
    motionDirection = UP;
    Serial.println("Motion detected at bottom sensor.");
  } else if (distanceTop > 0 && distanceTop < MAX_DISTANCE) {
    motionDetected = true;
    motionDirection = DOWN;
    Serial.println("Motion detected at top sensor.");
  }
}

bool detectMotionDuringIllumination() {
  float distanceBottom = measureDistance(TRIG_PIN_BOTTOM, ECHO_PIN_BOTTOM);
  float distanceTop = measureDistance(TRIG_PIN_TOP, ECHO_PIN_TOP);

  if ((distanceBottom > 0 && distanceBottom < MAX_DISTANCE) || (distanceTop > 0 && distanceTop < MAX_DISTANCE)) {
    Serial.println("Motion detected during illumination. Resetting timer.");
    return true;
  }
  return false;
}

float measureDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH, 30000); // Timeout after 30ms (max distance ~500cm)
  float distance = (duration * SOUND_SPEED) / 2;

  return distance;
}

void illuminateStairs(Direction dir) {
  if (dir == UP) {
    for (int i = 0; i < NUM_LEDS; i += LEDS_PER_STAIR) {
      fillFromCenter(i, true);
      delay(STAIR_DELAY);
    }
  } else if (dir == DOWN) {
    for (int i = NUM_LEDS - LEDS_PER_STAIR; i >= 0; i -= LEDS_PER_STAIR) {
      fillFromCenter(i, true);
      delay(STAIR_DELAY);
    }
  }
}

void fadeOutStairs(Direction dir) {
  if (dir == UP) {
    for (int i = NUM_LEDS - LEDS_PER_STAIR; i >= 0; i -= LEDS_PER_STAIR) {
      fillFromCenter(i, false);
      delay(STAIR_DELAY);
    }
  } else if (dir == DOWN) {
    for (int i = 0; i < NUM_LEDS; i += LEDS_PER_STAIR) {
      fillFromCenter(i, false);
      delay(STAIR_DELAY);
    }
  }
}

void fillFromCenter(int startIndex, bool turnOn) {
  int center = LEDS_PER_STAIR / 2;
  int step = 15; // Adjust brightness increment
  if (!turnOn) step = -15;

  int startBrightness = turnOn ? 0 : 255;
  int endBrightness = turnOn ? 255 : 0;

  for (int brightness = startBrightness; (turnOn ? brightness <= endBrightness : brightness >= endBrightness); brightness += step) {
    uint32_t color = strip.Color(brightness, brightness, brightness); // Adjust color as needed
    for (int j = 0; j <= center; j++) {
      int leftIndex = startIndex + center - j;
      int rightIndex = startIndex + center + j - 1;
      if (leftIndex >= startIndex && leftIndex < startIndex + LEDS_PER_STAIR) {
        strip.setPixelColor(leftIndex, color);
      }
      if (rightIndex >= startIndex && rightIndex < startIndex + LEDS_PER_STAIR) {
        strip.setPixelColor(rightIndex, color);
      }
    }
    strip.show();
    delay(FADE_SPEED);
  }
}