/*
 * NeoPixelUltrasonic_8LED.ino
 * XIAO ESP32-C3 + HC-SR04 + WS2812B (8 LEDs)
 *
 * Trig -> D1,  Echo -> D2,  NeoPixel DIN -> D3
 *
 * Closer distance -> more LEDs lit (bar graph)
 *   LED 0 = closest (red)  ->  LED 7 = farthest (white)
 *   Out of range -> all off
 */

#include <Adafruit_NeoPixel.h>

// --- Pins ---
const int trigPin     = D1;
const int echoPin     = D2;
const int neoPixelPin = D3;

// --- LED count ---
#define NUM_PIXELS 8

// --- Distance range ---
const float MIN_CM = 5.0;
const float MAX_CM = 40.0;

// --- NeoPixel ---
Adafruit_NeoPixel strip(NUM_PIXELS, neoPixelPin, NEO_GRB + NEO_KHZ800);

// One color per LED — index 0 = closest (red), index 7 = farthest (white)
const uint32_t palette[NUM_PIXELS] = {
  strip.Color(255,   0,   0),    // 0 — red
  strip.Color(255, 128,   0),    // 1 — orange
  strip.Color(255, 255,   0),    // 2 — yellow
  strip.Color(  0, 255,   0),    // 3 — green
  strip.Color(  0, 255, 255),    // 4 — cyan
  strip.Color(  0,   0, 255),    // 5 — blue
  strip.Color(255,   0, 255),    // 6 — magenta
  strip.Color(255, 255, 255)     // 7 — white
};

int lastLitCount = -1;

float readAverageDistanceCm() {
  float total = 0;
  int   valid = 0;

  for (int i = 0; i < 5; i++) {
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);

    long duration = pulseIn(echoPin, HIGH, 30000);

    if (duration > 0) {
      total += duration * 0.0343 / 2.0;
      valid++;
    }
    delay(10);
  }

  if (valid == 0) return -1.0;
  return total / valid;
}

int distanceToLitCount(float cm) {
  if (cm < 0 || cm > MAX_CM) return 0;
  if (cm <= MIN_CM)           return NUM_PIXELS;

  int count = map(
    (long)(cm * 10),
    (long)(MIN_CM * 10),
    (long)(MAX_CM * 10),
    NUM_PIXELS,
    1
  );

  return constrain(count, 0, NUM_PIXELS);
}

void setup() {
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  strip.begin();
  strip.setBrightness(50);
  strip.clear();
  strip.show();

  Serial.println("8-LED NeoPixel + Ultrasonic ready!");
}

void loop() {
  float distance = readAverageDistanceCm();
  int   litCount = distanceToLitCount(distance);

  if (litCount != lastLitCount) {
    strip.clear();

    for (int i = 0; i < litCount; i++) {
      strip.setPixelColor(i, palette[i]);
    }

    strip.show();
    lastLitCount = litCount;

    Serial.print("Distance: ");
    Serial.print(distance, 1);
    Serial.print(" cm -> LEDs lit: ");
    Serial.println(litCount);
  }

  delay(200);
}