#include <Adafruit_NeoPixel.h>

// --- CONFIGURATION ---
#define LED_PIN          2
#define LED_COUNT        60
#define BRIGHTNESS       150   // Set brightness (0-255). Be mindful of power consumption.

// --- GLOBAL VARIABLES ---
Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

// --- Beat Simulation Variables ---
unsigned long lastBeatTime = 0;
int beatInterval = 200; // Time between simulated beats, in milliseconds
int level = 0;          // Current length of the VU bar
int peak = 0;           // Highest point the bar has reached

// --- Effect-specific variables ---
int theaterChaseCounter = 0; // Tracks the position of the "chase"

// =================================================================
//                         SETUP & LOOP
// =================================================================

void setup() {
  strip.begin();
  strip.setBrightness(BRIGHTNESS);
  strip.show(); // Initialize strip to all 'off'
  randomSeed(analogRead(0)); // Seed the random number generator for variety
}

void loop() {
  // --- 1. SIMULATE A BEAT ---
  // Periodically trigger a new "beat" which sets the VU meter level.
  if (millis() - lastBeatTime > beatInterval) {
    lastBeatTime = millis();
    beatInterval = random(120, 350); // The next beat will be after a random interval
    triggerBeat();
  }

  // --- 2. DECAY THE LEVELS ---
  // Every frame, make the bar and the peak indicator fall slightly.
  decayLevels();

  // --- 3. RUN THE VISUAL EFFECT ---
  runTheaterChaseMeter();

  // --- 4. UPDATE THE LED STRIP ---
  strip.show();
  delay(30); // Controls the overall animation speed.
}

// =================================================================
//                 EFFECT IMPLEMENTATION
// =================================================================

/**
 * @brief Theater Chase VU Meter
 * The VU meter bar is drawn with a "chasing lights" effect. The length of
 * the bar is determined by the 'level' variable, and the bar itself animates
 * with a moving pattern, creating a marquee-style look.
 */
void runTheaterChaseMeter() {
  strip.clear(); // Clear the strip to draw the new frame

  // This counter increments each frame, creating the movement for the chase effect.
  theaterChaseCounter++;

  // Draw the main VU bar with the chase effect
  for (int i = 0; i < level; i++) {
    // The modulo operator (%) creates the repeating pattern.
    // (i + counter) % 4 creates a sequence 0, 1, 2, 3, 0, 1, ...
    // The condition `< 2` lights up pixels for sequence values 0 and 1,
    // and leaves them off for 2 and 3. This creates a "2 pixels on, 2 pixels off" chase.
    if ((i + theaterChaseCounter) % 4 < 2) {
      setPixelColorByLevel(i, LED_COUNT);
    }
  }

  // Draw the peak hold pixel. This is a single white pixel at the highest
  // point the bar has reached, which then slowly falls.
  if (peak > 0) {
    strip.setPixelColor(peak, strip.Color(255, 255, 255));
  }
}


// =================================================================
//                         HELPER FUNCTIONS
// =================================================================

/**
 * @brief Simulates a new beat by setting the bar level to a new random height.
 */
void triggerBeat() {
  // Set the bar to a random height, mostly in the upper range of the strip.
  level = random(LED_COUNT * 0.7, LED_COUNT + 1);

  // If the new level is higher than the current peak, update the peak.
  if (level > peak) {
    peak = level;
  }
}

/**
 * @brief Makes the VU meter bar and peak fall over time.
 */
void decayLevels() {
  // Reduce the level with a multiplier. A value like 0.90 provides a smooth fall.
  level *= 0.90;

  // The peak falls by one pixel per frame.
  if (peak > 0) {
    peak--;
  }
}

/**
 * @brief Sets a pixel's color based on its position (Green -> Yellow -> Red).
 * @param position The pixel index to set.
 * @param totalLength The total length of the meter (usually LED_COUNT).
 */
void setPixelColorByLevel(int position, int totalLength) {
  // Use a helper function to get the correct color and then set the pixel.
  strip.setPixelColor(position, getPixelColorByLevel(position, totalLength));
}


/**
 * @brief Returns a color based on the pixel's position in the bar.
 * @param position The pixel's position.
 * @param totalLength The total length of the meter.
 * @return A 32-bit color value (e.g., green, yellow, or red).
 */
uint32_t getPixelColorByLevel(int position, int totalLength) {
  if (position < totalLength * 0.60) {
    return strip.Color(0, 200, 0);   // Green
  } else if (position < totalLength * 0.85) {
    return strip.Color(200, 200, 0); // Yellow
  } else {
    return strip.Color(200, 0, 0);   // Red
  }
}