#define NUMELEMENTS(x) (sizeof(x) / sizeof(x[0]))

// Pin definitions
const byte dataPin = 2;
const byte clockPin = 3;
const byte latchPin = 4;

// Analog inputs for potentiometers
const int potPins[] = {A0, A1, A2, A3, A4, A5};
const int numPots = NUMELEMENTS(potPins);

// LED control variables
uint8_t data = 0;
uint16_t pulseWidths[] = { 200, 400, 600, 800, 1000, 1200, 2000 };

// Timing
unsigned long timerInterval = 2000;


// Fading LED (7th LED)
const int fadeLedIndex = 6; // zero-based index: 7th LED
int fadeValue = 0;


// --------------------------
// Setup
// --------------------------
void setup() {
  Serial.begin(115200);
  Serial.println(F("Software PWM with modular structure"));

  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);

  // Initialize pulse widths
  for (int i = 0; i < numPots + 1; i++) {
    pulseWidths[i] = 1000;
  }
}

// --------------------------
// Main Loop
// --------------------------
void loop() {
  unsigned long currentMicros = micros();

  // Update potmeter-based brightness
  handlePotmeters();

  // Update fading LED brightness
  handleFadingLed(currentMicros);

  // Handle the software PWM logic
  handleBrightness(currentMicros);

  // Send output to shift register
  updateShiftRegister();
}

// Read all potmeters and map to pulse widths
void handlePotmeters() {
  for (int i = 0; i < numPots; i++) {
    int potValue = analogRead(potPins[i]);
    pulseWidths[i] = map(potValue, 0, 1023, 0, 2000);
  }
}

// Create a fade effect for the 7th LED
void handleFadingLed(unsigned long currentMicros) {
  static unsigned long lastFadeUpdate = 0;
  const unsigned long fadeInterval = 5000; // µs between fade updates

  if (currentMicros - lastFadeUpdate >= fadeInterval) {
    lastFadeUpdate = currentMicros;

    fadeValue += 1;
    if (fadeValue >= 2000) {
      fadeValue = 2000;
    }

    pulseWidths[fadeLedIndex] = fadeValue;
  }
}

// Handle software PWM timing and data bitmask
void handleBrightness(unsigned long currentMicros) {
  static unsigned long previousMicros = 0;
  if (currentMicros - previousMicros >= timerInterval) {
    previousMicros = currentMicros;
    data = 0;

    // Turn LEDs ON based on pulse widths
    for (int i = 0; i < numPots + 1; i++) {
      if (pulseWidths[i] > 0) {
        data |= (1 << i);
      }
    }
  } else {
    // Turn LEDs OFF when their pulse width expires
    for (int i = 0; i < numPots + 1; i++) {
      if (currentMicros - previousMicros >= pulseWidths[i]) {
        data &= ~(1 << i);
      }
    }
  }
}

// Shift out the LED data
void updateShiftRegister() {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, data << 1);
  digitalWrite(latchPin, HIGH);
}