/*
  Knop 2 	Knop 1 	Knop 0 	   LED
  0 	      0 	      0      allemaal uit
  0 	      0       	1 	   eerste led aan, alle anderen uit
  0 	      1       	0 	   tweede led aan, alle anderen uit
  0 	      1       	1 	   derde led aan, alle anderen uit
  1 	      0        	0      vierde led aan, alle anderen uit
  1 	      0 	      1    	 vijfde led aan, alle anderen uit
  1       	1        	0 	   zesde led aan, alle anderen uit
  1 	      1       	1 	   zevende led aan, alle anderen uit
*/

byte dataPin = 2;
byte clockPin = 3;
byte latchPin = 4;
int outputEnablePin = 6;

byte button1 = 10;
byte button2 = 11;
byte button3 = 12;

int data = 0;
int previousData = -1;  // detect button state changes

unsigned long previousMillis = 0;
unsigned long previousMillis_fade = 0;

const int interval = 10;        // small delay to stabilize button reads
const int interval_fade = 20;   // fade speed

int pwm = 0;
bool fadeUp = false; // true = fade in, false = fade out

void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(outputEnablePin, OUTPUT);

  pinMode(button1, INPUT_PULLUP);
  pinMode(button2, INPUT_PULLUP);
  pinMode(button3, INPUT_PULLUP);

  Serial.begin(115200);
}

void loop() {
  unsigned long currentMillis = millis();

  // Read button states periodically
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    data = 1 * !digitalRead(button1);
    data += 2 * !digitalRead(button2);
    data += 4 * !digitalRead(button3);

    int leds_working = 1 << data;

    // Detect button change
    if (data != previousData) {
      previousData = data;

      if (data != 0) {
        fadeUp = true;
        pwm = 0;

        // Turn on the selected LED(s)
        digitalWrite(latchPin, LOW);
        shiftOut(dataPin, clockPin, MSBFIRST, leds_working);
        digitalWrite(latchPin, HIGH);
      } else {
        // All buttons released → fade out
        fadeUp = false;
      }
    }
  }

  // Handle fading timing separately
  if (currentMillis - previousMillis_fade >= interval_fade) {
    previousMillis_fade = currentMillis;

    if (fadeUp && pwm < 255) pwm++;
    else if (!fadeUp && pwm > 0) pwm--;

    analogWrite(outputEnablePin, 255 - pwm);

    // When fully faded out, clear all LEDs
    if (pwm == 0 && !fadeUp) {
      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, MSBFIRST, 0);
      digitalWrite(latchPin, HIGH);
    }
  }
}