#include <LedControl.h>
#include <EEPROM.h>

// ===== CONFIG =====
#define NUM_MODULES 1   // change to 4 for 32x8
#define MAX_VALUE (NUM_MODULES * 64)

#define DIN_PIN 11
#define CLK_PIN 13
#define CS_PIN  10

#define BTN_UP     2
#define BTN_DOWN   3
#define BTN_RESET  4

const unsigned long debounceDelay = 300;
const unsigned long eepromDelay   = 3000; // wait 3s after last change
// ==================

LedControl lc = LedControl(DIN_PIN, CLK_PIN, CS_PIN, NUM_MODULES);

int value = 0;
int lastStored = 0;

unsigned long lastChangeTime = 0;
unsigned long lastDebounce   = 0;

void setup() {
  pinMode(BTN_UP, INPUT_PULLUP);
  pinMode(BTN_DOWN, INPUT_PULLUP);
  pinMode(BTN_RESET, INPUT_PULLUP);

  for (int i = 0; i < NUM_MODULES; i++) {
    lc.shutdown(i, false);
    lc.setIntensity(i, 8);
    lc.clearDisplay(i);
  }

  EEPROM.get(0, value);
  value = constrain(value, 0, MAX_VALUE);

  lastStored = value;
  drawPixels();
}

void loop() {
  bool changed = false;

  if (millis() - lastDebounce > debounceDelay) {
    if (!digitalRead(BTN_UP) && value < MAX_VALUE) {
      value++;
      changed = true;
    }

    if (!digitalRead(BTN_DOWN) && value > 0) {
      value--;
      changed = true;
    }

    if (!digitalRead(BTN_RESET)) {
      value = 0;
      changed = true;
    }

    if (changed) {
      drawPixels();
      lastDebounce = millis();
      lastChangeTime = millis();
    }
  }

  // EEPROM write after inactivity
  if (value != lastStored &&
      millis() - lastChangeTime > eepromDelay) {

    EEPROM.put(0, value);
    lastStored = value;
  }
}

void drawPixels() {
  // Clear all
  for (int m = 0; m < NUM_MODULES; m++) {
    lc.clearDisplay(m);
  }

  // Turn on pixels [0 .. value-1]
  for (int i = 0; i < value; i++) {
    int module = i / 64;
    int pixel  = i % 64;

    int x = pixel % 8;
    int y = pixel / 8;

    lc.setLed(module, y, x, true);
  }
}