#include <Keypad.h>
#include <TM1637Display.h>

#define CLK 10
#define DIO 11
TM1637Display display(CLK, DIO);

// -------- Keypad ----------
const byte ROWS = 4;
const byte COLS = 4;

char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

byte rowPins[ROWS] = {2,3,4,5};
byte colPins[COLS] = {6,7,8,9};

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// -------- Countdown ----------
enum Mode { SET_MMSS, RUNNING, PAUSED };
Mode mode = SET_MMSS;

char mmss[5] = {'0','0','0','0','\0'}; // 4 Ziffern: MMSS
int secondsTotal = 0;

unsigned long lastTick = 0;

void displayMMSS(const char* t) {
  int mm = (t[0]-'0')*10 + (t[1]-'0');
  int ss = (t[2]-'0')*10 + (t[3]-'0');
  if (ss > 59) ss = 59;
  int value = mm * 100 + ss;
  display.showNumberDecEx(value, 0b01000000, true); // Doppelpunkt an
}

int mmssToSeconds(const char* t) {
  int mm = (t[0]-'0')*10 + (t[1]-'0');
  int ss = (t[2]-'0')*10 + (t[3]-'0');
  if (ss > 59) ss = 59;
  return mm * 60 + ss;
}

void secondsToMMSS(int s, char* out4) {
  if (s < 0) s = 0;
  int mm = s / 60;
  int ss = s % 60;
  if (mm > 99) mm = 99;
  out4[0] = char('0' + (mm / 10));
  out4[1] = char('0' + (mm % 10));
  out4[2] = char('0' + (ss / 10));
  out4[3] = char('0' + (ss % 10));
}

void shiftDigit(char d) {
  mmss[0] = mmss[1];
  mmss[1] = mmss[2];
  mmss[2] = mmss[3];
  mmss[3] = d;
}

void resetAll() {
  mode = SET_MMSS;
  mmss[0]='0'; mmss[1]='0'; mmss[2]='0'; mmss[3]='0';
  secondsTotal = 0;
  displayMMSS(mmss);
}

void setup() {
  display.setBrightness(7);
  resetAll();
}

void loop() {
  // ---- Keypad lesen ----
  char k = keypad.getKey();
  if (k) {
    // Ziffern nur im Set-Modus annehmen
    if (k >= '0' && k <= '9' && mode == SET_MMSS) {
      shiftDigit(k);
      displayMMSS(mmss);
    }

    // A = Start
    if (k == 'A') {
      if (mode == SET_MMSS) {
        secondsTotal = mmssToSeconds(mmss);
        if (secondsTotal > 0) {
          mode = RUNNING;
          lastTick = millis();
        } else {
          // Bei 00:00 nicht starten, im Set-Modus bleiben
          resetAll();
        }
      }
    }

    // B = Pause/Resume
    if (k == 'B') {
      if (mode == RUNNING) mode = PAUSED;
      else if (mode == PAUSED) { mode = RUNNING; lastTick = millis(); }
    }

    // C = Reset (immer)
    if (k == 'C') {
      resetAll();
    }

    // D = +10 Sekunden im Set-Modus
    if (k == 'D' && mode == SET_MMSS) {
      int s = mmssToSeconds(mmss);
      s += 10;
      if (s > 99*60 + 59) s = 99*60 + 59;
      secondsToMMSS(s, mmss);
      displayMMSS(mmss);
    }

    // * = Backspace (letzte Ziffer 0 setzen), nur Set-Modus
    if (k == '*' && mode == SET_MMSS) {
      mmss[3] = '0';
      displayMMSS(mmss);
    }
  }

  // ---- Countdown tick ----
  if (mode == RUNNING) {
    unsigned long now = millis();
    if (now - lastTick >= 1000) {
      lastTick += 1000;

      if (secondsTotal > 0) {
        secondsTotal--;
        secondsToMMSS(secondsTotal, mmss);
        displayMMSS(mmss);
      } else {
        // AUTOMATISCHER RESET BEI 0
        resetAll();
      }
    }
  }
}