#include <IRremote.h>

#define LATCH 9
#define CLOCK 10
#define DATA 8
#define BUZZER_PIN 12
#define RECEIVER_PIN 11

// 4 digit select pins (active LOW for common anode, HIGH for common cathode)
int digitPins[4] = {7, 6, 5, 4};

// Common-anode version of 0–9
byte table[] = {0x3f, 0x06, 0x5b, 0x4f, 0x66,
                0x6d, 0x7d, 0x07, 0x7f, 0x6f, 0x00};

const int IR_1 = 48;
const int IR_2 = 24;
const int IR_3 = 122;
const int IR_4 = 16;
const int IR_5 = 56;
const int IR_6 = 90;
const int IR_7 = 66;
const int IR_8 = 74;
const int IR_9 = 82;
const int IR_0 = 104;
const int IR_POWER = 162;  // Start / Pause
const int IR_RESET = 194;  // Reset

enum State { IDLE, RUNNING, FINISHED };
State state = IDLE;

unsigned int timerValue = 0; // supports up to 9999
unsigned long lastSecond = 0;
unsigned long lastDisplay = 0;

int digits[4] = {0, 0, 0, 0}; // individual digits

// ---------------- DISPLAY FUNCTIONS ----------------
void showDigit(byte digit, byte pos) {
  // Turn all digits OFF
  for (int i = 0; i < 4; i++) digitalWrite(digitPins[i], HIGH);

  // Send segment data
  digitalWrite(LATCH, LOW);
  shiftOut(DATA, CLOCK, MSBFIRST, table[digit]);
  digitalWrite(LATCH, HIGH);

  // Turn this digit ON
  digitalWrite(digitPins[pos], LOW); // active LOW
  delayMicroseconds(1000);           // short hold time
  digitalWrite(digitPins[pos], HIGH);
}

void updateDigits(unsigned int value) {
  digits[0] = value / 1000;
  digits[1] = (value / 100) % 10;
  digits[2] = (value / 10) % 10;
  digits[3] = value % 10;
}

void refreshDisplay() {
  for (int i = 0; i < 4; i++) {
    showDigit(digits[i], i);
  }
}

// ---------------- IR HANDLER ----------------
void handleIR() {
  int code = IrReceiver.decodedIRData.command;
  Serial.print("Received Button Code: ");
  Serial.println(code);

  if (code == IR_0) timerValue = timerValue * 10 + 0;
  else if (code == IR_1) timerValue = timerValue * 10 + 1;
  else if (code == IR_2) timerValue = timerValue * 10 + 2;
  else if (code == IR_3) timerValue = timerValue * 10 + 3;
  else if (code == IR_4) timerValue = timerValue * 10 + 4;
  else if (code == IR_5) timerValue = timerValue * 10 + 5;
  else if (code == IR_6) timerValue = timerValue * 10 + 6;
  else if (code == IR_7) timerValue = timerValue * 10 + 7;
  else if (code == IR_8) timerValue = timerValue * 10 + 8;
  else if (code == IR_9) timerValue = timerValue * 10 + 9;
  else if (code == IR_POWER) {
    if (state == IDLE && timerValue > 0) state = RUNNING;
    else if (state == RUNNING) state = IDLE;
  }
  else if (code == IR_RESET) {
    timerValue = 0;
    state = IDLE;
    digitalWrite(BUZZER_PIN, LOW);
  }

  if (timerValue > 9999) timerValue = 9999; // limit to 4 digits
  updateDigits(timerValue);
}

// ---------------- SETUP / LOOP ----------------
void setup() {
  Serial.begin(9600);
  Serial.println("IR Receiver + 4-digit Counter");

  pinMode(LATCH, OUTPUT);
  pinMode(CLOCK, OUTPUT);
  pinMode(DATA, OUTPUT);

  for (int i = 0; i < 4; i++) {
    pinMode(digitPins[i], OUTPUT);
    digitalWrite(digitPins[i], HIGH);
  }

  pinMode(BUZZER_PIN, OUTPUT);
  digitalWrite(BUZZER_PIN, LOW);

  IrReceiver.begin(RECEIVER_PIN, ENABLE_LED_FEEDBACK);

  updateDigits(timerValue);
}

void loop() {
  // Handle IR input
  if (IrReceiver.decode()) {
    handleIR();
    IrReceiver.resume();
  }

  // Countdown
  if (state == RUNNING && millis() - lastSecond >= 1000) {
    lastSecond = millis();
    if (timerValue > 0) {
      timerValue--;
      updateDigits(timerValue);
    }
    if (timerValue == 0) {
      state = FINISHED;
      digitalWrite(BUZZER_PIN, HIGH);
      delay(500);
      digitalWrite(BUZZER_PIN, LOW);
      timerValue = 0;
    state = IDLE;
    }
  }

  // Refresh display quickly
  refreshDisplay();
}