const display = document.querySelector("#display");
let previousNumber = 0;
let lastOperation = "";

function doOperation(operation, numA, numB) {
  numA = Number(numA);
  numB = Number(numB);
  switch (operation) {
    case "+":
      return numA + numB;
      break;
  }
}

//Set numbers logic
const numbers = document.querySelectorAll(".number");

numbers.forEach((number) => {
  number.addEventListener("click", (event) => {
    updateDisplay(event.target.innerText);
  });
});

function updateDisplay(number) {
  let currentResult = display.value;
  if (currentResult === "0") {
    display.value = number;
  } else {
    display.value += number;
  }
}

function reset() {
  display.value = "0";
  previousNumber = "0";
  lastOperation = "";
}

// Set clear button
const clearButton = document.querySelector(".clear");
clearButton.addEventListener("click", () => {
  reset();
});

// Set backspace button
backspaceButton = document.querySelector(".backspace");
backspaceButton.addEventListener("click", () => {
  let result = display.value;
  result = result.slice(0, -1);
  if (result.length === 0) {
    result = "0";
  }
  display.value = result;
});

// Operations
const operators = document.querySelectorAll(".operator");
operators.forEach((operator) => {
  operator.addEventListener("click", (event) => {
    if (lastOperation) {
      previousNumber = doOperation(
        lastOperation,
        previousNumber,
        display.value,
      );
    } else {
      previousNumber = Number(display.value);
    }

    display.value = "0";
    lastOperation = event.target.innerText;
  });
});

// Result button
const resultButton = document.querySelector(".result");
resultButton.addEventListener("click", (event) => {
  if (lastOperation) {
    display.value = doOperation(lastOperation, previousNumber, display.value);
  }
});

reset();