const addButton = document.getElementById("add");
const subtractButton = document.getElementById("subtract");
const divideButton = document.getElementById("divide");
const multiplyButton = document.getElementById("multiply");
const calculation = document.getElementById("calculation");
const result = document.getElementById("result");
const inputNum = document.getElementById("inputNumber");

function outputResult(answer, text) {
  result.textContent = answer;
  calculation.textContent = text;
}

const defaultResult = 0;
currentResult = defaultResult;
let logEntries = [];

function getUserInput() {
  return parseInt(inputNum.value);
}

function writeToLog(prevResult, operand, original) {
  let calcDescription = `${prevResult} ${operand} ${original}`;
  outputResult(currentResult, calcDescription);
}

function createLog(operationidentifier, older, olderTwo, newResult) {
  let logEntry = {
    operation: operationidentifier,
    numberOne: older,
    numberTwo: olderTwo,
    newResult: newResult,
  };
  logEntries.push(logEntry);
  console.log(logEntries);
}

function createOutput(conditional) {
  const enteredNumber = getUserInput();
  if (
    (conditional !== "ADD" &&
      conditional !== "SUBTRACT" &&
      conditional !== "DIVIDE" &&
      conditional !== "MULTIPLY") ||
    enteredNumber === 0
  ) {
    return;
  }

  let initialResult = currentResult;
  let differ;
  if (conditional === "ADD") {
    currentResult += parseInt(enteredNumber);
    differ = "+";
  } else if (conditional === "SUBTRACT") {
    currentResult -= parseInt(enteredNumber);
    differ = "-";
  } else if (conditional === "DIVIDE") {
    currentResult = currentResult / parseInt(enteredNumber);
    differ = "/";
  } else if (conditional === "MULTIPLY") {
    currentResult = currentResult * parseInt(enteredNumber);
    differ = "*";
  }

  writeToLog(initialResult, differ, enteredNumber);
  createLog(conditional, initialResult, enteredNumber, currentResult);
}

function add() {
  createOutput("ADD");
}

function subtract() {
  createOutput("SUBTRACT");
}

function divide() {
  createOutput("DIVIDE");
}

function multiply() {
  createOutput("MULTIPLY");
}

addButton.addEventListener("click", add);
subtractButton.addEventListener("click", subtract);
divideButton.addEventListener("click", divide);
multiplyButton.addEventListener("click", multiply);