const ADDITION_OP = "btn-addition"
const SUBTRACTION_OP = "btn-subtraction"
const MULTIPLY_OP = "btn-multiply"
const DIVIDE_OP = "btn-divide"
const NONE_OP = "NONE"
const NEGATE_OP = "NEGATE"
const PERCENTAGE_OP = "PERCENTAGE"

let number0, number1
let isReset = true
let isChoosingOperator = false
let opertator = NONE_OP

function clearAction() {
  if (isReset
    || getDisplayingNumber().toString().length < 2
    || (getDisplayingText().toString().length < 3 && getDisplayingText().includes("-"))) {
    isReset = true
    isChoosingOperator = false
    opertator = NONE_OP
    displaySetText(0)
    changeClearButtonLabel("AC")
  } else {
    displaySetText(getDisplayingNumber().toString().slice(0, -1))
  }
  holdingOperatorEffect(NONE_OP)
}

function digitAction(input) {
  if (isZero() || isReset) {
    displaySetText(input)
    isReset = false
  } else if (getDisplayingText() == "-0") {
    displaySetText("-" + input)
  } else {
    displayAppend(input)
  }
  isChoosingOperator = false
  changeClearButtonLabel("C")
  holdingOperatorEffect(NONE_OP)
}

function operatorAction(pressedOperator) {
  if (opertator == NONE_OP) {
    number0 = getDisplayingNumber()
  } else if (!isChoosingOperator) {
    equalAction()
  }
  opertator = pressedOperator
  isChoosingOperator = true
  isReset = true
  holdingOperatorEffect(pressedOperator)
  console.log(number0 + " " + number1);
}

function singleOperatorAction(input) {
  number0 = getDisplayingNumber()
  switch (input) {
    case NEGATE_OP:
      if (getDisplayingText() == "0") {
        logToScreen("-" + getDisplayingNumber())
        break
      } else if (getDisplayingText() == "-0") {
        displaySetText(0)
        break
      }
      number0 -= 2 * number0
      displaySetText(number0)
      break
    case PERCENTAGE_OP:
      isReset = true
      displaySetText(number0 / 100)
      break
  }

  holdingOperatorEffect(NONE_OP)
}

function equalAction() {
  if (opertator == NONE_OP) {
    isReset = true
    return
  }
  number1 = getDisplayingNumber()
  switch (opertator) {
    case ADDITION_OP:
      number0 += number1
      break
    case SUBTRACTION_OP:
      number0 -= number1
      break
    case MULTIPLY_OP:
      number0 *= number1
      break
    case DIVIDE_OP:
      if (number1 == 0) {
        displaySetText("Lỗi")
        opertator = NONE_OP
        isReset = true
        return
      }

      console.log(number0);
      number0 /= number1
      break
  }
  opertator = NONE_OP
  isChoosingOperator = false
  isReset = true
  displaySetText(number0)
  holdingOperatorEffect(NONE_OP)
}


function btn1Action() {
  digitAction(1)
}
function btn2Action() {
  digitAction(2)
}
function btn3Action() {
  digitAction(3)
}
function btn4Action() {
  digitAction(4)
}
function btn5Action() {
  digitAction(5)
}
function btn6Action() {
  digitAction(6)
}
function btn7Action() {
  digitAction(7)
}
function btn8Action() {
  digitAction(8)
}
function btn9Action() {
  digitAction(9)
}
function btn0Action() {
  digitAction(0)
}
function btnCommaAction() {
  if (document.getElementById('display-screen').innerHTML.toString().includes(".")) {
    return
  }
  if (isZero() || isReset) {
    logToScreen("0.")
  } else {
    displayAppend(".")
  }
  isReset = false
}

function btnNegateAction() {
  singleOperatorAction(NEGATE_OP)
}

function btnPercentage() {
  singleOperatorAction(PERCENTAGE_OP)
}

function btnAddition() {
  operatorAction(ADDITION_OP)
}
function btnSubtraction() {
  operatorAction(SUBTRACTION_OP)
}
function btnMultiply() {
  operatorAction(MULTIPLY_OP)
}
function btnDivide() {
  operatorAction(DIVIDE_OP)
}

function displayAppend(input) {
  if (document.getElementById('display-screen').innerHTML.length >= 10) {
    return
  }
  document.getElementById('display-screen').innerHTML += input
}

function displaySetText(input) {
  if (!isNaN(input)) {
    document.getElementById('display-screen').innerHTML = +parseFloat(input).toPrecision(8).toString()
  } else {
    document.getElementById('display-screen').innerHTML = input
  }
}

function logToScreen(message) {
  document.getElementById('display-screen').innerHTML = message
}

function getDisplayingNumber() {
  return +document.getElementById('display-screen').innerHTML
}

function getDisplayingText() {
  return document.getElementById('display-screen').innerHTML
}

function changeClearButtonLabel(label) {
  document.getElementById('btn-clear').innerHTML = label
}

function isZero() {
  let displayValue = document.getElementById('display-screen').innerHTML.toString()
  return displayValue == "0" || displayValue == "0.0"
}

function holdingOperatorEffect(pressedOperator) {
  let operators = document.getElementsByClassName("color-orange")
  for (const op of operators) {
    op.style.color = "whitesmoke"
    op.style.backgroundColor = "#ef8911"
  }
  if (pressedOperator != NONE_OP) {
    document.getElementById(pressedOperator).style.backgroundColor = "whitesmoke"
    document.getElementById(pressedOperator).style.color = "#ef8911"
  }
}

document.addEventListener('keydown', (e) => {
  switch (e.key) {
    case "Backspace":
      clearAction()
      break
    case "%":
      btnPercentage()
      break
    case "1":
      btn1Action()
      break
    case "2":
      btn2Action()
      break
    case "3":
      btn3Action()
      break
    case "4":
      btn4Action()
      break
    case "5":
      btn5Action()
      break
    case "6":
      btn6Action()
      break
    case "7":
      btn7Action()
      break
    case "8":
      btn8Action()
      break
    case "9":
      btn9Action()
      break
    case "0":
      btn0Action()
      break
    case ".":
      btnCommaAction()
      break
    case "+":
      btnAddition()
      break
    case "-":
      btnSubtraction()
      break
    case "*":
      btnMultiply()
      break
    case "/":
      btnDivide()
      break
    case "=":
    case "Enter":
      equalAction()
      break
  }
})

document.getElementById('btn-1').addEventListener("click", btn1Action)
document.getElementById('btn-2').addEventListener("click", btn2Action)
document.getElementById('btn-3').addEventListener("click", btn3Action)
document.getElementById('btn-4').addEventListener("click", btn4Action)
document.getElementById('btn-5').addEventListener("click", btn5Action)
document.getElementById('btn-6').addEventListener("click", btn6Action)
document.getElementById('btn-7').addEventListener("click", btn7Action)
document.getElementById('btn-8').addEventListener("click", btn8Action)
document.getElementById('btn-9').addEventListener("click", btn9Action)
document.getElementById('btn-0').addEventListener("click", btn0Action)
document.getElementById('btn-comma').addEventListener("click", btnCommaAction)
document.getElementById('btn-negate').addEventListener("click", btnNegateAction)
document.getElementById('btn-percentage').addEventListener("click", btnPercentage)
document.getElementById('btn-addition').addEventListener("click", btnAddition)
document.getElementById('btn-subtraction').addEventListener("click", btnSubtraction)
document.getElementById('btn-multiply').addEventListener("click", btnMultiply)
document.getElementById('btn-divide').addEventListener("click", btnDivide)
document.getElementById('btn-equal').addEventListener("click", equalAction)
document.getElementById('btn-clear').addEventListener("click", clearAction)