script.js

(function () {
  "use strict";

  const CASH_SETTLEMENT_RATE = 0.9;
  const CARD_SETTLEMENT_RATE = 0.875;
  const WITHHOLDING_TAX_RATE = 0.033;

  function getSalaryRate(settlementBasis) {
    if (settlementBasis < 10_000_000) return 0.3;
    if (settlementBasis < 13_000_000) return 0.32;
    if (settlementBasis < 16_000_000) return 0.34;
    return 0.36;
  }

  function calculateSalary(cashSales, cardSales) {
    const cashSettlement = cashSales * CASH_SETTLEMENT_RATE;
    const cardSettlement = cardSales * CARD_SETTLEMENT_RATE;
    const settlementBasis = cashSettlement + cardSettlement;
    const salaryRate = getSalaryRate(settlementBasis);
    const grossSalary = settlementBasis * salaryRate;
    const withholdingTax = grossSalary * WITHHOLDING_TAX_RATE;
    const finalSalary = grossSalary - withholdingTax;

    return {
      cashSettlement,
      cardSettlement,
      settlementBasis,
      salaryRate,
      grossSalary,
      withholdingTax,
      finalSalary,
    };
  }

  function parseAmount(value) {
    const digits = String(value).replace(/[^0-9]/g, "");
    return digits ? Number(digits) : 0;
  }

  function formatInput(value) {
    const digits = String(value).replace(/[^0-9]/g, "").replace(/^0+(?=\d)/, "");
    return digits ? Number(digits).toLocaleString("ko-KR") : "";
  }

  function formatWon(value) {
    return `${Math.round(value).toLocaleString("ko-KR")}원`;
  }

  function initializeCalculator() {
    const form = document.querySelector("#salary-form");
    if (!form) return;

    const cashInput = document.querySelector("#cash-sales");
    const cardInput = document.querySelector("#card-sales");
    const resetButton = document.querySelector("#reset-button");
    const formError = document.querySelector("#form-error");
    const results = document.querySelector("#results");
    const finalSalary = document.querySelector("#final-salary");
    const cashSettlement = document.querySelector("#cash-settlement");
    const cardSettlement = document.querySelector("#card-settlement");
    const settlementBasis = document.querySelector("#settlement-basis");
    const appliedRate = document.querySelector("#applied-rate");
    const grossSalary = document.querySelector("#gross-salary");
    const withholdingTax = document.querySelector("#withholding-tax");
    const rateBadge = document.querySelector("#rate-badge");
    const currentYear = document.querySelector("#current-year");

    const inputs = [cashInput, cardInput];

    inputs.forEach((input) => {
      input.addEventListener("input", (event) => {
        event.target.value = formatInput(event.target.value);
        formError.hidden = true;
      });
    });

    form.addEventListener("submit", (event) => {
      event.preventDefault();

      if (!cashInput.value && !cardInput.value) {
        formError.hidden = false;
        cashInput.focus();
        return;
      }

      const calculation = calculateSalary(
        parseAmount(cashInput.value),
        parseAmount(cardInput.value),
      );
      const percentage = Math.round(calculation.salaryRate * 100);

      cashSettlement.textContent = formatWon(calculation.cashSettlement);
      cardSettlement.textContent = formatWon(calculation.cardSettlement);
      settlementBasis.textContent = formatWon(calculation.settlementBasis);
      appliedRate.textContent = `${percentage}%`;
      grossSalary.textContent = formatWon(calculation.grossSalary);
      withholdingTax.textContent = `-${formatWon(calculation.withholdingTax)}`;
      rateBadge.textContent = `${percentage}%`;
      finalSalary.innerHTML = `${Math.round(calculation.finalSalary).toLocaleString("ko-KR")}<span>원</span>`;
      results.classList.remove("is-empty");

      if (window.matchMedia("(max-width: 759px)").matches) {
        results.scrollIntoView({ behavior: "smooth", block: "start" });
      }
    });

    resetButton.addEventListener("click", () => {
      form.reset();
      formError.hidden = true;
      cashSettlement.textContent = "0원";
      cardSettlement.textContent = "0원";
      settlementBasis.textContent = "0원";
      appliedRate.textContent = "—%";
      grossSalary.textContent = "0원";
      withholdingTax.textContent = "0원";
      rateBadge.textContent = "—%";
      finalSalary.innerHTML = "0<span>원</span>";
      results.classList.add("is-empty");
      cashInput.focus();
    });

    currentYear.textContent = new Date().getFullYear();
  }

  if (typeof module !== "undefined" && module.exports) {
    module.exports = {
      CASH_SETTLEMENT_RATE,
      CARD_SETTLEMENT_RATE,
      WITHHOLDING_TAX_RATE,
      getSalaryRate,
      calculateSalary,
      parseAmount,
      formatInput,
      formatWon,
    };
  }

  if (typeof document !== "undefined") {
    if (document.readyState === "loading") {
      document.addEventListener("DOMContentLoaded", initializeCalculator);
    } else {
      initializeCalculator();
    }
  }
})();