export default class IntegerKorean {
  static DigitName = [
    "영",
    "일",
    "이",
    "삼",
    "사",
    "오",
    "육",
    "칠",
    "팔",
    "구",
  ];
  static DigitModifier = ["", "십", "백", "천"];
  static Unit = [
    "",
    "만",
    "억",
    "조",
    "경",
    "해",
    "자",
    "양",
    "구",
    "간",
    "정",
    "재",
    "극",
    "항하사",
    "아승기",
    "나유타",
    "불가사의",
    "무량대수",
  ];

  private static stringifyKDigits(
    first: number,
    second: number,
    third: number,
    forth: number,
  ): string {
    const buf = [];

    if (forth) {
      if (forth >= 2) buf.push(this.DigitName[forth]);
      buf.push(this.DigitModifier[3]);
    }
    if (third) {
      if (third >= 2) buf.push(this.DigitName[third]);
      buf.push(this.DigitModifier[2]);
    }
    if (second) {
      if (second >= 2) buf.push(this.DigitName[second]);
      buf.push(this.DigitModifier[1]);
    }
    if (first || (!forth && !third && !second)) {
      buf.push(this.DigitName[first]);
    }

    return buf.join("");
  }
  private static parseKDigitsFromNumber(num: number): string {
    const first = num % 10;
    const second = Math.floor(num / 10) % 10;
    const third = Math.floor(num / 100) % 10;
    const forth = Math.floor(num / 1000) % 10;

    return this.stringifyKDigits(first, second, third, forth);
  }
  private static parseKDigitsFromString(num: string, offset: number): string {
    const first = +num[offset]!;
    const second = offset >= 1 ? +num[offset - 1]! : 0;
    const third = offset >= 2 ? +num[offset - 2]! : 0;
    const forth = offset >= 3 ? +num[offset - 3]! : 0;

    return this.stringifyKDigits(first, second, third, forth);
  }

  static convertFromString(num: string): string {
    num = num.replace(/,/g, "");
    let isNegative = false;
    if (num.startsWith("-")) {
      num = num.slice(1, -1);
      isNegative = true;
    }
    if (num == "0") {
      return isNegative ? "마이너스영" : "영";
    }

    const unitStack = [];
    let offset = num.length - 1;
    while (offset >= 0) {
      unitStack.push(this.parseKDigitsFromString(num, offset));
      offset -= 4;
    }

    const buf = [];
    if (isNegative) buf.push("마이너스");
    for (let i = unitStack.length - 1; i >= 0; i--) {
      const currUnit = this.Unit[i] ?? "";
      let currKDigits = unitStack[i] ?? "";

      if (currKDigits == "영") continue;
      if (i == 1 && currKDigits == "일") currKDigits = "";

      buf.push(currKDigits + currUnit);
    }

    return buf.join("");
  }
  static convertFromNumber(num: number): string {
    let isNegative = false;
    if (num < 0) {
      isNegative = true;
      num *= -1;
    }
    if (num == 0) {
      return "영";
    }

    const unitStack = [];
    while (num) {
      unitStack.push(this.parseKDigitsFromNumber(num));
      num = Math.floor(num / 10000);
    }

    const buf = [];
    if (isNegative) buf.push("마이너스");
    for (let i = unitStack.length - 1; i >= 0; i--) {
      const currUnit = this.Unit[i] ?? "";
      let currKDigits = unitStack[i] ?? "";

      if (currKDigits == "영") continue;
      if (i == 1 && currKDigits == "일") currKDigits = "";

      buf.push(currKDigits + currUnit);
    }

    return buf.join("");
  }
}