pb10001/integer-reader

import { Digits } from './Digits';
import { IReadableInteger } from './IReadableInteger';

export class ReadableJapaneseInteger implements IReadableInteger {
  public num: number;
  private names = {
    0: '',
    1: '一',
    2: '二',
    3: '三',
    4: '四',
    5: '五',
    6: '六',
    7: '七',
    8: '八',
    9: '九'
  };
  private digits = {
    1: '十',
    2: '百',
    3: '千',
    4: '万',
    8: '億',
    12: '兆',
    16: '京',
    20: '垓',
    24: '秭',
    28: '穣',
    32: '溝',
    36: '澗',
    40: '正',
    44: '載',
    48: '極',
    52: '恒河沙',
    56: '阿僧祇',
    60: '那由他',
    64: '不可思議',
    68: '無量大数'
  };
  constructor(num: number) {
    this.num = num;
  }
  public read(): string {
    if (this.num === 0) {
      return '〇';
    } else if (this.num > 0) {
      return this.solve(this.num, 0);
    } else {
      return null;
    }
  }
  private solve(target: number, depth: number): string {
    if (target !== 0 && !this.names[target]) {
      const d = new Digits(target).calcNum() - 1;
      const digitLength: number = d > 4 ? d - (d % 4) : d;
      const digitNum: number = Math.floor(Math.pow(10, digitLength)); // numを超えない最大の10のべき乗
      let res: string = this.solve(Math.floor(target / digitNum), depth + 1); // 一番上の桁(四桁区切り)
      if (res === '一' && ((d === 3 && depth === 0) || digitLength < 3)) {
        res = '';
      }
      this.names[target] = [
        res + this.digits[digitLength],
        this.solve(target % digitNum, depth + 1)
      ].join('');
    }
    return this.names[target];
  }
}