export class UnitProvider {
  postfixes: string[];

  constructor() {
    let lang = localStorage.getItem('lang');
    if (lang === 'zh-TW') {
      this.postfixes = ['', '', '', '', '萬', '', '', '', '', '', '', '', '', '', '', ''];
    } else if (lang === 'zh-CN') {
      this.postfixes = ['', '', '', '', '万', '', '', '', '', '', '', '', '', '', '', ''];
    } else {
      this.postfixes = ['', '', '', 'K', '', '', 'M', '', '', 'G', '', '', 'T', '', '', 'P', '', '', 'E'];
    }
  }
}

export interface IShortenNumberOptions {
  precision?: number,
  appendComma?: boolean,
  appendPostfix?: boolean,
  trailing?: boolean,
}

export class ShortenNumberFormater {
  options: IShortenNumberOptions = {
    precision: 0,
    appendComma: true,
    appendPostfix: true,
    trailing: true
  };
  postfixes: string[];
  trailing: boolean = true;

  constructor(options?: IShortenNumberOptions) {
    Object.assign(this.options, options || {});
    let unitProvider = new UnitProvider();
    this.postfixes = unitProvider.postfixes;
  }

  format(value: number) {
    let precision = this.options.precision;
    let appendComma = this.options.appendComma;
    let appendPostfix = this.options.appendPostfix;
    let trailing = this.options.trailing;

    let decimal,
      unit,
      newValue = value;

    for (let i = this.postfixes.length - 1; i >= 0; i--) {
      unit = this.postfixes[i];
      if (unit === '') {
        continue;
      }

      decimal = Math.pow(10, i);
      if (Math.abs(value) >= decimal) {
        newValue = (value / decimal);
        break;
      }
    }
    let formatted;
    if (appendComma) {
      formatted = newValue.toLocaleString('en', { minimumFractionDigits: precision, maximumFractionDigits: precision })
    } else {
      formatted = newValue.toFixed(precision);
    }
    if (trailing) { formatted = formatted.replace(/\.0+$/, ''); }
    if (appendPostfix) { formatted += unit; }

    return formatted;
  }
}