import { Pipe, PipeTransform } from '@angular/core';

import { isInteger, isNumberFinite, isPositive, toDecimal } from '../../utils';

export type ByteUnit = 'B' | 'KB' | 'MB' | 'GB' | 'TB';

/**
 * Bytes pipe
 * @author Daniel Sogl
 */
@Pipe({
  name: 'bytes'
})
export class BytesPipe implements PipeTransform {
  static formats: { [key: string]: { max: number; prev?: ByteUnit } } = {
    B: { max: 1024 },
    KB: { max: Math.pow(1024, 2), prev: 'B' },
    MB: { max: Math.pow(1024, 3), prev: 'KB' },
    GB: { max: Math.pow(1024, 4), prev: 'MB' },
    TB: { max: Number.MAX_SAFE_INTEGER, prev: 'GB' }
  };

  transform(input: any, decimal: number = 0, from: ByteUnit = 'B'): any {
    if (
      !(
        isNumberFinite(input) &&
        isNumberFinite(decimal) &&
        isInteger(decimal) &&
        isPositive(decimal)
      )
    ) {
      return input;
    }

    /* tslint:disable */
    let bytes = input;
    let unit = from;
    while (unit !== 'B') {
      bytes *= 1024;
      unit = BytesPipe.formats[unit].prev!;
    }

    for (const key in BytesPipe.formats) {
      const format = BytesPipe.formats[key];
      if (bytes < format.max) {
        const prev = format.prev ? BytesPipe.formats[format.prev] : undefined;

        const result = prev
          ? toDecimal(bytes / prev.max, decimal)
          : toDecimal(bytes, decimal);

        return `${result} ${key}`;
      }
    }
  }
}