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

@Pipe({
  name: 'bytes'
})
export class BytesPipe implements PipeTransform {

  /**
   * Format bytes as human-readable text.
   * 
   * @param bytes Number of bytes.
   * @param si True to use metric (SI) units, aka powers of 1000. False to use 
   *           binary (IEC), aka powers of 1024.
   * @param dp Number of decimal places to display.
   * 
   * @return Formatted string.
   * 
   * Credit: https://stackoverflow.com/questions/10420352/converting-file-size-in-bytes-to-human-readable-string
   */
  transform(bytes: number, si=true, dp=0): string {
    const thresh = si ? 1000 : 1024;

    if (Math.abs(bytes) < thresh) {
      return bytes + ' B';
    }

    const units = si 
      ? ['kB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'] 
      : ['KiB', 'MiB', 'GiB', 'TiB', 'PiB', 'EiB', 'ZiB', 'YiB'];
    let u = -1;
    const r = 10**dp;

    do {
      bytes /= thresh;
      ++u;
    } while (Math.round(Math.abs(bytes) * r) / r >= thresh && u < units.length - 1);


    return bytes.toFixed(dp) + ' ' + units[u];
  }

}