number-name/src/ConverterStream.ts

import { Transform } from 'stream'
import { StreamOptions } from './common'

export default class ConverterStream extends Transform {
  private buffer: string

  constructor(
    private readonly converter: (value: string | number | bigint) => string,
    readonly options: StreamOptions,
  ) {
    super()
    this.buffer = ''
  }

  _transform(chunk: Buffer, _encoding: BufferEncoding, callback: Function) {
    let chunkStr = chunk.toString(this.options.encoding)
    this.buffer += chunkStr
    callback()
  }

  _flush(callback: Function) {
    this.push(this.converter(this.buffer.trim()), this.options.encoding)
    callback()
  }
}