import { Readable, ReadableOptions } from 'stream'
import { ReadableTyped } from '../stream.model'

/**
 * Convenience function to create a Readable that can be pushed into (similar to RxJS Subject).
 * Push `null` to it to complete (similar to RxJS `.complete()`).
 *
 * Difference from Readable.from() is that this readable is not "finished" yet and allows pushing more to it.
 *
 * Caution!
 * The implementation of this Readable is not fully compliant,
 * e.g the read() method doesn't return anything, so, it will hand the Node process (or cause it to process.exit(0))
 * if read() will be called AFTER everything was pushed and Readable is closed (by pushing `null`).
 * Beware of it when e.g doing unit testing! Jest prefers to hang (not exit-0).
 *
 * @deprecated because of the caution above
 */
export function readableCreate<T>(
  items: Iterable<T> = [],
  opt?: ReadableOptions,
): ReadableTyped<T> {
  const readable = new Readable({
    objectMode: true,
    ...opt,
    read() {}, // Caution, if this is called and Readable has not finished yet (null wasn't pushed) - it'll hang the process!
  })
  for (const item of items) {
    readable.push(item)
  }
  return readable
}

/**
 * Convenience type-safe wrapper around Readable.from() that infers the Type of input.
 */
export function readableFrom<T>(
  items: Iterable<T> | AsyncIterable<T>,
  opt?: ReadableOptions,
): ReadableTyped<T> {
  return Readable.from(items, opt)
}