"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.createIntersperseStream = createIntersperseStream;
var _stream = require("stream");
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

/**
 *  Create a Transform stream that receives values in object mode,
 *  and intersperses a chunk between each object received.
 *
 *  This is useful for writing lists:
 *
 *    createListStream(['foo', 'bar'])
 *      .pipe(createIntersperseStream('\n'))
 *      .pipe(process.stdout) // outputs "foo\nbar"
 *
 *  Combine with a concat stream to get "join" like functionality:
 *
 *    await createPromiseFromStreams([
 *      createListStream(['foo', 'bar']),
 *      createIntersperseStream(' '),
 *      createConcatStream()
 *    ]) // produces a single value "foo bar"
 *
 *  @param  {String|Buffer} intersperseChunk
 *  @return {Transform}
 */
function createIntersperseStream(intersperseChunk) {
  let first = true;
  return new _stream.Transform({
    writableObjectMode: true,
    readableObjectMode: true,
    transform(chunk, enc, callback) {
      try {
        if (first) {
          first = false;
        } else {
          this.push(intersperseChunk);
        }
        this.push(chunk);
        callback();
      } catch (err) {
        callback(err);
      }
    }
  });
}