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// https://www.npmjs.com/package/split2
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/*
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Copyright (c) 2014-2021, Matteo Collina <hello@matteocollina.com>
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
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IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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'use strict'
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const { Transform } = require('stream')
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const { StringDecoder } = require('string_decoder')
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const kLast = Symbol('last')
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const kDecoder = Symbol('decoder')
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function transform (chunk, enc, cb) {
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  let list
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  if (this.overflow) { // Line buffer is full. Skip to start of next line.
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    const buf = this[kDecoder].write(chunk)
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    list = buf.split(this.matcher)
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    if (list.length === 1) return cb() // Line ending not found. Discard entire chunk.
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    // Line ending found. Discard trailing fragment of previous line and reset overflow state.
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    list.shift()
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    this.overflow = false
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  } else {
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    this[kLast] += this[kDecoder].write(chunk)
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    list = this[kLast].split(this.matcher)
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  }
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  this[kLast] = list.pop()
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  for (let i = 0; i < list.length; i++) {
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    try {
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      push(this, this.mapper(list[i]))
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    } catch (error) {
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      return cb(error)
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    }
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  }
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  this.overflow = this[kLast].length > this.maxLength
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  if (this.overflow && !this.skipOverflow) {
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    cb(new Error('maximum buffer reached'))
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    return
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  }
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  cb()
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}
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function flush (cb) {
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  // forward any gibberish left in there
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  this[kLast] += this[kDecoder].end()
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  if (this[kLast]) {
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    try {
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      push(this, this.mapper(this[kLast]))
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    } catch (error) {
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      return cb(error)
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    }
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  }
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  cb()
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}
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function push (self, val) {
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  if (val !== undefined) {
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    self.push(val)
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  }
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}
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function noop (incoming) {
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  return incoming
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}
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function split (matcher, mapper, options) {
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  // Set defaults for any arguments not supplied.
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  matcher = matcher || /\r?\n/
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  mapper = mapper || noop
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  options = options || {}
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  // Test arguments explicitly.
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  switch (arguments.length) {
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    case 1:
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      // If mapper is only argument.
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      if (typeof matcher === 'function') {
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        mapper = matcher
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        matcher = /\r?\n/
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      // If options is only argument.
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      } else if (typeof matcher === 'object' && !(matcher instanceof RegExp) && !matcher[Symbol.split]) {
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        options = matcher
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        matcher = /\r?\n/
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      }
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      break
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    case 2:
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      // If mapper and options are arguments.
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      if (typeof matcher === 'function') {
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        options = mapper
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        mapper = matcher
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        matcher = /\r?\n/
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      // If matcher and options are arguments.
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      } else if (typeof mapper === 'object') {
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        options = mapper
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        mapper = noop
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      }
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  }
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  options = Object.assign({}, options)
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  options.autoDestroy = true
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  options.transform = transform
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  options.flush = flush
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  options.readableObjectMode = true
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  const stream = new Transform(options)
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  stream[kLast] = ''
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  stream[kDecoder] = new StringDecoder('utf8')
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  stream.matcher = matcher
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  stream.mapper = mapper
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  stream.maxLength = options.maxLength
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  stream.skipOverflow = options.skipOverflow || false
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  stream.overflow = false
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  stream._destroy = function (err, cb) {
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    // Weird Node v12 bug that we need to work around
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    this._writableState.errorEmitted = false
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    cb(err)
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  }
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  return stream
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}
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module.exports = split