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