1  /*
  2  Copyright (c) 2014-2021, Matteo Collina <hello@matteocollina.com>
  3  
  4  Permission to use, copy, modify, and/or distribute this software for any
  5  purpose with or without fee is hereby granted, provided that the above
  6  copyright notice and this permission notice appear in all copies.
  7  
  8  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  9  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 10  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 11  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 12  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 13  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
 14  IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 15  */
 16  
 17  'use strict'
 18  
 19  const { Transform } = require('stream')
 20  const { StringDecoder } = require('string_decoder')
 21  const kLast = Symbol('last')
 22  const kDecoder = Symbol('decoder')
 23  
 24  function transform (chunk, enc, cb) {
 25    let list
 26    if (this.overflow) { // Line buffer is full. Skip to start of next line.
 27      const buf = this[kDecoder].write(chunk)
 28      list = buf.split(this.matcher)
 29  
 30      if (list.length === 1) return cb() // Line ending not found. Discard entire chunk.
 31  
 32      // Line ending found. Discard trailing fragment of previous line and reset overflow state.
 33      list.shift()
 34      this.overflow = false
 35    } else {
 36      this[kLast] += this[kDecoder].write(chunk)
 37      list = this[kLast].split(this.matcher)
 38    }
 39  
 40    this[kLast] = list.pop()
 41  
 42    for (let i = 0; i < list.length; i++) {
 43      try {
 44        push(this, this.mapper(list[i]))
 45      } catch (error) {
 46        return cb(error)
 47      }
 48    }
 49  
 50    this.overflow = this[kLast].length > this.maxLength
 51    if (this.overflow && !this.skipOverflow) {
 52      cb(new Error('maximum buffer reached'))
 53      return
 54    }
 55  
 56    cb()
 57  }
 58  
 59  function flush (cb) {
 60    // forward any gibberish left in there
 61    this[kLast] += this[kDecoder].end()
 62  
 63    if (this[kLast]) {
 64      try {
 65        push(this, this.mapper(this[kLast]))
 66      } catch (error) {
 67        return cb(error)
 68      }
 69    }
 70  
 71    cb()
 72  }
 73  
 74  function push (self, val) {
 75    if (val !== undefined) {
 76      self.push(val)
 77    }
 78  }
 79  
 80  function noop (incoming) {
 81    return incoming
 82  }
 83  
 84  function split (matcher, mapper, options) {
 85    // Set defaults for any arguments not supplied.
 86    matcher = matcher || /\r?\n/
 87    mapper = mapper || noop
 88    options = options || {}
 89  
 90    // Test arguments explicitly.
 91    switch (arguments.length) {
 92      case 1:
 93        // If mapper is only argument.
 94        if (typeof matcher === 'function') {
 95          mapper = matcher
 96          matcher = /\r?\n/
 97        // If options is only argument.
 98        } else if (typeof matcher === 'object' && !(matcher instanceof RegExp) && !matcher[Symbol.split]) {
 99          options = matcher
100          matcher = /\r?\n/
101        }
102        break
103  
104      case 2:
105        // If mapper and options are arguments.
106        if (typeof matcher === 'function') {
107          options = mapper
108          mapper = matcher
109          matcher = /\r?\n/
110        // If matcher and options are arguments.
111        } else if (typeof mapper === 'object') {
112          options = mapper
113          mapper = noop
114        }
115    }
116  
117    options = Object.assign({}, options)
118    options.autoDestroy = true
119    options.transform = transform
120    options.flush = flush
121    options.readableObjectMode = true
122  
123    const stream = new Transform(options)
124  
125    stream[kLast] = ''
126    stream[kDecoder] = new StringDecoder('utf8')
127    stream.matcher = matcher
128    stream.mapper = mapper
129    stream.maxLength = options.maxLength
130    stream.skipOverflow = options.skipOverflow || false
131    stream.overflow = false
132    stream._destroy = function (err, cb) {
133      // Weird Node v12 bug that we need to work around
134      this._writableState.errorEmitted = false
135      cb(err)
136    }
137  
138    return stream
139  }
140  
141  module.exports = split