'use strict';

const Buffer = require('buffer').Buffer;

module.exports = BufferList;

function BufferList() {
  this.head = null;
  this.tail = null;
  this.length = 0;
}

BufferList.prototype.push = function(v) {
  const entry = { data: v, next: null };
  if (this.length > 0)
    this.tail.next = entry;
  else
    this.head = entry;
  this.tail = entry;
  ++this.length;
};

BufferList.prototype.unshift = function(v) {
  const entry = { data: v, next: this.head };
  if (this.length === 0)
    this.tail = entry;
  this.head = entry;
  ++this.length;
};

BufferList.prototype.shift = function() {
  if (this.length === 0)
    return;
  const ret = this.head.data;
  if (this.length === 1)
    this.head = this.tail = null;
  else
    this.head = this.head.next;
  --this.length;
  return ret;
};

BufferList.prototype.clear = function() {
  this.head = this.tail = null;
  this.length = 0;
};

BufferList.prototype.join = function(s) {
  if (this.length === 0)
    return '';
  var p = this.head;
  var ret = '' + p.data;
  while (p = p.next)
    ret += s + p.data;
  return ret;
};

BufferList.prototype.concat = function(n) {
  if (this.length === 0)
    return Buffer.alloc(0);
  if (this.length === 1)
    return this.head.data;
  const ret = Buffer.allocUnsafe(n >>> 0);
  var p = this.head;
  var i = 0;
  while (p) {
    p.data.copy(ret, i);
    i += p.data.length;
    p = p.next;
  }
  return ret;
};