/*
 * pkcs7.pad
 * https://github.com/brightcove/pkcs7
 *
 * Copyright (c) 2014 Brightcove
 * Licensed under the apache2 license.
 */

'use strict';

var PADDING;

/**
 * Returns a new Uint8Array that is padded with PKCS#7 padding.
 * @param plaintext {Uint8Array} the input bytes before encryption
 * @return {Uint8Array} the padded bytes
 * @see http://tools.ietf.org/html/rfc5652
 */
module.exports = function pad(plaintext) {
  var padding = PADDING[(plaintext.byteLength % 16) || 0],
      result = new Uint8Array(plaintext.byteLength + padding.length);
  result.set(plaintext);
  result.set(padding, plaintext.byteLength);
  return result;
};

// pre-define the padding values
PADDING = [
  [16, 16, 16, 16,
   16, 16, 16, 16,
   16, 16, 16, 16,
   16, 16, 16, 16],

  [15, 15, 15, 15,
   15, 15, 15, 15,
   15, 15, 15, 15,
   15, 15, 15],

  [14, 14, 14, 14,
   14, 14, 14, 14,
   14, 14, 14, 14,
   14, 14],

  [13, 13, 13, 13,
   13, 13, 13, 13,
   13, 13, 13, 13,
   13],

  [12, 12, 12, 12,
   12, 12, 12, 12,
   12, 12, 12, 12],

  [11, 11, 11, 11,
   11, 11, 11, 11,
   11, 11, 11],

  [10, 10, 10, 10,
   10, 10, 10, 10,
   10, 10],

  [9, 9, 9, 9,
   9, 9, 9, 9,
   9],

  [8, 8, 8, 8,
   8, 8, 8, 8],

  [7, 7, 7, 7,
   7, 7, 7],

  [6, 6, 6, 6,
   6, 6],

  [5, 5, 5, 5,
   5],

  [4, 4, 4, 4],

  [3, 3, 3],

  [2, 2],

  [1]
];