/*
 * videojs-hls
 *
 * Copyright (c) 2014 Brightcove
 * All rights reserved.
 *
 * This file contains an adaptation of the AES decryption algorithm
 * from the Standford Javascript Cryptography Library. That work is
 * covered by the following copyright and permissions notice:
 *
 * Copyright 2009-2010 Emily Stark, Mike Hamburg, Dan Boneh.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials provided
 *    with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as representing
 * official policies, either expressed or implied, of the authors.
 */
(function(window, videojs, unpad) {
'use strict';

var AES, decrypt;

/**
 * Schedule out an AES key for both encryption and decryption. This
 * is a low-level class. Use a cipher mode to do bulk encryption.
 *
 * @constructor
 * @param key {Array} The key as an array of 4, 6 or 8 words.
 */
AES = function (key) {
  this._precompute();
  
  var i, j, tmp,
    encKey, decKey,
    sbox = this._tables[0][4], decTable = this._tables[1],
    keyLen = key.length, rcon = 1;
  
  if (keyLen !== 4 && keyLen !== 6 && keyLen !== 8) {
    throw new Error("Invalid aes key size");
  }
  
  encKey = key.slice(0);
  decKey = [];
  this._key = [encKey, decKey];
  
  // schedule encryption keys
  for (i = keyLen; i < 4 * keyLen + 28; i++) {
    tmp = encKey[i-1];
    
    // apply sbox
    if (i%keyLen === 0 || (keyLen === 8 && i%keyLen === 4)) {
      tmp = sbox[tmp>>>24]<<24 ^ sbox[tmp>>16&255]<<16 ^ sbox[tmp>>8&255]<<8 ^ sbox[tmp&255];
      
      // shift rows and add rcon
      if (i%keyLen === 0) {
        tmp = tmp<<8 ^ tmp>>>24 ^ rcon<<24;
        rcon = rcon<<1 ^ (rcon>>7)*283;
      }
    }
    
    encKey[i] = encKey[i-keyLen] ^ tmp;
  }
  
  // schedule decryption keys
  for (j = 0; i; j++, i--) {
    tmp = encKey[j&3 ? i : i - 4];
    if (i<=4 || j<4) {
      decKey[j] = tmp;
    } else {
      decKey[j] = decTable[0][sbox[tmp>>>24      ]] ^
                  decTable[1][sbox[tmp>>16  & 255]] ^
                  decTable[2][sbox[tmp>>8   & 255]] ^
                  decTable[3][sbox[tmp      & 255]];
    }
  }
};

AES.prototype = {
  /**
   * The expanded S-box and inverse S-box tables. These will be computed
   * on the client so that we don't have to send them down the wire.
   *
   * There are two tables, _tables[0] is for encryption and
   * _tables[1] is for decryption.
   *
   * The first 4 sub-tables are the expanded S-box with MixColumns. The
   * last (_tables[01][4]) is the S-box itself.
   *
   * @private
   */
  _tables: [[[],[],[],[],[]],[[],[],[],[],[]]],

  /**
   * Expand the S-box tables.
   *
   * @private
   */
  _precompute: function () {
   var encTable = this._tables[0], decTable = this._tables[1],
       sbox = encTable[4], sboxInv = decTable[4],
       i, x, xInv, d=[], th=[], x2, x4, x8, s, tEnc, tDec;

    // Compute double and third tables
   for (i = 0; i < 256; i++) {
     th[( d[i] = i<<1 ^ (i>>7)*283 )^i]=i;
   }
   
   for (x = xInv = 0; !sbox[x]; x ^= x2 || 1, xInv = th[xInv] || 1) {
     // Compute sbox
     s = xInv ^ xInv<<1 ^ xInv<<2 ^ xInv<<3 ^ xInv<<4;
     s = s>>8 ^ s&255 ^ 99;
     sbox[x] = s;
     sboxInv[s] = x;
     
     // Compute MixColumns
     x8 = d[x4 = d[x2 = d[x]]];
     tDec = x8*0x1010101 ^ x4*0x10001 ^ x2*0x101 ^ x*0x1010100;
     tEnc = d[s]*0x101 ^ s*0x1010100;
     
     for (i = 0; i < 4; i++) {
       encTable[i][x] = tEnc = tEnc<<24 ^ tEnc>>>8;
       decTable[i][s] = tDec = tDec<<24 ^ tDec>>>8;
     }
   }
   
   // Compactify. Considerable speedup on Firefox.
   for (i = 0; i < 5; i++) {
     encTable[i] = encTable[i].slice(0);
     decTable[i] = decTable[i].slice(0);
   }
  },
  
  /**
   * Decrypt an array of 4 big-endian words.
   * @param {Array} data The ciphertext.
   * @return {Array} The plaintext.
   */
  decrypt:function (input) {
    if (input.length !== 4) {
      throw new Error("Invalid aes block size");
    }
    
    var key = this._key[1],
        // state variables a,b,c,d are loaded with pre-whitened data
        a = input[0]           ^ key[0],
        b = input[3] ^ key[1],
        c = input[2]           ^ key[2],
        d = input[1] ^ key[3],
        a2, b2, c2,
        
        nInnerRounds = key.length/4 - 2,
        i,
        kIndex = 4,
        out = [0,0,0,0],
        table = this._tables[1],
        
        // load up the tables
        t0    = table[0],
        t1    = table[1],
        t2    = table[2],
        t3    = table[3],
        sbox  = table[4];
 
    // Inner rounds. Cribbed from OpenSSL.
    for (i = 0; i < nInnerRounds; i++) {
      a2 = t0[a>>>24] ^ t1[b>>16 & 255] ^ t2[c>>8 & 255] ^ t3[d & 255] ^ key[kIndex];
      b2 = t0[b>>>24] ^ t1[c>>16 & 255] ^ t2[d>>8 & 255] ^ t3[a & 255] ^ key[kIndex + 1];
      c2 = t0[c>>>24] ^ t1[d>>16 & 255] ^ t2[a>>8 & 255] ^ t3[b & 255] ^ key[kIndex + 2];
      d  = t0[d>>>24] ^ t1[a>>16 & 255] ^ t2[b>>8 & 255] ^ t3[c & 255] ^ key[kIndex + 3];
      kIndex += 4;
      a=a2; b=b2; c=c2;
    }
        
    // Last round.
    for (i = 0; i < 4; i++) {
      out[3 & -i] =
        sbox[a>>>24      ]<<24 ^ 
        sbox[b>>16  & 255]<<16 ^
        sbox[c>>8   & 255]<<8  ^
        sbox[d      & 255]     ^
        key[kIndex++];
      a2=a; a=b; b=c; c=d; d=a2;
    }
    
    return out;
  }
};

decrypt = function(encrypted, key, initVector) {
  var
    encryptedView = new DataView(encrypted.buffer),
    platformEndian = new Uint32Array(encrypted.byteLength / 4),
    decipher = new AES(key),
    decrypted = new Uint8Array(encrypted.byteLength),
    decryptedView = new DataView(decrypted.buffer),
    decryptedBlock,
    word, byte;

  // convert big-endian input to platform byte order for decryption
  for (byte = 0; byte < encrypted.byteLength; byte += 4) {
    platformEndian[byte >>> 2] = encryptedView.getUint32(byte);
  }
  // decrypt four word sequences, applying cipher-block chaining (CBC)
  // to each decrypted block
  for (word = 0; word < platformEndian.length; word += 4) {
    // decrypt the block
    decryptedBlock = decipher.decrypt(platformEndian.subarray(word, word + 4));

    // XOR with the IV, and restore network byte-order to obtain the
    // plaintext
    byte = word << 2;
    decryptedView.setUint32(byte, decryptedBlock[0] ^ initVector[0]);
    decryptedView.setUint32(byte + 4, decryptedBlock[1] ^ initVector[1]);
    decryptedView.setUint32(byte + 8, decryptedBlock[2] ^ initVector[2]);
    decryptedView.setUint32(byte + 12, decryptedBlock[3] ^ initVector[3]);

    // setup the IV for the next round
    initVector = platformEndian.subarray(word, word + 4);
  }

  // remove any padding
  return unpad(decrypted);
};

// exports
videojs.Hls.decrypt = decrypt;

})(window, window.videojs, window.pkcs7.unpad);