// GPG4Browsers - An OpenPGP implementation in javascript
// Copyright (C) 2011 Recurity Labs GmbH
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3.0 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

/**
 * @requires config
 * @requires crypto
 * @requires encoding/armor
 * @requires enums
 * @requires packet
 * @module message
 */

'use strict';

import util from './util.js';
import packet from './packet';
import enums from './enums.js';
import armor from './encoding/armor.js';
import config from './config';
import crypto from './crypto';
import keyModule from './key.js';

/**
 * @class
 * @classdesc Class that represents an OpenPGP message.
 * Can be an encrypted message, signed message, compressed message or literal message
 * @param  {module:packet/packetlist} packetlist The packets that form this message
 * See {@link http://tools.ietf.org/html/rfc4880#section-11.3}
 */

function Message(packetlist) {
  if (!(this instanceof Message)) {
    return new Message(packetlist);
  }
  this.packets = packetlist || new packet.List();
}

/**
 * Returns the key IDs of the keys to which the session key is encrypted
 * @return {Array<module:type/keyid>} array of keyid objects
 */
Message.prototype.getEncryptionKeyIds = function() {
  var keyIds = [];
  var pkESKeyPacketlist = this.packets.filterByTag(enums.packet.publicKeyEncryptedSessionKey);
  pkESKeyPacketlist.forEach(function(packet) {
    keyIds.push(packet.publicKeyId);
  });
  return keyIds;
};

/**
 * Returns the key IDs of the keys that signed the message
 * @return {Array<module:type/keyid>} array of keyid objects
 */
Message.prototype.getSigningKeyIds = function() {
  var keyIds = [];
  var msg = this.unwrapCompressed();
  // search for one pass signatures
  var onePassSigList = msg.packets.filterByTag(enums.packet.onePassSignature);
  onePassSigList.forEach(function(packet) {
    keyIds.push(packet.signingKeyId);
  });
  // if nothing found look for signature packets
  if (!keyIds.length) {
    var signatureList = msg.packets.filterByTag(enums.packet.signature);
    signatureList.forEach(function(packet) {
      keyIds.push(packet.issuerKeyId);
    });
  }
  return keyIds;
};

/**
 * Decrypt the message
 * @param {module:key~Key|String} privateKey private key with decrypted secret data, password or session key
 * @param {String} sessionKeyAlgorithm if privateKey is a session key, this must be set to the session key algorithm (i.e. 'aes256').
 *                              Do not set if privateKey is not a session key.
 * @return {Array<module:message~Message>} new message with decrypted content
 */
Message.prototype.decrypt = function(privateKey, sessionKeyAlgorithm) {
  var keyObj;
  if(sessionKeyAlgorithm) {
    keyObj = {key: privateKey, algo: sessionKeyAlgorithm};
  }
  else {
    keyObj = this.decryptSessionKey(privateKey);
  }
  if(keyObj) {
    var symEncryptedPacketlist = this.packets.filterByTag(enums.packet.symmetricallyEncrypted, enums.packet.symEncryptedIntegrityProtected);
    if (symEncryptedPacketlist.length !== 0) {
      var symEncryptedPacket = symEncryptedPacketlist[0];
      symEncryptedPacket.decrypt(keyObj.algo, keyObj.key);
      var resultMsg = new Message(symEncryptedPacket.packets);
      // remove packets after decryption
      symEncryptedPacket.packets = new packet.List();
      return resultMsg;
    }
  }
};

/**
 * Decrypt session key
 * @param {module:key~Key|String} privateKey private key with decrypted secret data or password
 * @return {Object} object with sessionKey, algo
 */
Message.prototype.decryptSessionKey = function(privateKey) {
  var keyPacket;
  if(String.prototype.isPrototypeOf(privateKey) || typeof privateKey === 'string') {
    var symEncryptedSessionKeyPacketlist = this.packets.filterByTag(enums.packet.symEncryptedSessionKey);
    var symLength = symEncryptedSessionKeyPacketlist.length;
    for (var i = 0; i < symLength; i++) {
      keyPacket = symEncryptedSessionKeyPacketlist[i];
      try {
        keyPacket.decrypt(privateKey);
        break;
      }
      catch(err) {
        if(i === (symLength-1)) {
          throw err;
        }
      }
    }

    if(!keyPacket) {
      throw new Error('No symmetrically encrypted session key packet found.');
    }
  }
  else {
    var encryptionKeyIds = this.getEncryptionKeyIds();
    if (!encryptionKeyIds.length) {
      // nothing to decrypt return unmodified message
      return this;
    }
    var privateKeyPacket = privateKey.getKeyPacket(encryptionKeyIds);
    if (!privateKeyPacket.isDecrypted) {
      throw new Error('Private key is not decrypted.');
    }
    var pkESKeyPacketlist = this.packets.filterByTag(enums.packet.publicKeyEncryptedSessionKey);
    for (var j = 0; j < pkESKeyPacketlist.length; j++) {
      if (pkESKeyPacketlist[j].publicKeyId.equals(privateKeyPacket.getKeyId())) {
        keyPacket = pkESKeyPacketlist[j];
        keyPacket.decrypt(privateKeyPacket);
        break;
      }
    }
  }

  if (keyPacket) {
    return {key: keyPacket.sessionKey, algo: keyPacket.sessionKeyAlgorithm};
  }
};

/**
 * Get literal data that is the body of the message
 * @return {(String|null)} literal body of the message as string
 */
Message.prototype.getLiteralData = function() {
  var literal = this.packets.findPacket(enums.packet.literal);
  return literal && literal.data || null;
};

/**
 * Get filename from literal data packet
 * @return {(String|null)} filename of literal data packet as string
 */
Message.prototype.getFilename = function() {
  var literal = this.packets.findPacket(enums.packet.literal);
  return literal && literal.getFilename() || null;
};

/**
 * Get literal data as text
 * @return {(String|null)} literal body of the message interpreted as text
 */
Message.prototype.getText = function() {
  var literal = this.packets.findPacket(enums.packet.literal);
  if (literal) {
    return literal.getText();
  } else {
    return null;
  }
};

/**
 * Encrypt the message
 * @param  {(Array<module:key~Key>|module:key~Key)} public key(s) for message encryption
 * @param  {(Array<String>|String)} password(s) for message encryption
 * @return {Array<module:message~Message>} new message with encrypted content
 */
Message.prototype.encrypt = function(keys, passwords) {

  /** Choose symAlgo */
  var symAlgo;
  if(keys) {
    symAlgo = keyModule.getPreferredSymAlgo(keys);
  }
  else if(passwords) {
    symAlgo = config.encryption_cipher;
  }
  else {
    throw new Error('No keys or passwords');
  }

  var sessionKey = crypto.generateSessionKey(enums.read(enums.symmetric, symAlgo));

  var msg = encryptSessionKey(sessionKey, enums.read(enums.symmetric, symAlgo), keys, passwords);
  var packetlist = msg.packets;

  var symEncryptedPacket;
  if (config.integrity_protect) {
    symEncryptedPacket = new packet.SymEncryptedIntegrityProtected();
  } else {
    symEncryptedPacket = new packet.SymmetricallyEncrypted();
  }
  symEncryptedPacket.packets = this.packets;
  symEncryptedPacket.encrypt(enums.read(enums.symmetric, symAlgo), sessionKey);
  packetlist.push(symEncryptedPacket);
  // remove packets after encryption
  symEncryptedPacket.packets = new packet.List();
  return msg;
};

/**
 * Encrypt a session key
 * @param  {String} session key for encryption
 * @param  {String} session key algorithm
 * @param  {(Array<module:key~Key>|module:key~Key)} public key(s) for message encryption
 * @param  {(Array<String>|String)} password(s) for message encryption
 * @return {Array<module:message~Message>} new message with encrypted content
 */
function encryptSessionKey(sessionKey, symAlgo, keys, passwords) {

  /** Convert to arrays if necessary */
  if(keys && !Array.prototype.isPrototypeOf(keys)) {
    keys = [keys];
  }
  if(passwords && !Array.prototype.isPrototypeOf(passwords)) {
    passwords = [passwords];
  }

  var packetlist = new packet.List();
  if(keys) {
    keys.forEach(function(key) {
      var encryptionKeyPacket = key.getEncryptionKeyPacket();
      if (encryptionKeyPacket) {
        var pkESKeyPacket = new packet.PublicKeyEncryptedSessionKey();
        pkESKeyPacket.publicKeyId = encryptionKeyPacket.getKeyId();
        pkESKeyPacket.publicKeyAlgorithm = encryptionKeyPacket.algorithm;
        pkESKeyPacket.sessionKey = sessionKey;
        pkESKeyPacket.sessionKeyAlgorithm = symAlgo;
        pkESKeyPacket.encrypt(encryptionKeyPacket);
        packetlist.push(pkESKeyPacket);
      } else {
        throw new Error('Could not find valid key packet for encryption in key ' + key.primaryKey.getKeyId().toHex());
      }
    });
  }
  if(passwords) {
    passwords.forEach(function(password) {
      var symEncryptedSessionKeyPacket = new packet.SymEncryptedSessionKey();
      symEncryptedSessionKeyPacket.sessionKey = sessionKey;
      symEncryptedSessionKeyPacket.sessionKeyAlgorithm = symAlgo;
      symEncryptedSessionKeyPacket.encrypt(password);
      packetlist.push(symEncryptedSessionKeyPacket);
    });
  }

  return new Message(packetlist);
}

/**
 * Sign the message (the literal data packet of the message)
 * @param  {Array<module:key~Key>} privateKey private keys with decrypted secret key data for signing
 * @return {module:message~Message}      new message with signed content
 */
Message.prototype.sign = function(privateKeys) {

  var packetlist = new packet.List();

  var literalDataPacket = this.packets.findPacket(enums.packet.literal);
  if (!literalDataPacket) {
    throw new Error('No literal data packet to sign.');
  }

  var literalFormat = enums.write(enums.literal, literalDataPacket.format);
  var signatureType = literalFormat === enums.literal.binary ?
                      enums.signature.binary : enums.signature.text;
  var i, signingKeyPacket;
  for (i = 0; i < privateKeys.length; i++) {
    if (privateKeys[i].isPublic()) {
      throw new Error('Need private key for signing');
    }
    var onePassSig = new packet.OnePassSignature();
    onePassSig.type = signatureType;
    //TODO get preferred hashg algo from key signature
    onePassSig.hashAlgorithm = config.prefer_hash_algorithm;
    signingKeyPacket = privateKeys[i].getSigningKeyPacket();
    if (!signingKeyPacket) {
      throw new Error('Could not find valid key packet for signing in key ' + privateKeys[i].primaryKey.getKeyId().toHex());
    }
    onePassSig.publicKeyAlgorithm = signingKeyPacket.algorithm;
    onePassSig.signingKeyId = signingKeyPacket.getKeyId();
    packetlist.push(onePassSig);
  }

  packetlist.push(literalDataPacket);

  for (i = privateKeys.length - 1; i >= 0; i--) {
    var signaturePacket = new packet.Signature();
    signaturePacket.signatureType = signatureType;
    signaturePacket.hashAlgorithm = config.prefer_hash_algorithm;
    signaturePacket.publicKeyAlgorithm = signingKeyPacket.algorithm;
    if (!signingKeyPacket.isDecrypted) {
      throw new Error('Private key is not decrypted.');
    }
    signaturePacket.sign(signingKeyPacket, literalDataPacket);
    packetlist.push(signaturePacket);
  }

  return new Message(packetlist);
};

/**
 * Verify message signatures
 * @param {Array<module:key~Key>} keys array of keys to verify signatures
 * @return {Array<({keyid: module:type/keyid, valid: Boolean})>} list of signer's keyid and validity of signature
 */
Message.prototype.verify = function(keys) {
  var result = [];
  var msg = this.unwrapCompressed();
  var literalDataList = msg.packets.filterByTag(enums.packet.literal);
  if (literalDataList.length !== 1) {
    throw new Error('Can only verify message with one literal data packet.');
  }
  var signatureList = msg.packets.filterByTag(enums.packet.signature);
  for (var i = 0; i < signatureList.length; i++) {
    var keyPacket = null;
    for (var j = 0; j < keys.length; j++) {
      keyPacket = keys[j].getSigningKeyPacket(signatureList[i].issuerKeyId);
      if (keyPacket) {
        break;
      }
    }

    var verifiedSig = {};
    if (keyPacket) {
      verifiedSig.keyid = signatureList[i].issuerKeyId;
      verifiedSig.valid = signatureList[i].verify(keyPacket, literalDataList[0]);
    } else {
      verifiedSig.keyid = signatureList[i].issuerKeyId;
      verifiedSig.valid = null;
    }
    result.push(verifiedSig);
  }
  return result;
};

/**
 * Unwrap compressed message
 * @return {module:message~Message} message Content of compressed message
 */
Message.prototype.unwrapCompressed = function() {
  var compressed = this.packets.filterByTag(enums.packet.compressed);
  if (compressed.length) {
    return new Message(compressed[0].packets);
  } else {
    return this;
  }
};

/**
 * Returns ASCII armored text of message
 * @return {String} ASCII armor
 */
Message.prototype.armor = function() {
  return armor.encode(enums.armor.message, this.packets.write());
};

/**
 * reads an OpenPGP armored message and returns a message object
 * @param {String} armoredText text to be parsed
 * @return {module:message~Message} new message object
 * @static
 */
function readArmored(armoredText) {
  //TODO how do we want to handle bad text? Exception throwing
  //TODO don't accept non-message armored texts
  var input = armor.decode(armoredText).data;
  return read(input);
}

/**
 * reads an OpenPGP binary string message and returns a message object
 * @param {Uint8Array} binary message
 * @return {module:message~Message} new message object
 * @static
 */
function read(input) {
  var packetlist = new packet.List();
  packetlist.read(input);
  return new Message(packetlist);
}

/**
 * Create a message object from signed content and a detached armored signature.
 * @param {String} content An 8 bit ascii string containing e.g. a MIME subtree with text nodes or attachments
 * @param {String} detachedSignature The detached ascii armored PGP signature
 */
function readSignedContent(content, detachedSignature) {
  var literalDataPacket = new packet.Literal();
  literalDataPacket.setBytes(util.str2Uint8Array(content), enums.read(enums.literal, enums.literal.binary));
  var packetlist = new packet.List();
  packetlist.push(literalDataPacket);
  var input = armor.decode(detachedSignature).data;
  packetlist.read(input);
  return new Message(packetlist);
}

/**
 * creates new message object from text
 * @param {String} text
 * @param {String} filename (optional)
 * @return {module:message~Message} new message object
 * @static
 */
function fromText(text, filename) {
  var literalDataPacket = new packet.Literal();
  // text will be converted to UTF8
  literalDataPacket.setText(text);
  if(filename !== undefined) {
    literalDataPacket.setFilename(filename);
  }
  var literalDataPacketlist = new packet.List();
  literalDataPacketlist.push(literalDataPacket);
  return new Message(literalDataPacketlist);
}

/**
 * creates new message object from binary data
 * @param {Uint8Array} bytes
 * @param {String} filename (optional)
 * @return {module:message~Message} new message object
 * @static
 */
function fromBinary(bytes, filename) {
  if(!Uint8Array.prototype.isPrototypeOf(bytes)) {
    throw new Error('Data must be in the form of a Uint8Array');
  }

  var literalDataPacket = new packet.Literal();
  if (filename) {
    literalDataPacket.setFilename(filename);
  }
  literalDataPacket.setBytes(bytes, enums.read(enums.literal, enums.literal.binary));
  if(filename !== undefined) {
    literalDataPacket.setFilename(filename);
  }
  var literalDataPacketlist = new packet.List();
  literalDataPacketlist.push(literalDataPacket);
  return new Message(literalDataPacketlist);
}

exports.Message = Message;
exports.read = read;
exports.readArmored = readArmored;
exports.readSignedContent = readSignedContent;
exports.fromText = fromText;
exports.fromBinary = fromBinary;
exports.encryptSessionKey = encryptSessionKey;