// 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 2.1 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

/** @module packet/public_key */

var util = require('../util'),
  type_mpi = require('../type/mpi.js'),
  type_keyid = require('../type/keyid.js'),
  enums = require('../enums.js'),
  crypto = require('../crypto');

/**
 * @class
 * @classdesc Implementation of the Key Material Packet (Tag 5,6,7,14)
 *   
 * RFC4480 5.5:
 * A key material packet contains all the information about a public or
 * private key.  There are four variants of this packet type, and two
 * major versions.  Consequently, this section is complex.
 */
module.exports = function packet_public_key() {
  /** Key creation date.
   * @type {Date} */
  this.created = new Date();
  /** A list of multiprecision integers
   * @type {module:type/mpi} */
  this.mpi = [];
  /** Public key algorithm
   * @type {openpgp.publickey} */
  this.algorithm = 'rsa_sign';


  /**
   * Internal Parser for public keys as specified in RFC 4880 section 
   * 5.5.2 Public-Key Packet Formats
   * called by read_tag<num>
   * @param {String} input Input string to read the packet from
   * @param {Integer} position Start position for the parser
   * @param {Integer} len Length of the packet or remaining length of input
   * @return {Object} This object with attributes set by the parser
   */
  this.readPublicKey = this.read = function(bytes) {
    // A one-octet version number (3 or 4).
    var version = bytes.charCodeAt(0);

    if (version == 4) {
      // - A four-octet number denoting the time that the key was created.
      this.created = util.readDate(bytes.substr(1, 4));

      // - A one-octet number denoting the public-key algorithm of this key.
      this.algorithm = enums.read(enums.publicKey, bytes.charCodeAt(5));

      var mpicount = crypto.getPublicMpiCount(this.algorithm);
      this.mpi = [];

      var bmpi = bytes.substr(6);
      var p = 0;

      for (var i = 0; i < mpicount && p < bmpi.length; i++) {

        this.mpi[i] = new type_mpi();

        p += this.mpi[i].read(bmpi.substr(p))

        if (p > bmpi.length)
          util.print_error("openpgp.packet.keymaterial.js\n" + 'error reading MPI @:' + p);
      }

      return p + 6;
    } else {
      throw new Error('Version ' + version + ' of the key packet is unsupported.');
    }
  }

  /*
   * Same as write_private_key, but has less information because of 
   * public key.
   * @param {Integer} keyType Follows the OpenPGP algorithm standard, 
   * IE 1 corresponds to RSA.
   * @param {RSA.keyObject} key
   * @param timePacket
   * @return {Object} {body: [string]OpenPGP packet body contents, 
   * header: [string] OpenPGP packet header, string: [string] header+body}
   */
  this.writePublicKey = this.write = function() {
    // Version
    var result = String.fromCharCode(4);
    result += util.writeDate(this.created);
    result += String.fromCharCode(enums.write(enums.publicKey, this.algorithm));

    var mpicount = crypto.getPublicMpiCount(this.algorithm);

    for (var i = 0; i < mpicount; i++) {
      result += this.mpi[i].write();
    }

    return result;
  }

  // Write an old version packet - it's used by some of the internal routines.
  this.writeOld = function() {
    var bytes = this.writePublicKey();

    return String.fromCharCode(0x99) +
      util.writeNumber(bytes.length, 2) +
      bytes;
  }

  /**
   * Calculates the key id of the key 
   * @return {String} A 8 byte key id
   */
  this.getKeyId = function() {
    var keyid = new type_keyid();
    keyid.read(this.getFingerprint().substr(12, 8));
    return keyid;
  }

  /**
   * Calculates the fingerprint of the key
   * @return {String} A string containing the fingerprint
   */
  this.getFingerprint = function() {
    var toHash = this.writeOld();
    return crypto.hash.sha1(toHash, toHash.length);
  }

}