// 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

/**
 * Implementation of the Key Material Packet (Tag 5,6,7,14)<br/>
 * <br/>
 * 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.
 * @requires crypto
 * @requires enums
 * @requires type/keyid
 * @requires type/mpi
 * @requires util
 * @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');

/**
 * @constructor
 */
module.exports = function () {
  this.version = 4;
  /** Key creation date.
   * @type {Date} */
  this.created = new Date();
  /** A list of multiprecision integers
   * @type {module:type/mpi} */
  this.mpi = [];
  /** Public key algorithm
   * @type {module:enums.publicKey} */
  this.algorithm = 'rsa_sign';
  // time in days (V3 only)
  this.expirationTimeV3 = 0;


  /**
   * Internal Parser for public keys as specified in RFC 4880 section 
   * 5.5.2 Public-Key Packet Formats
   * called by read_tag&lt;num&gt;
   * @param {String} input Input string to read the packet from
   * @return {Object} This object with attributes set by the parser
   */
  this.read = function(bytes) {
    var pos = 0;
    // A one-octet version number (3 or 4).
    this.version = bytes.charCodeAt(pos++);

    if (this.version == 3 || this.version == 4) {
      // - A four-octet number denoting the time that the key was created.
      this.created = util.readDate(bytes.substr(pos, 4));
      pos += 4;

      if (this.version == 3) {
        // - A two-octet number denoting the time in days that this key is
        //   valid.  If this number is zero, then it does not expire.
        this.expirationTimeV3 = util.readNumber(bytes.substr(pos, 2));
        pos += 2;
      }

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

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

      var bmpi = bytes.substr(pos);
      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) {
          throw new Error('Error reading MPI @:' + p);
        }
      }

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

  /**
   * Alias of read()
   * @function module:packet/public_key#readPublicKey
   * @see module:packet/public_key#read
   */
  this.readPublicKey = this.read;

  /**
   * Same as write_private_key, but has less information because of 
   * public key.
   * @return {Object} {body: [string]OpenPGP packet body contents,
   * header: [string] OpenPGP packet header, string: [string] header+body}
   */
  this.write = function() {
    // Version
    var result = String.fromCharCode(this.version);
    result += util.writeDate(this.created);
    if (this.version == 3) {
      result += util.writeNumber(this.expirationTimeV3, 2);
    }
    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;
  };

  /**
   * Alias of write()
   * @function module:packet/public_key#writePublicKey
   * @see module:packet/public_key#write
   */
  this.writePublicKey = this.write;

  /**
   * 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();
    if (this.version == 4) {
      keyid.read(this.getFingerprint().substr(12, 8));
    } else if (this.version == 3) {
      keyid.read(this.mpi[0].write().substr(-8));
    }
    return keyid;
  };

  /**
   * Calculates the fingerprint of the key
   * @return {String} A string containing the fingerprint
   */
  this.getFingerprint = function() {
    var toHash = '';
    if (this.version == 4) {
      toHash = this.writeOld();
      return crypto.hash.sha1(toHash);
    } else if (this.version == 3) {
      var mpicount = crypto.getPublicMpiCount(this.algorithm);
      for (var i = 0; i < mpicount; i++) {
        toHash += this.mpi[i].toBytes();
      }
      return crypto.hash.md5(toHash);
    }
  };
};