/**
 * Retrieve the hexadecimal value (as a string) of the current ASN.1 element
 * @returns {string}
 * @public
 */
ASN1.prototype.getHexStringValue = function(){
    var hexString = this.toHexString();
    var offset = this.header * 2;
    var length = this.length * 2;
    return hexString.substr(offset,length);
};

/**
 * Method to parse a pem encoded string containing both a public or private key.
 * The method will translate the pem encoded string in a der encoded string and
 * will parse private key and public key parameters. This method accepts public key
 * in the rsaencryption pkcs #1 format (oid: 1.2.840.113549.1.1.1). 
 * @todo Check how many rsa formats use the same format of pkcs #1. The format is defined as:
 * PublicKeyInfo ::= SEQUENCE {
 *   algorithm       AlgorithmIdentifier,
 *   PublicKey       BIT STRING
 * }
 * Where AlgorithmIdentifier is: 
 * AlgorithmIdentifier ::= SEQUENCE {
 *   algorithm       OBJECT IDENTIFIER,     the OID of the enc algorithm
 *   parameters      ANY DEFINED BY algorithm OPTIONAL (NULL for PKCS #1)
 * }
 * and PublicKey is a SEQUENCE encapsulated in a BIT STRING
 * RSAPublicKey ::= SEQUENCE {
 *   modulus           INTEGER,  -- n
 *   publicExponent    INTEGER   -- e
 * }
 * it's possible to examine the structure of the keys obtained from openssl using 
 * an asn.1 dumper as the one used here to parse the components: http://lapo.it/asn1js/
 * @argument {string} pem the pem encoded string, can include the BEGIN/END header/footer
 * @private
 */
RSAKey.prototype.parseKey = function(pem) {
    try{
        var reHex = /^\s*(?:[0-9A-Fa-f][0-9A-Fa-f]\s*)+$/;
        var der = reHex.test(pem) ? Hex.decode(pem) : Base64.unarmor(pem);
        var asn1 = ASN1.decode(der);
        if (asn1.sub.length === 9){
            // the data is a Private key
            //in order
            //Algorithm version, n, e, d, p, q, dmp1, dmq1, coeff
            //Alg version, modulus, public exponent, private exponent, prime 1, prime 2, exponent 1, exponent 2, coefficient
            var modulus = asn1.sub[1].getHexStringValue(); //bigint
            this.n = parseBigInt(modulus, 16);

            var public_exponent = asn1.sub[2].getHexStringValue(); //int
            this.e = parseInt(public_exponent, 16);

            var private_exponent = asn1.sub[3].getHexStringValue(); //bigint
            this.d = parseBigInt(private_exponent, 16);

            var prime1 = asn1.sub[4].getHexStringValue(); //bigint
            this.p = parseBigInt(prime1, 16);

            var prime2 = asn1.sub[5].getHexStringValue(); //bigint 
            this.q = parseBigInt(prime2, 16);

            var exponent1 = asn1.sub[6].getHexStringValue(); //bigint
            this.dmp1 = parseBigInt(exponent1, 16);

            var exponent2 = asn1.sub[7].getHexStringValue(); //bigint
            this.dmq1 = parseBigInt(exponent2, 16);

            var coefficient = asn1.sub[8].getHexStringValue(); //bigint
            this.coeff = parseBigInt(coefficient, 16);

        }else if (asn1.sub.length === 2){
            //Public key
            //The data PROBABLY is a public key
            var bit_string = asn1.sub[1];
            var sequence   = bit_string.sub[0];

            var modulus = sequence.sub[0].getHexStringValue();
            this.n = parseBigInt(modulus, 16);
            var public_exponent = sequence.sub[1].getHexStringValue();
            this.e = parseInt(public_exponent, 16);

        }else{
            return false;
        }
        return true;
    }catch(ex){
        return false;
    }
};

/**
 * Translate rsa parameters in a hex encoded string representing the rsa key.
 * The translation follow the ASN.1 notation :
 * RSAPrivateKey ::= SEQUENCE {
 *   version           Version,
 *   modulus           INTEGER,  -- n
 *   publicExponent    INTEGER,  -- e
 *   privateExponent   INTEGER,  -- d
 *   prime1            INTEGER,  -- p
 *   prime2            INTEGER,  -- q
 *   exponent1         INTEGER,  -- d mod (p1)
 *   exponent2         INTEGER,  -- d mod (q-1)
 *   coefficient       INTEGER,  -- (inverse of q) mod p
 * }
 * @returns {string}  DER Encoded String representing the rsa private key
 * @private
 */
RSAKey.prototype.getPrivateBaseKey = function() {
    //Algorithm version, n, e, d, p, q, dmp1, dmq1, coeff
    //Alg version, modulus, public exponent, private exponent, prime 1, prime 2, exponent 1, exponent 2, coefficient
    var options = {
        'array' : [
            new KJUR.asn1.DERInteger({'int'    : 0}),
            new KJUR.asn1.DERInteger({'bigint' : this.n}),
            new KJUR.asn1.DERInteger({'int'    : this.e}),
            new KJUR.asn1.DERInteger({'bigint' : this.d}),
            new KJUR.asn1.DERInteger({'bigint' : this.p}),
            new KJUR.asn1.DERInteger({'bigint' : this.q}),
            new KJUR.asn1.DERInteger({'bigint' : this.dmp1}),
            new KJUR.asn1.DERInteger({'bigint' : this.dmq1}),
            new KJUR.asn1.DERInteger({'bigint' : this.coeff})
        ]
    };
    var seq = new KJUR.asn1.DERSequence(options);
    return seq.getEncodedHex();
};

/**
 * base64 (pem) encoded version of the DER encoded representation
 * @returns {string} pem encoded representation without header and footer
 * @public
 */
RSAKey.prototype.getPrivateBaseKeyB64 = function (){
    return hex2b64(this.getPrivateBaseKey());
};

/**
 * Translate rsa parameters in a hex encoded string representing the rsa public key.
 * The representation follow the ASN.1 notation :
 * PublicKeyInfo ::= SEQUENCE {
 *   algorithm       AlgorithmIdentifier,
 *   PublicKey       BIT STRING
 * }
 * Where AlgorithmIdentifier is: 
 * AlgorithmIdentifier ::= SEQUENCE {
 *   algorithm       OBJECT IDENTIFIER,     the OID of the enc algorithm
 *   parameters      ANY DEFINED BY algorithm OPTIONAL (NULL for PKCS #1)
 * }
 * and PublicKey is a SEQUENCE encapsulated in a BIT STRING
 * RSAPublicKey ::= SEQUENCE {
 *   modulus           INTEGER,  -- n
 *   publicExponent    INTEGER   -- e
 * }
 * @returns {string} DER Encoded String representing the rsa public key
 * @private
 */
RSAKey.prototype.getPublicBaseKey = function() {
    var options = {
        'array' : [
            new KJUR.asn1.DERObjectIdentifier({'oid':'1.2.840.113549.1.1.1'}), //RSA Encryption pkcs #1 oid
            new KJUR.asn1.DERNull()
        ]
    };
    var first_sequence = new KJUR.asn1.DERSequence(options);
    
    options = {
        'array' : [
            new KJUR.asn1.DERInteger({'bigint' : this.n}),
            new KJUR.asn1.DERInteger({'int' : this.e})
        ]
    };
    var second_sequence = new KJUR.asn1.DERSequence(options);
    
    options = {
        'hex' : '00'+second_sequence.getEncodedHex()
    };
    var bit_string = new KJUR.asn1.DERBitString(options);
    
    options = {
        'array' : [
            first_sequence,
            bit_string
        ]
    };
    var seq = new KJUR.asn1.DERSequence(options);
    return seq.getEncodedHex();
};

/**
 * base64 (pem) encoded version of the DER encoded representation
 * @returns {string} pem encoded representation without header and footer
 * @public
 */
RSAKey.prototype.getPublicBaseKeyB64 = function (){
    return hex2b64(this.getPublicBaseKey());
};

/**
 * wrap the string in block of width chars. The default value for rsa keys is 64
 * characters.
 * @param {string} str the pem encoded string without header and footer
 * @param {Number} [width=64] - the length the string has to be wrapped at
 * @returns {string} 
 * @private
 */
RSAKey.prototype.wordwrap = function(str, width) {
    width = width || 64;
    if (!str)
        return str;
    var regex = '(.{1,' + width + '})( +|$\n?)|(.{1,' + width + '})';
    return str.match(RegExp(regex, 'g')).join('\n');
};

/**
 * Retrieve the pem encoded private key
 * @returns {string} the pem encoded private key with header/footer
 * @public
 */
RSAKey.prototype.getPrivateKey = function() {
    var key = "-----BEGIN RSA PRIVATE KEY-----\n";
    key += this.wordwrap(this.getPrivateBaseKeyB64()) + "\n";
    key += "-----END RSA PRIVATE KEY-----";
    return key;
};

/**
 * Retrieve the pem encoded public key
 * @returns {string} the pem encoded public key with header/footer
 * @public
 */
RSAKey.prototype.getPublicKey = function() {
    var key = "-----BEGIN PUBLIC KEY-----\n";
    key += this.wordwrap(this.getPublicBaseKeyB64()) + "\n";
    key += "-----END PUBLIC KEY-----";
    return key;
};

/**
 * Check if the object contains the necessary parameters to populate the rsa modulus
 * and public exponent parameters.
 * @param {Object} [obj={}] - An object that may contain the two public key
 * parameters
 * @returns {boolean} true if the object contains both the modulus and the public exponent
 * properties (n and e)
 * @todo check for types of n and e. N should be a parseable bigInt object, E should
 * be a parseable integer number
 * @private
 */
RSAKey.prototype.hasPublicKeyProperty = function(obj){
    obj = obj || {};
    return obj.hasOwnProperty('n') &&
           obj.hasOwnProperty('e');
};

/**
 * Check if the object contains ALL the parameters of an RSA key.
 * @param {Object} [obj={}] - An object that may contain nine rsa key
 * parameters
 * @returns {boolean} true if the object contains all the parameters needed
 * @todo check for types of the parameters all the parameters but the public exponent
 * should be parseable bigint objects, the public exponent should be a parseable integer number
 * @private
 */
RSAKey.prototype.hasPrivateKeyProperty = function(obj){
    obj = obj || {};
    return obj.hasOwnProperty('n') &&
           obj.hasOwnProperty('e') &&
           obj.hasOwnProperty('d') &&
           obj.hasOwnProperty('p') &&
           obj.hasOwnProperty('q') &&
           obj.hasOwnProperty('dmp1') &&
           obj.hasOwnProperty('dmq1') &&
           obj.hasOwnProperty('coeff');
};

/**
 * Parse the properties of obj in the current rsa object. Obj should AT LEAST
 * include the modulus and public exponent (n, e) parameters.
 * @param {Object} obj - the object containing rsa parameters
 * @private
 */
RSAKey.prototype.parsePropertiesFrom = function(obj){
    this.n = obj.n;
    this.e = obj.e;        
    
    if (obj.hasOwnProperty('d')){
        this.d = obj.d;
        this.p = obj.p;
        this.q = obj.q;
        this.dmp1 = obj.dmp1;
        this.dmq1 = obj.dmq1;
        this.coeff = obj.coeff;
    }
};

/**
 * Create a new JSEncryptRSAKey that extends Tom Wu's RSA key object.
 * This object is just a decorator for parsing the key parameter
 * @param {string|Object} key - The key in string format, or an object containing
 * the parameters needed to build a RSAKey object.
 * @constructor
 */
var JSEncryptRSAKey = function(key) {
    // Call the super constructor.
    RSAKey.call(this);
    // If a key key was provided.
    if (key) {
        // If this is a string...
        if (typeof key === 'string') {
            this.parseKey(key);
        }else if (this.hasPrivateKeyProperty(key)||this.hasPublicKeyProperty(key)) {
            // Set the values for the key.
            this.parsePropertiesFrom(key);
        }
    }
};

// Derive from RSAKey.
JSEncryptRSAKey.prototype = new RSAKey();

// Reset the contructor.
JSEncryptRSAKey.prototype.constructor = JSEncryptRSAKey;


/**
 * 
 * @param {Object} [options = {}] - An object to customize JSEncrypt behaviour 
 * possible parameters are:
 * - default_key_size        {number}  default: 1024 the key size in bit
 * - default_public_exponent {string}  default: '010001' the hexadecimal representation of the public exponent
 * - log                     {boolean} default: false whether log warn/error or not
 * @constructor
 */
var JSEncrypt = function(options) {
    options = options || {};
    this.default_key_size = parseInt(options.default_key_size) || 1024;
    this.default_public_exponent = options.default_public_exponent || '010001'; //65537 default openssl public exponent for rsa key type
    this.log = options.log || false; 
    // The private and public key.
    this.key = null;
};

/**
 * Method to set the rsa key parameter (one method is enough to set both the public
 * and the private key, since the private key contains the public key paramenters)
 * Log a warning if logs are enabled
 * @param {Object|string} key the pem encoded string or an object (with or without header/footer)
 * @public
 */
JSEncrypt.prototype.setKey = function(key){
    if (this.log && this.key)
        console.warn('A key was already set, overriding existing.');
    this.key = new JSEncryptRSAKey(key);
};

/**
 * Proxy method for setKey, for api compatibility
 * @see setKey
 * @public
 */
JSEncrypt.prototype.setPrivateKey = function(privkey) {
    // Create the key.
    this.setKey(privkey);
};

/**
 * Proxy method for setKey, for api compatibility
 * @see setKey
 * @public
 */
JSEncrypt.prototype.setPublicKey = function(pubkey) {
    // Sets the public key.
    this.setKey(pubkey);
};

/**
 * Proxy method for RSAKey object's decrypt, decrypt the string using the private
 * components of the rsa key object. Note that if the object was not set will be created
 * on the fly (by the getKey method) using the parameters passed in the JSEncrypt constructor
 * @param {string} string base64 encoded crypted string to decrypt
 * @return {string} the decrypted string
 * @public
 */
JSEncrypt.prototype.decrypt = function(string) {
    // Return the decrypted string.
    try{
        return this.getKey().decrypt(b64tohex(string));
    }catch(ex){
        return false;
    }
};

/**
 * Proxy method for RSAKey object's encrypt, encrypt the string using the public
 * components of the rsa key object. Note that if the object was not set will be created
 * on the fly (by the getKey method) using the parameters passed in the JSEncrypt constructor
 * @param {string} string the string to encrypt
 * @return {string} the encrypted string encoded in base64
 * @public
 */
JSEncrypt.prototype.encrypt = function(string) {
    // Return the encrypted string.
    try{
        return hex2b64(this.getKey().encrypt(string));
    }catch(ex){
        return false;
    }
};

/**
 * Getter for the current JSEncryptRSAKey object. If it doesn't exists a new object 
 * will be created and returned
 * @param {callback} [cb] the callback to be called if we want the key to be generated
 * in an async fashion
 * @returns {JSEncryptRSAKey} the JSEncryptRSAKey object
 * @public
 */
JSEncrypt.prototype.getKey = function(cb){
    // Only create new if it does not exist.
    if (!this.key) {
        // Get a new private key.
        this.key = new JSEncryptRSAKey();
        if (cb && {}.toString.call(cb) === '[object Function]'){
            this.key.generateAsync(this.default_key_size, this.default_public_exponent,cb);
            return;
        }
        // Generate the key.
        this.key.generate(this.default_key_size, this.default_public_exponent);
    }
    return this.key;
};

/**
 * Returns the pem encoded representation of the private key
 * If the key doesn't exists a new key will be created
 * @returns {string} pem encoded representation of the private key WITH header and footer
 * @public
 */
JSEncrypt.prototype.getPrivateKey = function() {
    // Return the private representation of this key.
    return this.getKey().getPrivateKey();
};

/**
 * Returns the pem encoded representation of the private key
 * If the key doesn't exists a new key will be created
 * @returns {string} pem encoded representation of the private key WITHOUT header and footer
 * @public
 */
JSEncrypt.prototype.getPrivateKeyB64 = function() {
    // Return the private representation of this key.
    return this.getKey().getPrivateBaseKeyB64();
};


/**
 * Returns the pem encoded representation of the public key
 * If the key doesn't exists a new key will be created
 * @returns {string} pem encoded representation of the public key WITH header and footer
 * @public
 */
JSEncrypt.prototype.getPublicKey = function() {
    // Return the private representation of this key.
    return this.getKey().getPublicKey();
};

/**
 * Returns the pem encoded representation of the public key
 * If the key doesn't exists a new key will be created
 * @returns {string} pem encoded representation of the public key WITHOUT header and footer
 * @public
 */
JSEncrypt.prototype.getPublicKeyB64 = function() {
    // Return the private representation of this key.
    return this.getKey().getPublicBaseKeyB64();
};