/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*
 * XSEC
 *
 * XSECCryptoProvider := Base virtual class to define a hash algorithm
 *
 * Author(s): Berin Lautenbach
 *
 * $Id$
 *
 */

#ifndef XSECCRYPTOHASH_INCLUDE
#define XSECCRYPTOHASH_INCLUDE

#include <xsec/framework/XSECDefs.hpp>

#define XSEC_MAX_HASH_SIZE         256        /* Max size of any expected hash algorithms (oversized) */
#define XSEC_MAX_HASH_BLOCK_SIZE    64        /* Max size of blocks used - MD5 and SHA1 are both 64 bytes*/

// Forward definitions
class XSECCryptoKey;

/**
 * @ingroup crypto
 */

/**
 * \brief Interface definition for Hash functions.
 *
 * The XSECCryptoHash function is used by the library to manipulate
 * Hashing (Digest) functions.
 *
 * It is also used as the base class for HMAC functions, and thus has
 * a #setKey() method.
 *
 * @todo bring the interface here in-line with that provided for
 * XSECCryptoBase64 - really should have only one way of calling these
 * kinds of objects.
 *
 */

class XSEC_EXPORT XSECCryptoHash {


public :

    /**
     * \brief Enumeration of Hash (Digest) types
     *
     * The hash types known to XSEC
     */

    enum HashType {
        HASH_NONE              = 0,
        HASH_SHA1              = 1,
        HASH_MD5               = 2,
        HASH_SHA224            = 3,
        HASH_SHA256            = 4,
        HASH_SHA384            = 5,
        HASH_SHA512            = 6
    };

    // Constructors/Destructors

    XSECCryptoHash() {}
    virtual ~XSECCryptoHash() {}

    /** @name Digest/Hash functions */
    //@{

    /**
     * \brief Rest the hash function
     *
     * XSEC will call the #reset() function prior to re-using a CryptoHash
     * object.
     */

    virtual void reset() = 0;                    // Reset the hash

    /**
     * \brief Hash some data.
     *
     * Take length bytes of data from the data buffer and update the hash
     * that already exists.  This function may (and normally will) be called
     * many times for large blocks of data.
     *
     * @param data The buffer containing the data to be hashed.
     * @param length The number of bytes to be read from data
     */

    virtual void hash(unsigned char* data,
                             unsigned int length) = 0;

    /**
     * \brief Finish up a Digest operation and read the result.
     *
     * This call tells the CryptoHash object that the input is complete and
     * to finalise the Digest.  The output of the digest is read into the
     * hash buffer (at most maxLength bytes)
     *
     * @param hash The buffer the hash should be read into.
     * @param maxLength The maximum number of bytes to be read into hash
     * @returns The number of bytes copied into the hash buffer
     */

    virtual unsigned int finish(unsigned char* hash,
                                unsigned int maxLength) = 0;// Finish and get hash

    //@}

    /** @name Information functions */
    //@{

    /**
     *\brief
     *
     * Determine the hash type of this object
     *
     * @returns The hash type
     */

    virtual HashType getHashType() const = 0;

    //@}

    /** @name HMAC Functions */
    //@{

    /**
     *\brief
     *
     * The HMAC classes are treated in the library as standard hash
     * objects that just happen to take a key.  Thus all hash functions
     * implement this function (potentially just to throw an exception)
     *
     * Sets the key - which needs to have a base class of
     * XSECCryptoKeyHMAC.
     *
     * @param key The key the HMAC function should use.
     */

    virtual void setKey(const XSECCryptoKey* key) = 0;

    //@}

};

#endif /* XSECCRYPTOHASH_INCLUDE */