/*
 *  Copyright (c) 2016 Samsung Electronics Co., Ltd All Rights Reserved
 *
 *  Licensed 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
 */

using System;

namespace Tizen.Security.SecureRepository.Crypto
{
    /// <summary>
    /// This class provides the methods encrypting and decrypting data.
    /// </summary>
    /// <since_tizen> 3 </since_tizen>
    public class Cipher
    {
        private readonly CipherParameters _parameters;

        /// <summary>
        /// A constructor of Cipher that takes the algorithm specific parameters.
        /// </summary>
        /// <since_tizen> 3 </since_tizen>
        /// <param name="parameters">The algorithm specific parameters.</param>
        public Cipher(CipherParameters parameters)
        {
            _parameters = parameters;
        }

        /// <summary>
        /// The algorithm specific parameters.
        /// </summary>
        /// <since_tizen> 3 </since_tizen>
        public CipherParameters Parameters
        {
            get { return _parameters; }
        }

        /// <summary>
        /// Decrypts data using selected key and algorithm.
        /// </summary>
        /// <since_tizen> 3 </since_tizen>
        /// <param name="keyAlias">Alias of the key to be used for decryption.</param>
        /// <param name="password">
        /// The password used in decrypting a key value. If password of policy is
        /// provided in SaveKey(), the same password should be provided
        /// </param>
        /// <param name="cipherText">
        /// Data to be decrypted (some algorithms may require additional information
        /// embedded in encrypted data.AES GCM is an example).
        /// </param>
        /// <returns>Decrypted data.</returns>
        /// <exception cref="ArgumentNullException">
        /// keyAlias or cipherText is null.
        /// </exception>
        /// <exception cref="ArgumentException">
        /// Mandatory algorithm parameter is missing or invalid.
        /// Optional algorithm parameter is invalid.
        /// </exception>
        /// <exception cref="InvalidOperationException">
        /// Key-protecting password isn't matched.
        /// Key does not exist with keyAlias.
        /// </exception>
        /// <remarks>
        /// The key type specified by keyAlias should be compatible with the algorithm
        /// specified in Parameters.
        /// </remarks>
        public byte[] Decrypt(string keyAlias, string password, byte[] cipherText)
        {
            if (keyAlias == null || cipherText == null)
                throw new ArgumentNullException("alias and ciphertxt should not be null");

            IntPtr ptr = IntPtr.Zero;

            try
            {
                Interop.CheckNThrowException(
                    Interop.CkmcManager.DecryptData(
                        Parameters.Ptr, keyAlias, password,
                        new Interop.CkmcRawBuffer(
                            new PinnedObject(cipherText), cipherText.Length),
                        out ptr),
                    "Failed to decrypt data");
                return new SafeRawBufferHandle(ptr).Data;
            }
            finally
            {
                if (ptr != IntPtr.Zero)
                    Interop.CkmcTypes.BufferFree(ptr);
            }
        }

        /// <summary>
        /// Encrypts data using selected key and algorithm.
        /// </summary>
        /// <since_tizen> 3 </since_tizen>
        /// <param name="keyAlias">Alias of the key to be used for encryption.</param>
        /// <param name="password">
        /// The password used in decrypting a key value. If password of policy is
        /// provided in SaveKey(), the same password should be provided.
        /// </param>
        /// <param name="plainText">
        /// Data to be encrypted. In case of AES algorithm there are no restrictions on
        /// the size of data. For RSA the size must be smaller or equal to (key_size_in
        /// bytes - 42). Example: for 1024 RSA key the maximum data size is
        /// 1024/8 - 42 = 86.
        /// </param>
        /// <returns>Encrypted data.</returns>
        /// <exception cref="ArgumentNullException">
        /// keyAlias or plainText is null.
        /// </exception>
        /// <exception cref="ArgumentException">
        /// Mandatory algorithm parameter is missing or invalid.
        /// Optional algorithm parameter is invalid.
        /// </exception>
        /// <exception cref="InvalidOperationException">
        /// Key-protecting password isn't matched.
        /// Key does not exist with keyAlias.
        /// </exception>
        /// <remarks>
        /// The key type specified by keyAlias should be compatible with the algorithm
        /// specified in Parameters.
        /// </remarks>
        public byte[] Encrypt(string keyAlias, string password, byte[] plainText)
        {
            if (keyAlias == null || plainText == null)
                throw new ArgumentNullException("alias or plaintxt should not be null");

            IntPtr ptr = IntPtr.Zero;

            try
            {
                Interop.CheckNThrowException(
                    Interop.CkmcManager.EncryptData(
                        Parameters.Ptr, keyAlias, password,
                        new Interop.CkmcRawBuffer(
                            new PinnedObject(plainText), plainText.Length),
                        out ptr),
                    "Failed to encrypt data");
                return new SafeRawBufferHandle(ptr).Data;
            }
            finally
            {
                if (ptr != IntPtr.Zero)
                    Interop.CkmcTypes.BufferFree(ptr);
            }
        }
    }
}