// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename       : SHA512Context.cs
// Author(s)      : Natalia Portillo <claunia@claunia.com>
//
// Component      : Checksums.
//
// --[ Description ] ----------------------------------------------------------
//
//     Wraps up .NET SHA512 implementation to a Init(), Update(), Final() context.
//
// --[ License ] --------------------------------------------------------------
//
//     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, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2023 Natalia Portillo
// ****************************************************************************/

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using Aaru.CommonTypes.Interfaces;

namespace Aaru.Checksums
{
    /// <inheritdoc />
    /// <summary>Wraps up .NET SHA512 implementation to a Init(), Update(), Final() context.</summary>
    public sealed class Sha512Context : IChecksum
    {
        readonly SHA512 _provider;

        /// <summary>Initializes the SHA512 hash provider</summary>
        public Sha512Context() => _provider = SHA512.Create();

        /// <inheritdoc />
        /// <summary>Updates the hash with data.</summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="len">Length of buffer to hash.</param>
        public void Update(byte[] data, uint len) => _provider.TransformBlock(data, 0, (int)len, data, 0);

        /// <inheritdoc />
        /// <summary>Updates the hash with data.</summary>
        /// <param name="data">Data buffer.</param>
        public void Update(byte[] data) => Update(data, (uint)data.Length);

        /// <inheritdoc />
        /// <summary>Returns a byte array of the hash value.</summary>
        public byte[] Final()
        {
            _provider.TransformFinalBlock(Array.Empty<byte>(), 0, 0);

            return _provider.Hash;
        }

        /// <inheritdoc />
        /// <summary>Returns a hexadecimal representation of the hash value.</summary>
        public string End()
        {
            _provider.TransformFinalBlock(Array.Empty<byte>(), 0, 0);
            var sha512Output = new StringBuilder();

            foreach(byte h in _provider.Hash)
                sha512Output.Append(h.ToString("x2"));

            return sha512Output.ToString();
        }

        /// <summary>Gets the hash of a file</summary>
        /// <param name="filename">File path.</param>
        public static byte[] File(string filename)
        {
            var    localSha512Provider = SHA512.Create();
            var    fileStream          = new FileStream(filename, FileMode.Open);
            byte[] result              = localSha512Provider.ComputeHash(fileStream);
            fileStream.Close();

            return result;
        }

        /// <summary>Gets the hash of a file in hexadecimal and as a byte array.</summary>
        /// <param name="filename">File path.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string File(string filename, out byte[] hash)
        {
            var localSha512Provider = SHA512.Create();
            var fileStream          = new FileStream(filename, FileMode.Open);
            hash = localSha512Provider.ComputeHash(fileStream);
            var sha512Output = new StringBuilder();

            foreach(byte h in hash)
                sha512Output.Append(h.ToString("x2"));

            fileStream.Close();

            return sha512Output.ToString();
        }

        /// <summary>Gets the hash of the specified data buffer.</summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="len">Length of the data buffer to hash.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string Data(byte[] data, uint len, out byte[] hash)
        {
            var localSha512Provider = SHA512.Create();
            hash = localSha512Provider.ComputeHash(data, 0, (int)len);
            var sha512Output = new StringBuilder();

            foreach(byte h in hash)
                sha512Output.Append(h.ToString("x2"));

            return sha512Output.ToString();
        }

        /// <summary>Gets the hash of the specified data buffer.</summary>
        /// <param name="data">Data buffer.</param>
        /// <param name="hash">Byte array of the hash value.</param>
        public static string Data(byte[] data, out byte[] hash) => Data(data, (uint)data.Length, out hash);
    }
}