// Copyright (c) 2020 Oracle and/or its affiliates.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
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// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program 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 General Public License, version 2.0, for more details.
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// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using Microsoft.EntityFrameworkCore.Storage;
using System;
using System.Data;
using System.Data.Common;
using System.Text;

namespace MySql.Data.EntityFrameworkCore.Storage.Internal
{
  /// <summary>
  ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
  ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
  ///     any release. You should only use it directly in your code with extreme caution and knowing that
  ///     doing so can result in application failures when updating to a new Entity Framework Core release.
  /// </summary>
  internal class MySQLByteArrayTypeMapping : ByteArrayTypeMapping
  {
    private const int MaxSize = 8000;

    private readonly int _maxSpecificSize;

    /// <summary>
    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    public MySQLByteArrayTypeMapping(
        string storeType = null,
        int? size = null,
        bool fixedLength = false)
        : this(System.Data.DbType.Binary,
            storeType,
            size.HasValue && size < MaxSize ? size : null,
            fixedLength)
    {
    }

    /// <summary>
    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    protected MySQLByteArrayTypeMapping(
        DbType type,
        string storeType,
        int? size,
        bool fixedLength)
        : this(
            new RelationalTypeMappingParameters(
                new CoreTypeMappingParameters(typeof(byte[])),
                storeType ?? GetBaseType(size, fixedLength),
                GetStoreTypePostfix(size),
                type,
                size: size,
                fixedLength: fixedLength))
    {
    }

    private static string GetBaseType(int? size, bool isFixedLength)
        => size == null
            ? "longblob"
            : isFixedLength ? "binary" : "varbinary";

    private static StoreTypePostfix GetStoreTypePostfix(int? size)
        => size != null && size <= MaxSize ? StoreTypePostfix.Size : StoreTypePostfix.None;

    /// <summary>
    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    protected MySQLByteArrayTypeMapping(RelationalTypeMappingParameters parameters)
        : base(parameters)
    {
      _maxSpecificSize = CalculateSize(parameters.Size);
    }

    /// <summary>
    ///     Creates a copy of this mapping.
    /// </summary>
    /// <param name="parameters"> The parameters for this mapping. </param>
    /// <returns> The newly created mapping. </returns>
    protected override RelationalTypeMapping Clone(RelationalTypeMappingParameters parameters)
        => new MySQLByteArrayTypeMapping(parameters);

    private static int CalculateSize(int? size)
        => size.HasValue && size < MaxSize ? size.Value : MaxSize;

    /// <summary>
    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
    ///     directly from your code. This API may change or be removed in future releases.
    /// </summary>
    protected override void ConfigureParameter(DbParameter parameter)
    {
      // For strings and byte arrays, set the max length to the size facet if specified, or
      // 8000 bytes if no size facet specified, if the data will fit so as to avoid query cache
      // fragmentation by setting lots of different Size values otherwise always set to
      // -1 (unbounded) to avoid SQL client size inference.

      var value = parameter.Value;
      var length = (value as string)?.Length ?? (value as byte[])?.Length;

      parameter.Size = value == null || value == DBNull.Value || length != null && length <= _maxSpecificSize
          ? _maxSpecificSize
          : -1;
    }

    /// <summary>
    ///     Generates the SQL representation of a literal value.
    /// </summary>
    /// <param name="value">The literal value.</param>
    /// <returns>
    ///     The generated string.
    /// </returns>
    protected override string GenerateNonNullSqlLiteral(object value) => ToHex((byte[])value);

    private static readonly char[] _lookup = new char[16]
        {
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
        };

    private string ToHex([NotNull] byte[] b)
    {
      if (b.Length == 0)
      {
        return "X''";
      }

      var builder = new StringBuilder("0x", 2 + (b.Length * 2));
      for (var i = 0; i < b.Length; i++)
      {
        var b1 = (byte)(b[i] >> 4);
        var b2 = (byte)(b[i] & 0xF);
        builder.Append(_lookup[b1]);
        builder.Append(_lookup[b2]);
      }
      return builder.ToString();
    }
  }
}