/*
 * MinIO .NET Library for Amazon S3 Compatible Cloud Storage, (C) 2019 MinIO, Inc.
 *
 * 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.Text;
using Minio.Helper;

namespace Minio.DataModel.Encryption;

/// <summary>
///     Server-side encryption with AWS KMS managed keys
/// </summary>
public class SSEKMS : IServerSideEncryption
{
    public SSEKMS(string key, IDictionary<string, string> context = null)
    {
        if (string.IsNullOrEmpty(key))
            throw new ArgumentException("KMS Key cannot be empty", nameof(key));
        Key = key;
        Context = context;
    }

    protected IDictionary<string, string> Context { get; set; }

    // Specifies the customer master key(CMK).Cannot be null
    protected string Key { get; set; }

    public EncryptionType GetEncryptionType()
    {
        return EncryptionType.SSE_KMS;
    }

    public void Marshal(IDictionary<string, string> headers)
    {
        if (headers is null) throw new ArgumentNullException(nameof(headers));

        headers.Add(Constants.SSEKMSKeyId, Key);
        headers.Add(Constants.SSEGenericHeader, "aws:kms");
        if (Context is not null) headers.Add(Constants.SSEKMSContext, MarshalContext());
    }

    /// <summary>
    ///     Serialize context into JSON string.
    /// </summary>
    /// <returns>Serialized JSON context</returns>
    private string MarshalContext()
    {
        var sb = new StringBuilder();

        sb.Append('{');
        var i = 0;
        var len = Context.Count;
        foreach (var pair in Context)
        {
            sb.Append('"').Append(pair.Key).Append('"');
            sb.Append(':');
            sb.Append('"').Append(pair.Value).Append('"');
            i++;
            if (i != len) sb.Append(':');
        }

        sb.Append('}');
        ReadOnlySpan<byte> contextBytes = Encoding.UTF8.GetBytes(sb.ToString());
#if NETSTANDARD
        return Convert.ToBase64String(contextBytes.ToArray());
#else
        return Convert.ToBase64String(contextBytes);
#endif
    }
}