/* SPDX-License-Identifier: Apache-2.0
*
* The OpenSearch Contributors require contributions made to
* this file be licensed under the Apache-2.0 license or a
* compatible open source license.
*/
/*
* Modifications Copyright OpenSearch Contributors. See
* GitHub history for details.
*
*  Licensed to Elasticsearch B.V. under one or more contributor
*  license agreements. See the NOTICE file distributed with
*  this work for additional information regarding copyright
*  ownership. Elasticsearch B.V. 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.
*/

using System;
using OpenSearch.Net.Utf8Json;

namespace OpenSearch.Client
{
	internal class UnionFormatter<TFirst, TSecond> : IJsonFormatter<Union<TFirst, TSecond>>
	{
		private readonly bool _attemptTSecondIfTFirstIsNull;

		public UnionFormatter() => _attemptTSecondIfTFirstIsNull = false;

		public UnionFormatter(bool attemptTSecondIfTFirstIsNull) => _attemptTSecondIfTFirstIsNull = attemptTSecondIfTFirstIsNull;

		public Union<TFirst, TSecond> Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
		{
			var segment = reader.ReadNextBlockSegment();
			if (TryRead(ref segment, formatterResolver, out TFirst first))
			{
				if (first == null && _attemptTSecondIfTFirstIsNull)
				{
					if (TryRead(ref segment, formatterResolver, out TSecond second))
						return second;
				}
				else
				{
					return first;
				}
			}
			else if (TryRead(ref segment, formatterResolver, out TSecond second))
				return second;

			return null;
		}

		public void Serialize(ref JsonWriter writer, Union<TFirst, TSecond> value, IJsonFormatterResolver formatterResolver)
		{
			if (value == null)
			{
				writer.WriteNull();
				return;
			}

			switch (value.Tag)
			{
				case 0:
				{
					var formatter = formatterResolver.GetFormatter<TFirst>();
					formatter.Serialize(ref writer, value.Item1, formatterResolver);
					break;
				}
				case 1:
				{
					var formatter = formatterResolver.GetFormatter<TSecond>();
					formatter.Serialize(ref writer, value.Item2, formatterResolver);
					break;
				}
				default:
					throw new Exception($"Unrecognized tag value: {value.Tag}");
			}
		}

		public bool TryRead<T>(ref ArraySegment<byte> segment, IJsonFormatterResolver formatterResolver, out T v)
		{
			var segmentReader = new JsonReader(segment.Array, segment.Offset);
			try
			{
				var formatter = formatterResolver.GetFormatter<T>();
				v = formatter.Deserialize(ref segmentReader, formatterResolver);
				return true;
			}
			catch
			{
				v = default;
				return false;
			}
		}
	}
}