/* 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 System.Collections.Generic;
using System.Linq;
using OpenSearch.Net.Utf8Json;

namespace OpenSearch.Client
{
	internal class MultiGetRequestFormatter : IJsonFormatter<IMultiGetRequest>
	{
		private static readonly IdFormatter IdFormatter = new IdFormatter();

		public IMultiGetRequest Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver) =>
			throw new NotSupportedException();

		public void Serialize(ref JsonWriter writer, IMultiGetRequest value, IJsonFormatterResolver formatterResolver)
		{
			writer.WriteBeginObject();
			if (!(value?.Documents.HasAny()).GetValueOrDefault(false))
			{
				writer.WriteEndObject();
				return;
			}

			List<IMultiGetOperation> docs;

			// if an index is specified at the request level and all documents have the same index, remove the index
			if (value.Index != null)
			{
				var settings = formatterResolver.GetConnectionSettings();
				var resolvedIndex = value.Index.GetString(settings);
				docs = value.Documents.Select(d =>
					{
						if (d.Index == null)
							return d;

						// TODO: not nice to resolve index for each doc here for comparison, only for it to be resolved later in serialization.
						// Might be better to simply remove the flattening logic.
						var docIndex = d.Index.GetString(settings);
						if (string.Equals(resolvedIndex, docIndex)) d.Index = null;
						return d;
					})
					.ToList();
			}
			else
				docs = value.Documents.ToList();

			var flatten = docs.All(p => p.CanBeFlattened);

			writer.WritePropertyName(flatten ? "ids" : "docs");

			IJsonFormatter<IMultiGetOperation> formatter = null;
			if (!flatten)
				formatter = formatterResolver.GetFormatter<IMultiGetOperation>();

			writer.WriteBeginArray();
			for (var index = 0; index < docs.Count; index++)
			{
				if (index > 0)
					writer.WriteValueSeparator();

				var doc = docs[index];
				if (flatten)
					IdFormatter.Serialize(ref writer, doc.Id, formatterResolver);
				else
					formatter.Serialize(ref writer, doc, formatterResolver);
			}
			writer.WriteEndArray();
			writer.WriteEndObject();
		}
	}
}