/* 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.Globalization;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace OpenSearch.Client
{
	/// <summary>
	/// Provides convenience extension methods to get many _source's given a list of ids.
	/// </summary>
	public static class SourceManyExtensions
	{

		private static Func<MultiGetOperationDescriptor<T>, string, IMultiGetOperation> Lookup<T>(IndexName index)
			where T : class
		{
			if (index == null) return null;

			return (d, id) => d.Index(index);
		}

		/// <summary>
		/// SourceMany allows you to get a list of T documents out of OpenSearch, internally it calls into MultiGet()
		/// <para>
		/// Multi GET API allows to get multiple documents based on an index, type (optional) and id (and possibly routing).
		/// The response includes a docs array with all the fetched documents, each element similar in structure to a document
		/// provided by the get API.
		/// </para>
		/// <para> </para>
		/// https://opensearch.org/docs/latest/opensearch/rest-api/document-apis/multi-get/
		/// </summary>
		/// <typeparam name="T">The type used to infer the default index and typename</typeparam>
		/// <param name="client"></param>
		/// <param name="ids">A list of ids as string</param>
		/// <param name="index">Optionally override the default inferred indexname for T</param>
		public static IEnumerable<T> SourceMany<T>(this IOpenSearchClient client, IEnumerable<string> ids, string index = null)
			where T : class
		{
			var result = client.MultiGet(s => s
				.Index(index)
				.RequestConfiguration(r => r.ThrowExceptions())
				.GetMany<T>(ids, Lookup<T>(index))
			);
			return result.SourceMany<T>(ids);
		}

		/// <summary>
		/// SourceMany allows you to get a list of T documents out of OpenSearch, internally it calls into MultiGet()
		/// <para>
		/// Multi GET API allows to get multiple documents based on an index, type (optional) and id (and possibly routing).
		/// The response includes a docs array with all the fetched documents, each element similar in structure to a document
		/// provided by the get API.
		/// </para>
		/// <para> </para>
		/// https://opensearch.org/docs/latest/opensearch/rest-api/document-apis/multi-get/
		/// </summary>
		/// <typeparam name="T">The type used to infer the default index and typename</typeparam>
		/// <param name="client"></param>
		/// <param name="ids">A list of ids as int</param>
		/// <param name="index">Optionally override the default inferred indexname for T</param>
		public static IEnumerable<T> SourceMany<T>(this IOpenSearchClient client, IEnumerable<long> ids, string index = null)
			where T : class => client.SourceMany<T>(ids.Select(i => i.ToString(CultureInfo.InvariantCulture)), index);

		/// <summary>
		/// SourceMany allows you to get a list of T documents out of OpenSearch, internally it calls into MultiGet()
		/// <para>
		/// Multi GET API allows to get multiple documents based on an index, type (optional) and id (and possibly routing).
		/// The response includes a docs array with all the fetched documents, each element similar in structure to a document
		/// provided by the get API.
		/// </para>
		/// <para> </para>
		/// https://opensearch.org/docs/latest/opensearch/rest-api/document-apis/multi-get/
		/// </summary>
		/// <typeparam name="T">The type used to infer the default index and typename</typeparam>
		/// <param name="client"></param>
		/// <param name="ids">A list of ids as string</param>
		/// <param name="index">Optionally override the default inferred indexname for T</param>
		public static async Task<IEnumerable<T>> SourceManyAsync<T>(
			this IOpenSearchClient client, IEnumerable<string> ids, string index = null, CancellationToken cancellationToken = default
		)
			where T : class
		{
			var response = await client.MultiGetAsync(s => s
					.Index(index)
					.RequestConfiguration(r => r.ThrowExceptions())
					.GetMany<T>(ids, Lookup<T>(index)), cancellationToken)
				.ConfigureAwait(false);
			return response.SourceMany<T>(ids);
		}

		/// <summary>
		/// SourceMany allows you to get a list of T documents out of OpenSearch, internally it calls into MultiGet()
		/// <para>
		/// Multi GET API allows to get multiple documents based on an index, type (optional) and id (and possibly routing).
		/// The response includes a docs array with all the fetched documents, each element similar in structure to a document
		/// provided by the get API.
		/// </para>
		/// <para> </para>
		/// https://opensearch.org/docs/latest/opensearch/rest-api/document-apis/multi-get/
		/// </summary>
		/// <typeparam name="T">The type used to infer the default index and typename</typeparam>
		/// <param name="client"></param>
		/// <param name="ids">A list of ids as int</param>
		/// <param name="index">Optionally override the default inferred indexname for T</param>
		public static Task<IEnumerable<T>> SourceManyAsync<T>(
			this IOpenSearchClient client, IEnumerable<long> ids, string index = null,
			CancellationToken cancellationToken = default
		)
			where T : class => client.SourceManyAsync<T>(ids.Select(i => i.ToString(CultureInfo.InvariantCulture)), index, cancellationToken);
	}
}