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

namespace OpenSearch.Client
{
	/// <summary>
	/// An aggregation on the request
	/// </summary>
	[InterfaceDataContract]
	public interface IAggregation
	{
		/// <summary>
		/// metadata to associate with the individual aggregation at request time that
		/// will be returned in place at response time
		/// </summary>
		IDictionary<string, object> Meta { get; set; }

		/// <summary>
		/// name of the aggregation
		/// </summary>
		string Name { get; set; }
	}

	/// <inheritdoc />
	public abstract class AggregationBase : IAggregation
	{
		internal AggregationBase() { }

		protected AggregationBase(string name) => ((IAggregation)this).Name = name;

		/// <inheritdoc />
		public IDictionary<string, object> Meta { get; set; }

		/// <inheritdoc />
		string IAggregation.Name { get; set; }

		internal abstract void WrapInContainer(AggregationContainer container);

		//always evaluate to false so that each side of && equation is evaluated
		public static bool operator false(AggregationBase a) => false;

		//always evaluate to false so that each side of && equation is evaluated
		public static bool operator true(AggregationBase a) => false;

		public static AggregationBase operator &(AggregationBase left, AggregationBase right) =>
			new AggregationCombinator(null, left, right);
	}

	/// <summary>
	/// Combines aggregations into a single list of aggregations
	/// </summary>
	internal class AggregationCombinator : AggregationBase, IAggregation
	{
		public AggregationCombinator(string name, AggregationBase left, AggregationBase right) : base(name)
		{
			AddAggregation(left);
			AddAggregation(right);
		}

		internal List<AggregationBase> Aggregations { get; } = new List<AggregationBase>();

		internal override void WrapInContainer(AggregationContainer container) { }

		private void AddAggregation(AggregationBase agg)
		{
			switch (agg)
			{
				case null:
					return;
				case AggregationCombinator combinator when combinator.Aggregations.Any():
					Aggregations.AddRange(combinator.Aggregations);
					break;
				default:
					Aggregations.Add(agg);
					break;
			}
		}
	}
}