/* 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;

namespace OpenSearch.Net.VirtualizedCluster.Rules
{
	/// <summary>
	/// Represents the union of two types, <typeparamref name="TFirst" /> and <typeparamref name="TSecond" />.
	/// Used to represent a rule with multiple return states
	/// </summary>
	/// <typeparam name="TFirst">The first type</typeparam>
	/// <typeparam name="TSecond">The second type</typeparam>
	public class RuleOption<TFirst, TSecond>
	{
		internal readonly int Tag;
		internal readonly TFirst Item1;
		internal readonly TSecond Item2;

		/// <summary>
		/// Creates an new instance of <see cref="RuleOption{TFirst,TSecond}" /> that encapsulates <paramref name="item" /> value
		/// </summary>
		/// <param name="item">The value to encapsulate</param>
		public RuleOption(TFirst item)
		{
			Item1 = item;
			Tag = 0;
		}

		/// <summary>
		/// Creates an new instance of <see cref="RuleOption{TFirst,TSecond}" /> that encapsulates <paramref name="item" /> value
		/// </summary>
		/// <param name="item">The value to encapsulate</param>
		public RuleOption(TSecond item)
		{
			Item2 = item;
			Tag = 1;
		}

		/// <summary>
		/// Runs an <see cref="Action{T}" /> delegate against the encapsulated value
		/// </summary>
		/// <param name="first">The delegate to run when this instance encapsulates an instance of <typeparamref name="TFirst" /></param>
		/// <param name="second">The delegate to run when this instance encapsulates an instance of <typeparamref name="TSecond" /></param>
		public void Match(Action<TFirst> first, Action<TSecond> second)
		{
			switch (Tag)
			{
				case 0:
					first(Item1);
					break;
				case 1:
					second(Item2);
					break;
				default: throw new Exception($"Unrecognized tag value: {Tag}");
			}
		}

		/// <summary>
		/// Runs a <see cref="Func{T,TResult}" /> delegate against the encapsulated value
		/// </summary>
		/// <param name="first">The delegate to run when this instance encapsulates an instance of <typeparamref name="TFirst" /></param>
		/// <param name="second">The delegate to run when this instance encapsulates an instance of <typeparamref name="TSecond" /></param>
		public T Match<T>(Func<TFirst, T> first, Func<TSecond, T> second)
		{
			switch (Tag)
			{
				case 0: return first(Item1);
				case 1: return second(Item2);
				default: throw new Exception($"Unrecognized tag value: {Tag}");
			}
		}

		public static implicit operator RuleOption<TFirst, TSecond>(TFirst first) => new RuleOption<TFirst, TSecond>(first);

		public static implicit operator RuleOption<TFirst, TSecond>(TSecond second) => new RuleOption<TFirst, TSecond>(second);
	}
}