/* 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.Diagnostics;

namespace OpenSearch.Net.Diagnostics
{
	/// <summary>
	/// Diagnostic that creates, starts and stops <see cref="Activity"/> that implements <see cref="IDisposable"/> to
	/// make it easier to use.
	/// </summary>
	internal class Diagnostic<TState> : Diagnostic<TState, TState>
	{
		public Diagnostic(string operationName, DiagnosticSource source, TState state)
			: base(operationName, source, state) =>
			EndState = state;
	}

	internal class Diagnostic<TState, TStateEnd> : IDisposable
	{
		public static Diagnostic<TState, TStateEnd> Default { get; } = new();

		private readonly DiagnosticSource _source;
		private readonly bool _default;
		private readonly Activity _activity;
		private TStateEnd _endState;

		private Diagnostic() => _default = true;

		public Diagnostic(string operationName, DiagnosticSource source, TState state)
		{
			_source = source;
			_activity = new Activity(operationName);
			_source.StartActivity(_activity, state);
		}

		public TStateEnd EndState
		{
			get => _endState;
			internal set
			{
				//do not store state on default instance
				if (_default) return;
				_endState =  value;
			}
		}

		public void Dispose()
		{
			_source?.StopActivity(_activity, EndState);
			_activity?.Dispose();
		}
	}
}