//******************************************************************************************************
//  DataReceiver.cs - Gbtc
//
//  Copyright © 2019, Grid Protection Alliance.  All Rights Reserved.
//
//  Licensed to the Grid Protection Alliance (GPA) under one or more contributor license agreements. See
//  the NOTICE file distributed with this work for additional information regarding copyright ownership.
//  The GPA licenses this file to you under the MIT License (MIT), the "License"; you may not use this
//  file except in compliance with the License. You may obtain a copy of the License at:
//
//      http://opensource.org/licenses/MIT
//
//  Unless agreed to in writing, the subject software distributed under the License is distributed on an
//  "AS-IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. Refer to the
//  License for the specific language governing permissions and limitations.
//
//  Code Modification History:
//  ----------------------------------------------------------------------------------------------------
//  02/11/2019 - J. Ritchie Carroll
//       Generated original version of source code.
//
//******************************************************************************************************

using GSF;
using GSF.TimeSeries;
using GSF.TimeSeries.Transport;
using System;
using System.Collections.Generic;

namespace DataExtractor
{
    /// <summary>
    /// Retrieves data from openHistorian using GEP
    /// </summary>
    internal sealed class DataReceiver : IDisposable
    {
        #region [ Members ]

        // Fields
        private DataSubscriber m_subscriber;
        private readonly UnsynchronizedSubscriptionInfo m_subscriptionInfo;
        private bool m_disposed;

        #endregion

        #region [ Constructors ]

        /// <summary>
        /// Creates a new <see cref="DataReceiver"/> instance with the specified <paramref name="connectionString"/>.
        /// </summary>
        /// <param name="connectionString">GEP connection string for openHistorian.</param>
        /// <param name="filterExpression">Filter expression defining measurements to query.</param>
        /// <param name="startTime">Temporal subscription start time.</param>
        /// <param name="stopTime">Temporal subscription stop time.</param>
        public DataReceiver(string connectionString, string filterExpression, DateTime startTime, DateTime stopTime)
        {
            m_subscriber = new DataSubscriber
            {
                ConnectionString = connectionString,
                OperationalModes = OperationalModes.UseCommonSerializationFormat | OperationalModes.CompressPayloadData,
                CompressionModes = CompressionModes.TSSC
            };

            m_subscriptionInfo = new UnsynchronizedSubscriptionInfo(false)
            {
                FilterExpression = filterExpression,
                StartTime = startTime.ToString(TimeTagBase.DefaultFormat),
                StopTime = stopTime.ToString(TimeTagBase.DefaultFormat),
                ProcessingInterval = 0, // Zero value requests data as fast as possible
                UseMillisecondResolution = true
            };

            // Attach to needed subscriber events
            m_subscriber.ConnectionEstablished += m_subscriber_ConnectionEstablished;
            m_subscriber.NewMeasurements += m_subscriber_NewMeasurements;
            m_subscriber.StatusMessage += m_subscriber_StatusMessage;
            m_subscriber.ProcessException += m_subscriber_ProcessException;
            m_subscriber.ProcessingComplete += m_subscriber_ProcessingComplete;

            // Initialize the subscriber
            m_subscriber.Initialize();

            // Start subscriber connection cycle
            m_subscriber.Start();
        }

        /// <summary>
        /// Releases the unmanaged resources before the <see cref="DataReceiver"/> object is reclaimed by <see cref="GC"/>.
        /// </summary>
        ~DataReceiver() => Dispose(false);

        public Action<ICollection<IMeasurement>> NewMeasurementsCallback { get; set; }

        public Action<string> StatusMessageCallback { get; set; }

        public Action<Exception> ProcessExceptionCallback { get; set; }

        public Action ReadCompletedCallback { get; set; }

        #endregion

        #region [ Methods ]

        /// <summary>
        /// Releases all the resources used by the <see cref="DataReceiver"/> object.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases the unmanaged resources used by the <see cref="DataReceiver"/> object and optionally releases the managed resources.
        /// </summary>
        /// <param name="disposing">true to release both managed and unmanaged resources; false to release only unmanaged resources.</param>
        private void Dispose(bool disposing)
        {
            if (!m_disposed)
            {
                try
                {
                    if (disposing)
                    {
                        if ((object)m_subscriber != null)
                        {
                            m_subscriber.Unsubscribe();
                            m_subscriber.Stop();

                            // Detach from subscriber events
                            m_subscriber.ConnectionEstablished -= m_subscriber_ConnectionEstablished;
                            m_subscriber.NewMeasurements -= m_subscriber_NewMeasurements;
                            m_subscriber.StatusMessage -= m_subscriber_StatusMessage;
                            m_subscriber.ProcessException -= m_subscriber_ProcessException;
                            m_subscriber.ProcessingComplete -= m_subscriber_ProcessingComplete;

                            m_subscriber.Dispose();
                            m_subscriber = null;
                        }
                    }
                }
                finally
                {
                    m_disposed = true;  // Prevent duplicate dispose.
                }
            }
        }

        private void m_subscriber_ConnectionEstablished(object sender, EventArgs e) => m_subscriber.UnsynchronizedSubscribe(m_subscriptionInfo);

        private void m_subscriber_NewMeasurements(object sender, EventArgs<ICollection<IMeasurement>> e) => NewMeasurementsCallback?.Invoke(e.Argument);

        private void m_subscriber_StatusMessage(object sender, EventArgs<string> e) => StatusMessageCallback?.Invoke(e.Argument);

        private void m_subscriber_ProcessException(object sender, EventArgs<Exception> e) => ProcessExceptionCallback?.Invoke(e.Argument);

        private void m_subscriber_ProcessingComplete(object sender, EventArgs<string> e) => ReadCompletedCallback?.Invoke();

        #endregion
    }
}