sandbox/plc4net/api/PlcDriverManager.cs

/*
Licensed to the Apache Software Foundation (ASF) under one
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distributed with this work for additional information
regarding copyright ownership.  The ASF 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
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*/

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using org.apache.plc4net.api;
using org.apache.plc4net.api.authentication;
using org.apache.plc4net.exceptions;

namespace org.apache.plc4net
{
    /// <summary>
    /// Manages connections to PLCs
    /// </summary>
    public class PlcDriverManager
    {
        /// <summary>
        /// Singleton instance of the manager
        /// </summary>
        private static PlcDriverManager _instance;

        /// <summary>
        /// Get the singleton instance
        /// </summary>
        public static PlcDriverManager Instance => _instance ?? (_instance = new PlcDriverManager());

        /// <summary>
        /// Dictionary for the drivers
        /// </summary>
        private readonly Dictionary<string, IPlcDriver> _drivers;

        /// <summary>
        /// Private constructor for the singleton driver manager.
        /// </summary>
        private PlcDriverManager()
        {
            _drivers = new Dictionary<string, IPlcDriver>();

            /*
             * TODO: Implement some mechanism to provide drivers -> MEF?
             */
        }

        /// <summary>
        /// Get the connection to the a PLC identified by the URL
        /// </summary>
        /// <param name="url">URL including the schema to connect to the PLC</param>
        /// <param name="authentication">Authentication to use</param>
        /// <returns>Created PLC connection</returns>
        public async Task<IPlcConnection> GetConnection(string url, IPlcAuthentication authentication)
        {
            var plcDriver = GetDriver(url);
            var connection = await plcDriver.ConnectAsync(url, authentication);
            
            //TODO: Does the driver method already connect or is a separate connect needed?
            //TODO: Should we do it like this?
            if (!connection.IsConnected)
            {
                await connection.ConnectAsync();
            }

            return connection;
        }

        public IPlcDriver GetDriver(string url)
        {
            try
            {
                Uri plcUri = new Uri(url);
                var proto = plcUri.Scheme;

                _drivers.TryGetValue(proto, out var plcDriver);

                if (plcDriver == null)
                {
                    throw new PlcConnectionException($"Unknown driver for protocol '{proto}'");
                }

                return plcDriver;
            }
            catch (UriFormatException invalidUriException)
            {
                throw new PlcConnectionException($"Provided connection string '{url}' is invalid", invalidUriException);
            }
        }
    }
}