ChatTrackingContext.cs

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using Microsoft.Extensions.Logging;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Tgstation.Server.Host.Components.Chat.Commands;

namespace Tgstation.Server.Host.Components.Chat
{
    sealed class ChatTrackingContext : IChatTrackingContext
    {
        public bool Active
        {
            get => active;
            set
            {
                logger.LogTrace(value ? "Activated" : "Deactivated");
                active = value;
            }
        }

        public IReadOnlyCollection<ChannelRepresentation> Channels { get; private set; }

        public IEnumerable<CustomCommand> CustomCommands
        {
            get => customCommands;
            set
            {
                customCommands = (value ?? throw new InvalidOperationException("value cannot be null!"))
                .Select(customCommand =>
                {
                    customCommand.SetHandler(customCommandHandler);
                    return customCommand;
                })
                .ToList();
                logger.LogTrace("Custom commands set.");
            }
        }

        readonly ICustomCommandHandler customCommandHandler;

        readonly ILogger<ChatTrackingContext> logger;

        readonly object synchronizationLock;

        IReadOnlyCollection<CustomCommand> customCommands;

        IChannelSink channelSink;

        Action onDispose;

        bool active;

        public ChatTrackingContext(
            ICustomCommandHandler customCommandHandler,
            IEnumerable<ChannelRepresentation> initialChannels,
            ILogger<ChatTrackingContext> logger,
            Action onDispose)
        {
            this.customCommandHandler = customCommandHandler ?? throw new ArgumentNullException(nameof(customCommandHandler));
            Channels = initialChannels?.ToList() ?? throw new ArgumentNullException(nameof(initialChannels));
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
            this.onDispose = onDispose ?? throw new ArgumentNullException(nameof(onDispose));

            synchronizationLock = new object();
            Active = true;
            customCommands = Array.Empty<CustomCommand>();
        }

        public void Dispose()
        {
            lock (synchronizationLock)
            {
                onDispose?.Invoke();
                onDispose = null;
            }
        }

        public void SetChannelSink(IChannelSink channelSink)
        {
            if (channelSink == null)
                throw new ArgumentNullException(nameof(channelSink));

            lock (synchronizationLock)
            {
                if (this.channelSink != null)
                    throw new InvalidOperationException("channelSink already set!");

                this.channelSink = channelSink;
            }
        }

        public Task UpdateChannels(IEnumerable<ChannelRepresentation> newChannels, CancellationToken cancellationToken)
        {
            var completed = newChannels.ToList();
            Task updateTask;
            lock (synchronizationLock)
            {
                Channels = completed;
                updateTask = channelSink?.UpdateChannels(newChannels, cancellationToken) ?? Task.CompletedTask;
            }

            return updateTask;
        }
    }
}