From a0e80f881d747effb5cbcb1025eb27f4db01c779 Mon Sep 17 00:00:00 2001
From: Jason Dove <jason@jasondove.me>
Date: Sun, 14 Feb 2021 06:29:38 -0600
Subject: [PATCH] lock media source during refresh

---
 .../Commands/ScanLocalMediaSource.cs          |  3 +-
 .../Commands/ScanLocalMediaSourceHandler.cs   | 23 ++++++++--
 .../Interfaces/Locking/IEntityLocker.cs       | 12 +++++
 .../Locking/EntityLocker.cs                   | 40 +++++++++++++++++
 ErsatzTV/Pages/LocalMediaSourceEditor.razor   |  8 +++-
 ErsatzTV/Services/SchedulerService.cs         | 11 ++++-
 ErsatzTV/Shared/LocalMediaSources.razor       | 45 +++++++++++++++----
 ErsatzTV/Startup.cs                           |  3 ++
 ErsatzTV/_Imports.razor                       |  1 +
 9 files changed, 128 insertions(+), 18 deletions(-)
 create mode 100644 ErsatzTV.Core/Interfaces/Locking/IEntityLocker.cs
 create mode 100644 ErsatzTV.Infrastructure/Locking/EntityLocker.cs

diff --git a/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSource.cs b/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSource.cs
index d04458786..e4d5debd5 100644
--- a/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSource.cs
+++ b/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSource.cs
@@ -4,6 +4,7 @@ using MediatR;
 
 namespace ErsatzTV.Application.MediaSources.Commands
 {
-    public record ScanLocalMediaSource(int MediaSourceId, bool RefreshAllMetadata) : IRequest<Either<BaseError, string>>,
+    public record ScanLocalMediaSource(int MediaSourceId, bool RefreshAllMetadata) :
+        IRequest<Either<BaseError, string>>,
         IBackgroundServiceRequest;
 }
diff --git a/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSourceHandler.cs b/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSourceHandler.cs
index e6d67e6d1..76ff69ac3 100644
--- a/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSourceHandler.cs
+++ b/ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSourceHandler.cs
@@ -3,37 +3,52 @@ using System.Threading;
 using System.Threading.Tasks;
 using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Interfaces.Locking;
 using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
 using LanguageExt;
 using MediatR;
+using Unit = LanguageExt.Unit;
 
 namespace ErsatzTV.Application.MediaSources.Commands
 {
     public class ScanLocalMediaSourceHandler : IRequestHandler<ScanLocalMediaSource, Either<BaseError, string>>
     {
         private readonly IConfigElementRepository _configElementRepository;
+        private readonly IEntityLocker _entityLocker;
         private readonly ILocalMediaScanner _localMediaScanner;
         private readonly IMediaSourceRepository _mediaSourceRepository;
 
         public ScanLocalMediaSourceHandler(
             IMediaSourceRepository mediaSourceRepository,
             IConfigElementRepository configElementRepository,
-            ILocalMediaScanner localMediaScanner)
+            ILocalMediaScanner localMediaScanner,
+            IEntityLocker entityLocker)
         {
             _mediaSourceRepository = mediaSourceRepository;
             _configElementRepository = configElementRepository;
             _localMediaScanner = localMediaScanner;
+            _entityLocker = entityLocker;
         }
 
         public Task<Either<BaseError, string>>
             Handle(ScanLocalMediaSource request, CancellationToken cancellationToken) =>
             Validate(request)
-                .MapT(
-                    p => _localMediaScanner.ScanLocalMediaSource(p.LocalMediaSource, p.FFprobePath, request.RefreshAllMetadata)
-                        .Map(_ => p.LocalMediaSource.Folder))
+                .MapT(parameters => PerformScan(request, parameters).Map(_ => parameters.LocalMediaSource.Folder))
                 .Bind(v => v.ToEitherAsync());
 
+        private async Task<Unit> PerformScan(ScanLocalMediaSource request, RequestParameters parameters)
+        {
+            await _localMediaScanner.ScanLocalMediaSource(
+                parameters.LocalMediaSource,
+                parameters.FFprobePath,
+                request.RefreshAllMetadata);
+
+            _entityLocker.UnlockMediaSource(parameters.LocalMediaSource.Id);
+
+            return Unit.Default;
+        }
+
         private async Task<Validation<BaseError, RequestParameters>> Validate(ScanLocalMediaSource request) =>
             (await LocalMediaSourceMustExist(request), await ValidateFFprobePath())
             .Apply((localMediaSource, ffprobePath) => new RequestParameters(localMediaSource, ffprobePath));
diff --git a/ErsatzTV.Core/Interfaces/Locking/IEntityLocker.cs b/ErsatzTV.Core/Interfaces/Locking/IEntityLocker.cs
new file mode 100644
index 000000000..f750db1b7
--- /dev/null
+++ b/ErsatzTV.Core/Interfaces/Locking/IEntityLocker.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace ErsatzTV.Core.Interfaces.Locking
+{
+    public interface IEntityLocker
+    {
+        public event EventHandler OnMediaSourceChanged;
+        public bool LockMediaSource(int mediaSourceId);
+        public bool UnlockMediaSource(int mediaSourceId);
+        public bool IsMediaSourceLocked(int mediaSourceId);
+    }
+}
diff --git a/ErsatzTV.Infrastructure/Locking/EntityLocker.cs b/ErsatzTV.Infrastructure/Locking/EntityLocker.cs
new file mode 100644
index 000000000..6cfcd2200
--- /dev/null
+++ b/ErsatzTV.Infrastructure/Locking/EntityLocker.cs
@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Concurrent;
+using ErsatzTV.Core.Interfaces.Locking;
+
+namespace ErsatzTV.Infrastructure.Locking
+{
+    public class EntityLocker : IEntityLocker
+    {
+        private readonly ConcurrentDictionary<int, byte> _lockedMediaSources;
+
+        public EntityLocker() => _lockedMediaSources = new ConcurrentDictionary<int, byte>();
+
+        public event EventHandler OnMediaSourceChanged;
+
+        public bool LockMediaSource(int mediaSourceId)
+        {
+            if (_lockedMediaSources.TryAdd(mediaSourceId, 0))
+            {
+                OnMediaSourceChanged?.Invoke(this, EventArgs.Empty);
+                return true;
+            }
+
+            return false;
+        }
+
+        public bool UnlockMediaSource(int mediaSourceId)
+        {
+            if (_lockedMediaSources.TryRemove(mediaSourceId, out byte _))
+            {
+                OnMediaSourceChanged?.Invoke(this, EventArgs.Empty);
+                return true;
+            }
+
+            return false;
+        }
+
+        public bool IsMediaSourceLocked(int mediaSourceId) =>
+            _lockedMediaSources.ContainsKey(mediaSourceId);
+    }
+}
diff --git a/ErsatzTV/Pages/LocalMediaSourceEditor.razor b/ErsatzTV/Pages/LocalMediaSourceEditor.razor
index ad72d8fd9..a36599d29 100644
--- a/ErsatzTV/Pages/LocalMediaSourceEditor.razor
+++ b/ErsatzTV/Pages/LocalMediaSourceEditor.razor
@@ -5,6 +5,7 @@
 @inject ILogger<LocalMediaSourceEditor> Logger
 @inject ISnackbar Snackbar
 @inject IMediator Mediator
+@inject IEntityLocker Locker
 @inject ChannelWriter<IBackgroundServiceRequest> Channel
 
 <div style="max-width: 400px;">
@@ -84,8 +85,11 @@
                 },
                 Right: async vm =>
                 {
-                    await Channel.WriteAsync(new ScanLocalMediaSource(vm.Id, false));
-                    NavigationManager.NavigateTo("/media/sources");
+                    if (Locker.LockMediaSource(vm.Id))
+                    {
+                        await Channel.WriteAsync(new ScanLocalMediaSource(vm.Id, false));
+                        NavigationManager.NavigateTo("/media/sources");
+                    }
                 });
         }
     }
diff --git a/ErsatzTV/Services/SchedulerService.cs b/ErsatzTV/Services/SchedulerService.cs
index 57d00e13c..3ea11ebb7 100644
--- a/ErsatzTV/Services/SchedulerService.cs
+++ b/ErsatzTV/Services/SchedulerService.cs
@@ -6,6 +6,7 @@ using System.Threading.Tasks;
 using ErsatzTV.Application;
 using ErsatzTV.Application.MediaSources.Commands;
 using ErsatzTV.Application.Playouts.Commands;
+using ErsatzTV.Core.Interfaces.Locking;
 using ErsatzTV.Infrastructure.Data;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
@@ -16,15 +17,18 @@ namespace ErsatzTV.Services
     public class SchedulerService : IHostedService
     {
         private readonly ChannelWriter<IBackgroundServiceRequest> _channel;
+        private readonly IEntityLocker _entityLocker;
         private readonly IServiceScopeFactory _serviceScopeFactory;
         private Timer _timer;
 
         public SchedulerService(
             IServiceScopeFactory serviceScopeFactory,
-            ChannelWriter<IBackgroundServiceRequest> channel)
+            ChannelWriter<IBackgroundServiceRequest> channel,
+            IEntityLocker entityLocker)
         {
             _serviceScopeFactory = serviceScopeFactory;
             _channel = channel;
+            _entityLocker = entityLocker;
         }
 
         public Task StartAsync(CancellationToken cancellationToken)
@@ -75,7 +79,10 @@ namespace ErsatzTV.Services
 
             foreach (int mediaSourceId in localMediaSourceIds)
             {
-                await _channel.WriteAsync(new ScanLocalMediaSource(mediaSourceId, false), cancellationToken);
+                if (_entityLocker.LockMediaSource(mediaSourceId))
+                {
+                    await _channel.WriteAsync(new ScanLocalMediaSource(mediaSourceId, false), cancellationToken);
+                }
             }
         }
     }
diff --git a/ErsatzTV/Shared/LocalMediaSources.razor b/ErsatzTV/Shared/LocalMediaSources.razor
index b9820c7f1..39ba78d69 100644
--- a/ErsatzTV/Shared/LocalMediaSources.razor
+++ b/ErsatzTV/Shared/LocalMediaSources.razor
@@ -1,11 +1,13 @@
 @using ErsatzTV.Application.MediaSources
 @using ErsatzTV.Application.MediaSources.Commands
 @using ErsatzTV.Application.MediaSources.Queries
+@implements IDisposable
 @inject IDialogService Dialog
 @inject IMediator Mediator
+@inject IEntityLocker Locker
 @inject ChannelWriter<IBackgroundServiceRequest> Channel
 
-<MudTable Hover="true" Items="_mediaSources">
+<MudTable Hover="true" Items="_mediaSources" Dense="true">
     <ToolBarContent>
         <MudText Typo="Typo.h6">Local Media Sources</MudText>
     </ToolBarContent>
@@ -20,12 +22,27 @@
     <RowTemplate>
         <MudTd DataLabel="Folder">@context.Folder</MudTd>
         <MudTd>
-            <div style="display: flex">
-                <MudTooltip Text="Refresh All Metadata">
-                    <MudIconButton Icon="@Icons.Material.Filled.Refresh" Disabled="@_refreshing" OnClick="@(_ => RefreshAllMetadata(context))"></MudIconButton>
-                </MudTooltip>
+            <div style="align-items: center; display: flex;">
+                @if (Locker.IsMediaSourceLocked(context.Id))
+                {
+                    <div style="align-items: center; display: flex; height: 48px; justify-content: center; width: 48px;">
+                        <MudProgressCircular Color="Color.Primary" Size="Size.Small" Indeterminate="true"/>
+                    </div>
+                }
+                else
+                {
+                    <MudTooltip Text="Refresh All Metadata">
+                        <MudIconButton Icon="@Icons.Material.Filled.Refresh"
+                                       Disabled="@Locker.IsMediaSourceLocked(context.Id)"
+                                       OnClick="@(_ => RefreshAllMetadata(context))">
+                        </MudIconButton>
+                    </MudTooltip>
+                }
                 <MudTooltip Text="Delete Media Source">
-                    <MudIconButton Icon="@Icons.Material.Filled.Delete" OnClick="@(_ => DeleteMediaSource(context))"></MudIconButton>
+                    <MudIconButton Icon="@Icons.Material.Filled.Delete"
+                                   Disabled="@Locker.IsMediaSourceLocked(context.Id)"
+                                   OnClick="@(_ => DeleteMediaSource(context))">
+                    </MudIconButton>
                 </MudTooltip>
             </div>
         </MudTd>
@@ -37,7 +54,9 @@
 
 @code {
     private IList<LocalMediaSourceViewModel> _mediaSources;
-    private bool _refreshing = false;
+
+    protected override void OnInitialized() =>
+        Locker.OnMediaSourceChanged += LockChanged;
 
     protected override async Task OnParametersSetAsync() => await LoadMediaSources();
 
@@ -68,8 +87,16 @@
 
     private async Task RefreshAllMetadata(LocalMediaSourceViewModel mediaSource)
     {
-        _refreshing = true;
-        await Channel.WriteAsync(new ScanLocalMediaSource(mediaSource.Id, true));
+        if (Locker.LockMediaSource(mediaSource.Id))
+        {
+            await Channel.WriteAsync(new ScanLocalMediaSource(mediaSource.Id, true));
+            StateHasChanged();
+        }
     }
 
+    private void LockChanged(object sender, EventArgs e) =>
+        InvokeAsync(StateHasChanged);
+
+    void IDisposable.Dispose() => Locker.OnMediaSourceChanged -= LockChanged;
+
 }
\ No newline at end of file
diff --git a/ErsatzTV/Startup.cs b/ErsatzTV/Startup.cs
index eea3a74ff..e6f92b097 100644
--- a/ErsatzTV/Startup.cs
+++ b/ErsatzTV/Startup.cs
@@ -8,6 +8,7 @@ using ErsatzTV.Core;
 using ErsatzTV.Core.FFmpeg;
 using ErsatzTV.Core.Interfaces.FFmpeg;
 using ErsatzTV.Core.Interfaces.Images;
+using ErsatzTV.Core.Interfaces.Locking;
 using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Plex;
 using ErsatzTV.Core.Interfaces.Repositories;
@@ -18,6 +19,7 @@ using ErsatzTV.Formatters;
 using ErsatzTV.Infrastructure.Data;
 using ErsatzTV.Infrastructure.Data.Repositories;
 using ErsatzTV.Infrastructure.Images;
+using ErsatzTV.Infrastructure.Locking;
 using ErsatzTV.Infrastructure.Plex;
 using ErsatzTV.Serialization;
 using ErsatzTV.Services;
@@ -155,6 +157,7 @@ namespace ErsatzTV
             services.AddSingleton<IPlexSecretStore, PlexSecretStore>();
             services.AddSingleton<IPlexTvApiClient, PlexTvApiClient>(); // TODO: does this need to be singleton?
             services.AddSingleton<IPlexServerApiClient, PlexServerApiClient>();
+            services.AddSingleton<IEntityLocker, EntityLocker>();
             AddChannel<IBackgroundServiceRequest>(services);
             AddChannel<IPlexBackgroundServiceRequest>(services);
 
diff --git a/ErsatzTV/_Imports.razor b/ErsatzTV/_Imports.razor
index fad2bdf07..f6dc56d31 100644
--- a/ErsatzTV/_Imports.razor
+++ b/ErsatzTV/_Imports.razor
@@ -20,6 +20,7 @@
 @using ErsatzTV.Application
 @using ErsatzTV.Core
 @using ErsatzTV.Core.Domain
+@using ErsatzTV.Core.Interfaces.Locking
 @using ErsatzTV.Infrastructure.Data
 @using ErsatzTV.Shared
 @using ErsatzTV.ViewModels
\ No newline at end of file