scan media sources once every six hours

ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSource.cs

@@ -4,6 +4,6 @@ using MediatR;
 
 namespace ErsatzTV.Application.MediaSources.Commands
 {
-    public record ScanLocalMediaSource(int MediaSourceId) : IRequest<Either<BaseError, string>>,
+    public record ScanLocalMediaSource(int MediaSourceId) : IRequest<Either<Seq<BaseError>, string>>,
         IBackgroundServiceRequest;
 }

ErsatzTV.Application/MediaSources/Commands/ScanLocalMediaSourceHandler.cs

@@ -1,18 +1,21 @@
-using System.IO;
+using System;
+using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Errors;
 using ErsatzTV.Core.Interfaces.Locking;
 using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
 using LanguageExt;
 using MediatR;
+using static LanguageExt.Prelude;
 using Unit = LanguageExt.Unit;
 
 namespace ErsatzTV.Application.MediaSources.Commands
 {
-    public class ScanLocalMediaSourceHandler : IRequestHandler<ScanLocalMediaSource, Either<BaseError, string>>
+    public class ScanLocalMediaSourceHandler : IRequestHandler<ScanLocalMediaSource, Either<Seq<BaseError>, string>>
     {
         private readonly IConfigElementRepository _configElementRepository;
         private readonly IEntityLocker _entityLocker;
@@ -34,11 +37,11 @@ namespace ErsatzTV.Application.MediaSources.Commands
             _entityLocker = entityLocker;
         }
 
-        public Task<Either<BaseError, string>>
+        public Task<Either<Seq<BaseError>, string>>
             Handle(ScanLocalMediaSource request, CancellationToken cancellationToken) =>
             Validate(request)
                 .MapT(parameters => PerformScan(parameters).Map(_ => parameters.LocalMediaSource.Folder))
-                .Bind(v => v.ToEitherAsync());
+                .Bind(v => v.ToEither().MapAsync<Seq<BaseError>, Task<string>, string>(identity));
 
         private async Task<Unit> PerformScan(RequestParameters parameters)
         {
@@ -52,21 +55,33 @@ namespace ErsatzTV.Application.MediaSources.Commands
                     break;
             }
 
+            parameters.LocalMediaSource.LastScan = DateTimeOffset.Now;
+            await _mediaSourceRepository.Update(parameters.LocalMediaSource);
             _entityLocker.UnlockMediaSource(parameters.LocalMediaSource.Id);
 
             return Unit.Default;
         }
 
         private async Task<Validation<BaseError, RequestParameters>> Validate(ScanLocalMediaSource request) =>
-            (await LocalMediaSourceMustExist(request), await ValidateFFprobePath())
+            (await ValidateLocalMediaSource(request), await ValidateFFprobePath())
             .Apply((localMediaSource, ffprobePath) => new RequestParameters(localMediaSource, ffprobePath));
 
+        private Task<Validation<BaseError, LocalMediaSource>> ValidateLocalMediaSource(ScanLocalMediaSource request) =>
+            LocalMediaSourceMustExist(request).BindT(ValidateLastScan);
+
         private Task<Validation<BaseError, LocalMediaSource>> LocalMediaSourceMustExist(
             ScanLocalMediaSource request) =>
             _mediaSourceRepository.Get(request.MediaSourceId)
                 .Map(maybeMediaSource => maybeMediaSource.Map(ms => ms as LocalMediaSource))
                 .Map(v => v.ToValidation<BaseError>($"Local media source {request.MediaSourceId} does not exist."));
 
+        private Task<Validation<BaseError, LocalMediaSource>> ValidateLastScan(
+            LocalMediaSource localMediaSource) =>
+            Optional(localMediaSource)
+                .Filter(lms => lms.LastScan is null || lms.LastScan < DateTimeOffset.Now - TimeSpan.FromHours(6))
+                .ToValidation<BaseError>(new MediaSourceRecentlyScanned(localMediaSource.Folder))
+                .AsTask();
+
         private Task<Validation<BaseError, string>> ValidateFFprobePath() =>
             _configElementRepository.GetValue<string>(ConfigElementKey.FFprobePath)
                 .FilterT(File.Exists)

ErsatzTV.Core/Domain/MediaSource.cs

@@ -1,9 +1,12 @@
-namespace ErsatzTV.Core.Domain
+using System;
+
+namespace ErsatzTV.Core.Domain
 {
     public abstract class MediaSource
     {
         public int Id { get; set; }
         public MediaSourceType SourceType { get; set; }
         public string Name { get; set; }
+        public DateTimeOffset? LastScan { get; set; }
     }
 }

ErsatzTV.Core/Errors/MediaSourceRecentlyScanned.cs

@@ -0,0 +1,10 @@
+namespace ErsatzTV.Core.Errors
+{
+    public class MediaSourceRecentlyScanned : BaseError
+    {
+        public MediaSourceRecentlyScanned(string folder) :
+            base($"Media source {folder} was already scanned recently; skipping scan.")
+        {
+        }
+    }
+}

ErsatzTV.Core/Interfaces/Repositories/IMediaSourceRepository.cs

@@ -14,6 +14,7 @@ namespace ErsatzTV.Core.Interfaces.Repositories
         Task<Option<MediaSource>> Get(int id);
         Task<Option<PlexMediaSource>> GetPlex(int id);
         Task<int> CountMediaItems(int id);
+        Task Update(LocalMediaSource localMediaSource);
         Task Update(PlexMediaSource plexMediaSource);
         Task Delete(int id);
     }

ErsatzTV.Infrastructure/Data/Repositories/MediaSourceRepository.cs

@@ -60,11 +60,15 @@ namespace ErsatzTV.Infrastructure.Data.Repositories
         public Task<int> CountMediaItems(int id) =>
             _dbContext.MediaItems.CountAsync(i => i.MediaSourceId == id);
 
-        public async Task Update(PlexMediaSource plexMediaSource)
-        {
-            _dbContext.PlexMediaSources.Update(plexMediaSource);
-            await _dbContext.SaveChangesAsync();
-        }
+        public Task Update(LocalMediaSource localMediaSource) =>
+            _dbContext.LocalMediaSources.Update(localMediaSource)
+                .AsTask()
+                .Bind(_ => _dbContext.SaveChangesAsync());
+
+        public Task Update(PlexMediaSource plexMediaSource) =>
+            _dbContext.PlexMediaSources.Update(plexMediaSource)
+                .AsTask()
+                .Bind(_ => _dbContext.SaveChangesAsync());
 
         public async Task Delete(int id)
         {

ErsatzTV.Infrastructure/Migrations/20210222120255_MediaSourceLastScan.cs

@@ -0,0 +1,24 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace ErsatzTV.Infrastructure.Migrations
+{
+    public partial class MediaSourceLastScan : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<DateTimeOffset>(
+                name: "LastScan",
+                table: "MediaSources",
+                type: "TEXT",
+                nullable: true);
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "LastScan",
+                table: "MediaSources");
+        }
+    }
+}

ErsatzTV.Infrastructure/Migrations/TvContextModelSnapshot.cs

@@ -248,6 +248,9 @@ namespace ErsatzTV.Infrastructure.Migrations
                         .ValueGeneratedOnAdd()
                         .HasColumnType("INTEGER");
 
+                    b.Property<DateTimeOffset?>("LastScan")
+                        .HasColumnType("TEXT");
+
                     b.Property<string>("Name")
                         .HasColumnType("TEXT");
 

ErsatzTV/Services/WorkerService.cs

@@ -6,6 +6,7 @@ using ErsatzTV.Application;
 using ErsatzTV.Application.MediaSources.Commands;
 using ErsatzTV.Application.Playouts.Commands;
 using ErsatzTV.Core;
+using ErsatzTV.Core.Errors;
 using LanguageExt;
 using MediatR;
 using Microsoft.Extensions.DependencyInjection;
@@ -56,17 +57,28 @@ namespace ErsatzTV.Services
                                     error.Value));
                             break;
                         case ScanLocalMediaSource scanLocalMediaSource:
-                            Either<BaseError, string> scanResult = await mediator.Send(
+                            Either<Seq<BaseError>, string> scanResult = await mediator.Send(
                                 scanLocalMediaSource,
                                 cancellationToken);
                             scanResult.BiIter(
                                 name => _logger.LogDebug(
                                     "Done scanning local media source {MediaSource}",
                                     name),
-                                error => _logger.LogWarning(
-                                    "Unable to scan local media source {MediaSourceId}: {Error}",
-                                    scanLocalMediaSource.MediaSourceId,
-                                    error.Value));
+                                errors =>
+                                {
+                                    BaseError error = errors.Head;
+                                    if (error is MediaSourceRecentlyScanned recentlyScanned)
+                                    {
+                                        _logger.LogInformation(recentlyScanned.Value);
+                                    }
+                                    else
+                                    {
+                                        _logger.LogWarning(
+                                            "Unable to scan local media source {MediaSourceId}: {Error}",
+                                            scanLocalMediaSource.MediaSourceId,
+                                            error.Value);
+                                    }
+                                });
                             break;
                     }
                 }