94 lines
4.8 KiB
C#
94 lines
4.8 KiB
C#
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using System.Reactive.Linq;
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using System.Reactive.Concurrency;
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namespace StarsAssistant.Helpers;
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public class FsWatcher
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{
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/// <summary>
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/// Throttle a FileSystemObserver and eliminate all duplicates.
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/// </summary>
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/// <remarks>
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/// Curtesy of https://endjin.com/blog/2024/05/observe-file-system-changes-with-rx-dotnet
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/// </remarks>
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/// <param name="watcher">An observer created with <c>ObserveFileSystem</c></param>
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/// <param name="inactivitySeconds">Throttling window, defaults to 1 second.</param>
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/// <param name="scheduler">Scheduler to user for throttling, default is set by <c>Quiescent</c></param>
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/// <returns>A throttled observer with duplicate elimination.</returns>
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public static IObservable<IEnumerable<FileSystemEventArgs>> ThrottleAndDistinctObserver (
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IObservable<FileSystemEventArgs> watcher,
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int inactivitySeconds = 1,
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IScheduler? scheduler = null)
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{
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return watcher
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.Quiescent(TimeSpan.FromSeconds(inactivitySeconds), scheduler)
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.Select(changes => changes.DistinctBy(x => (x.ChangeType, x.FullPath)));
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}
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/// <summary>
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/// Helper to convert a FileSystemWatcher into an obervable stream. See FileSystemWatcher
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/// documentation for further details on the parameters.
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/// </summary>
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/// <remarks>
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/// Curtesy of https://endjin.com/blog/2024/05/observe-file-system-changes-with-rx-dotnet
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/// </remarks>
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/// <param name="directoryPath">The base directory to watch over.</param>
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/// <param name="filters">An optional list of filter expressions to look for, default is no filter.</param>
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/// <param name="includeSubdirectories">Scan subdirectories, default is exclude subdirs</param>
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/// <param name="notifyFilter">Set this to override the default event selection to filter.</param>
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/// <returns>An observable for further use, usually throttled by Quiescent.</returns>
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public static IObservable<FileSystemEventArgs> ObserveFileSystem(
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string directoryPath,
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IEnumerable<string>? filters = null,
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bool includeSubdirectories = false,
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NotifyFilters? notifyFilter = null)
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{
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return
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// Observable.Defer enables us to avoid doing any work
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// until we have a subscriber.
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Observable.Defer(() =>
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{
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FileSystemWatcher fsw = new(directoryPath);
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if (filters != null)
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foreach (string filter in filters)
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fsw.Filters.Add(filter);
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if (notifyFilter != null)
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fsw.NotifyFilter = (NotifyFilters) notifyFilter;
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fsw.EnableRaisingEvents = true;
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fsw.IncludeSubdirectories = includeSubdirectories;
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return Observable.Return(fsw);
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})
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// Once the preceding part emits the FileSystemWatcher
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// (which will happen when someone first subscribes), we
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// want to wrap all the events as IObservable<T>s, for which
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// we'll use a projection. To avoid ending up with an
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// IObservable<IObservable<FileSystemEventArgs>>, we use
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// SelectMany, which effectively flattens it by one level.
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.SelectMany(fsw =>
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Observable.Merge(new[]
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{
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Observable.FromEventPattern<FileSystemEventHandler, FileSystemEventArgs>(
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h => fsw.Created += h, h => fsw.Created -= h),
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Observable.FromEventPattern<FileSystemEventHandler, FileSystemEventArgs>(
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h => fsw.Changed += h, h => fsw.Changed -= h),
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Observable.FromEventPattern<RenamedEventHandler, FileSystemEventArgs>(
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h => fsw.Renamed += h, h => fsw.Renamed -= h),
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Observable.FromEventPattern<FileSystemEventHandler, FileSystemEventArgs>(
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h => fsw.Deleted += h, h => fsw.Deleted -= h)
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})
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// FromEventPattern supplies both the sender and the event
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// args. Extract just the latter.
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.Select(ep => ep.EventArgs)
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// The Finally here ensures the watcher gets shut down once
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// we have no subscribers.
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.Finally(fsw.Dispose))
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// This combination of Publish and RefCount means that multiple
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// subscribers will get to share a single FileSystemWatcher,
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// but that it gets shut down if all subscribers unsubscribe.
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.Publish()
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.RefCount();
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}
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}
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