IEvent

IEvent is root interface event interfaces.

/// <summary>
/// File entry event.
/// 
/// See sub-interfaces:
/// <list type="bullet">
///     <item><see cref="ICreateEvent"/></item>
///     <item><see cref="IDeleteEvent"/></item>
///     <item><see cref="IChangeEvent"/></item>
///     <item><see cref="IRenameEvent"/></item>
///     <item><see cref="IErrorEvent"/></item>
///     <item><see cref="IStartEvent"/></item>
///     <item><see cref="IMountEvent"/></item>
///     <item><see cref="IUnmountEvent"/></item>
///     <item><see cref="IEventDecoration"/></item>
/// </list>
/// </summary>
public interface IEvent
{
    /// <summary>The observer object that monitors the filesystem.</summary>
    IFileSystemObserver Observer { get; }
    /// <summary>The time the event occured, or approximation if not exactly known.</summary>
    DateTimeOffset EventTime { get; }

    /// <summary>
    /// Affected file or directory entry if applicable. 
    /// 
    /// Path is relative to the filesystems's root.
    /// Directory separator is "/". Root path doesn't use separator.
    /// Example: "dir/file.ext"
    /// 
    /// If event is <see cref="IRenameEvent"/> the value is same as <see cref="IRenameEvent.OldPath"/>.
    /// </summary>
    string? Path { get; }
}

IRenameEvent is rename event.

/// <summary>File renamed event.</summary>
public interface IRenameEvent : IEvent
{
    /// <summary>
    /// The affected file or directory.
    /// 
    /// Path is relative to the <see cref="FileSystem"/>'s root.
    /// 
    /// Directory separator is "/". Root path doesn't use separator.
    /// 
    /// Example: "dir/file.ext"
    /// 
    /// This value is same as inherited <see cref="IEvent.Path"/>.
    /// </summary>
    String OldPath { get; }

    /// <summary>
    /// The new file or directory path.
    /// </summary>
    String NewPath { get; }
}

ICreateEvent is file or folder created event.

/// <summary>File created event</summary>
public interface ICreateEvent : IEvent { }

IDeleteEvent is file or folder deleted event.

/// <summary>File delete event</summary>
public interface IDeleteEvent : IEvent { }

IChangeEvent is file changed event.

/// <summary>File contents changed event.</summary>
public interface IChangeEvent : IEvent { }

IErrorEvent is error event.

/// <summary>Event for error with <see cref="IFileSystem"/> or a file entry.</summary>
public interface IErrorEvent : IEvent
{
    /// <summary>Error as exception.</summary>
    Exception Error { get; }
}

IStartEvent is observe started event.

/// <summary>
/// The very first event when <see cref="IFileSystemObserve.Observe"/> is called.
/// 
/// <see cref="IStartEvent"/> must be handled in the thread that calls .Observe() 
/// in the implementation of Observe() and before Observe() returns. It ignores .EventDispatcher property.
/// </summary>
public interface IStartEvent : IEvent
{
}

IEventDecoration is interface for decoration implementations.

/// <summary>Signals that the event object decorates another event object.</summary>
public interface IEventDecoration : IEvent
{
    /// <summary>Original event that is decorated.</summary>
    IEvent? Original { get; }
}

IEventDispatcher is event dispatchers.

/// <summary>
/// Dispatches <see cref="IEvent"/>s.
/// 
/// Dispatcher implementation may capture unexpected exceptions from event handlers, or
/// it may let them fly to the caller. 
/// </summary>
public interface IEventDispatcher
{
    /// <summary>
    /// Dispatch <paramref name="events"/> to observers.
    /// 
    /// If it recommended that the implementation enumerates <paramref name="events"/>, as this allows the caller to pass on heavy enumeration operations.
    /// </summary>
    /// <param name="events">(optional) Events</param>
    /// <exception cref="Exception">Any exception from observer may be captured or passed to caller</exception>
    void DispatchEvents(IEnumerable<IEvent> events);

    /// <summary>
    /// Dispatch single <paramref name="event"/> to observers.
    /// </summary>
    /// <param name="event">(optional) events</param>
    /// <exception cref="Exception">Any exception from observer may be captured or passed to caller</exception>
    void DispatchEvent(IEvent @event);
}