using System.Runtime.ExceptionServices;

namespace NEventStore

{

/// <summary>

/// Represents an async observer that can receive and stores commits from a stream.

/// Can be used as base class for other observers.

/// </summary>

public class CommitStreamObserver : IAsyncObserver<ICommit>

{

/// <summary>

/// The list of commits read from the stream.

/// </summary>

public IList<ICommit> Commits { get; } = [];

/// <summary>

/// Indicates if the read operation has completed.

/// </summary>

public bool ReadCompleted { get; private set; }

/// <summary>

/// Store the commits received from the stream in the <see cref="Commits"/> collection.

/// </summary>

public virtual Task<bool> OnNextAsync(ICommit value, CancellationToken cancellationToken)

{

Commits.Add(value);

return Task.FromResult(true);

}

/// <summary>

/// <para>Notifies the observer that the provider has experienced an error condition.</para>

/// <para>

/// Preserve the stack trace and rethrow the exception that occurred while reading commits from the stream.

/// </para>

/// <para>

/// Override this method to log and handle the error.

/// </para>

/// </summary>

public virtual Task OnErrorAsync(Exception ex, CancellationToken cancellationToken)

{

// Preserve the stack trace and rethrow the exception

ExceptionDispatchInfo.Capture(ex).Throw();

return Task.CompletedTask;

}

/// <inheritdoc/>

public virtual Task OnCompletedAsync(CancellationToken cancellationToken)

{

ReadCompleted = true;

return Task.CompletedTask;

}

}

}