using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace MediaBrowser.Controller.Session;

/// <summary>
/// The single-instance <see cref="ISessionDirectory"/>: nothing is published and no session is held
/// anywhere but here, which is exactly the behaviour of a deployment without a shared store.
/// </summary>
public sealed class NullSessionDirectory : ISessionDirectory
{
    /// <summary>
    /// Gets the shared instance.
    /// </summary>
    public static NullSessionDirectory Instance { get; } = new NullSessionDirectory();

    /// <inheritdoc />
    public Task<long> AllocateConnectionEpochAsync(string sessionId, CancellationToken cancellationToken = default)
        => Task.FromResult(0L);

    /// <inheritdoc />
    public Task<bool> PublishAsync(SessionDirectoryEntry entry, long connectionEpoch, CancellationToken cancellationToken = default)
        => Task.FromResult(false);

    /// <inheritdoc />
    public Task RemoveAsync(string sessionId, string ownerPod, CancellationToken cancellationToken = default)
        => Task.CompletedTask;

    /// <inheritdoc />
    public Task<SessionDirectoryEntry?> GetAsync(string sessionId, CancellationToken cancellationToken = default)
        => Task.FromResult<SessionDirectoryEntry?>(null);

    /// <inheritdoc />
    public Task<IReadOnlyList<SessionDirectoryEntry>> GetAllAsync(CancellationToken cancellationToken = default)
        => Task.FromResult<IReadOnlyList<SessionDirectoryEntry>>(Array.Empty<SessionDirectoryEntry>());
}