jellyLMS/Jellyfin.Plugin.JellyLMS/Services/LmsStatusPoller.cs

using System;
using System.Threading;
using System.Threading.Tasks;
using Jellyfin.Plugin.JellyLMS.Configuration;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.JellyLMS.Services;

/// <summary>
/// Polls LMS player status to confirm state transitions.
/// </summary>
public class LmsStatusPoller
{
    private readonly ILmsApiClient _lmsClient;
    private readonly ILogger _logger;

    /// <summary>
    /// Initializes a new instance of the <see cref="LmsStatusPoller"/> class.
    /// </summary>
    /// <param name="lmsClient">The LMS API client.</param>
    /// <param name="logger">The logger instance.</param>
    public LmsStatusPoller(ILmsApiClient lmsClient, ILogger logger)
    {
        _lmsClient = lmsClient;
        _logger = logger;
    }

    private static PluginConfiguration Config => Plugin.Instance?.Configuration ?? new PluginConfiguration();

    /// <summary>
    /// Waits for LMS to report that playback has started (mode="play").
    /// </summary>
    /// <param name="playerMac">The player's MAC address.</param>
    /// <param name="timeout">Maximum time to wait.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>True if playback started within the timeout.</returns>
    public async Task<bool> WaitForPlaybackStartAsync(
        string playerMac,
        TimeSpan timeout,
        CancellationToken cancellationToken = default)
    {
        return await WaitForModeAsync(playerMac, "play", timeout, cancellationToken).ConfigureAwait(false);
    }

    /// <summary>
    /// Waits for LMS to report a specific playback mode.
    /// </summary>
    /// <param name="playerMac">The player's MAC address.</param>
    /// <param name="expectedMode">The expected mode ("play", "pause", "stop").</param>
    /// <param name="timeout">Maximum time to wait.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>True if the expected mode was detected within the timeout.</returns>
    public async Task<bool> WaitForModeAsync(
        string playerMac,
        string expectedMode,
        TimeSpan timeout,
        CancellationToken cancellationToken = default)
    {
        var pollInterval = TimeSpan.FromMilliseconds(Config.TransitionPollIntervalMs);
        var startTime = DateTime.UtcNow;

        _logger.LogDebug(
            "Waiting for player {Mac} to reach mode '{Mode}' (timeout: {Timeout}s)",
            playerMac,
            expectedMode,
            timeout.TotalSeconds);

        while (DateTime.UtcNow - startTime < timeout)
        {
            cancellationToken.ThrowIfCancellationRequested();

            try
            {
                var status = await _lmsClient.GetPlayerStatusAsync(playerMac).ConfigureAwait(false);
                if (status?.Mode == expectedMode)
                {
                    _logger.LogDebug(
                        "Player {Mac} reached mode '{Mode}' after {Elapsed}ms",
                        playerMac,
                        expectedMode,
                        (DateTime.UtcNow - startTime).TotalMilliseconds);
                    return true;
                }

                _logger.LogDebug(
                    "Player {Mac} current mode: '{CurrentMode}', waiting for '{ExpectedMode}'",
                    playerMac,
                    status?.Mode ?? "unknown",
                    expectedMode);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Error polling player {Mac} status", playerMac);
            }

            await Task.Delay(pollInterval, cancellationToken).ConfigureAwait(false);
        }

        _logger.LogWarning(
            "Timeout waiting for player {Mac} to reach mode '{Mode}' after {Timeout}s",
            playerMac,
            expectedMode,
            timeout.TotalSeconds);

        return false;
    }

    /// <summary>
    /// Waits for LMS to report a position within tolerance of the target.
    /// Used to confirm seek operations completed.
    /// </summary>
    /// <param name="playerMac">The player's MAC address.</param>
    /// <param name="targetPositionSeconds">The target position in seconds.</param>
    /// <param name="toleranceSeconds">Acceptable tolerance (default 2 seconds).</param>
    /// <param name="timeout">Maximum time to wait.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>True if the position was reached within the timeout.</returns>
    public async Task<bool> WaitForSeekCompleteAsync(
        string playerMac,
        double targetPositionSeconds,
        double toleranceSeconds,
        TimeSpan timeout,
        CancellationToken cancellationToken = default)
    {
        var pollInterval = TimeSpan.FromMilliseconds(Config.TransitionPollIntervalMs);
        var startTime = DateTime.UtcNow;

        _logger.LogDebug(
            "Waiting for player {Mac} to seek to {Target}s (tolerance: {Tolerance}s, timeout: {Timeout}s)",
            playerMac,
            targetPositionSeconds,
            toleranceSeconds,
            timeout.TotalSeconds);

        while (DateTime.UtcNow - startTime < timeout)
        {
            cancellationToken.ThrowIfCancellationRequested();

            try
            {
                var status = await _lmsClient.GetPlayerStatusAsync(playerMac).ConfigureAwait(false);
                if (status != null)
                {
                    var positionDiff = Math.Abs(status.Time - targetPositionSeconds);
                    if (positionDiff <= toleranceSeconds)
                    {
                        _logger.LogDebug(
                            "Player {Mac} reached position {Position}s (target: {Target}s) after {Elapsed}ms",
                            playerMac,
                            status.Time,
                            targetPositionSeconds,
                            (DateTime.UtcNow - startTime).TotalMilliseconds);
                        return true;
                    }

                    _logger.LogDebug(
                        "Player {Mac} at position {Position}s, waiting for {Target}s (diff: {Diff}s)",
                        playerMac,
                        status.Time,
                        targetPositionSeconds,
                        positionDiff);
                }
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Error polling player {Mac} status during seek", playerMac);
            }

            await Task.Delay(pollInterval, cancellationToken).ConfigureAwait(false);
        }

        _logger.LogWarning(
            "Timeout waiting for player {Mac} to seek to {Target}s after {Timeout}s",
            playerMac,
            targetPositionSeconds,
            timeout.TotalSeconds);

        return false;
    }

    /// <summary>
    /// Executes an action with automatic retry on failure.
    /// </summary>
    /// <param name="action">The async action to execute.</param>
    /// <param name="maxRetries">Maximum number of retries.</param>
    /// <param name="onRetry">Optional callback when retrying.</param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>True if the action succeeded within retry limit.</returns>
    public async Task<bool> ExecuteWithRetryAsync(
        Func<Task<bool>> action,
        int maxRetries,
        Action<int>? onRetry = null,
        CancellationToken cancellationToken = default)
    {
        var retryCount = 0;
        var baseDelayMs = 500;

        while (retryCount <= maxRetries)
        {
            cancellationToken.ThrowIfCancellationRequested();

            try
            {
                if (await action().ConfigureAwait(false))
                {
                    return true;
                }
            }
            catch (Exception ex) when (retryCount < maxRetries)
            {
                _logger.LogWarning(ex, "Action failed, will retry ({Retry}/{Max})", retryCount + 1, maxRetries);
            }

            retryCount++;
            if (retryCount <= maxRetries)
            {
                onRetry?.Invoke(retryCount);

                // Exponential backoff: 500ms, 1000ms, 2000ms, etc.
                var delayMs = baseDelayMs * (int)Math.Pow(2, retryCount - 1);
                _logger.LogDebug("Retrying in {Delay}ms (attempt {Retry}/{Max})", delayMs, retryCount, maxRetries);
                await Task.Delay(delayMs, cancellationToken).ConfigureAwait(false);
            }
        }

        return false;
    }
}