using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using ytLive.Helpers;
using ytLive.Services;
using ytLive.Services.Encoder;

namespace ytLive.ViewModels;

/// <summary>
/// TASK 32·1 — a dropped push is retried instead of ending the session. The loop itself lives in
/// <see cref="StreamRecovery"/> (pure, testable); this partial supplies the app-side steps and reports
/// each episode into the left panel's alert stack.
/// <para>Deliberately narrow: only the ENCODER dying is recoverable. A compositor fault still goes
/// through <see cref="OnFramePumpFailed"/> and ends the session, because retrying it would loop.</para>
/// </summary>
public partial class MainViewModel
{
    private CancellationTokenSource? _recoveryCts;

    /// <summary>True while a push is being relaunched — slice 2 binds the amber sign to this.</summary>
    public bool IsReconnecting { get; private set; }

    /// <summary>The attempt currently in flight (0 when idle).</summary>
    public int ReconnectAttempt { get; private set; }

    private void OnEncoderFailed(object? sender, string message)
    {
        if (!IsLive && !IsRecording) return;
        if (_recoveryCts != null) return;       // one recovery at a time
        if (!IsLive) return;                    // a recording-only session has nothing to relive

        AppLog.Write($"RECONNECT: encoder process failed: {message}");
        _recoveryCts = new CancellationTokenSource();
        _ = RecoverStreamAsync(message, _recoveryCts.Token);
    }

    private async Task RecoverStreamAsync(string reason, CancellationToken cancellationToken)
    {
        IsReconnecting = true;
        ReconnectAttempt = 0;

        var logFrom = AppLog.SnapshotCurrentLaunch().Count > 0
            ? AppLog.SnapshotCurrentLaunch()[^1].Sequence + 1
            : 1;

        var recovery = new StreamRecovery(
            StreamRetryPolicy.Default,
            new StreamRecoverySteps
            {
                RestartAudio = _ =>
                {
                    // The audio pipe's server is single-instance and its client just died, so it has
                    // to be recreated before ffmpeg can attach — otherwise the restart fails on a
                    // missing input.
                    _audioMixer.StopLive();
                    _audioMixer.StartLive(EncoderOptions.DefaultAudioPipeName);
                    return Task.CompletedTask;
                },
                StartPush = async ct =>
                {
                    await _framePump.StartAsync(ct);
                    return _framePump.IsRunning;
                },
                CheckBroadcast = async ct =>
                {
                    if (_currentBroadcastId == null || _reusableStream?.Id == null)
                        return BroadcastLiveness.Unknown;
                    var status = await _youtubeStream.GetBroadcastStatusAsync(_currentBroadcastId);
                    return status switch
                    {
                        "complete" => BroadcastLiveness.Complete,
                        null => BroadcastLiveness.Unknown,
                        _ => BroadcastLiveness.Live,
                    };
                },
                Report = text =>
                {
                    var progress = text.StartsWith("Stream dropped", StringComparison.Ordinal)
                        ? ParseAttempt(text)
                        : 0;
                    if (progress > 0) ReconnectAttempt = progress;

                    var to = AppLog.SnapshotCurrentLaunch() is { Count: > 0 } entries
                        ? entries[^1].Sequence
                        : logFrom;
                    PushAttentionAlert(
                        "stream-recovery",
                        text,
                        logFrom,
                        Math.Max(logFrom, to));
                },
                Log = line => AppLog.Write(line, AppLogMessageType.Error, AppLogErrorClass.Class2),
            });

        try
        {
            var result = await recovery.RunAsync(cancellationToken);

            switch (result.Outcome)
            {
                case RecoveryOutcome.Recovered:
                    ReconnectAttempt = result.Attempts;
                    AppLog.WriteSuccess(
                        $"RECONNECT: recovered on attempt {result.Attempts} after {result.Elapsed.TotalSeconds:0.0} s");
                    break;

                case RecoveryOutcome.Cancelled:
                    // The creator stopped the stream mid-recovery: nothing to report.
                    break;

                default:
                    // Gave up, or the broadcast was already complete: this session is over. The alert
                    // stack keeps the reason; the normal stop path clears pills, audio and recording.
                    AppLog.Write("RECONNECT: session ended — the broadcast could not be recovered",
                        AppLogMessageType.Error, AppLogErrorClass.Class1);
                    StopStream();
                    break;
            }
        }
        catch (Exception ex)
        {
            AppLog.Write(ex, "RECONNECT: recovery loop faulted");
            StopStream();
        }
        finally
        {
            IsReconnecting = false;
            ReconnectAttempt = 0;
            _recoveryCts?.Dispose();
            _recoveryCts = null;
        }
    }

    private static int ParseAttempt(string text)
    {
        // "Stream dropped — reconnecting (attempt 2 of 4)"
        var marker = text.IndexOf("attempt ", StringComparison.Ordinal);
        if (marker < 0) return 0;
        var rest = text[(marker + "attempt ".Length)..];
        var space = rest.IndexOf(' ');
        return int.TryParse(space > 0 ? rest[..space] : rest, out var attempt) ? attempt : 0;
    }

    /// <summary>The creator asked to stop: never race a stop against a relaunch.</summary>
    private void CancelStreamRecovery() => _recoveryCts?.Cancel();
}