namespace NucleicApp.Services;

public enum OnboardingPhase
{
    Idle,
    StartingHost,
    Connecting,
    Ready,
    Failed,
}

/// First-run coordinator for the item-11 core. Component installation and OAuth screens plug
/// into the same phase surface once their host intents land; host launch + authenticated local
/// sync are real today.
public sealed class OnboardingService
{
    private readonly HostdLauncher launcher;
    private readonly HostConnection connection;

    public OnboardingPhase Phase { get; private set; } = OnboardingPhase.Idle;
    public string? Failure { get; private set; }
    public event Action<OnboardingPhase>? PhaseChanged;

    public OnboardingService(HostdLauncher launcher, HostConnection connection)
    {
        this.launcher = launcher;
        this.connection = connection;
    }

    public async Task StartAsync(string rendezvousPath, CancellationToken cancellationToken = default)
    {
        try
        {
            SetPhase(OnboardingPhase.StartingHost);
            _ = await launcher.EnsureRunningAsync(cancellationToken).ConfigureAwait(false);
            SetPhase(OnboardingPhase.Connecting);

            var ready = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
            void Changed(HostConnectionState state)
            {
                if (state == HostConnectionState.Connected) ready.TrySetResult();
                else if (state == HostConnectionState.Failed)
                    ready.TrySetException(new InvalidOperationException(
                        connection.LastProtocolState?.Message ?? "local host connection failed"));
            }
            connection.StateChanged += Changed;
            try
            {
                await connection.StartLocalAsync(rendezvousPath, cancellationToken).ConfigureAwait(false);
                await ready.Task.WaitAsync(TimeSpan.FromSeconds(30), cancellationToken).ConfigureAwait(false);
            }
            finally { connection.StateChanged -= Changed; }
            SetPhase(OnboardingPhase.Ready);
        }
        catch (Exception error)
        {
            Failure = error.Message;
            SetPhase(OnboardingPhase.Failed);
            throw;
        }
    }

    private void SetPhase(OnboardingPhase phase)
    {
        if (Phase == phase) return;
        Phase = phase;
        PhaseChanged?.Invoke(phase);
    }
}