using SteamKit2;
using SteamKit2.Authentication;

namespace CVRManager.Services;

public sealed class SteamLink : IAsyncDisposable
{
    readonly CallbackManager manager;
    readonly CancellationTokenSource stop = new();
    readonly TaskCompletionSource connected = new(TaskCreationOptions.RunContinuationsAsynchronously);
    TaskCompletionSource<SteamUser.LoggedOnCallback>? loggedOn;
    Task pump = Task.CompletedTask;

    public SteamClient Client { get; } = new();
    public SteamUser User { get; }
    public SteamApps Apps { get; }
    public SteamContent Content { get; }
    public bool IsAnonymous { get; private set; }

    readonly uint loginId = (uint)Random.Shared.NextInt64(0x10000, uint.MaxValue);

    SteamLink()
    {
        manager = new CallbackManager(Client);
        User = Client.GetHandler<SteamUser>()!;
        Apps = Client.GetHandler<SteamApps>()!;
        Content = Client.GetHandler<SteamContent>()!;
        manager.Subscribe<SteamClient.ConnectedCallback>(_ => connected.TrySetResult());
        manager.Subscribe<SteamClient.DisconnectedCallback>(_ =>
        {
            var e = new InvalidOperationException("Lost the connection to Steam.");
            connected.TrySetException(e);
            loggedOn?.TrySetException(e);
        });
        manager.Subscribe<SteamUser.LoggedOnCallback>(cb => loggedOn?.TrySetResult(cb));
    }

    public static async Task<SteamLink> ConnectAsync(CancellationToken ct)
    {
        var link = new SteamLink();
        link.pump = Task.Run(() =>
        {
            while (!link.stop.IsCancellationRequested) link.manager.RunWaitCallbacks(TimeSpan.FromMilliseconds(200));
        });
        link.Client.Connect();
        try
        {
            await WaitAsync(link.connected.Task, TimeSpan.FromSeconds(20), "Could not reach Steam.", ct);
            return link;
        }
        catch
        {
            await link.DisposeAsync();
            throw;
        }
    }

    public static async Task<SteamLink> OpenAsync(string account, string refreshToken, CancellationToken ct)
    {
        var link = await ConnectAsync(ct);
        try
        {
            if (string.IsNullOrEmpty(refreshToken)) await link.LogOnAnonymousAsync(ct);
            else await link.LogOnAsync(account, refreshToken, ct);
            return link;
        }
        catch
        {
            await link.DisposeAsync();
            throw;
        }
    }

    public async Task LogOnAnonymousAsync(CancellationToken ct)
    {
        IsAnonymous = true;
        loggedOn = new(TaskCreationOptions.RunContinuationsAsynchronously);
        User.LogOnAnonymous();
        Check(await WaitAsync(loggedOn.Task, TimeSpan.FromSeconds(20), "Steam did not answer the login.", ct));
    }

    public async Task LogOnAsync(string account, string refreshToken, CancellationToken ct)
    {
        loggedOn = new(TaskCreationOptions.RunContinuationsAsynchronously);
        User.LogOn(new SteamUser.LogOnDetails { Username = account, AccessToken = refreshToken, ShouldRememberPassword = true, LoginID = loginId });
        Check(await WaitAsync(loggedOn.Task, TimeSpan.FromSeconds(20), "Steam did not answer the login.", ct));
    }

    static void Check(SteamUser.LoggedOnCallback cb)
    {
        if (cb.Result != EResult.OK)
            throw new InvalidOperationException(cb.Result is EResult.AccessDenied or EResult.InvalidPassword or EResult.Expired or EResult.LoggedInElsewhere
                ? $"Steam refused the saved sign-in ({cb.Result}); sign in again."
                : $"Steam login failed: {cb.Result}");
    }

    public static async Task<string> SignInAsync(
        string account, string password, Action onDeviceConfirmation, Func<bool, Task<string>> deviceCode, Func<string, bool, Task<string>> emailCode, CancellationToken ct)
    {
        await using var link = await ConnectAsync(ct);
        var session = await link.Client.Authentication.BeginAuthSessionViaCredentialsAsync(new AuthSessionDetails
        {
            Username = account,
            Password = password,
            IsPersistentSession = true,
            DeviceFriendlyName = "CVRManager",
            Authenticator = new Authenticator(onDeviceConfirmation, deviceCode, emailCode),
        });
        var result = await session.PollingWaitForResultAsync(ct);
        return result.RefreshToken;
    }

    sealed class Authenticator(Action confirmation, Func<bool, Task<string>> device, Func<string, bool, Task<string>> email) : IAuthenticator
    {
        public Task<string> GetDeviceCodeAsync(bool previousCodeWasIncorrect) => device(previousCodeWasIncorrect);
        public Task<string> GetEmailCodeAsync(string emailAddress, bool previousCodeWasIncorrect) => email(emailAddress, previousCodeWasIncorrect);

        public Task<bool> AcceptDeviceConfirmationAsync()
        {
            confirmation();
            return Task.FromResult(true);
        }
    }

    static async Task<T> WaitAsync<T>(Task<T> task, TimeSpan timeout, string message, CancellationToken ct)
    {
        var delay = Task.Delay(timeout, ct);
        if (await Task.WhenAny(task, delay) == delay) throw new TimeoutException(message);
        return await task;
    }

    static async Task WaitAsync(Task task, TimeSpan timeout, string message, CancellationToken ct)
    {
        var delay = Task.Delay(timeout, ct);
        if (await Task.WhenAny(task, delay) == delay) throw new TimeoutException(message);
        await task;
    }

    public async ValueTask DisposeAsync()
    {
        stop.Cancel();
        try { Client.Disconnect(); } catch { }
        await pump;
        stop.Dispose();
    }
}