#if WINDOWS
using System.Collections.Concurrent;
using CommunityToolkit.WinUI.Notifications;
using MeetingAssistant.Notifications;
using MeetingAssistant.Recording;

namespace MeetingAssistant.Calendar;

public sealed class WindowsMeetingStartPromptService : IMeetingStartPromptService, IHostedService, IDisposable
{
    private const string NotificationSource = "meeting-start-prompt";
    private const string NotificationGroup = "meeting-start";
    private readonly ConcurrentDictionary<string, Func<MeetingStartPromptResponse, CancellationToken, Task>> pendingPrompts = new(StringComparer.OrdinalIgnoreCase);
    private readonly ILogger<WindowsMeetingStartPromptService> logger;
    private readonly object registrationGate = new();
    private bool registered;

    public WindowsMeetingStartPromptService(ILogger<WindowsMeetingStartPromptService> logger)
    {
        this.logger = logger;
    }

    public Task ShowPromptAsync(
        MeetingStartPromptRequest request,
        Func<MeetingStartPromptResponse, CancellationToken, Task> handleResponseAsync,
        CancellationToken cancellationToken)
    {
        if (!OperatingSystem.IsWindowsVersionAtLeast(10, 0, 17763))
        {
            logger.LogWarning("Windows app notifications require Windows 10 version 1809 or later");
            return Task.CompletedTask;
        }

        if (cancellationToken.IsCancellationRequested)
        {
            return Task.FromCanceled(cancellationToken);
        }

        try
        {
            EnsureRegistered();
            var promptId = Guid.NewGuid().ToString("N");
            pendingPrompts[promptId] = handleResponseAsync;
            BuildNotification(promptId, request).Show(toast =>
            {
                toast.Group = NotificationGroup;
                toast.Tag = promptId;
                toast.ExpirationTime = MeetingToastExpirationPolicy.StartRecordingPromptExpiration(DateTimeOffset.Now);
            });
            logger.LogInformation(
                "Displayed native Windows meeting-start notification {PromptId} for {Subject}",
                promptId,
                request.Meeting.Subject);
        }
        catch (Exception exception)
        {
            logger.LogError(exception, "Failed to display native Windows meeting-start notification");
        }

        return Task.CompletedTask;
    }

    public Task StartAsync(CancellationToken cancellationToken)
    {
        if (!OperatingSystem.IsWindowsVersionAtLeast(10, 0, 17763))
        {
            logger.LogWarning("Windows app notifications require Windows 10 version 1809 or later");
            return Task.CompletedTask;
        }

        EnsureRegistered();
        return Task.CompletedTask;
    }

    public Task StopAsync(CancellationToken cancellationToken)
    {
        return Task.CompletedTask;
    }

    public void Dispose()
    {
        if (!registered)
        {
            return;
        }

        try
        {
            ToastNotificationManagerCompat.OnActivated -= OnNotificationInvoked;
        }
        catch (Exception exception)
        {
            logger.LogWarning(exception, "Failed to detach native Windows meeting-start notification activation handler");
        }
    }

    private void EnsureRegistered()
    {
        if (registered)
        {
            return;
        }

        lock (registrationGate)
        {
            if (registered)
            {
                return;
            }

            ToastNotificationManagerCompat.OnActivated += OnNotificationInvoked;
            registered = true;
            logger.LogInformation("Registered native Windows meeting-start notification activation handler");
        }
    }

    private static ToastContentBuilder BuildNotification(
        string promptId,
        MeetingStartPromptRequest request)
    {
        var yesButton = new ToastButton()
            .SetContent("Yes")
            .AddArgument("source", NotificationSource)
            .AddArgument("promptId", promptId)
            .AddArgument("response", "record")
            .SetBackgroundActivation();

        var noButton = new ToastButton()
            .SetContent("No")
            .AddArgument("source", NotificationSource)
            .AddArgument("promptId", promptId)
            .AddArgument("response", "skip")
            .SetBackgroundActivation();

        return new ToastContentBuilder()
            .AddArgument("source", NotificationSource)
            .AddArgument("promptId", promptId)
            .SetToastScenario(ToastScenario.Reminder)
            .SetToastDuration(ToastDuration.Long)
            .AddText("Record meeting?")
            .AddText($"{request.Meeting.Subject} starts at {request.Meeting.Start.LocalDateTime:t}.")
            .AddButton(yesButton)
            .AddButton(noButton);
    }

    private void OnNotificationInvoked(ToastNotificationActivatedEventArgsCompat args)
    {
        var arguments = NotificationActivationArguments.Parse(args.Argument);
        if (!TryGetArgument(arguments, "source", out var source) ||
            !string.Equals(source, NotificationSource, StringComparison.OrdinalIgnoreCase))
        {
            return;
        }

        if (!TryGetArgument(arguments, "promptId", out var promptId))
        {
            logger.LogWarning("Ignoring native Windows meeting-start notification activation without prompt id");
            return;
        }

        if (!pendingPrompts.TryRemove(promptId, out var handleResponseAsync))
        {
            logger.LogWarning(
                "Ignoring native Windows meeting-start notification {PromptId} activation because no pending callback exists",
                promptId);
            return;
        }

        var response = TryGetArgument(arguments, "response", out var responseValue) &&
            string.Equals(responseValue, "record", StringComparison.OrdinalIgnoreCase)
                ? MeetingStartPromptResponse.Record
                : MeetingStartPromptResponse.Skip;
        _ = Task.Run(async () =>
        {
            try
            {
                logger.LogInformation(
                    "Native Windows meeting-start notification {PromptId} activated with response {Response}",
                    promptId,
                    response);
                await handleResponseAsync(response, CancellationToken.None);
            }
            catch (Exception exception)
            {
                logger.LogError(
                    exception,
                    "Failed to handle native Windows meeting-start notification response {Response}",
                    response);
            }
        });
    }

    private static bool TryGetArgument(
        IReadOnlyDictionary<string, string> arguments,
        string key,
        out string value)
    {
        if (arguments.TryGetValue(key, out value!))
        {
            return true;
        }

        value = "";
        return false;
    }
}
#endif