#if WINDOWS
using System.Collections;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace MeetingAssistant.MeetingNotes;

internal static class OutlookClassicCom
{
    private const int OutlookCalendarFolder = 9;

    public static OutlookCalendarSession? OpenDefaultCalendar(
        ILogger logger,
        string logContext)
    {
        EnsureOutlookRunning(logger, logContext);

        object? application = null;
        object? session = null;
        object? calendar = null;
        object? items = null;

        try
        {
            var applicationType = Type.GetTypeFromProgID("Outlook.Application");
            if (applicationType is null)
            {
                return null;
            }

            application = Activator.CreateInstance(applicationType);
            if (application is null)
            {
                return null;
            }

            session = GetProperty(application, "Session");
            calendar = Invoke(session!, "GetDefaultFolder", OutlookCalendarFolder);
            items = GetProperty(calendar!, "Items");
            Invoke(items!, "Sort", "[Start]");
            SetProperty(items!, "IncludeRecurrences", true);

            return new OutlookCalendarSession(application, session, calendar, items!);
        }
        catch
        {
            ReleaseComObject(items);
            ReleaseComObject(calendar);
            ReleaseComObject(session);
            ReleaseComObject(application);
            throw;
        }
    }

    public static Task<T> RunStaAsync<T>(
        Func<T> action,
        CancellationToken cancellationToken,
        string threadName)
    {
        var completion = new TaskCompletionSource<T>(TaskCreationOptions.RunContinuationsAsynchronously);
        var thread = new Thread(() =>
        {
            try
            {
                completion.TrySetResult(action());
            }
            catch (Exception exception)
            {
                completion.TrySetException(exception);
            }
        })
        {
            IsBackground = true,
            Name = threadName
        };
        thread.SetApartmentState(ApartmentState.STA);

        var registration = cancellationToken.Register(() => completion.TrySetCanceled(cancellationToken));
        _ = completion.Task.ContinueWith(
            _ => registration.Dispose(),
            CancellationToken.None,
            TaskContinuationOptions.ExecuteSynchronously,
            TaskScheduler.Default);
        thread.Start();
        return completion.Task;
    }

    public static IEnumerable<object?> EnumerateItems(object items)
    {
        if (items is IEnumerable enumerable)
        {
            foreach (var item in enumerable)
            {
                yield return item;
            }
        }
    }

    public static bool IsAppointment(object item)
    {
        try
        {
            return Convert.ToInt32(GetProperty(item, "Class")) == 26;
        }
        catch
        {
            return false;
        }
    }

    public static bool IsCanceledAppointment(object appointment)
    {
        var meetingStatus = TryGetProperty(appointment, "MeetingStatus");
        if (meetingStatus is not null)
        {
            try
            {
                var status = Convert.ToInt32(meetingStatus);
                if (status is 5 or 7)
                {
                    return true;
                }
            }
            catch (Exception exception) when (exception is FormatException or InvalidCastException or OverflowException)
            {
                // Fall back to subject prefixes when Outlook exposes a non-numeric status value.
            }
        }

        var subject = Convert.ToString(TryGetProperty(appointment, "Subject")) ?? "";
        return SubjectIndicatesCancellation(subject);
    }

    internal static bool SubjectIndicatesCancellation(string subject)
    {
        var normalized = subject.TrimStart();
        return normalized.StartsWith("Canceled:", StringComparison.OrdinalIgnoreCase) ||
            normalized.StartsWith("Cancelled:", StringComparison.OrdinalIgnoreCase) ||
            normalized.StartsWith("Abgesagt:", StringComparison.OrdinalIgnoreCase);
    }

    public static DateTimeOffset ToLocalOffset(DateTime value)
    {
        return new DateTimeOffset(DateTime.SpecifyKind(value, DateTimeKind.Local));
    }

    public static object? TryGetProperty(object target, string name)
    {
        try
        {
            return GetProperty(target, name);
        }
        catch
        {
            return null;
        }
    }

    public static object? GetProperty(object target, string name)
    {
        return target.GetType().InvokeMember(
            name,
            System.Reflection.BindingFlags.GetProperty,
            null,
            target,
            null);
    }

    public static void SetProperty(object target, string name, object value)
    {
        target.GetType().InvokeMember(
            name,
            System.Reflection.BindingFlags.SetProperty,
            null,
            target,
            [value]);
    }

    public static object? Invoke(object target, string name, params object[] arguments)
    {
        return target.GetType().InvokeMember(
            name,
            System.Reflection.BindingFlags.InvokeMethod,
            null,
            target,
            arguments);
    }

    public static void ReleaseComObject(object? value)
    {
        if (value is not null && Marshal.IsComObject(value))
        {
            Marshal.FinalReleaseComObject(value);
        }
    }

    private static void EnsureOutlookRunning(ILogger logger, string logContext)
    {
        if (Process.GetProcessesByName("OUTLOOK").Length > 0)
        {
            return;
        }

        try
        {
            Process.Start(new ProcessStartInfo
            {
                FileName = "outlook.exe",
                UseShellExecute = true
            });
            Thread.Sleep(TimeSpan.FromSeconds(5));
        }
        catch (Exception exception)
        {
            logger.LogDebug(exception, "Could not start Outlook Classic before {OutlookContext}", logContext);
        }
    }
}

internal sealed class OutlookCalendarSession : IDisposable
{
    private readonly object? application;
    private readonly object? session;
    private readonly object? calendar;

    public OutlookCalendarSession(
        object? application,
        object? session,
        object? calendar,
        object items)
    {
        this.application = application;
        this.session = session;
        this.calendar = calendar;
        Items = items;
    }

    public object Items { get; }

    public void Dispose()
    {
        OutlookClassicCom.ReleaseComObject(Items);
        OutlookClassicCom.ReleaseComObject(calendar);
        OutlookClassicCom.ReleaseComObject(session);
        OutlookClassicCom.ReleaseComObject(application);
    }
}
#endif