using System.Diagnostics;
using MeetingAssistant.Calendar;

namespace MeetingAssistant.MeetingNotes;

public sealed class OutlookClassicMeetingMetadataProvider : IMeetingMetadataProvider, IMeetingMetadataDiagnosticProvider
{
    private readonly ILogger<OutlookClassicMeetingMetadataProvider> logger;

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

    public Task<MeetingMetadata?> GetCurrentMeetingAsync(
        DateTimeOffset startedAt,
        CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();
        try
        {
            return OutlookClassicCom.RunStaAsync(
                () => GetCurrentMeeting(startedAt),
                cancellationToken,
                "Meeting Assistant Outlook COM Lookup");
        }
        catch (Exception exception) when (exception is not OperationCanceledException)
        {
            logger.LogDebug(exception, "Outlook Classic meeting metadata was not available");
            return Task.FromResult<MeetingMetadata?>(null);
        }
    }

    public async Task<MeetingMetadataDiagnosticResult> DiagnoseCurrentMeetingAsync(
        DateTimeOffset startedAt,
        TimeSpan timeout,
        CancellationToken cancellationToken)
    {
        var stopwatch = Stopwatch.StartNew();
        try
        {
            var lookup = OutlookClassicCom.RunStaAsync(
                () => GetCurrentMeeting(startedAt),
                cancellationToken,
                "Meeting Assistant Outlook COM Lookup");
            var metadata = timeout > TimeSpan.Zero
                ? await lookup.WaitAsync(timeout, cancellationToken)
                : await lookup.WaitAsync(cancellationToken);
            stopwatch.Stop();
            return new MeetingMetadataDiagnosticResult(
                nameof(OutlookClassicMeetingMetadataProvider),
                startedAt,
                metadata is not null,
                false,
                stopwatch.ElapsedMilliseconds,
                metadata,
                metadata is null ? "No matching Teams appointment was found." : null);
        }
        catch (TimeoutException exception)
        {
            stopwatch.Stop();
            return new MeetingMetadataDiagnosticResult(
                nameof(OutlookClassicMeetingMetadataProvider),
                startedAt,
                false,
                true,
                stopwatch.ElapsedMilliseconds,
                null,
                exception.Message);
        }
        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
        {
            throw;
        }
        catch (Exception exception)
        {
            stopwatch.Stop();
            return new MeetingMetadataDiagnosticResult(
                nameof(OutlookClassicMeetingMetadataProvider),
                startedAt,
                false,
                false,
                stopwatch.ElapsedMilliseconds,
                null,
                exception.Message);
        }
    }

    private MeetingMetadata? GetCurrentMeeting(DateTimeOffset startedAt)
    {
        using var calendar = OutlookClassicCom.OpenDefaultCalendar(logger, "metadata lookup");
        if (calendar is null)
        {
            return null;
        }

        var startedLocal = startedAt.LocalDateTime;
        var windowStart = startedLocal.AddHours(-4);
        var windowEnd = startedLocal.AddMinutes(5);

        var candidates = new List<OutlookAppointmentCandidate>();
        foreach (var item in OutlookClassicCom.EnumerateItems(calendar.Items))
        {
            if (item is null)
            {
                continue;
            }

            var keepAppointment = false;
            try
            {
                if (!OutlookClassicCom.IsAppointment(item))
                {
                    continue;
                }

                var start = Convert.ToDateTime(OutlookClassicCom.GetProperty(item, "Start"));
                if (start > windowEnd)
                {
                    break;
                }

                var end = Convert.ToDateTime(OutlookClassicCom.GetProperty(item, "End"));
                if (end < windowStart ||
                    OutlookClassicCom.IsCanceledAppointment(item) ||
                    !OutlookClassicAppointmentMetadata.IsTeamsAppointment(item))
                {
                    continue;
                }

                candidates.Add(new OutlookAppointmentCandidate(item, start, end));
                keepAppointment = true;
            }
            finally
            {
                if (!keepAppointment)
                {
                    OutlookClassicCom.ReleaseComObject(item);
                }
            }
        }

        try
        {
            var selected = OutlookMeetingCandidateSelector.Select(
                candidates,
                startedLocal,
                candidate => candidate.Start,
                candidate => candidate.End);
            if (selected is null)
            {
                return null;
            }

            return OutlookClassicAppointmentMetadata.CreateMetadata(selected.Appointment, selected.End);
        }
        finally
        {
            foreach (var candidate in candidates)
            {
                OutlookClassicCom.ReleaseComObject(candidate.Appointment);
            }
        }
    }

    private sealed record OutlookAppointmentCandidate(
        object Appointment,
        DateTime Start,
        DateTime End);
}