using MeetingAssistant.Calendar;

namespace MeetingAssistant.MeetingNotes;

internal static class CalendarAppointmentMetadata
{
    public static MeetingMetadata Create(
        string? subject,
        IEnumerable<string> attendees,
        string? body,
        DateTimeOffset end)
    {
        return new MeetingMetadata(
            ReadSubject(subject),
            NormalizeAttendees(attendees),
            ExtractAgenda(body ?? ""),
            end);
    }

    public static string ReadSubject(string? subject)
    {
        var trimmed = subject?.Trim();
        return string.IsNullOrWhiteSpace(trimmed) ? "Teams meeting" : trimmed;
    }

    public static bool IsTeamsAppointment(
        string? subject,
        string? location,
        string? body,
        string? url = null)
    {
        return TeamsMeetingMarkerDetector.IsTeamsAppointment(
            subject ?? "",
            location ?? "",
            string.Join(Environment.NewLine, body, url));
    }

    public static string ExtractAgenda(string body)
    {
        if (string.IsNullOrWhiteSpace(body))
        {
            return "";
        }

        var lines = body
            .Replace("\r\n", "\n", StringComparison.Ordinal)
            .Replace('\r', '\n')
            .Split('\n');
        var agendaLines = new List<string>();
        foreach (var line in lines)
        {
            if (IsTeamsSeparator(line) || TeamsMeetingMarkerDetector.ContainsTeamsMarker(line))
            {
                break;
            }

            agendaLines.Add(line);
        }

        return string.Join(Environment.NewLine, agendaLines).Trim();
    }

    public static IReadOnlyList<string> NormalizeAttendees(IEnumerable<string> attendees)
    {
        return attendees
            .Select(NormalizeAttendee)
            .Where(attendee => !string.IsNullOrWhiteSpace(attendee))
            .GroupBy(GetAttendeeDeduplicationKey, StringComparer.OrdinalIgnoreCase)
            .Select(group => group
                .OrderByDescending(attendee => attendee.Contains('<', StringComparison.Ordinal))
                .ThenBy(attendee => attendee.Length)
                .First())
            .ToList();
    }

    private static bool IsTeamsSeparator(string line)
    {
        var trimmed = line.Trim();
        return trimmed.Length >= 8 &&
            trimmed.All(character => character is '_' or '-' or '*' or ' ');
    }

    private static string NormalizeAttendee(string attendee)
    {
        var normalized = attendee.Trim()
            .Replace("mailto:", "", StringComparison.OrdinalIgnoreCase);
        while (normalized.Contains("  ", StringComparison.Ordinal))
        {
            normalized = normalized.Replace("  ", " ", StringComparison.Ordinal);
        }

        var emailStart = normalized.IndexOf('<', StringComparison.Ordinal);
        var emailEnd = normalized.LastIndexOf('>');
        if (emailStart > 0 && emailEnd > emailStart)
        {
            var name = normalized[..emailStart].Trim();
            var email = normalized[(emailStart + 1)..emailEnd].Trim();
            if (name.Equals(email, StringComparison.OrdinalIgnoreCase))
            {
                return email;
            }

            return $"{name} <{email}>";
        }

        return normalized;
    }

    private static string GetAttendeeDeduplicationKey(string attendee)
    {
        var emailStart = attendee.IndexOf('<', StringComparison.Ordinal);
        var emailEnd = attendee.LastIndexOf('>');
        return emailStart > 0 && emailEnd > emailStart
            ? attendee[(emailStart + 1)..emailEnd].Trim()
            : attendee.Trim();
    }
}