using System.Globalization;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Desktop.ViewModels.ClassTeacher;
using LehrerApp.Templating;

namespace LehrerApp.Desktop.Services;

public enum AttendanceCalendarSize { Small, Medium, Large }

public sealed record AttendanceCalendarOptions(DateOnly StartMonth, int MonthCount,
    AttendanceCalendarSize Size = AttendanceCalendarSize.Medium)
{
    public DateOnly NormalizedStartMonth => new(StartMonth.Year, StartMonth.Month, 1);
    public int NormalizedMonthCount => Math.Clamp(MonthCount, 1, 3);
}

/// <summary>Erzeugt den portablen Advanced-Content-Platzhalter für Elternbriefe aus derselben
/// priorisierten Monatsansicht, die im Klassenlehrer-Sidebar-Widget verwendet wird.</summary>
public static class StudentAttendanceCalendarDrawingBuilder
{
    public const string PlaceholderName = "Student.AttendanceCalendar";

    public static DrawingValue Build(string studentName, DateOnly month,
        IReadOnlyList<ClassAbsenceDaySummaryRow> absences,
        IReadOnlyList<UntisForeignClassRegisterEventDto> registerEntries) =>
        Build(studentName, new AttendanceCalendarOptions(month, 1), absences, registerEntries);

    public static DrawingValue Build(string studentName, AttendanceCalendarOptions options,
        IReadOnlyList<ClassAbsenceDaySummaryRow> absences,
        IReadOnlyList<UntisForeignClassRegisterEventDto> registerEntries)
    {
        const float width = 170;
        var scale = options.Size switch
        {
            AttendanceCalendarSize.Small => .7f,
            AttendanceCalendarSize.Large => 1f,
            _ => .85f,
        };
        var contentWidth = width * scale;
        var cellWidth = contentWidth / 7;
        var cellHeight = 10 * scale;
        var monthGap = 6 * scale;
        var first = options.NormalizedStartMonth;
        var monthCount = options.NormalizedMonthCount;
        var commands = new List<DrawingCommand>
        {
            new DrawStringEx(0, 0, 7 * scale, contentWidth, "Anwesenheit",
                DrawingTextAlignment.AlignLeft, 11 * scale, Color: "#1F2937", Bold: true),
            new DrawStringEx(0, 7 * scale, 6 * scale, contentWidth, studentName,
                DrawingTextAlignment.AlignLeft, 8 * scale, Color: "#6B7280"),
        };
        var weekdays = new[] { "Mo", "Di", "Mi", "Do", "Fr", "Sa", "So" };
        var y = 15 * scale;
        for (var monthIndex = 0; monthIndex < monthCount; monthIndex++)
        {
            var current = first.AddMonths(monthIndex);
            var days = ClassTeacherOverviewViewModel.BuildCompactMonthDays(current, absences, registerEntries,
                DateOnly.FromDateTime(DateTime.Today), studentName);
            var offset = ((int)current.DayOfWeek + 6) % 7;
            var weeks = (int)Math.Ceiling((offset + days.Count) / 7d);
            commands.Add(new DrawStringEx(0, y, 7 * scale, contentWidth,
                current.ToString("MMMM yyyy", CultureInfo.GetCultureInfo("de-DE")),
                DrawingTextAlignment.AlignLeft, 9 * scale, Color: "#374151", Bold: true));
            y += 7 * scale;
            for (var column = 0; column < 7; column++)
                commands.Add(new DrawStringEx(column * cellWidth, y, 6 * scale, cellWidth, weekdays[column],
                    DrawingTextAlignment.AlignCenter, 7 * scale, Color: "#6B7280", Bold: true));
            y += 7 * scale;

            foreach (var day in days)
            {
                var index = offset + day.Date.Day - 1;
                var column = index % 7;
                var row = index / 7;
                var x = column * cellWidth;
                var cellY = y + row * cellHeight;
                commands.Add(new DrawRectangle(x + scale, cellY, cellWidth - 2 * scale, cellHeight - scale,
                    "#D1D5DB", .35f, day.HasSignal ? day.SignalColorHex : "#FFFFFF"));
                commands.Add(new DrawStringEx(x, cellY + scale, cellHeight - 2 * scale, cellWidth,
                    day.HasSignal ? day.SignalCode : day.DayNumber, DrawingTextAlignment.AlignCenter, 7 * scale,
                    Color: day.HasSignal ? "#FFFFFF" : "#374151", Bold: day.HasSignal));
            }
            y += weeks * cellHeight + monthGap;
        }

        commands.Add(new DrawStringEx(0, y, 8 * scale, contentWidth,
            "U unentschuldigt · A abwesend · V verspätet · E entschuldigt · ! Klassenbuch",
            DrawingTextAlignment.AlignLeft, 6.5f * scale, Color: "#6B7280"));
        return new DrawingValue(commands, y + 9 * scale);
    }
}

/// <summary>Liest ausschließlich den lokalen WebUntis-Cache. Das Öffnen oder Rendern eines
/// Elternbriefs löst dadurch keinen unerwarteten Netzwerkabruf aus.</summary>
public sealed class StudentAttendanceCalendarService(
    WebUntisSettingsService settings,
    IUntisAbsenceCacheRepository absenceCache,
    IUntisClassRegisterCacheRepository registerCache,
    IUntisStudentRosterCacheRepository rosterCache)
{
    public DrawingValue Build(Student student, DateOnly month) =>
        Build(student, new AttendanceCalendarOptions(month, 1));

    public DrawingValue Build(Student student, AttendanceCalendarOptions options)
    {
        var className = settings.HomeroomClassName;
        if (string.IsNullOrWhiteSpace(className)) return new DrawingValue([], 0);

        var first = options.NormalizedStartMonth;
        var last = first.AddMonths(options.NormalizedMonthCount).AddDays(-1);
        var rosterName = rosterCache.GetByClass(className)
            .FirstOrDefault(r => UntisNameMatching.NamesMatch(r.DisplayName, student.FullName))?.DisplayName
            ?? student.FullName;
        var start = first.Year * 10000 + first.Month * 100 + first.Day;
        var end = last.Year * 10000 + last.Month * 100 + last.Day;
        var absences = absenceCache.GetByClassAndRange(className, start, end)
            .Select(e => new UntisClassAbsenceEntryDto(e.StudentName, e.ExternKey, e.ClassName, e.Date,
                e.AbsentPeriods, e.AbsentMinutes, e.TeacherUsernames, e.Subject, e.AbsenceReason, e.Note,
                e.EntryId, e.HandledOn, e.Counts, e.ExcuseNote, e.PeriodNumber, e.Status, e.CountsAsFullDay))
            .ToList();
        var register = registerCache.GetByClassAndRange(className, start, end)
            .Select(e => new UntisForeignClassRegisterEventDto(e.ClassName, e.Date, e.Subject, e.StudentName,
                e.TeacherUsername, e.CategoryName, e.CategoryGroup, e.Text))
            .ToList();
        return StudentAttendanceCalendarDrawingBuilder.Build(rosterName, options,
            ClassAbsenceDaySummaryRow.GroupByStudentAndDay(absences), register);
    }
}