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,
        };
        // Die Breite richtet sich nach der DRAWBOX-Deklaration im Layout-Skript (fest, unabhängig
        // von der Größenwahl) - nur Schrift/Zellenhöhe skalieren mit "Größe". Würde die Breite mit
        // skalieren, würde "Groß" (scale=1) exakt die Skript-Box ausfüllen, "Klein"/"Normal" aber
        // nur einen Teil davon - und eine größere Skalierung als 1 liefe über die Box hinaus und
        // würde am rechten Rand abgeschnitten (SVG overflow="hidden").
        var contentWidth = width;
        var cellHeight = 10 * scale;
        // War 10 - bei 3 Monaten nebeneinander größer als eine einzelne Tageskachel und zog damit
        // spürbar Platz von den Kacheln ab, ohne selbst als Inhalt wahrgenommen zu werden.
        var monthGapX = 6f;
        var first = options.NormalizedStartMonth;
        var monthCount = options.NormalizedMonthCount;
        var monthWidth = (contentWidth - monthGapX * (monthCount - 1)) / monthCount;
        var cellWidth = monthWidth / 7;
        // Kachel-Zwischenraum (Trennung zu Nachbarzellen) deutlich knapper als vorher (war "scale",
        // also bis zu 1mm auf jeder Seite - bei einer ~7mm breiten Zelle ein gutes Viertel reiner
        // Leerraum). Die Kachel selbst füllt dadurch ihren Rasterplatz sichtbar besser aus.
        var cellInset = scale * .4f;
        var cellCornerRadius = Math.Min(cellWidth, cellHeight) * .2f;
        var commands = new List<DrawingCommand>();
        var y = 0f;
        commands.Add(new DrawStringEx(0, y, 14 * scale, contentWidth, "Anwesenheit",
            DrawingTextAlignment.AlignLeft, 11 * scale, Color: "#1F2937", Bold: true));
        y += 14 * scale;
        commands.Add(new DrawStringEx(0, y, 10 * scale, contentWidth, studentName,
            DrawingTextAlignment.AlignLeft, 8 * scale, Color: "#6B7280"));
        y += 10 * scale + 2 * scale;
        var weekdays = new[] { "Mo", "Di", "Mi", "Do", "Fr", "Sa", "So" };
        var gridStartY = y;
        var maxWeeks = 0;
        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);
            maxWeeks = Math.Max(maxWeeks, weeks);
            var xOffset = monthIndex * (monthWidth + monthGapX);
            var monthY = gridStartY;
            commands.Add(new DrawStringEx(xOffset, monthY, 11 * scale, monthWidth,
                current.ToString("MMMM yyyy", CultureInfo.GetCultureInfo("de-DE")),
                DrawingTextAlignment.AlignLeft, 9 * scale, Color: "#374151", Bold: true));
            monthY += 11 * scale;
            for (var column = 0; column < 7; column++)
                commands.Add(new DrawStringEx(xOffset + column * cellWidth, monthY, 9 * scale, cellWidth,
                    weekdays[column], DrawingTextAlignment.AlignCenter, 7 * scale, Color: "#6B7280", Bold: true));
            monthY += 9 * scale;

            foreach (var day in days)
            {
                var index = offset + day.Date.Day - 1;
                var column = index % 7;
                var row = index / 7;
                var x = xOffset + column * cellWidth;
                var cellY = monthY + row * cellHeight;
                commands.Add(new DrawRoundedRectangle(x + cellInset, cellY, cellWidth - 2 * cellInset,
                    cellHeight - cellInset, cellCornerRadius, "#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 = gridStartY + 11 * scale + 9 * scale + maxWeeks * cellHeight + monthGapX;

        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>Chronologische, portable Fehlzeitenliste für Elternbriefvorlagen.</summary>
public static class StudentAbsenceDayListDrawingBuilder
{
    public const string PlaceholderName = "Student.AbsenceDays";

    public static DrawingValue Build(string studentName, AttendanceCalendarOptions options,
        IReadOnlyList<ClassAbsenceDaySummaryRow> absences)
    {
        const float width = 170;
        var scale = options.Size switch
        {
            AttendanceCalendarSize.Small => .75f,
            AttendanceCalendarSize.Large => 1f,
            _ => .88f,
        };
        // Breite bleibt an die DRAWBOX-Deklaration im Layout-Skript gebunden (siehe
        // StudentAttendanceCalendarDrawingBuilder) - nur Zeilenhöhe/Schrift skalieren mit "Größe".
        var contentWidth = width;
        var rowHeight = 12 * scale;
        var start = options.NormalizedStartMonth;
        var end = start.AddMonths(options.NormalizedMonthCount).AddDays(-1);
        var rows = absences
            .Where(a => a.Date >= start && a.Date <= end &&
                        UntisNameMatching.NamesMatch(a.StudentName, studentName))
            .OrderBy(a => a.Date)
            .ToList();
        var commands = new List<DrawingCommand>();
        var y = 0f;
        commands.Add(new DrawStringEx(0, y, 14 * scale, contentWidth, "Fehltage",
            DrawingTextAlignment.AlignLeft, 11 * scale, Color: "#1F2937", Bold: true));
        y += 14 * scale;
        commands.Add(new DrawStringEx(0, y, 10 * scale, contentWidth, studentName,
            DrawingTextAlignment.AlignLeft, 8 * scale, Color: "#6B7280"));
        y += 10 * scale + 2 * scale;
        // Spaltenbreiten so gewählt, dass auch die Datenzeilen (nicht nur die kurzen Kopfzeilen-
        // Labels) hineinpassen - "Datum" als Kopfzeile ist kürzer als "dd.MM.yyyy" und wurde bei
        // 31 zu schmal bemessen, wodurch das Datum am rechten Rand abgeschnitten wurde.
        const float dateColumnX = 2, dateColumnWidth = 38;
        const float extentColumnX = 44, extentColumnWidth = 66;
        const float statusColumnX = 114, statusColumnWidth = 54;
        commands.Add(new DrawRectangle(0, y, contentWidth, rowHeight, "#CBD5E1", .4f, "#F3F4F6"));
        commands.Add(new DrawStringEx(dateColumnX, y + scale, rowHeight - scale, dateColumnWidth, "Datum",
            DrawingTextAlignment.AlignLeft, 7.5f * scale, Color: "#374151", Bold: true));
        commands.Add(new DrawStringEx(extentColumnX, y + scale, rowHeight - scale, extentColumnWidth, "Umfang",
            DrawingTextAlignment.AlignLeft, 7.5f * scale, Color: "#374151", Bold: true));
        commands.Add(new DrawStringEx(statusColumnX, y + scale, rowHeight - scale, statusColumnWidth, "Status",
            DrawingTextAlignment.AlignLeft, 7.5f * scale, Color: "#374151", Bold: true));
        y += rowHeight;

        if (rows.Count == 0)
        {
            commands.Add(new DrawStringEx(2, y + 2 * scale, rowHeight, contentWidth - 4,
                "Keine Fehltage im gewählten Zeitraum", DrawingTextAlignment.AlignLeft, 8 * scale,
                Color: "#6B7280", Italic: true));
            y += rowHeight + 3 * scale;
        }
        else
        {
            for (var index = 0; index < rows.Count; index++)
            {
                var row = rows[index];
                var fill = index % 2 == 0 ? "#FFFFFF" : "#F9FAFB";
                var extent = row.CountsAsFullDay
                    ? "Ganzer Fehltag"
                    : row.TotalAbsentPeriods > 0
                        ? $"Fehlzeit · {row.TotalAbsentPeriods} Std."
                        : $"Fehlzeit · {row.TotalAbsentMinutes} Min.";
                var status = row.IsUnexcused
                    ? "Unentschuldigt"
                    : row.FriendlyStatusLabel.Contains("Entschuldigt", StringComparison.OrdinalIgnoreCase)
                        ? "Entschuldigt"
                        : row.FriendlyStatusLabel;
                var statusColor = row.IsUnexcused ? "#C62828" : "#2E7D32";
                commands.Add(new DrawRectangle(0, y, contentWidth, rowHeight, "#E5E7EB", .3f, fill));
                commands.Add(new DrawStringEx(dateColumnX, y + scale, rowHeight - scale, dateColumnWidth,
                    row.Date.ToString("dd.MM.yyyy"), DrawingTextAlignment.AlignLeft, 7.5f * scale,
                    Color: "#374151"));
                commands.Add(new DrawStringEx(extentColumnX, y + scale, rowHeight - scale, extentColumnWidth,
                    extent, DrawingTextAlignment.AlignLeft, 7.5f * scale, Color: "#374151"));
                commands.Add(new DrawStringEx(statusColumnX, y + scale, rowHeight - scale, statusColumnWidth,
                    status, DrawingTextAlignment.AlignLeft, 7.5f * scale, Color: statusColor,
                    Bold: row.IsUnexcused));
                y += rowHeight;
            }
        }
        return new DrawingValue(commands, y);
    }
}

/// <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 matchName = $"{student.FirstName} {student.LastName}";
        var rosterName = rosterCache.GetByClass(className)
            .FirstOrDefault(r => UntisNameMatching.NamesMatch(r.DisplayName, matchName))?.DisplayName
            ?? matchName;
        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);
    }

    public DrawingValue BuildAbsenceDayList(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 matchName = $"{student.FirstName} {student.LastName}";
        var rosterName = rosterCache.GetByClass(className)
            .FirstOrDefault(r => UntisNameMatching.NamesMatch(r.DisplayName, matchName))?.DisplayName
            ?? matchName;
        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));
        return StudentAbsenceDayListDrawingBuilder.Build(rosterName, options,
            ClassAbsenceDaySummaryRow.GroupByStudentAndDay(absences));
    }
}