namespace LehrerApp.Templating;

public static class StudentReportTemplate
{
    public const string Participation = "Student.ParticipationChart";
    public const string Competencies = "Student.Competencies";
    public const string Homework = "Student.Homework";
    public const string Documentation = "Student.Documentation";
    public static IReadOnlyList<string> Drawings { get; } =
        [ReportTextDrawing.InterimGrades, Participation, Competencies, Homework, Documentation];

    public const string Layout = """
        PAGE 210 297 mm
        #pragma format-version 3
        #pragma page-template first
        TEXT 20 12 "Schülerbericht: $Student.Name" size=15
        TEXT 20 22 "Lerngruppe: $Group.Name · $Report.Period" size=10
        #pragma flow-slot body x=20 y=34 w=170 h=240
        #pragma end-page-template
        #pragma content-flow body
        FLOWDRAWBOX $Student.InterimGrades w=170 h=230 fit=content gap=5
        FLOWDRAWBOX $Student.ParticipationChart w=170 h=230 fit=content gap=5
        FLOWDRAWBOX $Student.Competencies w=170 h=230 fit=content gap=5
        FLOWDRAWBOX $Student.Homework w=170 h=230 fit=content gap=5
        FLOWDRAWBOX $Student.Documentation w=170 h=230 fit=content gap=5
        FLOWBOX $Report.Comment w=170 size=10
        #pragma end-content-flow
        """;

    public static DrawingValue SampleDrawing(string name, DeclaredDrawingBox? declared = null)
    {
        var box = declared ?? new DeclaredDrawingBox(170, 240, 1, false);
        var from = new DateOnly(2026, 1, 1);
        if (name == Participation)
            return ParticipationReportDrawing.Build([new("Gewichtete Mitarbeit", "#6C5CE7",
                [new(from, -.5), new(from.AddDays(7), .5), new(from.AddDays(14), 1.2)])], from, from.AddDays(20), box.Width, box.MillimeterScale);
        var (title, text) = name switch
        {
            ReportTextDrawing.RepeatInfo => ("Wiederholungsarbeit", new[] { "Erste Arbeit: Atombau vom 18.12.2025", "Note der ersten Arbeit: 4", "Für die Bewertung zählt die bessere Note aus beiden Arbeiten." }),
            ReportTextDrawing.InterimGrades => ("Vorläufiger Notenzwischenstand", new[] { "Stichtag: 15.01.2026 · Sprechtag", "Mündlich: 2", "Schriftlich: 3", "Vorläufige Zeugnisnote: 2-3" }),
            Competencies => ("Kompetenzen", new[] { "CH1 Aufbau der Atome beschreiben: 75 % (4 Bewertungen)" }),
            Homework => ("Hausaufgaben", new[] { "12.01.2026: Hausaufgabe gemacht", "14.01.2026: Hausaufgabe nachgereicht" }),
            _ => ("Klassenbucheinträge und Unterrichtsnotizen", new[] { "15.01.2026 · Gespräch: Lernentwicklung", "Erika arbeitet inzwischen regelmäßig mit." }),
        };
        return ReportTextDrawing.Build(title, text, box.Width, box.MillimeterScale, box.Height, box.IsFixed);
    }

    public static LoadedTemplate Create() => new(new TemplateManifest
    {
        Id = "student-report-standard", Name = "Schülerbericht Standard",
        Metadata = new() { [TemplateMetadataKeys.ReportType] = TemplateReportTypes.StudentReport },
        Placeholders = new[]
        {
            new PlaceholderDefinition("Student.Name", PlaceholderType.Text),
            new PlaceholderDefinition("Group.Name", PlaceholderType.Text),
            new PlaceholderDefinition("Report.Period", PlaceholderType.Text),
            new PlaceholderDefinition("Report.Comment", PlaceholderType.Multiline),
        }.Concat(Drawings.Select(n => new PlaceholderDefinition(n, PlaceholderType.Drawing))).ToList(),
    }, new LayoutParser().Parse(Layout), new Dictionary<string, byte[]>());
}

public sealed record ReportChartPoint(DateOnly Date, double Value);
public sealed record ReportChartSeries(string Label, string Color, IReadOnlyList<ReportChartPoint> Points);

public static class ParticipationReportDrawing
{
    public static DrawingValue Build(IReadOnlyList<ReportChartSeries> series, DateOnly from, DateOnly to,
        float width = 170, float scale = 1)
    {
        if (from > to || width < 50 * scale || scale <= 0 || !float.IsFinite(width) || !float.IsFinite(scale))
            throw new InvalidDataException("Der Mitarbeitsgraph benötigt mindestens 50 mm Breite und einen gültigen Zeitraum.");
        if (series.All(s => s.Points.Count == 0))
            return ReportTextDrawing.Build("Mitarbeitsentwicklung", ["Keine bewerteten Sitzungen im gewählten Zeitraum."], width, scale);
        var commands = new List<DrawingCommand>();
        void Text(float x, float y, string text, string color = "#334155", bool bold = false) =>
            commands.Add(new DrawString(x * scale, y * scale, text, 9, color, Bold: bold));
        var right = width / scale - 4;
        const float left = 12, top = 14, height = 40;
        Text(1, 0, "Mitarbeitsentwicklung (-2 bis +2)", bold: true);
        for (var value = -2; value <= 2; value++)
        {
            var y = top + (2 - value) / 4f * height;
            Text(1, y - 2, value.ToString(System.Globalization.CultureInfo.InvariantCulture));
            commands.Add(new DrawLine(left * scale, y * scale, right * scale, y * scale, "#CBD5E1", .2f * scale));
        }
        var days = Math.Max(1, to.DayNumber - from.DayNumber);
        foreach (var item in series)
        {
            (float X, float Y)? previous = null;
            foreach (var point in item.Points.Where(p => p.Date >= from && p.Date <= to).OrderBy(p => p.Date))
            {
                var x = (left + (point.Date.DayNumber - from.DayNumber) / (float)days * (right - left)) * scale;
                var y = (top + (2 - (float)Math.Clamp(point.Value, -2, 2)) / 4 * height) * scale;
                if (previous is { } prev) commands.Add(new DrawLine(prev.X, prev.Y, x, y, item.Color, .5f * scale));
                commands.Add(new DrawCircle(x, y, .8f * scale, item.Color, .2f * scale, item.Color));
                previous = (x, y);
            }
        }
        Text(left, 57, from.ToString("dd.MM.yyyy"));
        Text(Math.Max(left, right - 26), 57, to.ToString("dd.MM.yyyy"));
        var legendY = 64f;
        foreach (var item in series)
        {
            // Jede Kurve bekommt eine eigene beschriftete Legendenzeile.
            commands.Add(new DrawLine(left * scale, (legendY + 2) * scale, (left + 6) * scale, (legendY + 2) * scale, item.Color, .6f * scale));
            var legend = ReportTextDrawing.Build("", [item.Label], (right - left - 10) * scale, scale);
            // Legendentexte konservativ umbrechen, auch bei individuell langen Aspektnamen.
            foreach (var line in legend.Commands.OfType<DrawStringEx>().Skip(1))
                commands.Add(line with { X = (left + 9) * scale, Y = line.Y - 5 * scale + legendY * scale, Color = item.Color });
            legendY += legend.ContentHeight / scale - 5;
        }
        return new DrawingValue(commands, (legendY + 2) * scale);
    }
}