using LehrerApp.Core.Models;
using LehrerApp.Templating;

namespace LehrerApp.Desktop.Services;

/// <summary>
/// Baut die Standard-Platzhalterwerte für Elternbrief-Vorlagen (Datum, Anrede, Kontaktadresse,
/// Schülerdaten, Brieftext, ...). Ursprünglich Teil von
/// <see cref="ViewModels.Students.CreateLetterDialogViewModel"/>, hierher extrahiert, damit
/// <c>LetterTemplateTools</c> (MCP, siehe Planungsdokument) dieselbe Logik nutzt statt sie zu
/// duplizieren — beide Aufrufer müssen exakt dieselben Platzhalternamen befüllen, sonst driften
/// Dialog-generierte und KI-generierte Briefe unbemerkt auseinander.
/// </summary>
public static class LetterPlaceholderBuilder
{
    public static Dictionary<string, PlaceholderValue> BuildStandardValues(
        Student student, Contact? contact, LearningGroup? group, DateOnly date,
        string letterText, string teacherName, DrawingValue? attendanceCalendar = null,
        DrawingValue? absenceDays = null)
    {
        var address = FormatAddress(contact);
        return new Dictionary<string, PlaceholderValue>(StringComparer.Ordinal)
        {
            ["Datum"] = new DateValue(date), ["CurrentDate"] = new DateValue(date),
            ["Empfaenger"] = new TextValue(contact?.Name ?? ""), ["Anrede"] = new TextValue(contact?.LetterSalutation ?? ""),
            ["Brieftext"] = new MultilineValue(letterText), ["LehrerName"] = new TextValue(teacherName),
            ["Student.FirstName"] = new TextValue(student.FirstName), ["Student.LastName"] = new TextValue(student.LastName),
            ["Student.Name"] = new TextValue(student.FullName),
            ["Contact.Name"] = new TextValue(contact?.Name ?? ""), ["Contact.Address"] = new MultilineValue(address),
            ["Contact.Street"] = new TextValue(contact?.Street ?? ""), ["Contact.PostalCode"] = new TextValue(contact?.PostalCode ?? ""),
            ["Contact.City"] = new TextValue(contact?.City ?? ""), ["Letter.Salutation"] = new TextValue(contact?.LetterSalutation ?? ""),
            ["Group.Name"] = new TextValue(group?.Name ?? ""), ["SchoolYear"] = new TextValue(group?.SchoolYear ?? ""),
            [StudentAttendanceCalendarDrawingBuilder.PlaceholderName] = attendanceCalendar ?? new DrawingValue([], 0),
            [StudentAbsenceDayListDrawingBuilder.PlaceholderName] = absenceDays ?? new DrawingValue([], 0),
        };
    }

    /// <summary>Mehrzeilige Anschrift (Name/Straße/PLZ Ort) für Adressvorschau im Dialog und
    /// den <c>Contact.Address</c>-Platzhalter - eine Formatierung für beide Verwendungen.</summary>
    public static string FormatAddress(Contact? contact)
    {
        var cityLine = string.Join(" ", new[] { contact?.PostalCode, contact?.City }.Where(x => !string.IsNullOrWhiteSpace(x)));
        return string.Join(Environment.NewLine, new[] { contact?.Name, contact?.Street, cityLine }.Where(x => !string.IsNullOrWhiteSpace(x)));
    }

    public static bool IsEmpty(PlaceholderValue value) => value switch
    {
        TextValue x => string.IsNullOrWhiteSpace(x.Value),
        MultilineValue x => string.IsNullOrWhiteSpace(x.Value),
        DrawingValue x => x.ContentHeight <= 0 || x.Commands.Count == 0,
        _ => false,
    };

    /// <summary>Tatsächliche DRAWBOX/FLOWDRAWBOX-Breite eines Platzhalters (in der Maßeinheit der
    /// Vorlage) plus dem Umrechnungsfaktor "1mm in dieser Maßeinheit". DrawingValue-Builder wie
    /// <see cref="StudentAttendanceCalendarDrawingBuilder"/> entwerfen ihr Raster in Millimetern;
    /// ohne MillimeterScale bliebe das bei einer in "pt" (statt "mm") deklarierten Vorlage viel zu
    /// klein (1 "mm-Einheit" würde als 1pt ≈ 0.35mm gerendert).</summary>
    public readonly record struct DeclaredDrawingBox(float Width, float MillimeterScale);

    public static DeclaredDrawingBox? FindDeclaredDrawingBox(LoadedTemplate template, string placeholderName) =>
        FindDeclaredDrawingBox(template.Layout, placeholderName) ??
        (template.ContinuationLayout is not null ? FindDeclaredDrawingBox(template.ContinuationLayout, placeholderName) : null);

    private static DeclaredDrawingBox? FindDeclaredDrawingBox(TemplateLayout layout, string placeholderName)
    {
        var width = layout.Elements.Concat(layout.PageTemplates.SelectMany(p => p.Elements))
            .Concat(layout.ContentFlows.SelectMany(f => f.Elements))
            .Select(e => e switch
            {
                DrawBoxElement draw when draw.Placeholder == placeholderName => (float?)draw.Width,
                FlowDrawBoxElement flow when flow.Placeholder == placeholderName => (float?)flow.Width,
                _ => null,
            })
            .FirstOrDefault(w => w is not null);
        if (width is null) return null;
        var millimeterScale = UnitConverter.Points(1, "mm") / UnitConverter.Points(1, layout.Unit);
        return new DeclaredDrawingBox(width.Value, millimeterScale);
    }
}