namespace LehrerApp.Templating;

/// <summary>Lesbare, umbrechende Textblöcke für Berichtsbausteine. Jede Zeile ist ein eigener
/// Zeichenbefehl, damit FLOWDRAWBOX auch lange Berichte an Zeilengrenzen aufteilen kann.</summary>
public static class ReportTextDrawing
{
    public const string RepeatInfo = "Exam.RepeatInfo";
    public const string InterimGrades = "Student.InterimGrades";

    public static DrawingValue Build(string title, IEnumerable<string> paragraphs,
        float width = 170, float scale = 1, float pageHeight = 240, bool fixedBox = false)
    {
        if (!float.IsFinite(width) || !float.IsFinite(scale) || !float.IsFinite(pageHeight)
            || scale <= 0 || width < 20 * scale || pageHeight < 12 * scale)
            throw new InvalidDataException("Der Berichtsbaustein benötigt mindestens 20 × 12 mm Platz.");
        var commands = new List<DrawingCommand>();
        var lineHeight = 5f * scale;
        var y = 0f;
        // Konservative Zeichenbreiten in Gevierten der Standardschrift. Breite Buchstaben
        // bekommen mehr Raum; auch einzelne überlange Wörter werden umgebrochen.
        var available = (width - 2 * scale) / (10 * 25.4f / 72 * scale);
        static float Advance(char c) => char.IsWhiteSpace(c) ? .4f
            : c is 'm' or 'w' or 'M' or 'W' ? 1.1f
            : c > 255 ? 1.1f : char.IsUpper(c) ? 1f : .7f;
        void Line(string text, bool bold)
        {
            var offset = y % pageHeight;
            if (offset + lineHeight > pageHeight + .001f) y += pageHeight - offset;
            if (fixedBox && y + lineHeight > pageHeight + .001f)
                throw new InvalidDataException("Der Berichtsbaustein passt nicht in die feste DRAWBOX. Bitte FLOWDRAWBOX verwenden oder die Box vergrößern.");
            commands.Add(new DrawStringEx(scale, y, lineHeight, width - 2 * scale, text,
                DrawingTextAlignment.AlignLeft, 10, Bold: bold));
            y += lineHeight;
        }
        foreach (var paragraph in new[] { title }.Concat(paragraphs))
        {
            foreach (var original in paragraph.Replace("\r\n", "\n").Split('\n'))
            {
                var remaining = original.Trim();
                if (remaining.Length == 0) { Line("", false); continue; }
                while (remaining.Length > 0)
                {
                    var length = 0;
                    var used = 0f;
                    while (length < remaining.Length && used + Advance(remaining[length]) <= available)
                        used += Advance(remaining[length++]);
                    length = Math.Max(1, length);
                    var cut = length;
                    if (length < remaining.Length)
                    {
                        var space = remaining.LastIndexOf(' ', length - 1, length);
                        if (space > 0) cut = space;
                    }
                    Line(remaining[..cut], paragraph == title);
                    remaining = remaining[cut..].TrimStart();
                }
            }
        }
        return new DrawingValue(commands, y);
    }
}