using System.Text;
using DevExpress.Docs.Presentation;

string ExtractText(Stream inputStream, List<int> slideRange, bool extractFromShapes, bool extractFromTables, bool extractNotes) {
    using var presentation = new Presentation(inputStream);
    bool shouldExportFromAllSlides = slideRange.Count == 0;
    var sb = new StringBuilder();
    for(int i = 0; i < presentation.Slides.Count; i++) {
        if(shouldExportFromAllSlides || slideRange.Contains(i)) {
            var slide = presentation.Slides[i];
            sb.AppendLine($"## Slide {i + 1}");

            ExtractShapeText(sb, slide.Shapes, extractFromShapes, extractFromTables);
            if(extractNotes) {
                var notesText = ExtractTextFromNotes(slide);
                if(!string.IsNullOrWhiteSpace(notesText)) {
                    sb.AppendLine("### Notes");
                    sb.AppendLine(notesText);
                }
            }
            sb.AppendLine();
        }
    }
    return sb.ToString();
}
void ExtractShapeText(StringBuilder sb, ShapeCollection shapes, bool extractFromShapes, bool extractFromTables) {
    var sortedShapes = shapes.OrderBy(shape => shape.Y).ThenBy(shape => shape.X);
    foreach(ShapeBase shape in sortedShapes) {
        switch(shape) {
            case Shape textShape:
                if(extractFromShapes && textShape.TextArea != null)
                    sb.AppendLine(textShape.TextArea.Text);
                break;
            case Table table:
                if(extractFromTables)
                    sb.Append(ExtractTextFromTable(table));
                break;
            case GroupShape groupShape:

                ExtractShapeText(sb, groupShape.Shapes, extractFromShapes, extractFromTables);
                break;
        }
    }
}
public string ExtractTextFromNotes(Slide slide) {
    var notesText = string.Empty;
    if(slide.Notes != null) {
        var notesSlide = slide.Notes;
        var notesBody = notesSlide.Shapes.Where(shape => shape is Shape noteShape && noteShape.PlaceholderSettings.Type == PlaceholderType.Body).FirstOrDefault();
        notesText += notesBody != null ? ((Shape)notesBody).TextArea.Text : string.Empty;
    }
    return notesText;
}
public string ExtractTextFromTable(Table table) {
    var sb = new StringBuilder();
    for(int r = 0; r < table.Rows.Count; r++) {
        for(int c = 0; c < table.Columns.Count; c++) {
            var cell = table[r, c];
            var cellText = cell.TextArea?.Text ?? string.Empty;
            sb.Append(cellText);
            if(c != table.Columns.Count - 1)
                sb.Append('\t');
        }
        sb.AppendLine();
    }
    return sb.ToString();
}