using iText.IO.Font;
using iText.IO.Font.Otf;
using iText.Kernel.Font;
using iText.Layout.Element;
using iText.Layout.Properties;
using iText.Layout.Renderer;
using System;

namespace Elwig.Documents {
    public class KernedParagraph : Paragraph {

        public KernedParagraph(float fontSize) :
            base() {
            SetFontKerning(FontKerning.YES);
            SetFixedLeading(fontSize);
            SetFontSize(fontSize);
        }

        public KernedParagraph(string text, float fontSize) :
            base(text) {
            SetFontKerning(FontKerning.YES);
            SetFixedLeading(fontSize);
            SetFontSize(fontSize);
        }

        public KernedParagraph(Text text, float fontSize) :
            base(text) {
            SetFontKerning(FontKerning.YES);
            SetFixedLeading(fontSize);
            SetFontSize(fontSize);
        }

        public override KernedParagraph Add(ILeafElement element) {
            if (element is Text t) {
                t.SetFontKerning(FontKerning.YES);
                t.SetNextRenderer(new KerningTextRenderer(t));
            }
            base.Add(element);
            return this;
        }

        public override Paragraph Add(IBlockElement element) {
            base.Add(element);
            return this;
        }

        public class KerningTextRenderer(Text textElement) : TextRenderer(textElement) {

            public override IRenderer GetNextRenderer() {
                return new KerningTextRenderer((Text)modelElement);
            }

            public override void ApplyOtf() {
                PdfFont font;
                try {
                    font = GetPropertyAsFont(Property.FONT);
                } catch (InvalidCastException) {
                    return;
                }
                if (strToBeConverted != null) {
                    SetProcessedGlyphLineAndFont(TextPreprocessingUtil.ReplaceSpecialWhitespaceGlyphs(font.CreateGlyphLine(strToBeConverted), font), font);
                }
                if (otfFeaturesApplied || text.GetStart() >= text.GetEnd()) {
                    return;
                }
                if (GetProperty(Property.FONT_KERNING, (FontKerning?)FontKerning.NO) == FontKerning.YES) {
                    ApplyKerning(font.GetFontProgram(), text);
                }
                otfFeaturesApplied = true;
            }

            private static void ApplyKerning(FontProgram font, GlyphLine text) {
                for (int i = 1; i < text.Size(); i++) {
                    var kerning = font.GetKerning(text.Get(i - 1), text.Get(i));
                    if (kerning != 0) {
                        text.Set(i - 1, new Glyph(text.Get(i - 1), 0, 0, kerning, 0, 0));
                    }
                }
            }
        }
    }
}