QWERTYkez.OpenXmlProcessors/QWERTYkez.WordProcessor/FontPropsExtractor.cs

namespace QWERTYkez.WordProcessor;

internal static class FontPropsExtractor
{
    // ============================================================
    // Создаёт FontProps на основе Run + разрешает унаследованный шрифт.
    // ============================================================
    internal static FontProps CreateFontPropsFromRun(Run run, Paragraph paragraph)
    {
        var runProperties = run?.RunProperties;
        var fontProps = new FontProps();

        if (runProperties is not null)
        {
            var runFonts = runProperties.GetFirstChild<RunFonts>();
            var ff = ExtractFontFamily(runFonts, paragraph);
            if (!string.IsNullOrEmpty(ff))
                fontProps = fontProps with { FontFamily = ff };

            var fontSize = runProperties.GetFirstChild<FontSize>();
            if (fontSize is not null && !string.IsNullOrEmpty(fontSize.Val) &&
                uint.TryParse(fontSize.Val, out uint halfPoints))
            {
                fontProps = fontProps with { Size = halfPoints / 2.0 };
            }

            var bold = runProperties.GetFirstChild<Bold>();
            if (bold is not null)
            {
                bool isBold = bold.Val?.Value ?? true;
                fontProps = fontProps with { IsBold = isBold };
            }

            var italic = runProperties.GetFirstChild<Italic>();
            if (italic is not null)
            {
                bool isItalic = italic.Val?.Value ?? true;
                fontProps = fontProps with { IsItalic = isItalic };
            }

            var underline = runProperties.GetFirstChild<Underline>();
            if (underline?.Val is not null)
                fontProps = fontProps with { Underline = underline.Val.Value };

            var color = runProperties.GetFirstChild<Color>();
            if (color is not null && !string.IsNullOrEmpty(color.Val))
                fontProps = fontProps with { Color = color.Val };

            var verticalAlignment = runProperties.GetFirstChild<VerticalTextAlignment>();
            if (verticalAlignment?.Val is not null)
                fontProps = fontProps with { SubSup = verticalAlignment.Val.Value };
        }

        // Фолбэк: если в run шрифт не задан — идём по цепочке стилей
        if (string.IsNullOrEmpty(fontProps.FontFamily))
        {
            var fallback = ResolveInheritedFontFamily(paragraph);
            if (!string.IsNullOrEmpty(fallback))
                fontProps = fontProps with { FontFamily = fallback };
        }

        return fontProps;
    }

    // ============================================================
    // Разрешение шрифта по цепочке:
    // pStyle → BasedOn → default paragraph style → DocDefaults
    // ============================================================
    private static string? ResolveInheritedFontFamily(Paragraph paragraph)
    {
        if (paragraph is null) return null;

        var mainPart = paragraph.Ancestors<Document>().FirstOrDefault()?.OpenXmlPart as MainDocumentPart;
        var styles = mainPart?.StyleDefinitionsPart?.Styles;

        // 1. Стиль абзаца
        var pStyleId = paragraph.ParagraphProperties?.ParagraphStyleId?.Val?.Value;
        if (!string.IsNullOrEmpty(pStyleId) && styles is not null)
        {
            var ff = ResolveFromStyleChain(styles, pStyleId, mainPart);
            if (!string.IsNullOrEmpty(ff)) return ff;
        }

        // 2. Дефолтный стиль абзаца
        if (styles is not null)
        {
            var defaultParaStyle = styles.Elements<Style>()
                .FirstOrDefault(s => s.Default?.Value == true && s.Type?.Value == StyleValues.Paragraph);
            var defId = defaultParaStyle?.StyleId?.Value;
            if (!string.IsNullOrEmpty(defId))
            {
                var ff = ResolveFromStyleChain(styles, defId, mainPart);
                if (!string.IsNullOrEmpty(ff)) return ff;
            }
        }

        // 3. DocDefaults
        var docDefaultsFonts = styles?.DocDefaults?
            .RunPropertiesDefault?
            .RunPropertiesBaseStyle?
            .RunFonts;
        var docDefault = ExtractFontFamily(docDefaultsFonts, paragraph);
        if (!string.IsNullOrEmpty(docDefault)) return docDefault;

        // 4. Theme fallback (minor)
        var themeFont = TryResolveThemeFont(mainPart, isMajor: false);
        if (!string.IsNullOrEmpty(themeFont)) return themeFont;

        return null;
    }

    private static string? ResolveFromStyleChain(Styles styles, string styleId, MainDocumentPart? mainPart)
    {
        var visited = new HashSet<string>();
        var currentId = styleId;

        while (!string.IsNullOrEmpty(currentId) && visited.Add(currentId))
        {
            var style = styles.Elements<Style>()
                .FirstOrDefault(s => s.StyleId?.Value == currentId);
            if (style is null) break;

            var fonts = style.StyleRunProperties?.RunFonts;
            var ff = ExtractFontFamily(fonts, mainPart);
            if (!string.IsNullOrEmpty(ff)) return ff;

            // linked style (w:link) — иногда шрифт лежит в парном character-style
            var linkedId = style.LinkedStyle?.Val?.Value;
            if (!string.IsNullOrEmpty(linkedId) && visited.Add(linkedId))
            {
                var linked = styles.Elements<Style>()
                    .FirstOrDefault(s => s.StyleId?.Value == linkedId);
                var linkedFf = ExtractFontFamily(linked?.StyleRunProperties?.RunFonts, mainPart);
                if (!string.IsNullOrEmpty(linkedFf)) return linkedFf;
            }

            currentId = style.BasedOn?.Val?.Value;
        }
        return null;
    }

    // ============================================================
    // RunFonts → строка. Разрешает темы.
    // ============================================================
    internal static string? ExtractFontFamily(RunFonts? fonts, Paragraph? paragraph)
        => ExtractFontFamily(fonts, paragraph?.Ancestors<Document>().FirstOrDefault()?.OpenXmlPart as MainDocumentPart);

    internal static string? ExtractFontFamily(RunFonts? fonts, MainDocumentPart? mainPart)
    {
        if (fonts is null) return null;

        if (!string.IsNullOrEmpty(fonts.Ascii)) return fonts.Ascii;
        if (!string.IsNullOrEmpty(fonts.HighAnsi)) return fonts.HighAnsi;
        if (!string.IsNullOrEmpty(fonts.ComplexScript)) return fonts.ComplexScript;

        // Атрибуты темы
        bool isMajor =
            fonts.AsciiTheme?.Value == ThemeFontValues.MajorAscii ||
            fonts.AsciiTheme?.Value == ThemeFontValues.MajorHighAnsi ||
            fonts.HighAnsiTheme?.Value == ThemeFontValues.MajorAscii ||
            fonts.HighAnsiTheme?.Value == ThemeFontValues.MajorHighAnsi;

        bool hasTheme =
            fonts.AsciiTheme?.Value is not null ||
            fonts.HighAnsiTheme?.Value is not null;

        if (hasTheme)
        {
            var t = TryResolveThemeFont(mainPart, isMajor);
            if (!string.IsNullOrEmpty(t)) return t;
        }

        return null;
    }

    private static string? TryResolveThemeFont(MainDocumentPart? mainPart, bool isMajor)
    {
        var fontScheme = mainPart?.ThemePart?.Theme?.ThemeElements?.FontScheme;
        if (fontScheme is null) return null;

        var latin = isMajor
            ? fontScheme.MajorFont?.LatinFont
            : fontScheme.MinorFont?.LatinFont;

        return latin?.Typeface?.Value;
    }
}