pdf/engine/src/parser/pdfium_page_model.cpp

#include "parser/pdfium_internal.hpp"

namespace pdfengine::parser {

std::expected<PageModel, EngineError> PdfiumPage::extractDocumentModel() const {
#ifdef PDFENGINE_WITH_PDFIUM
    if (!page_) {
        return std::unexpected(EngineError::Unknown);
    }
    ensureTextPageLoaded();
    if (!textPage_) {
        return std::unexpected(EngineError::Unknown);
    }

    PageModel model;
    model.width = width();
    model.height = height();
    model.pageIndex = pageIndex_;

    int charCount = FPDFText_CountChars(textPage_);
    if (charCount <= 0) {
        return model;
    }

    std::unordered_map<std::string, FontInfo> fontMap;
    if (auto fontsRes = getFonts()) {
        for (const auto& f : *fontsRes) {
            fontMap[f.fontName] = f;
        }
    }

    std::vector<Glyph> documentGlyphs;
    documentGlyphs.reserve(charCount);

    std::unordered_map<FPDF_PAGEOBJECT, int> objToIndex;
    int objCount = FPDFPage_CountObjects(page_);
    for (int i = 0; i < objCount; ++i) {
        objToIndex[FPDFPage_GetObject(page_, i)] = i;
    }

    for (int i = 0; i < charCount; ++i) {
        unsigned int codeUnit = FPDFText_GetUnicode(textPage_, i);
        unsigned int cp = codeUnit;
        
        if (codeUnit >= 0xD800 && codeUnit <= 0xDBFF && i + 1 < charCount) {
            unsigned int nextUnit = FPDFText_GetUnicode(textPage_, i + 1);
            if (nextUnit >= 0xDC00 && nextUnit <= 0xDFFF) {
                cp = 0x10000 + ((codeUnit - 0xD800) << 10) + (nextUnit - 0xDC00);
            }
        }
        
        std::string utf8_char = code_point_to_utf8(cp);
        if (utf8_char.empty() || cp == '\r' || cp == '\n') {
            if (cp > 0xFFFF) ++i;
            continue;
        }

        Glyph g;
        g.text = std::move(utf8_char);
        g.unicode = cp;
        g.srcIndex = i;

        double left, right, bottom, top;
        FPDFText_GetCharBox(textPage_, i, &left, &right, &bottom, &top);
        g.bboxX = (std::min)(left, right);
        g.bboxY = (std::min)(bottom, top);
        g.bboxW = std::abs(right - left);
        g.bboxH = std::abs(top - bottom);
        
        FPDFText_GetCharOrigin(textPage_, i, &g.originX, &g.originY);
        g.angle = FPDFText_GetCharAngle(textPage_, i);
        
        g.fontSize = FPDFText_GetFontSize(textPage_, i);
        int flags = 0;
        unsigned long len = FPDFText_GetFontInfo(textPage_, i, nullptr, 0, &flags);
        if (len > 0) {
            std::vector<char> buf(len);
            if (FPDFText_GetFontInfo(textPage_, i, buf.data(), len, &flags) > 0) {
                g.fontName = std::string(buf.data());
            }
        }
        g.flags = flags;

        FPDF_PAGEOBJECT textObj = FPDFText_GetTextObject(textPage_, i);
        if (textObj) {
            auto it = objToIndex.find(textObj);
            if (it != objToIndex.end()) {
                g.pageObjectIndex = it->second;
            }
        }

        documentGlyphs.push_back(g);
        
        if (cp > 0xFFFF) ++i;
    }
    
    std::sort(documentGlyphs.begin(), documentGlyphs.end(), [](const Glyph& a, const Glyph& b) {
        if (std::abs(a.originY - b.originY) > 1.0) {
            return a.originY > b.originY;
        }
        return a.originX < b.originX;
    });

    std::vector<TextLine> lines;
    if (!documentGlyphs.empty()) {
        TextLine currentLine;
        currentLine.angle = documentGlyphs[0].angle;
        double currentOriginY = documentGlyphs[0].originY;
        
        for (const auto& g : documentGlyphs) {
            if (currentLine.glyphs.empty()) {
                currentLine.glyphs.push_back(g);
                continue;
            }
            
            if (std::abs(g.angle - currentLine.angle) < 0.1 &&
                std::abs(g.originY - currentOriginY) < 1.0) {
                currentLine.glyphs.push_back(g);
            } else {
                lines.push_back(std::move(currentLine));
                currentLine = TextLine();
                currentLine.angle = g.angle;
                currentOriginY = g.originY;
                currentLine.glyphs.push_back(g);
            }
        }
        if (!currentLine.glyphs.empty()) {
            lines.push_back(std::move(currentLine));
        }
    }

    for (auto& line : lines) {
        std::sort(line.glyphs.begin(), line.glyphs.end(), [](const Glyph& a, const Glyph& b) {
            if (a.originX != b.originX) return a.originX < b.originX;
            return a.srcIndex < b.srcIndex;
        });

        std::vector<double> gaps;
        for (size_t i = 1; i < line.glyphs.size(); ++i) {
            double gap = line.glyphs[i].bboxX - (line.glyphs[i-1].bboxX + line.glyphs[i-1].bboxW);
            if (gap > 0) {
                gaps.push_back(gap);
            }
        }
        double p25Gap = 0.0;
        if (!gaps.empty()) {
            std::sort(gaps.begin(), gaps.end());
            p25Gap = gaps[gaps.size() / 4];
        }

        double lineEm = 0.0;
        {
            std::vector<double> hs;
            for (const auto& gg : line.glyphs) if (gg.bboxH > 0.1) hs.push_back(gg.bboxH);
            if (!hs.empty()) {
                std::sort(hs.begin(), hs.end());
                double capH = hs[(hs.size() * 9) / 10]; 
                lineEm = capH / 0.7;
            }
        }

        TextRun currentRun;
        if (!line.glyphs.empty()) {
            const Glyph* firstG = &line.glyphs[0];
            currentRun.fontName = firstG->fontName;
            currentRun.fontSize = firstG->fontSize;
            currentRun.flags = firstG->flags;
            if (auto it = fontMap.find(currentRun.fontName); it != fontMap.end()) {
                currentRun.internalFontId = it->second.internalFontId;
                currentRun.isEmbedded = it->second.isEmbedded;
                currentRun.type = it->second.type;
                currentRun.fontFidelity = classifyFontFidelity(it->second);
            }
            currentRun.glyphs.push_back(*firstG);
            currentRun.text += firstG->text;

            for (size_t i = 1; i < line.glyphs.size(); ++i) {
                const auto& prevG = line.glyphs[i-1];
                const auto& currG = line.glyphs[i];
                
                double gap = currG.bboxX - (prevG.bboxX + prevG.bboxW);
                double em = (std::max)(static_cast<double>(currG.fontSize), lineEm);
                double spaceThreshold = em * 0.2;
                if (p25Gap > spaceThreshold) {
                    spaceThreshold = (std::min)(p25Gap * 1.5, em * 0.38);
                }

                bool addSpace = gap > spaceThreshold && prevG.text != " " && currG.text != " ";
                bool breakRun = currG.fontName != currentRun.fontName || 
                                std::abs(currG.fontSize - currentRun.fontSize) > 0.1 ||
                                currG.flags != currentRun.flags;
                
                if (addSpace) {
                    Glyph spaceGlyph;
                    spaceGlyph.text = " ";
                    spaceGlyph.unicode = ' ';
                    spaceGlyph.fontSize = currG.fontSize;
                    spaceGlyph.fontName = currG.fontName;
                    spaceGlyph.flags = currG.flags;
                    spaceGlyph.originX = prevG.bboxX + prevG.bboxW;
                    spaceGlyph.originY = currG.originY;
                    spaceGlyph.angle = currG.angle;
                    spaceGlyph.bboxX = spaceGlyph.originX;
                    spaceGlyph.bboxY = currG.bboxY;
                    spaceGlyph.bboxW = gap;
                    spaceGlyph.bboxH = currG.bboxH;
                    
                    if (breakRun) {
                        for (const auto& g : currentRun.glyphs) {
                            if (g.pageObjectIndex != -1 && std::find(currentRun.objectIndices.begin(), currentRun.objectIndices.end(), g.pageObjectIndex) == currentRun.objectIndices.end()) {
                                currentRun.objectIndices.push_back(g.pageObjectIndex);
                            }
                        }
                        line.runs.push_back(std::move(currentRun));
                        currentRun = TextRun();
                        currentRun.fontName = currG.fontName;
                        currentRun.fontSize = currG.fontSize;
                        currentRun.flags = currG.flags;
                        if (auto it = fontMap.find(currentRun.fontName); it != fontMap.end()) {
                            currentRun.internalFontId = it->second.internalFontId;
                            currentRun.isEmbedded = it->second.isEmbedded;
                            currentRun.type = it->second.type;
                            currentRun.fontFidelity = classifyFontFidelity(it->second);
                        }
                    }
                    currentRun.glyphs.push_back(spaceGlyph);
                    currentRun.text += spaceGlyph.text;
                } else if (breakRun) {
                    for (const auto& g : currentRun.glyphs) {
                        if (g.pageObjectIndex != -1 && std::find(currentRun.objectIndices.begin(), currentRun.objectIndices.end(), g.pageObjectIndex) == currentRun.objectIndices.end()) {
                            currentRun.objectIndices.push_back(g.pageObjectIndex);
                        }
                    }
                    line.runs.push_back(std::move(currentRun));
                    currentRun = TextRun();
                    currentRun.fontName = currG.fontName;
                    currentRun.fontSize = currG.fontSize;
                    currentRun.flags = currG.flags;
                    if (auto it = fontMap.find(currentRun.fontName); it != fontMap.end()) {
                        currentRun.internalFontId = it->second.internalFontId;
                        currentRun.isEmbedded = it->second.isEmbedded;
                        currentRun.type = it->second.type;
                        currentRun.fontFidelity = classifyFontFidelity(it->second);
                    }
                }
                
                currentRun.glyphs.push_back(currG);
                currentRun.text += currG.text;
            }
            if (!currentRun.glyphs.empty()) {
                for (const auto& g : currentRun.glyphs) {
                    if (g.pageObjectIndex != -1 && std::find(currentRun.objectIndices.begin(), currentRun.objectIndices.end(), g.pageObjectIndex) == currentRun.objectIndices.end()) {
                        currentRun.objectIndices.push_back(g.pageObjectIndex);
                    }
                }
                line.runs.push_back(std::move(currentRun));
            }
        }
    }

    for (auto& line : lines) {
        for (auto& run : line.runs) {
            std::string repaired = pdfengine::parser::repairMojibake(run.text);
            if (repaired != run.text) run.text = std::move(repaired);
        }
    }

    std::vector<Paragraph> paragraphs;
    auto lineStyleKey = [](const TextLine& ln) -> std::pair<bool,bool> {
        for (const auto& r : ln.runs) {
            if (r.text.empty()) continue;
            std::string n = r.fontName + "|" + r.internalFontId;
            std::transform(n.begin(), n.end(), n.begin(), [](unsigned char c){ return static_cast<char>(std::tolower(c)); });
            bool bold = n.find("bold") != std::string::npos;
            bool sans = n.find("arial") != std::string::npos || n.find("helvetica") != std::string::npos;
            return {bold, sans};
        }
        return {false, false};
    };
    if (!lines.empty()) {
        Paragraph currentPara;
        currentPara.lines.push_back(std::move(lines[0]));

        for (size_t i = 1; i < lines.size(); ++i) {
            auto& prevLine = currentPara.lines.back();
            auto& currLine = lines[i];

            double prevY = prevLine.glyphs.empty() ? 0 : prevLine.glyphs[0].originY;
            double currY = currLine.glyphs.empty() ? 0 : currLine.glyphs[0].originY;
            double fontSize = currLine.runs.empty() ? 12.0 : currLine.runs[0].fontSize;
            double capH = 0.0;
            for (const auto& g : currLine.glyphs) if (g.bboxH > capH) capH = g.bboxH;
            if (capH > 0.0) fontSize = (std::max)(fontSize, capH / 0.7);
            double vGap = std::abs(prevY - currY);

            bool styleChanged = lineStyleKey(currLine) != lineStyleKey(prevLine);
            if (vGap > fontSize * 1.5 || styleChanged) {
                paragraphs.push_back(std::move(currentPara));
                currentPara = Paragraph();
            }
            currentPara.lines.push_back(std::move(currLine));
        }
        if (!currentPara.lines.empty()) {
            paragraphs.push_back(std::move(currentPara));
        }
    }
    
    auto computeRunBBox = [](TextRun& r) {
        if (r.glyphs.empty()) return;
        double minX = r.glyphs[0].bboxX;
        double minY = r.glyphs[0].bboxY;
        double maxX = r.glyphs[0].bboxX + r.glyphs[0].bboxW;
        double maxY = r.glyphs[0].bboxY + r.glyphs[0].bboxH;
        for (size_t i = 1; i < r.glyphs.size(); ++i) {
            minX = (std::min)(minX, r.glyphs[i].bboxX);
            minY = (std::min)(minY, r.glyphs[i].bboxY);
            maxX = (std::max)(maxX, r.glyphs[i].bboxX + r.glyphs[i].bboxW);
            maxY = (std::max)(maxY, r.glyphs[i].bboxY + r.glyphs[i].bboxH);
        }
        r.x = minX;
        r.y = minY;
        r.w = maxX - minX;
        r.h = maxY - minY;
    };
    
    auto computeLineBBox = [](TextLine& l) {
        if (l.runs.empty()) return;
        double minX = l.runs[0].x;
        double minY = l.runs[0].y;
        double maxX = l.runs[0].x + l.runs[0].w;
        double maxY = l.runs[0].y + l.runs[0].h;
        for (size_t i = 1; i < l.runs.size(); ++i) {
            minX = (std::min)(minX, l.runs[i].x);
            minY = (std::min)(minY, l.runs[i].y);
            maxX = (std::max)(maxX, l.runs[i].x + l.runs[i].w);
            maxY = (std::max)(maxY, l.runs[i].y + l.runs[i].h);
        }
        l.x = minX;
        l.y = minY;
        l.w = maxX - minX;
        l.h = maxY - minY;
    };
    
    auto computeParaBBox = [](Paragraph& p) {
        if (p.lines.empty()) return;
        double minX = p.lines[0].x;
        double minY = p.lines[0].y;
        double maxX = p.lines[0].x + p.lines[0].w;
        double maxY = p.lines[0].y + p.lines[0].h;
        for (size_t i = 1; i < p.lines.size(); ++i) {
            minX = (std::min)(minX, p.lines[i].x);
            minY = (std::min)(minY, p.lines[i].y);
            maxX = (std::max)(maxX, p.lines[i].x + p.lines[i].w);
            maxY = (std::max)(maxY, p.lines[i].y + p.lines[i].h);
        }
        p.x = minX;
        p.y = minY;
        p.w = maxX - minX;
        p.h = maxY - minY;
    };

    auto hex2 = [](unsigned int c) -> std::string {
        static const char* h = "0123456789abcdef";
        c &= 0xFF;
        return std::string{h[(c >> 4) & 0xF], h[c & 0xF]};
    };
    auto computeRunColor = [&](TextRun& r) {
        if (r.objectIndices.empty()) return;
        std::vector<int> idxs = r.objectIndices;
        std::sort(idxs.begin(), idxs.end());
        for (int idx : idxs) {
            FPDF_PAGEOBJECT obj = FPDFPage_GetObject(page_, idx);
            if (!obj || FPDFPageObj_GetType(obj) != FPDF_PAGEOBJ_TEXT) continue;
            unsigned int cr = 0, cg = 0, cb = 0, ca = 0;
            bool got = (FPDFPageObj_GetFillColor(obj, &cr, &cg, &cb, &ca) && ca != 0) ||
                       (FPDFPageObj_GetStrokeColor(obj, &cr, &cg, &cb, &ca) && ca != 0);
            if (got) {
                r.fillColor = "#" + hex2(cr) + hex2(cg) + hex2(cb);
            }
            return;
        }
    };

    auto computeRunParaId = [&](TextRun& r) {
        if (r.objectIndices.empty()) return;
        int minIdx = r.objectIndices[0];
        for (int idx : r.objectIndices) if (idx < minIdx) minIdx = idx;
        FPDF_PAGEOBJECT obj = FPDFPage_GetObject(page_, minIdx);
        if (obj) r.paraId = repagGetParaId(obj);
    };

    for (auto& p : paragraphs) {
        for (auto& l : p.lines) {
            l.baselineY = l.glyphs.empty() ? 0.0 : l.glyphs[0].originY;
            for (auto& r : l.runs) {
                computeRunBBox(r);
                computeRunColor(r);
                computeRunParaId(r);
            }
            computeLineBBox(l);
        }
        computeParaBBox(p);
    }

    model.paragraphs = std::move(paragraphs);

    return model;
#else
    return std::unexpected(EngineError::Unknown);
#endif
}

std::expected<std::vector<std::string>, EngineError> PdfiumPage::extractAnnotationsText() const {
#ifdef PDFENGINE_WITH_PDFIUM
    if (!page_) {
        return std::unexpected(EngineError::Unknown);
    }
    std::vector<std::string> result;
    int count = FPDFPage_GetAnnotCount(page_);
    for (int i = 0; i < count; ++i) {
        FPDF_ANNOTATION annot = FPDFPage_GetAnnot(page_, i);
        if (!annot) continue;
        
        if (FPDFAnnot_GetSubtype(annot) == FPDF_ANNOT_FREETEXT) {
            unsigned long len = FPDFAnnot_GetStringValue(annot, "Contents", nullptr, 0);
            if (len > 2) {
                std::vector<uint8_t> buf(len);
                FPDFAnnot_GetStringValue(annot, "Contents", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
                while (!text.empty() && text.back() == '\0') {
                    text.pop_back();
                }
                if (!text.empty()) {
                    result.push_back(text);
                }
            }
        }
    }
    return result;
#else
    return std::unexpected(EngineError::Unknown);
#endif
}

std::expected<std::vector<PdfPage::AnnotationInfo>, EngineError> PdfiumPage::extractAnnotations() const {
#ifdef PDFENGINE_WITH_PDFIUM
    if (!page_) {
        return std::unexpected(EngineError::Unknown);
    }
    
    FPDF_FORMFILLINFO formInfo;
    memset(&formInfo, 0, sizeof(formInfo));
    formInfo.version = 1;
    FPDF_FORMHANDLE formHandle = FPDFDOC_InitFormFillEnvironment(doc_, &formInfo);

    std::vector<PdfPage::AnnotationInfo> result;
    int count = FPDFPage_GetAnnotCount(page_);
    for (int i = 0; i < count; ++i) {
        FPDF_ANNOTATION annot = FPDFPage_GetAnnot(page_, i);
        if (!annot) continue;
        
        PdfPage::AnnotationInfo info;
        info.pageIndex = pageIndex_;
        
        unsigned long len = FPDFAnnot_GetStringValue(annot, "NM", nullptr, 0);
        if (len > 2) {
            std::vector<uint8_t> buf(len);
            FPDFAnnot_GetStringValue(annot, "NM", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
            std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
            while (!text.empty() && text.back() == '\0') text.pop_back();
            info.id = text;
        }
        if (info.id.empty()) {
            info.id = "anno_" + std::to_string(pageIndex_) + "_" + std::to_string(i);
        }

        int subtype = FPDFAnnot_GetSubtype(annot);
        if (subtype == FPDF_ANNOT_HIGHLIGHT) {
            info.type = "highlight";
        } else if (subtype == FPDF_ANNOT_FREETEXT || subtype == FPDF_ANNOT_TEXT) {
            info.type = "comment";
        } else if (subtype == FPDF_ANNOT_INK) {
            info.type = "ink";
        } else if (subtype == FPDF_ANNOT_STRIKEOUT) {
            info.type = "strikeout";
        } else if (subtype == FPDF_ANNOT_UNDERLINE) {
            info.type = "underline";
        } else if (subtype == FPDF_ANNOT_SQUIGGLY) {
            info.type = "squiggly";
        } else if (subtype == FPDF_ANNOT_WIDGET) {
            info.type = "widget";
            
            int fieldType = FPDFAnnot_GetFormFieldType(formHandle, annot);
            
            if (fieldType == 1 || fieldType == 2 || fieldType == 3) {
                info.fieldType = "Btn";
            } else if (fieldType == 4 || fieldType == 5) {
                info.fieldType = "Ch";
            } else if (fieldType == 6) {
                info.fieldType = "Tx";
            } else if (fieldType == 7) {
                info.fieldType = "Sig";
            } else {
                info.fieldType = "Unknown";
            }
            
            info.fieldFlags = FPDFAnnot_GetFormFieldFlags(formHandle, annot);
            
            unsigned long nameLen = FPDFAnnot_GetFormFieldName(formHandle, annot, nullptr, 0);
            if (nameLen > 2) {
                std::vector<FPDF_WCHAR> nameBuf(nameLen / 2);
                FPDFAnnot_GetFormFieldName(formHandle, annot, nameBuf.data(), nameLen);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(nameBuf.data()), nameBuf.size());
                while (!text.empty() && text.back() == '\0') text.pop_back();
                info.fieldName = text;
            }
            
            unsigned long valLen = FPDFAnnot_GetFormFieldValue(formHandle, annot, nullptr, 0);
            if (valLen > 2) {
                std::vector<FPDF_WCHAR> valBuf(valLen / 2);
                FPDFAnnot_GetFormFieldValue(formHandle, annot, valBuf.data(), valLen);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(valBuf.data()), valBuf.size());
                while (!text.empty() && text.back() == '\0') text.pop_back();
                info.fieldValue = text;
            }
            
            if (info.fieldType == "Ch") {
                int optCount = FPDFAnnot_GetOptionCount(formHandle, annot);
                for (int o = 0; o < optCount; ++o) {
                    unsigned long optLen = FPDFAnnot_GetOptionLabel(formHandle, annot, o, nullptr, 0);
                    if (optLen > 2) {
                        std::vector<FPDF_WCHAR> optBuf(optLen / 2);
                        FPDFAnnot_GetOptionLabel(formHandle, annot, o, optBuf.data(), optLen);
                        std::string optText = utf16le_to_utf8(reinterpret_cast<const char16_t*>(optBuf.data()), optBuf.size());
                        while (!optText.empty() && optText.back() == '\0') optText.pop_back();
                        info.fieldOptions.push_back(optText);
                    }
                }
            }

        } else {
            info.type = "unknown";
        }

        if (info.type != "unknown") {
            FS_RECTF rect;
            if (FPDFAnnot_GetRect(annot, &rect)) {
                int dw = static_cast<int>(std::round(width()));
                int dh = static_cast<int>(std::round(height()));
                DevicePoint topLeft = pageToDevice({rect.left, rect.top}, dw, dh, 0);
                DevicePoint bottomRight = pageToDevice({rect.right, rect.bottom}, dw, dh, 0);
                
                info.x = (std::min)(topLeft.x, bottomRight.x);
                info.y = (std::min)(topLeft.y, bottomRight.y);
                info.width = std::abs(bottomRight.x - topLeft.x);
                info.height = std::abs(bottomRight.y - topLeft.y);
            }

            len = FPDFAnnot_GetStringValue(annot, "T", nullptr, 0);
            if (len > 2) {
                std::vector<uint8_t> buf(len);
                FPDFAnnot_GetStringValue(annot, "T", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
                while (!text.empty() && text.back() == '\0') text.pop_back();
                info.author = text;
            }

            len = FPDFAnnot_GetStringValue(annot, "Contents", nullptr, 0);
            if (len > 2) {
                std::vector<uint8_t> buf(len);
                FPDFAnnot_GetStringValue(annot, "Contents", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
                while (!text.empty() && text.back() == '\0') text.pop_back();
                info.content = text;
            }

            len = FPDFAnnot_GetStringValue(annot, "M", nullptr, 0);
            if (len <= 2) {
                len = FPDFAnnot_GetStringValue(annot, "CreationDate", nullptr, 0);
                if (len > 2) {
                    std::vector<uint8_t> buf(len);
                    FPDFAnnot_GetStringValue(annot, "CreationDate", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
                    std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
                    while (!text.empty() && text.back() == '\0') text.pop_back();
                    info.timestamp = text;
                }
            } else {
                std::vector<uint8_t> buf(len);
                FPDFAnnot_GetStringValue(annot, "M", reinterpret_cast<FPDF_WCHAR*>(buf.data()), len);
                std::string text = utf16le_to_utf8(reinterpret_cast<const char16_t*>(buf.data()), len / sizeof(char16_t));
                while (!text.empty() && text.back() == '\0') text.pop_back();
                info.timestamp = text;
            }

            unsigned int R = 0, G = 0, B = 0, A = 0;
            if (FPDFAnnot_GetColor(annot, FPDFANNOT_COLORTYPE_Color, &R, &G, &B, &A)) {
                char hex[10];
                snprintf(hex, sizeof(hex), "#%02x%02x%02x", R, G, B);
                info.color = hex;
            }

            if (subtype == FPDF_ANNOT_INK) {
                const double pageH = height();
                unsigned long strokeCount = FPDFAnnot_GetInkListCount(annot);
                for (unsigned long s = 0; s < strokeCount; ++s) {
                    unsigned long ptCount = FPDFAnnot_GetInkListPath(annot, s, nullptr, 0);
                    if (ptCount == 0) continue;
                    std::vector<FS_POINTF> pts(ptCount);
                    FPDFAnnot_GetInkListPath(annot, s, pts.data(), ptCount);
                    std::vector<Point2D> stroke;
                    stroke.reserve(ptCount);
                    for (const auto& p : pts) {
                        stroke.push_back(Point2D{static_cast<double>(p.x), pageH - static_cast<double>(p.y)});
                    }
                    if (!stroke.empty()) info.paths.push_back(std::move(stroke));
                }
            } else if (subtype == FPDF_ANNOT_HIGHLIGHT || subtype == FPDF_ANNOT_STRIKEOUT || subtype == FPDF_ANNOT_UNDERLINE || subtype == FPDF_ANNOT_SQUIGGLY) {
                const double pageH = height();
                size_t quadCount = FPDFAnnot_CountAttachmentPoints(annot);
                for (size_t q = 0; q < quadCount; ++q) {
                    FS_QUADPOINTSF quad;
                    if (FPDFAnnot_GetAttachmentPoints(annot, q, &quad)) {
                        std::array<Point2D, 4> pts = {{
                            {static_cast<double>(quad.x1), pageH - static_cast<double>(quad.y1)},
                            {static_cast<double>(quad.x2), pageH - static_cast<double>(quad.y2)},
                            {static_cast<double>(quad.x3), pageH - static_cast<double>(quad.y3)},
                            {static_cast<double>(quad.x4), pageH - static_cast<double>(quad.y4)}
                        }};
                        info.quadPoints.push_back(pts);
                    }
                }
            }

            result.push_back(info);
        }

        FPDFPage_CloseAnnot(annot);
    }
    
    FPDFDOC_ExitFormFillEnvironment(formHandle);
    
    return result;
#else
    return std::unexpected(EngineError::Unknown);
#endif
}


}