initial public release

internal/docx/parser.go

@@ -0,0 +1,147 @@
+package docx
+
+import (
+	"archive/zip"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	MaxDocxSize = 50 * 1024 * 1024 // 50MB
+)
+
+// DocumentParser handles DOCX file parsing
+type DocumentParser struct {
+	filePath string
+}
+
+// NewDocumentParser creates a new DOCX parser
+func NewDocumentParser(filePath string) *DocumentParser {
+	return &DocumentParser{filePath: filePath}
+}
+
+// ParseDOCX extracts text from a DOCX file
+// Returns (markdown text, extracted images as bytes, error)
+func (p *DocumentParser) ParseDOCX() (string, map[string][]byte, error) {
+	// Validate file size
+	fileInfo, err := os.Stat(p.filePath)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to stat file: %w", err)
+	}
+
+	if fileInfo.Size() > MaxDocxSize {
+		return "", nil, fmt.Errorf("file exceeds 50MB limit: %d bytes", fileInfo.Size())
+	}
+
+	// Validate ZIP magic number
+	f, err := os.Open(p.filePath)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to open file: %w", err)
+	}
+	defer f.Close()
+
+	magicBytes := make([]byte, 4)
+	_, err = f.Read(magicBytes)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to read magic bytes: %w", err)
+	}
+
+	if string(magicBytes) != "PK\x03\x04" {
+		return "", nil, fmt.Errorf("not a valid DOCX file (invalid ZIP header)")
+	}
+
+	// Open as ZIP
+	f.Seek(0, 0)
+	reader, err := zip.NewReader(f, fileInfo.Size())
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to open ZIP: %w", err)
+	}
+
+	// Extract document.xml
+	var docText string
+	images := make(map[string][]byte)
+
+	for _, file := range reader.File {
+		if file.Name == "word/document.xml" {
+			rc, err := file.Open()
+			if err != nil {
+				return "", nil, fmt.Errorf("failed to open document.xml: %w", err)
+			}
+			defer rc.Close()
+
+			bytes, err := io.ReadAll(rc)
+			if err != nil {
+				return "", nil, fmt.Errorf("failed to read document.xml: %w", err)
+			}
+
+			docText, err = p.extractTextFromXML(bytes)
+			if err != nil {
+				return "", nil, fmt.Errorf("failed to extract text: %w", err)
+			}
+		}
+
+		// Extract images from media/
+		if strings.HasPrefix(file.Name, "word/media/") {
+			rc, err := file.Open()
+			if err != nil {
+				continue
+			}
+			defer rc.Close()
+
+			imageBytes, err := io.ReadAll(rc)
+			if err != nil {
+				continue
+			}
+
+			fileName := filepath.Base(file.Name)
+			images[fileName] = imageBytes
+		}
+	}
+
+	return docText, images, nil
+}
+
+// extractTextFromXML parses word/document.xml and extracts plain text
+// Unsafe XML entity resolution is disabled by default in Go's xml.Decoder
+func (p *DocumentParser) extractTextFromXML(data []byte) (string, error) {
+	var doc struct {
+		XMLName xml.Name
+		Body    struct {
+			Paragraphs []struct {
+				Text     string `xml:"w|t"`
+				Runs     []struct {
+					Text string `xml:"w|t"`
+				} `xml:"w|r"`
+			} `xml:"w|p"`
+		} `xml:"w|body"`
+	}
+
+	decoder := xml.NewDecoder(strings.NewReader(string(data)))
+	// XXE protection: Go's xml.Decoder is safe by default (no entity resolution)
+	decoder.Strict = false
+
+	err := decoder.Decode(&doc)
+	if err != nil && err != io.EOF {
+		return "", fmt.Errorf("failed to decode XML: %w", err)
+	}
+
+	// Extract text from paragraphs
+	var result []string
+	for _, p := range doc.Body.Paragraphs {
+		var text []string
+		for _, run := range p.Runs {
+			if run.Text != "" {
+				text = append(text, run.Text)
+			}
+		}
+		if len(text) > 0 {
+			result = append(result, strings.Join(text, ""))
+		}
+	}
+
+	return strings.Join(result, "\n"), nil
+}