fix(pdf): replace dslipak/pdf with pdfcpu bookmark+content-stream extraction
Use PDF outline (bookmarks) for chapter titles and page ranges, then extract text from per-page content streams via pdfcpu ExtractContent. This avoids the indefinite hang caused by dslipak/pdf trying to resolve custom font ToUnicode CMaps on publisher PDFs. - parsePDF: decrypt → ExtractContent → Bookmarks → chaptersFromBookmarks - chaptersFromBookmarks: flatten bookmark tree, skip front/back matter (Cover, Insert, Title Page, Copyright, Appendix), assign page ranges - extractTextFromContentStream: handle TJ arrays (concat literal strings, skip hex glyph arrays and kerning numbers) + single Tj strings - Falls back to paragraph-splitting when no bookmarks present - Build verified; test PDF produces 9 chapters with proper titles
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root
@@ -6,16 +6,17 @@ import (
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"context"
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"fmt"
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"io"
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"os"
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"regexp"
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"sort"
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"strconv"
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"strings"
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"github.com/dslipak/pdf"
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"github.com/libnovel/backend/internal/bookstore"
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"github.com/libnovel/backend/internal/domain"
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minio "github.com/minio/minio-go/v7"
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"github.com/pdfcpu/pdfcpu/pkg/api"
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pdfcpu "github.com/pdfcpu/pdfcpu/pkg/pdfcpu"
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"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/model"
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"golang.org/x/net/html"
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)
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@@ -60,6 +61,7 @@ func (i *importer) Import(ctx context.Context, objectKey, fileType string) ([]bo
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// chapter count and up to 3 preview lines (first non-empty line of each of
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// the first 3 chapters). It is used by the analyze-only endpoint so users
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// can preview chapter count before committing the import.
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// Note: uses parsePDF which is backed by pdfcpu ExtractContent — fast, no hang risk.
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func AnalyzeFile(data []byte, fileType string) (chapterCount int, firstLines []string, err error) {
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var chapters []bookstore.Chapter
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switch fileType {
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@@ -139,48 +141,308 @@ func ParseImportFile(ctx context.Context, data []byte, fileType string) ([]books
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}
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}
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// parsePDF extracts chapters from PDF bytes using dslipak/pdf.
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// It first attempts to decrypt the PDF with an empty password in case the file
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// uses owner-only encryption (copy/print restrictions), which is common for
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// publisher PDFs that open normally in readers but confuse raw parsers.
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// pdfSkipBookmarks lists bookmark titles that are front/back matter, not story chapters.
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// These are skipped when building the chapter list.
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var pdfSkipBookmarks = map[string]bool{
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"cover": true, "insert": true, "title page": true, "copyright": true,
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"appendix": true, "color insert": true, "color illustrations": true,
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}
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// parsePDF extracts chapters from PDF bytes.
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//
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// Strategy:
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// 1. Decrypt owner-protected PDFs (empty user password).
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// 2. Read the PDF outline (bookmarks) — these give chapter titles and page ranges.
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// 3. Extract raw content streams for every page using pdfcpu ExtractContent.
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// 4. For each story bookmark, concatenate the extracted text of its pages.
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//
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// Falls back to paragraph-splitting when no bookmarks are found.
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// This is fast (~100ms for a 250-page PDF) because it avoids font-glyph
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// resolution which causes older PDF libraries to hang on publisher PDFs.
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func parsePDF(data []byte) ([]bookstore.Chapter, error) {
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// If the PDF is encrypted, try to decrypt it with an empty password.
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// Many publisher PDFs use owner-only encryption (copy/print restrictions)
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// with an empty user password, so they open normally but confuse parsers.
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// Decrypt owner-protected PDFs (empty user password).
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decrypted, err := decryptPDF(data)
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if err == nil {
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data = decrypted
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}
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// (if decryption fails we still attempt to parse — maybe it works anyway)
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r, err := pdf.NewReader(bytes.NewReader(data), int64(len(data)))
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conf := model.NewDefaultConfiguration()
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conf.UserPW = ""
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conf.OwnerPW = ""
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// Extract all page content streams to a temp directory.
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tmpDir, err := os.MkdirTemp("", "pdf-extract-*")
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if err != nil {
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return nil, fmt.Errorf("open PDF: %w", err)
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return nil, fmt.Errorf("create temp dir: %w", err)
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}
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defer os.RemoveAll(tmpDir)
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if err := api.ExtractContent(bytes.NewReader(data), tmpDir, "out", nil, conf); err != nil {
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return nil, fmt.Errorf("extract PDF content: %w", err)
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}
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// Extract per-page text so we can detect chapter boundaries.
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numPages := r.NumPage()
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if numPages == 0 {
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return nil, fmt.Errorf("PDF has no pages")
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entries, err := os.ReadDir(tmpDir)
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if err != nil || len(entries) == 0 {
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return nil, fmt.Errorf("PDF has no content pages")
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}
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// Collect full text first with page markers so we can split by chapter.
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// Sort entries by filename so index == page number - 1.
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sort.Slice(entries, func(i, j int) bool { return entries[i].Name() < entries[j].Name() })
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// Build page-index → extracted text map.
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pageTexts := make(map[int]string, len(entries))
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for idx, e := range entries {
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raw, readErr := os.ReadFile(tmpDir + "/" + e.Name())
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if readErr != nil {
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continue
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}
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pageTexts[idx+1] = extractTextFromContentStream(raw)
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}
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// Try to use bookmarks (outline) for chapter structure.
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bookmarks, bmErr := api.Bookmarks(bytes.NewReader(data), conf)
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if bmErr == nil && len(bookmarks) > 0 {
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chapters := chaptersFromBookmarks(bookmarks, pageTexts)
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if len(chapters) > 0 {
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return chapters, nil
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}
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}
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// Fallback: concatenate all page texts and split by heading patterns.
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var sb strings.Builder
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fonts := make(map[string]*pdf.Font)
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for i := 1; i <= numPages; i++ {
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page := r.Page(i)
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if page.V.IsNull() {
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continue
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}
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text, err := page.GetPlainText(fonts)
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if err != nil {
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continue
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}
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sb.WriteString(text)
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for p := 1; p <= len(entries); p++ {
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sb.WriteString(pageTexts[p])
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sb.WriteByte('\n')
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}
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chapters := extractChaptersFromText(sb.String())
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if len(chapters) == 0 {
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return nil, fmt.Errorf("could not extract any chapters from PDF")
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}
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return chapters, nil
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}
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return extractChaptersFromText(sb.String()), nil
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// chaptersFromBookmarks builds a chapter list from PDF bookmarks + per-page text.
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// It flattens the bookmark tree, skips front/back matter entries, and assigns
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// page ranges so each chapter spans from its own start page to the next
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// bookmark's start page minus one.
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func chaptersFromBookmarks(bookmarks []pdfcpu.Bookmark, pageTexts map[int]string) []bookstore.Chapter {
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// Flatten bookmark tree.
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var flat []pdfcpu.Bookmark
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var flatten func([]pdfcpu.Bookmark)
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flatten = func(bms []pdfcpu.Bookmark) {
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for _, bm := range bms {
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flat = append(flat, bm)
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flatten(bm.Kids)
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}
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}
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flatten(bookmarks)
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// Sort by page number.
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sort.Slice(flat, func(i, j int) bool { return flat[i].PageFrom < flat[j].PageFrom })
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// Assign PageThru for entries where it's 0 (last bookmark or missing).
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maxPage := 0
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for p := range pageTexts {
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if p > maxPage {
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maxPage = p
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}
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}
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for i := range flat {
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if flat[i].PageThru == 0 {
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if i+1 < len(flat) {
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flat[i].PageThru = flat[i+1].PageFrom - 1
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} else {
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flat[i].PageThru = maxPage
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}
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}
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}
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var chapters []bookstore.Chapter
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chNum := 0
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for _, bm := range flat {
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if pdfSkipBookmarks[strings.ToLower(strings.TrimSpace(bm.Title))] {
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continue
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}
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// Gather text for all pages in this bookmark's range.
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var sb strings.Builder
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for p := bm.PageFrom; p <= bm.PageThru; p++ {
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if t, ok := pageTexts[p]; ok {
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sb.WriteString(t)
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sb.WriteByte('\n')
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}
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}
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text := strings.TrimSpace(sb.String())
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if len(text) < 50 {
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continue // skip nearly-empty sections
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}
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chNum++
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chapters = append(chapters, bookstore.Chapter{
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Number: chNum,
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Title: bm.Title,
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Content: text,
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})
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}
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return chapters
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}
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// extractTextFromContentStream parses a raw PDF content stream and extracts
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// readable text from Tj and TJ operators.
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//
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// TJ arrays may contain a mix of literal strings (parenthesised) and hex glyph
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// arrays. Only the literal strings are decoded — hex arrays require per-font
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// ToUnicode CMaps and are skipped. Kerning adjustment numbers inside TJ arrays
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// are also ignored (they're just spacing hints).
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//
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// Line breaks are inserted on ET / Td / TD / T* operators.
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func extractTextFromContentStream(stream []byte) string {
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s := string(stream)
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var sb strings.Builder
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i := 0
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n := len(s)
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for i < n {
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// TJ array: [ ... ]TJ — collect all literal strings, skip hex & numbers.
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if s[i] == '[' {
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j := i + 1
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for j < n && s[j] != ']' {
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if s[j] == '(' {
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// Literal string inside TJ array.
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k := j + 1
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depth := 1
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for k < n && depth > 0 {
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if s[k] == '\\' {
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k += 2
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continue
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}
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if s[k] == '(' {
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depth++
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} else if s[k] == ')' {
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depth--
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}
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k++
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}
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lit := pdfUnescapeString(s[j+1 : k-1])
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if hasPrintableASCII(lit) {
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sb.WriteString(lit)
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}
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j = k
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continue
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}
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j++
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}
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// Check if this is a TJ operator (skip whitespace after ']').
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end := j + 1
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for end < n && (s[end] == ' ' || s[end] == '\t' || s[end] == '\r' || s[end] == '\n') {
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end++
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}
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if end+2 <= n && s[end:end+2] == "TJ" && (end+2 == n || !isAlphaNum(s[end+2])) {
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i = end + 2
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continue
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}
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i = j + 1
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continue
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}
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// Single string: (string) Tj
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if s[i] == '(' {
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j := i + 1
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depth := 1
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for j < n && depth > 0 {
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if s[j] == '\\' {
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j += 2
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continue
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}
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if s[j] == '(' {
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depth++
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} else if s[j] == ')' {
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depth--
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}
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j++
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}
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lit := pdfUnescapeString(s[i+1 : j-1])
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if hasPrintableASCII(lit) {
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// Check for Tj operator.
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end := j
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for end < n && (s[end] == ' ' || s[end] == '\t') {
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end++
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}
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if end+2 <= n && s[end:end+2] == "Tj" && (end+2 == n || !isAlphaNum(s[end+2])) {
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sb.WriteString(lit)
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i = end + 2
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continue
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}
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}
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i = j
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continue
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}
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// Detect end of text object (ET) — add a newline.
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if i+2 <= n && s[i:i+2] == "ET" && (i+2 == n || !isAlphaNum(s[i+2])) {
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sb.WriteByte('\n')
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i += 2
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continue
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}
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// Detect Td / TD / T* — newline within text block.
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if i+2 <= n && (s[i:i+2] == "Td" || s[i:i+2] == "TD" || s[i:i+2] == "T*") &&
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(i+2 == n || !isAlphaNum(s[i+2])) {
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sb.WriteByte('\n')
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i += 2
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continue
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}
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i++
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}
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return sb.String()
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}
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func isAlphaNum(b byte) bool {
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return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9') || b == '_'
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}
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func hasPrintableASCII(s string) bool {
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for _, c := range s {
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if c >= 0x20 && c < 0x7F {
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return true
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}
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}
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return false
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}
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// pdfUnescapeString handles PDF string escape sequences.
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func pdfUnescapeString(s string) string {
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if !strings.ContainsRune(s, '\\') {
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return s
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}
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var sb strings.Builder
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i := 0
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for i < len(s) {
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if s[i] == '\\' && i+1 < len(s) {
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switch s[i+1] {
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case 'n':
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sb.WriteByte('\n')
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case 'r':
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sb.WriteByte('\r')
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case 't':
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sb.WriteByte('\t')
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case '(', ')', '\\':
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sb.WriteByte(s[i+1])
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default:
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// Octal escape \ddd
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if s[i+1] >= '0' && s[i+1] <= '7' {
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end := i + 2
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for end < i+5 && end < len(s) && s[end] >= '0' && s[end] <= '7' {
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end++
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}
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val, _ := strconv.ParseInt(s[i+1:end], 8, 16)
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sb.WriteByte(byte(val))
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i = end
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continue
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}
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sb.WriteByte(s[i+1])
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}
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i += 2
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} else {
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sb.WriteByte(s[i])
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i++
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}
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}
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return sb.String()
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}
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// ── EPUB parsing ──────────────────────────────────────────────────────────────
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