fix(scanner): resolve EPUB covers via structured OPF parsing, Calibre chain
The cover lookup scraped the OPF with attribute-order-sensitive regexes. Real books serialize attributes in any order - Grand Central's '3 Days to Live' puts href before id on manifest items and content before name on the cover meta - so all three regex paths missed and the book fell through to filename guessing, extracting no cover at all. Attribute order is meaningless in XML; the regexes were never safe. Replace them with a structured parse (encoding/xml, namespace and attribute-order agnostic; see the new media_scanner_opf.go) and follow Calibre's read_raster_cover resolution order: 1. manifest item with properties=cover-image (non-(X)HTML media only) 2. <meta name=cover> resolved through the manifest, same media guard 3. first spine item that is itself a raster image (store manga) 4. NEW cover-page fallback: books declaring no raster cover at all - the classic EPUB2/Adobe cover.xhtml wrapper - are mined for <img src> / SVG <image xlink:href> references (Calibre renders the page with Qt; extracting the referenced image covers the practical cases without a rendering engine) 5. existing zip filename guessing stays as the last resort, and the old regex chain survives as findCoverInOPFLegacy for OPFs too malformed for a real XML parse. Hrefs are now URL-decoded and posix-normalized against the OPF's own path (path.Join semantics), so '../art/cover.jpg' from a nested cover page and %20-encoded names resolve correctly. Tests: attribute-order chaos modeled on the failing Patterson book, SVG-wrapped cover pages via guide references, image-first spines, and path resolution edge cases. Verified live against the real '3 Days to Live' EPUB, which previously produced no cover.
This commit is contained in:
John O'Keefe
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package services
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import (
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"archive/zip"
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"os"
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"path/filepath"
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"testing"
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)
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// helper to build an EPUB zip from a file map for cover tests
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func writeEPUB(t *testing.T, path string, files map[string]string) {
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t.Helper()
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f, err := os.Create(path)
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if err != nil {
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t.Fatal(err)
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}
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defer f.Close()
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w := zip.NewWriter(f)
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mimetype, err := w.CreateHeader(&zip.FileHeader{Name: "mimetype", Method: zip.Store})
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if err != nil {
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t.Fatal(err)
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}
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mimetype.Write([]byte("application/epub+zip"))
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for name, content := range files {
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fw, err := w.Create(name)
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if err != nil {
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t.Fatal(err)
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}
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if _, err := fw.Write([]byte(content)); err != nil {
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t.Fatal(err)
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}
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}
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if err := w.Close(); err != nil {
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t.Fatal(err)
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}
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}
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const containerXML = `<?xml version="1.0"?><container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container"><rootfiles><rootfile full-path="OEBPS/package.opf" media-type="application/oebps-package+xml"/></rootfiles></container>`
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const tinyJPEG = "\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01\x01\x00\x00\x01\x00\x01\x00\x00\xff\xd9"
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// TestFindCoverInOPFAttributeOrder guards the regression where attribute
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// order defeated regex scraping: this OPF mirrors Grand Central's "3 Days to
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// Live" serialization (href before id, content before name on the meta tag).
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func TestFindCoverInOPFAttributeOrder(t *testing.T) {
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opf := `<?xml version="1.0"?>
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<package xmlns="http://www.idpf.org/2007/opf" version="3.0" unique-identifier="pub-id">
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<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
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<dc:title>3 Days to Live</dc:title>
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<meta content="cover-image" name="cover"/>
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</metadata>
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<manifest>
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<item href="images/9781538752760.jpg" id="cover-image" media-type="image/jpeg" properties="cover-image"/>
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</manifest>
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<spine/>
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</package>`
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files := map[string]string{
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"META-INF/container.xml": containerXML,
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"OEBPS/package.opf": opf,
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"OEBPS/images/9781538752760.jpg": tinyJPEG,
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}
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epubPath := filepath.Join(t.TempDir(), "book.epub")
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writeEPUB(t, epubPath, files)
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s := NewMediaScanner(nil)
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coverPath, err := s.extractEPUBCover(epubPath)
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if err != nil {
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t.Fatalf("extractEPUBCover() error: %v", err)
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}
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if coverPath == "" {
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t.Fatal("cover not extracted - attribute order still defeats resolution")
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}
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if _, err := os.Stat(coverPath); err != nil {
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t.Fatalf("cover file not written: %v", err)
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}
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}
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// TestFindCoverInOPFCoverPage covers books that declare no raster cover at
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// all: the classic EPUB2/Adobe structure where cover.xhtml wraps the image
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// (here via SVG), reachable through the guide reference or first spine item.
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func TestFindCoverInOPFCoverPage(t *testing.T) {
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opf := `<?xml version="1.0"?>
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<package xmlns="http://www.idpf.org/2007/opf" version="2.0">
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<metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
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<dc:title>Old Adobe Book</dc:title>
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</metadata>
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<manifest>
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<item id="coverpage" href="text/cover.xhtml" media-type="application/xhtml+xml"/>
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<item id="coverimg" href="art/cover-wrap.jpg" media-type="image/jpeg"/>
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</manifest>
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<spine><itemref idref="coverpage"/></spine>
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<guide><reference type="cover" href="text/cover.xhtml"/></guide>
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</package>`
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coverPage := `<?xml version="1.0"?>
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<div><svg xmlns="http://www.w3.org/2000/svg"><image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="../art/cover-wrap.jpg"/></svg></div>
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</body>
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</html>`
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files := map[string]string{
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"META-INF/container.xml": containerXML,
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"OEBPS/package.opf": opf,
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"OEBPS/text/cover.xhtml": coverPage,
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"OEBPS/art/cover-wrap.jpg": tinyJPEG,
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}
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epubPath := filepath.Join(t.TempDir(), "adobe.epub")
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writeEPUB(t, epubPath, files)
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s := NewMediaScanner(nil)
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coverPath, err := s.extractEPUBCover(epubPath)
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if err != nil {
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t.Fatalf("extractEPUBCover() error: %v", err)
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}
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if coverPath == "" {
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t.Fatal("cover-page fallback failed to find SVG-wrapped image")
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}
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}
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// TestFindCoverInOPFImageFirstSpine covers store manga whose first spine
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// item is a raster image itself (Calibre's third resolution step).
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func TestFindCoverInOPFImageFirstSpine(t *testing.T) {
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opf := `<?xml version="1.0"?>
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<package xmlns="http://www.idpf.org/2007/opf" version="3.0">
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<metadata xmlns:dc="http://purl.org/dc/elements/1.1/"><dc:title>Manga Vol 1</dc:title></metadata>
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<manifest>
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<item id="p1" href="pages/0001.jpg" media-type="image/jpeg"/>
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</manifest>
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<spine><itemref idref="p1"/></spine>
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</package>`
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files := map[string]string{
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"META-INF/container.xml": containerXML,
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"OEBPS/package.opf": opf,
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"OEBPS/pages/0001.jpg": tinyJPEG,
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}
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epubPath := filepath.Join(t.TempDir(), "manga.epub")
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writeEPUB(t, epubPath, files)
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s := NewMediaScanner(nil)
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coverPath, err := s.extractEPUBCover(epubPath)
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if err != nil {
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t.Fatalf("extractEPUBCover() error: %v", err)
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}
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if coverPath == "" {
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t.Fatal("image-first spine cover not detected")
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}
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}
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// TestResolveOPFPath checks URL decoding and posix normalization of
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// OPF-relative hrefs.
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func TestResolveOPFPath(t *testing.T) {
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tests := []struct {
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opfPath, href, want string
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}{
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{"OEBPS/package.opf", "images/cover.jpg", "OEBPS/images/cover.jpg"},
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{"package.opf", "cover.jpg", "cover.jpg"},
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{"OEBPS/package.opf", "../cover.jpg", "cover.jpg"},
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{"OEBPS/package.opf", "my%20covers/a%20cover.jpg", "OEBPS/my covers/a cover.jpg"},
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}
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for _, tt := range tests {
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if got := resolveOPFPath(tt.opfPath, tt.href); got != tt.want {
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t.Errorf("resolveOPFPath(%q, %q) = %q, want %q", tt.opfPath, tt.href, got, tt.want)
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}
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}
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}
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