Xteink-X4-crosspoint-reader/lib/Epub/Epub/parsers/TocNavParser.h
Pavel Liashkov 0332e1103a
Add EPUB 3 nav.xhtml TOC support (#197)
## Summary

* **What is the goal of this PR?** Add EPUB 3 support by implementing
native navigation document (nav.xhtml) parsing with NCX fallback,
addressing issue Fixes: #143.

  * **What changes are included?**
- New `TocNavParser` for parsing EPUB 3 HTML5 navigation documents
(`<nav epub:type="toc">`)
- Detection of nav documents via `properties="nav"` attribute in OPF
manifest
- Fallback logic: try EPUB 3 nav first, fall back to NCX (EPUB 2) if
unavailable
- Graceful degradation: books without any TOC now load with a warning
instead of failing

  ## Additional Context

* The implementation follows the existing streaming XML parser pattern
using Expat to minimize RAM usage on the ESP32-C3
* EPUB 3 books that include both nav.xhtml and toc.ncx will prefer the
nav document (per EPUB 3 spec recommendation)
* No breaking changes - existing EPUB 2 books continue to work as before
* Tested on examples from
https://idpf.github.io/epub3-samples/30/samples.html
2026-01-03 19:10:35 +11:00

48 lines
1.4 KiB
C++

#pragma once
#include <Print.h>
#include <expat.h>
#include <string>
class BookMetadataCache;
// Parser for EPUB 3 nav.xhtml navigation documents
// Parses HTML5 nav elements with epub:type="toc" to extract table of contents
class TocNavParser final : public Print {
enum ParserState {
START,
IN_HTML,
IN_BODY,
IN_NAV_TOC, // Inside <nav epub:type="toc">
IN_OL, // Inside <ol>
IN_LI, // Inside <li>
IN_ANCHOR, // Inside <a>
};
const std::string& baseContentPath;
size_t remainingSize;
XML_Parser parser = nullptr;
ParserState state = START;
BookMetadataCache* cache;
// Track nesting depth for <ol> elements to determine TOC depth
uint8_t olDepth = 0;
// Current entry data being collected
std::string currentLabel;
std::string currentHref;
static void startElement(void* userData, const XML_Char* name, const XML_Char** atts);
static void characterData(void* userData, const XML_Char* s, int len);
static void endElement(void* userData, const XML_Char* name);
public:
explicit TocNavParser(const std::string& baseContentPath, const size_t xmlSize, BookMetadataCache* cache)
: baseContentPath(baseContentPath), remainingSize(xmlSize), cache(cache) {}
~TocNavParser() override;
bool setup();
size_t write(uint8_t) override;
size_t write(const uint8_t* buffer, size_t size) override;
};