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Crosspoint/lib/KOReaderSync/ChapterXPathIndexer.h
T
jpirnayandClaude Opus 4.6 fd70b3a231 Add paragraph index LUT for accurate KOReader position sync
Store per-page paragraph indices in section cache to enable precise
XPath-to-page and page-to-XPath mapping without reparsing XHTML.

Forward path (upload): generates XPath directly from paragraph LUT
instead of byte-offset estimation, eliminating drift in chapters
with non-uniform content density.

Reverse path (download): resolves incoming KOReader XPath p[N] to
the exact page via paragraph LUT lookup.

Paragraph counter counts all <p> elements including display:none
to match ChapterXPathIndexer and crengine's standard XPath counting.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-22 12:29:30 +01:00

80 lines
3.0 KiB
C++

#pragma once
#include <Epub.h>
#include <memory>
#include <string>
/**
* Lightweight XPath/progress bridge for KOReader sync.
*
* Why this exists:
* - CrossPoint stores reading position as chapter/page.
* - KOReader sync uses XPath + percentage.
*
* This utility reparses exactly one spine XHTML item with Expat to translate
* between the two formats. It streams through the parse using O(1) memory
* (no anchor list), so it handles arbitrarily large chapters without OOM.
*
* Design constraints (ESP32-C3):
* - No persistent full-book structures.
* - Parse-on-demand and free memory immediately.
* - Keep fallback behavior deterministic if parsing/matching fails.
*/
class ChapterXPathIndexer {
public:
/**
* Convert an intra-spine progress ratio to the nearest element-level XPath.
*
* @param epub Loaded EPUB instance
* @param spineIndex Current spine item index
* @param intraSpineProgress Position within the spine item [0.0, 1.0]
* @return Best matching XPath for KOReader, or empty string on failure
*/
static std::string findXPathForProgress(const std::shared_ptr<Epub>& epub, int spineIndex, float intraSpineProgress);
/**
* Resolve a KOReader XPath to an intra-spine progress ratio.
*
* Matching strategy:
* 1) exact anchor path match,
* 2) index-insensitive path match,
* 3) ancestor fallback.
*
* @param epub Loaded EPUB instance
* @param spineIndex Spine item index to parse
* @param xpath Incoming KOReader XPath
* @param outIntraSpineProgress Resolved position within spine [0.0, 1.0]
* @param outExactMatch True only for full exact path match
* @return true if any match was resolved; false means caller should fallback
*/
static bool findProgressForXPath(const std::shared_ptr<Epub>& epub, int spineIndex, const std::string& xpath,
float& outIntraSpineProgress, bool& outExactMatch);
/**
* Parse DocFragment index from KOReader-style path segment:
* /body/DocFragment[N]/body/...
*
* KOReader uses 1-based DocFragment indices; N is converted to the 0-based
* spine index stored in outSpineIndex (i.e. outSpineIndex = N - 1).
*
* @param xpath KOReader XPath
* @param outSpineIndex 0-based spine index derived from DocFragment[N]
* @return true when DocFragment[N] exists and N is a valid integer >= 1
* (converted to 0-based outSpineIndex); false otherwise
*/
static bool tryExtractSpineIndexFromXPath(const std::string& xpath, int& outSpineIndex);
/**
* Extract the paragraph index from a KOReader XPath.
* Looks for the first /p[N] segment after /body/ and returns N (1-based).
*
* Example: "/body/DocFragment[7]/body/p[685]/text().96" → outParagraphIndex = 685
*
* @param xpath KOReader XPath
* @param outParagraphIndex 1-based paragraph index
* @return true if a /p[N] segment was found
*/
static bool tryExtractParagraphIndexFromXPath(const std::string& xpath, uint16_t& outParagraphIndex);
};