#include "ProgressMapper.h"

#include <Logging.h>

#include <algorithm>
#include <cmath>

#include "ChapterXPathIndexer.h"

KOReaderPosition ProgressMapper::toKOReader(const std::shared_ptr<Epub>& epub, const CrossPointPosition& pos) {
  KOReaderPosition result;

  // Calculate page progress within current spine item
  float intraSpineProgress = 0.0f;
  if (pos.totalPages > 0) {
    intraSpineProgress = static_cast<float>(pos.pageNumber) / static_cast<float>(pos.totalPages);
  }

  // Calculate overall book progress (0.0-1.0)
  result.percentage = epub->calculateProgress(pos.spineIndex, intraSpineProgress);

  // Generate the best available XPath for the current chapter position.
  // Prefer element-level XPaths from a lightweight XHTML reparse; fall back
  // to a synthetic chapter-level path if parsing fails.
  result.xpath = ChapterXPathIndexer::findXPathForProgress(epub, pos.spineIndex, intraSpineProgress);
  if (result.xpath.empty()) {
    result.xpath = generateXPath(pos.spineIndex);
  }

  // Get chapter info for logging
  const int tocIndex = epub->getTocIndexForSpineIndex(pos.spineIndex);
  const std::string chapterName = (tocIndex >= 0) ? epub->getTocItem(tocIndex).title : "unknown";

  LOG_DBG("ProgressMapper", "CrossPoint -> KOReader: chapter='%s', page=%d/%d -> %.2f%% at %s", chapterName.c_str(),
          pos.pageNumber, pos.totalPages, result.percentage * 100, result.xpath.c_str());

  return result;
}

CrossPointPosition ProgressMapper::toCrossPoint(const std::shared_ptr<Epub>& epub, const KOReaderPosition& koPos,
                                                int currentSpineIndex, int totalPagesInCurrentSpine) {
  CrossPointPosition result;
  result.spineIndex = 0;
  result.pageNumber = 0;
  result.totalPages = 0;

  if (!epub || epub->getSpineItemsCount() <= 0) {
    return result;
  }

  const int spineCount = epub->getSpineItemsCount();

  float resolvedIntraSpineProgress = -1.0f;
  bool xpathExactMatch = false;
  bool usedXPathMapping = false;

  int xpathSpineIndex = -1;
  if (ChapterXPathIndexer::tryExtractSpineIndexFromXPath(koPos.xpath, xpathSpineIndex) && xpathSpineIndex >= 0 &&
      xpathSpineIndex < spineCount) {
    float intraFromXPath = 0.0f;
    if (ChapterXPathIndexer::findProgressForXPath(epub, xpathSpineIndex, koPos.xpath, intraFromXPath,
                                                  xpathExactMatch)) {
      result.spineIndex = xpathSpineIndex;
      resolvedIntraSpineProgress = intraFromXPath;
      usedXPathMapping = true;
    }
  }

  if (!usedXPathMapping) {
    const size_t bookSize = epub->getBookSize();
    if (bookSize == 0) {
      return result;
    }

    if (!std::isfinite(koPos.percentage)) {
      return result;
    }

    const float sanitizedPercentage = std::clamp(koPos.percentage, 0.0f, 1.0f);
    const size_t targetBytes = static_cast<size_t>(bookSize * sanitizedPercentage);

    bool spineFound = false;
    for (int i = 0; i < spineCount; i++) {
      const size_t cumulativeSize = epub->getCumulativeSpineItemSize(i);
      if (cumulativeSize >= targetBytes) {
        result.spineIndex = i;
        spineFound = true;
        break;
      }
    }

    if (!spineFound && spineCount > 0) {
      result.spineIndex = spineCount - 1;
    }

    if (result.spineIndex < epub->getSpineItemsCount()) {
      const size_t prevCumSize = (result.spineIndex > 0) ? epub->getCumulativeSpineItemSize(result.spineIndex - 1) : 0;
      const size_t currentCumSize = epub->getCumulativeSpineItemSize(result.spineIndex);
      const size_t spineSize = currentCumSize - prevCumSize;

      if (spineSize > 0) {
        const size_t bytesIntoSpine = (targetBytes > prevCumSize) ? (targetBytes - prevCumSize) : 0;
        resolvedIntraSpineProgress = static_cast<float>(bytesIntoSpine) / static_cast<float>(spineSize);
        resolvedIntraSpineProgress = std::max(0.0f, std::min(1.0f, resolvedIntraSpineProgress));
      }
    }
  }

  // Estimate page number within the selected spine item
  if (result.spineIndex < epub->getSpineItemsCount()) {
    const size_t prevCumSize = (result.spineIndex > 0) ? epub->getCumulativeSpineItemSize(result.spineIndex - 1) : 0;
    const size_t currentCumSize = epub->getCumulativeSpineItemSize(result.spineIndex);
    const size_t spineSize = currentCumSize - prevCumSize;

    int estimatedTotalPages = 0;

    if (result.spineIndex == currentSpineIndex && totalPagesInCurrentSpine > 0) {
      estimatedTotalPages = totalPagesInCurrentSpine;
    } else if (currentSpineIndex >= 0 && currentSpineIndex < epub->getSpineItemsCount() && totalPagesInCurrentSpine > 0) {
      const size_t prevCurrCumSize =
          (currentSpineIndex > 0) ? epub->getCumulativeSpineItemSize(currentSpineIndex - 1) : 0;
      const size_t currCumSize = epub->getCumulativeSpineItemSize(currentSpineIndex);
      const size_t currSpineSize = currCumSize - prevCurrCumSize;

      if (currSpineSize > 0) {
        float ratio = static_cast<float>(spineSize) / static_cast<float>(currSpineSize);
        estimatedTotalPages = static_cast<int>(totalPagesInCurrentSpine * ratio);
        if (estimatedTotalPages < 1) estimatedTotalPages = 1;
      }
    }

    result.totalPages = estimatedTotalPages;

    if (estimatedTotalPages > 0 && resolvedIntraSpineProgress >= 0.0f) {
      const float clampedProgress = std::max(0.0f, std::min(1.0f, resolvedIntraSpineProgress));
      result.pageNumber = static_cast<int>(clampedProgress * static_cast<float>(estimatedTotalPages));
      result.pageNumber = std::max(0, std::min(result.pageNumber, estimatedTotalPages - 1));
    } else if (spineSize > 0 && estimatedTotalPages > 0) {
      result.pageNumber = 0;
    }
  }

  LOG_DBG("ProgressMapper", "KOReader -> CrossPoint: %.2f%% at %s -> spine=%d, page=%d (%s, exact=%s)",
          koPos.percentage * 100, koPos.xpath.c_str(), result.spineIndex, result.pageNumber,
          usedXPathMapping ? "xpath" : "percentage", xpathExactMatch ? "yes" : "no");

  return result;
}

std::string ProgressMapper::generateXPath(int spineIndex) {
  // Fallback path when element-level XPath extraction is unavailable.
  // KOReader uses 1-based XPath predicates; spineIndex is 0-based internally.
  return "/body/DocFragment[" + std::to_string(spineIndex + 1) + "]/body";
}