Xteink-X4-crosspoint-reader/lib/Epub/Epub/hyphenation/Hyphenator.cpp

#include "Hyphenator.h"

#include <Utf8.h>

#include <algorithm>
#include <array>
#include <vector>

#include "EnglishHyphenator.h"
#include "HyphenationCommon.h"
#include "LanguageHyphenator.h"
#include "RussianHyphenator.h"

namespace {

// Central registry for language-specific hyphenators supported on device.
const std::array<const LanguageHyphenator*, 2>& registeredHyphenators() {
  static const std::array<const LanguageHyphenator*, 2> hyphenators = {
      &EnglishHyphenator::instance(),
      &RussianHyphenator::instance(),
  };
  return hyphenators;
}

// Finds the hyphenator matching the detected script.
const LanguageHyphenator* hyphenatorForScript(const Script script) {
  for (const auto* hyphenator : registeredHyphenators()) {
    if (hyphenator->script() == script) {
      return hyphenator;
    }
  }
  return nullptr;
}

// Converts the UTF-8 word into codepoint metadata for downstream rules.
std::vector<CodepointInfo> collectCodepoints(const std::string& word) {
  std::vector<CodepointInfo> cps;
  cps.reserve(word.size());

  const unsigned char* base = reinterpret_cast<const unsigned char*>(word.c_str());
  const unsigned char* ptr = base;
  while (*ptr != 0) {
    const unsigned char* current = ptr;
    const uint32_t cp = utf8NextCodepoint(&ptr);
    cps.push_back({cp, static_cast<size_t>(current - base)});
  }

  return cps;
}

// Rejects words containing punctuation or digits unless forced.
bool hasOnlyAlphabetic(const std::vector<CodepointInfo>& cps) {
  if (cps.empty()) {
    return false;
  }

  for (const auto& info : cps) {
    if (!isAlphabetic(info.value)) {
      return false;
    }
  }
  return true;
}

// Asks the language hyphenator for legal break positions inside the word.
std::vector<size_t> collectBreakIndexes(const std::vector<CodepointInfo>& cps) {
  if (cps.size() < MIN_PREFIX_CP + MIN_SUFFIX_CP) {
    return {};
  }

  const Script script = detectScript(cps);
  if (const auto* hyphenator = hyphenatorForScript(script)) {
    auto indexes = hyphenator->breakIndexes(cps);
    return indexes;
  }

  return {};
}

// Maps a codepoint index back to its byte offset inside the source word.
size_t byteOffsetForIndex(const std::vector<CodepointInfo>& cps, const size_t index) {
  if (index >= cps.size()) {
    return cps.empty() ? 0 : cps.back().byteOffset;
  }
  return cps[index].byteOffset;
}

}  // namespace

std::vector<size_t> Hyphenator::breakOffsets(const std::string& word, const bool includeFallback) {
  std::vector<size_t> byteOffsets;
  if (word.empty()) {
    return byteOffsets;
  }

  auto cps = collectCodepoints(word);
  if (cps.size() < MIN_PREFIX_CP + MIN_SUFFIX_CP) {
    return byteOffsets;
  }

  std::vector<size_t> indexes;
  indexes.reserve(cps.size());

  if (hasOnlyAlphabetic(cps)) {
    auto dictBreaks = collectBreakIndexes(cps);
    indexes.insert(indexes.end(), dictBreaks.begin(), dictBreaks.end());
  }

  if (includeFallback) {
    for (size_t idx = MIN_PREFIX_CP; idx + MIN_SUFFIX_CP <= cps.size(); ++idx) {
      indexes.push_back(idx);
    }
  }

  if (indexes.empty()) {
    return byteOffsets;
  }

  std::sort(indexes.begin(), indexes.end());
  indexes.erase(std::unique(indexes.begin(), indexes.end()), indexes.end());

  byteOffsets.reserve(indexes.size());
  for (const size_t idx : indexes) {
    byteOffsets.push_back(byteOffsetForIndex(cps, idx));
  }

  return byteOffsets;
}