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#include "rewriter/user_dictionary_rewriter.h"

#include <cstddef>

#include "absl/log/check.h"
#include "converter/attribute.h"
#include "converter/candidate.h"
#include "converter/segments.h"
#include "request/conversion_request.h"

namespace mozc {

// User-dictionary candidates are not always placed at the top.
// Since user expects that user-dictionary candidates may appear
// on the top, we simply move user-dictionary-candidate just
// "after" the top candidate.
bool UserDictionaryRewriter::Rewrite(const ConversionRequest& request,
                                     Segments* segments) const {
  DCHECK(segments);

  bool modified = false;
  for (Segment& segment : segments->conversion_segments()) {
    // final destination of the user dictionary candidate.
    int move_to_start = 1;

    for (size_t move_from = 2; move_from < segment.candidates_size();
         ++move_from) {
      if (!(segment.candidate(move_from).attributes &
            converter::Attribute::USER_DICTIONARY)) {
        continue;
      }

      // find the final destination of user dictionary
      // from [move_to_start .. move_from).
      int move_to = -1;
      for (int j = move_to_start; j < static_cast<int>(move_from); ++j) {
        if (!(segment.candidate(j).attributes &
              converter::Attribute::USER_DICTIONARY)) {
          move_to = j;
          break;
        }
      }

      // if move_to is not nil, move the candidate.
      if (move_to == -1) {
        move_to_start = move_from + 1;
      } else {
        segment.move_candidate(move_from, move_to);
        modified = true;
        move_to_start = move_to + 1;
      }
    }
  }

  return modified;
}
}  // namespace mozc
