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#include "rewriter/rewriter_util.h"

#include <algorithm>
#include <cstddef>

#include "converter/attribute.h"
#include "converter/candidate.h"
#include "converter/segments.h"

namespace mozc {

// Candidates from user history: "h"
// Other existing candidates : "o"
// Inserting candidates from the rewriter: "R"
// The number of inserting "R": 2
// offset: 2
//
// The output candidates would be:
// [o, o, R, R, o, o, o, o, ...]
// [h, o, o, R, R, o, o, o, ...]
// [h, h, o, o, R, R, o, o, ...]
// [h, h, h, o, o, R, R, o, ...]
// [h, h, h, h, o, o, R, R  ...]
// For the number of history candidates.
size_t RewriterUtil::CalculateInsertPosition(const Segment& segment,
                                             size_t offset) {
  size_t existing_history_candidates_num = 0;
  for (int i = 0; i < segment.candidates_size(); ++i) {
    // Assume that the user history prediction candidates are inserted
    // sequentially from top.
    if (segment.candidate(i).attributes &
        converter::Attribute::USER_HISTORY_PREDICTION) {
      ++existing_history_candidates_num;
    } else if (existing_history_candidates_num > 0) {
      break;
    }
  }
  return std::min(offset + existing_history_candidates_num,
                  segment.candidates_size());
}

}  // namespace mozc
