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#include "rewriter/unicode_rewriter.h"

#include <cctype>

#include "base/util.h"
#include "converter/converter_interface.h"
#include "converter/segments.h"

namespace mozc {

UnicodeRewriter::UnicodeRewriter() {}
UnicodeRewriter::~UnicodeRewriter() {}

namespace {

// Checks given string is ucs4 expression or not.
bool IsValidUCS4Expression(const string &input) {
  if (input.size() < 3 || input.size() > 8) {
    return false;
  }

  if (!Util::StartsWith(input, "U+")) {
    return false;
  }

  const string hexcode = input.substr(2, input.npos);

  for (size_t i = 0; i < hexcode.size(); ++i) {
    if (!::isxdigit(hexcode.at(i))) {
      return false;
    }
  }
  return true;
}

// Converts given string to 32bit unsigned integer.
bool UCS4ExpressionToInteger(const string &input, uint32 *ucs4) {
  DCHECK(ucs4);
  const string hexcode = input.substr(2, input.npos);
  return Util::SafeHexStrToUInt32(hexcode, ucs4);
}

// Checks if given ucs4 value is acceptable or not.
bool IsAcceptableUnicode(uint32 ucs4) {
  if (Util::GetScriptType(ucs4) != Util::UNKNOWN_SCRIPT) {
    return true;
  }

  // Expands acceptable characters.
  // 0x20 to 0x7E is visible characters.
  if (ucs4 >= 0x20 && ucs4 <= 0x7E) {
    return true;
  }

  return false;
}

}  // namespace

bool UnicodeRewriter::Rewrite(Segments *segments) const {
  string key;
  DCHECK(segments);
  for (size_t i = 0; i < segments->conversion_segments_size(); ++i) {
    key += segments->conversion_segment(i).key();
  }

  if (!IsValidUCS4Expression(key)) {
    return false;
  }

  uint32 ucs4 = 0;
  if (!UCS4ExpressionToInteger(key, &ucs4)) {
    return false;
  }

  if (!IsAcceptableUnicode(ucs4)) {
    return false;
  }

  string output;
  Util::UCS4ToUTF8(ucs4, &output);

  if (output.empty()) {
    return false;
  }
  mozc::ConverterInterface *converter
      = mozc::ConverterFactory::GetConverter();
  if (converter == NULL) {
    return false;
  }

  if (segments->conversion_segments_size() > 1) {
    if (segments->resized()) {
      // The given segments are resized by user so don't modify anymore.
      return false;
    }
    const uint32 resize_len = Util::CharsLen(key) -
        Util::CharsLen(segments->conversion_segment(0).key());
    if (!converter->ResizeSegment(segments, 0, resize_len)) {
      return false;
    }
  }

  Segment* seg = segments->mutable_conversion_segment(0);
  DCHECK(seg);
  Segment::Candidate *candidate = seg->insert_candidate(0);
  DCHECK(candidate);

  candidate->Init();
  seg->set_key(key);
  candidate->key = key;
  candidate->value = output;
  candidate->content_value = output;
  // "Unicode 変換(" + key + ")"
  candidate->description = "Unicode \xE5\xA4\x89\xE6\x8F\x9B ("+key+")";
  candidate->attributes |= Segment::Candidate::NO_LEARNING;
  return true;
}

}  // namespace mozc