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#include "win32/tip/tip_surrounding_text.h"
#include <string>

#include "base/win32/wide_char.h"
#include "testing/gunit.h"

namespace mozc {
namespace win32 {
namespace tsf {
namespace {

TEST(TipSurroundingTextUtilTest, MeasureCharactersBackward) {
  {
    constexpr char kSource[] = "abcde";
    const std::wstring source = Utf8ToWide(kSource);
    size_t characters_in_utf16 = 0;
    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 0, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 0);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 1, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 1);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 5, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 5);

    EXPECT_FALSE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 6, &characters_in_utf16));
  }
  {
    constexpr char kSource[] = "𠮟咤";
    const std::wstring source = Utf8ToWide(kSource);
    size_t characters_in_utf16 = 0;
    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 1, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 1);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 2, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 3);

    EXPECT_FALSE(TipSurroundingTextUtil::MeasureCharactersBackward(
        source, 3, &characters_in_utf16));
  }

  const wchar_t kHighSurrogateStart = 0xd800;
  const wchar_t kLowSurrogateStart = 0xdc00;

  // Only Low surrogate.
  {
    const wchar_t kSource[] = {kLowSurrogateStart, kLowSurrogateStart, L'\0'};
    size_t characters_in_utf16 = 0;

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 0, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 0);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 1, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 1);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 2, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 2);

    EXPECT_FALSE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 3, &characters_in_utf16));
  }

  // Only High surrogate.
  {
    const wchar_t kSource[] = {kHighSurrogateStart, kHighSurrogateStart, L'\0'};
    size_t characters_in_utf16 = 0;
    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 0, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 0);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 1, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 1);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 2, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 2);

    EXPECT_FALSE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 3, &characters_in_utf16));
  }

  // An isolated high surrogate and one surrogate pair.
  {
    const wchar_t kSource[] = {kHighSurrogateStart, kHighSurrogateStart,
                               kLowSurrogateStart, L'\0'};
    size_t characters_in_utf16 = 0;
    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 0, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 0);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 1, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 2);

    EXPECT_TRUE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 2, &characters_in_utf16));
    EXPECT_EQ(characters_in_utf16, 3);

    EXPECT_FALSE(TipSurroundingTextUtil::MeasureCharactersBackward(
        kSource, 3, &characters_in_utf16));
  }
}

}  // namespace
}  // namespace tsf
}  // namespace win32
}  // namespace mozc
