/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS 1
#endif

#include <folly/Conv.h>

#include <algorithm>
#include <cinttypes>
#include <limits>
#include <sstream>
#include <stdexcept>
#include <string>
#include <tuple>

#include <fmt/format.h>
#include <glog/logging.h>

#include <folly/Random.h>
#include <folly/container/Foreach.h>
#include <folly/portability/GTest.h>

using namespace std;
using namespace folly;

// Test to<T>(T)
TEST(Conv, Type2Type) {
  bool boolV = true;
  EXPECT_EQ(to<bool>(boolV), true);

  int intV = 42;
  EXPECT_EQ(to<int>(intV), 42);

  float floatV = 4.2f;
  EXPECT_EQ(to<float>(floatV), 4.2f);

  double doubleV = 0.42;
  EXPECT_EQ(to<double>(doubleV), 0.42);

  std::string stringV = "StdString";
  EXPECT_EQ(to<std::string>(stringV), "StdString");

  folly::fbstring fbStrV = "FBString";
  EXPECT_EQ(to<folly::fbstring>(fbStrV), "FBString");

  folly::StringPiece spV("StringPiece");
  EXPECT_EQ(to<folly::StringPiece>(spV), "StringPiece");

  // Rvalues
  EXPECT_EQ(to<bool>(true), true);
  EXPECT_EQ(to<int>(42), 42);
  EXPECT_EQ(to<float>(4.2f), 4.2f);
  EXPECT_EQ(to<double>(.42), .42);
  EXPECT_EQ(to<std::string>(std::string("Hello")), "Hello");
  EXPECT_EQ(to<folly::fbstring>(folly::fbstring("hello")), "hello");
  EXPECT_EQ(
      to<folly::StringPiece>(folly::StringPiece("Forty Two")), "Forty Two");
}

TEST(Conv, Integral2Integral) {
  // Same size, different signs
  int64_t s64 = numeric_limits<uint8_t>::max();
  EXPECT_EQ(to<uint8_t>(s64), s64);

  s64 = numeric_limits<int8_t>::max();
  EXPECT_EQ(to<int8_t>(s64), s64);
}

TEST(Conv, Floating2Floating) {
  float f1 = 1e3f;
  double d1 = to<double>(f1);
  EXPECT_EQ(f1, d1);

  double d2 = 23.0;
  auto f2 = to<float>(d2);
  EXPECT_EQ(double(f2), d2);

  double invalidFloat = std::numeric_limits<double>::max();
  EXPECT_ANY_THROW(to<float>(invalidFloat));
  invalidFloat = -std::numeric_limits<double>::max();
  EXPECT_ANY_THROW(to<float>(invalidFloat));

  try {
    auto shouldWork = to<float>(std::numeric_limits<double>::min());
    // The value of `shouldWork' is an implementation defined choice
    // between the following two alternatives.
    EXPECT_TRUE(
        shouldWork == std::numeric_limits<float>::min() || shouldWork == 0.f);
  } catch (...) {
    ADD_FAILURE();
  }
}

template <class String>
void testIntegral2String() {}

template <class String, class Int, class... Ints>
void testIntegral2String() {
  typedef folly::make_unsigned_t<Int> Uint;
  typedef folly::make_signed_t<Int> Sint;

  Uint value = 123;
  EXPECT_EQ(to<String>(value), "123");
  Sint svalue = 123;
  EXPECT_EQ(to<String>(svalue), "123");
  svalue = -123;
  EXPECT_EQ(to<String>(svalue), "-123");

  value = numeric_limits<Uint>::min();
  EXPECT_EQ(to<Uint>(to<String>(value)), value);
  value = numeric_limits<Uint>::max();
  EXPECT_EQ(to<Uint>(to<String>(value)), value);

  svalue = numeric_limits<Sint>::min();
  EXPECT_EQ(to<Sint>(to<String>(svalue)), svalue);
  value = numeric_limits<Sint>::max();
  EXPECT_EQ(to<Sint>(to<String>(svalue)), svalue);

  testIntegral2String<String, Ints...>();
}

#if FOLLY_HAVE_INT128_T
template <class String>
void test128Bit2String() {
  typedef unsigned __int128 Uint;
  typedef __int128 Sint;

  EXPECT_EQ(detail::digitsEnough<unsigned __int128>(), 39);

  Uint value = 123;
  EXPECT_EQ(to<String>(value), "123");
  Sint svalue = 123;
  EXPECT_EQ(to<String>(svalue), "123");
  svalue = -123;
  EXPECT_EQ(to<String>(svalue), "-123");

  value = __int128(1) << 64;
  EXPECT_EQ(to<String>(value), "18446744073709551616");

  svalue = -(__int128(1) << 64);
  EXPECT_EQ(to<String>(svalue), "-18446744073709551616");

  value = 0;
  EXPECT_EQ(to<String>(value), "0");

  svalue = 0;
  EXPECT_EQ(to<String>(svalue), "0");

  value = ~__int128(0);
  EXPECT_EQ(to<String>(value), "340282366920938463463374607431768211455");

  svalue = -(Uint(1) << 127);
  EXPECT_EQ(to<String>(svalue), "-170141183460469231731687303715884105728");

  svalue = (Uint(1) << 127) - 1;
  EXPECT_EQ(to<String>(svalue), "170141183460469231731687303715884105727");

  value = numeric_limits<Uint>::min();
  EXPECT_EQ(to<Uint>(to<String>(value)), value);
  value = numeric_limits<Uint>::max();
  EXPECT_EQ(to<Uint>(to<String>(value)), value);

  svalue = numeric_limits<Sint>::min();
  EXPECT_EQ(to<Sint>(to<String>(svalue)), svalue);
  value = numeric_limits<Sint>::max();
  EXPECT_EQ(to<Sint>(to<String>(svalue)), svalue);

  {
    Uint v = 1;
    for (size_t zeros = 0; zeros < 39; ++zeros, v *= 10) {
      EXPECT_EQ(to<String>(v), String("1") + String(zeros, '0'));
    }
  }

  // Compare the results with fmt on random values. If they disagree, either
  // to() or fmt is incorrect.
  for (size_t b = 0; b <= 64; ++b) {
    for (size_t i = 0; i < 1000; ++i) {
      const auto low = folly::Random::rand64();
      if (b < 64) {
        const auto high = folly::Random::rand64(uint64_t(1) << b);
        const auto v =
            (folly::Random::oneIn(2) ? -1 : 1) * ((Sint(high) << 64) | low);
        const auto s = to<String>(v);
        EXPECT_EQ(s, fmt::format("{}", v));
        EXPECT_EQ(to<Sint>(s), v);
      } else {
        const auto high = folly::Random::rand64();
        const auto v = (Uint(high) << 64) | low;
        const auto s = to<String>(v);
        EXPECT_EQ(s, fmt::format("{}", v));
        EXPECT_EQ(to<Uint>(s), v);
      }
    }
  }
}

#endif

TEST(Conv, Integral2String) {
  testIntegral2String<std::string, int8_t, int16_t, int32_t, int64_t>();
  testIntegral2String<fbstring, int8_t, int16_t, int32_t, int64_t>();

#if FOLLY_HAVE_INT128_T
  test128Bit2String<std::string>();
  test128Bit2String<fbstring>();
#endif
}

template <class String>
void testString2Integral() {}

template <class String, class Int, class... Ints>
void testString2Integral() {
  typedef folly::make_unsigned_t<Int> Uint;
  typedef folly::make_signed_t<Int> Sint;

  // Unsigned numbers small enough to fit in a signed type
  static const String strings[] = {
      "0",
      "00",
      "2 ",
      " 84",
      " \n 123    \t\n",
      " 127",
      "0000000000000000000000000042",
  };
  static const Uint values[] = {
      0,
      0,
      2,
      84,
      123,
      127,
      42,
  };
  FOR_EACH_RANGE (i, 0, sizeof(strings) / sizeof(*strings)) {
    EXPECT_EQ(to<Uint>(strings[i]), values[i]);
    EXPECT_EQ(to<Sint>(strings[i]), values[i]);
  }

  // Unsigned numbers that won't fit in the signed variation
  static const String uStrings[] = {
      " 128",
      "213",
      "255",
  };
  static const Uint uValues[] = {
      128,
      213,
      255,
  };
  FOR_EACH_RANGE (i, 0, sizeof(uStrings) / sizeof(*uStrings)) {
    EXPECT_EQ(to<Uint>(uStrings[i]), uValues[i]);
    if (sizeof(Int) == 1) {
      EXPECT_THROW(to<Sint>(uStrings[i]), std::range_error);
    }
  }

  if (sizeof(Int) >= 4) {
    static const String strings2[] = {
        "256",
        "6324 ",
        "63245675 ",
        "2147483647",
    };
    static const Uint values2[] = {
        (Uint)256,
        (Uint)6324,
        (Uint)63245675,
        (Uint)2147483647,
    };
    FOR_EACH_RANGE (i, 0, sizeof(strings2) / sizeof(*strings2)) {
      EXPECT_EQ(to<Uint>(strings2[i]), values2[i]);
      EXPECT_EQ(to<Sint>(strings2[i]), values2[i]);
    }

    static const String uStrings2[] = {
        "2147483648",
        "3147483648",
        "4147483648",
        "4000000000",
    };
    static const Uint uValues2[] = {
        (Uint)2147483648U,
        (Uint)3147483648U,
        (Uint)4147483648U,
        (Uint)4000000000U,
    };
    FOR_EACH_RANGE (i, 0, sizeof(uStrings2) / sizeof(*uStrings2)) {
      EXPECT_EQ(to<Uint>(uStrings2[i]), uValues2[i]);
      if (sizeof(Int) == 4) {
        EXPECT_THROW(to<Sint>(uStrings2[i]), std::range_error);
      }
    }
  }

  if (sizeof(Int) >= 8) {
    static_assert(sizeof(Int) <= 8, "Now that would be interesting");
    static const String strings3[] = {
        "2147483648",
        "5000000001",
        "25687346509278435",
        "100000000000000000",
        "9223372036854775807",
    };
    static const Uint values3[] = {
        (Uint)2147483648ULL,
        (Uint)5000000001ULL,
        (Uint)25687346509278435ULL,
        (Uint)100000000000000000ULL,
        (Uint)9223372036854775807ULL,
    };
    FOR_EACH_RANGE (i, 0, sizeof(strings3) / sizeof(*strings3)) {
      EXPECT_EQ(to<Uint>(strings3[i]), values3[i]);
      EXPECT_EQ(to<Sint>(strings3[i]), values3[i]);
    }

    static const String uStrings3[] = {
        "9223372036854775808",
        "9987435987394857987",
        "17873648761234698740",
        "18446744073709551615",
    };
    static const Uint uValues3[] = {
        (Uint)9223372036854775808ULL,
        (Uint)9987435987394857987ULL,
        (Uint)17873648761234698740ULL,
        (Uint)18446744073709551615ULL,
    };
    FOR_EACH_RANGE (i, 0, sizeof(uStrings3) / sizeof(*uStrings3)) {
      EXPECT_EQ(to<Uint>(uStrings3[i]), uValues3[i]);
      if (sizeof(Int) == 8) {
        EXPECT_THROW(to<Sint>(uStrings3[i]), std::range_error);
      }
    }
  }

  // Minimum possible negative values, and negative sign overflow
  static const String strings4[] = {
      "-128",
      "-32768",
      "-2147483648",
      "-9223372036854775808",
  };
  static const String strings5[] = {
      "-129",
      "-32769",
      "-2147483649",
      "-9223372036854775809",
  };
  static const Sint values4[] = {
      (Sint)-128LL,
      (Sint)-32768LL,
      (Sint)-2147483648LL,
      (Sint)(-9223372036854775807LL - 1),
  };
  FOR_EACH_RANGE (i, 0, sizeof(strings4) / sizeof(*strings4)) {
    if (sizeof(Int) > std::pow(2, i)) {
      EXPECT_EQ(values4[i], to<Sint>(strings4[i]));
      EXPECT_EQ(values4[i] - 1, to<Sint>(strings5[i]));
    } else if (sizeof(Int) == std::pow(2, i)) {
      EXPECT_EQ(values4[i], to<Sint>(strings4[i]));
      EXPECT_THROW(to<Sint>(strings5[i]), std::range_error);
    } else {
      EXPECT_THROW(to<Sint>(strings4[i]), std::range_error);
      EXPECT_THROW(to<Sint>(strings5[i]), std::range_error);
    }
  }

  // Bogus string values
  static const String bogusStrings[] = {
      "",
      "0x1234",
      "123L",
      "123a",
      "x 123 ",
      "234 y",
      "- 42", // whitespace is not allowed between the sign and the value
      " +   13 ",
      "12345678901234567890123456789",
  };
  for (const auto& str : bogusStrings) {
    EXPECT_THROW(to<Sint>(str), std::range_error);
    EXPECT_THROW(to<Uint>(str), std::range_error);
  }

  // A leading '+' character is only allowed when converting to signed types.
  String posSign("+42");
  EXPECT_EQ(42, to<Sint>(posSign));
  EXPECT_THROW(to<Uint>(posSign), std::range_error);

  testString2Integral<String, Ints...>();
}

TEST(Conv, String2Integral) {
  testString2Integral<const char*, int8_t, int16_t, int32_t, int64_t>();
  testString2Integral<std::string, int8_t, int16_t, int32_t, int64_t>();
  testString2Integral<std::string_view, int8_t, int16_t, int32_t, int64_t>();
  testString2Integral<fbstring, int8_t, int16_t, int32_t, int64_t>();

  // Testing the behavior of the StringPiece* API
  // StringPiece* normally parses as much valid data as it can,
  // and advances the StringPiece to the end of the valid data.
  char buf1[] = "100foo";
  StringPiece sp1(buf1);
  EXPECT_EQ(100, to<uint8_t>(&sp1));
  EXPECT_EQ(buf1 + 3, sp1.begin());
  // However, if the next character would cause an overflow it throws a
  // range_error rather than consuming only as much as it can without
  // overflowing.
  char buf2[] = "1002";
  StringPiece sp2(buf2);
  EXPECT_THROW(to<uint8_t>(&sp2), std::range_error);
  EXPECT_EQ(buf2, sp2.begin());
}

TEST(Conv, StringPiece2Integral) {
  string s = "  +123  hello world  ";
  StringPiece sp = s;
  EXPECT_EQ(to<int>(&sp), 123);
  EXPECT_EQ(sp, "  hello world  ");
}

TEST(Conv, StringPieceAppend) {
  string s = "foobar";
  {
    StringPiece sp(s, 0, 3);
    string result = to<string>(s, sp);
    EXPECT_EQ(result, "foobarfoo");
  }
  {
    StringPiece sp1(s, 0, 3);
    StringPiece sp2(s, 3, 3);
    string result = to<string>(sp1, sp2);
    EXPECT_EQ(result, s);
  }
}

TEST(Conv, BadStringToIntegral) {
  // Note that leading spaces (e.g.  " 1") are valid.
  vector<string> v = {"a", "", " ", "\n", " a0", "abcdef", "1Z", "!#"};
  for (auto& s : v) {
    EXPECT_THROW(to<int>(s), std::range_error) << "s=" << s;
  }
}

template <class String>
void testIdenticalTo() {
  String s("Yukkuri shiteitte ne!!!");

  String result = to<String>(s);
  EXPECT_EQ(result, s);
}

template <class String>
void testVariadicTo() {
  String s;
  toAppend(&s);
  toAppend("Lorem ipsum ", 1234, String(" dolor amet "), 567.89, '!', &s);
  EXPECT_EQ(s, "Lorem ipsum 1234 dolor amet 567.89!");

  s = to<String>();
  EXPECT_TRUE(s.empty());

  s = to<String>("Lorem ipsum ", nullptr, 1234, " dolor amet ", 567.89, '.');
  EXPECT_EQ(s, "Lorem ipsum 1234 dolor amet 567.89.");
}

template <class String>
void testIdenticalToDelim() {
  String s("Yukkuri shiteitte ne!!!");

  String charDelim = toDelim<String>('$', s);
  EXPECT_EQ(charDelim, s);

  String strDelim = toDelim<String>(String(">_<"), s);
  EXPECT_EQ(strDelim, s);
}

template <class String>
void testVariadicToDelim() {
  String s;
  toAppendDelim(":", &s);
  toAppendDelim(
      ":", "Lorem ipsum ", 1234, String(" dolor amet "), 567.89, '!', &s);
  EXPECT_EQ(s, "Lorem ipsum :1234: dolor amet :567.89:!");

  s = toDelim<String>(':');
  EXPECT_TRUE(s.empty());

  s = toDelim<String>(
      ":", "Lorem ipsum ", nullptr, 1234, " dolor amet ", 567.89, '.');
  EXPECT_EQ(s, "Lorem ipsum ::1234: dolor amet :567.89:.");
}

TEST(Conv, NullString) {
  string s1 = to<string>((char*)nullptr);
  EXPECT_TRUE(s1.empty());
  fbstring s2 = to<fbstring>((char*)nullptr);
  EXPECT_TRUE(s2.empty());
}

TEST(Conv, VariadicTo) {
  testIdenticalTo<string>();
  testIdenticalTo<fbstring>();
  testVariadicTo<string>();
  testVariadicTo<fbstring>();
}

TEST(Conv, VariadicToDelim) {
  testIdenticalToDelim<string>();
  testIdenticalToDelim<fbstring>();
  testVariadicToDelim<string>();
  testVariadicToDelim<fbstring>();
}

template <class String>
void testDoubleToString() {
  EXPECT_EQ(to<String>(0.0), "0");
  EXPECT_EQ(to<String>(-0.0), "-0");
  EXPECT_EQ(to<String>(0.5), "0.5");
  EXPECT_EQ(to<String>(10.25), "10.25");
  EXPECT_EQ(to<String>(0.000001), "0.000001");
  EXPECT_EQ(to<String>(0.0000001), "1E-7");
  EXPECT_EQ(
      to<String>(111111111111111111111.0),
      // These decimal strings both represent the same IEEE-754 value
      detail::kConvFloatToStringImpl == detail::FloatToStringImpl::StdToChars
          ? "111111111111111114752"
          : "111111111111111110000");
  EXPECT_EQ(to<String>(100000000000000000000.0), "100000000000000000000");
  EXPECT_EQ(to<String>(100000000000000000000.1), "100000000000000000000");
  EXPECT_EQ(
      to<String>(1111111111111111111111.0),
      // These decimal strings both represent the same IEEE-754 value
      detail::kConvFloatToStringImpl == detail::FloatToStringImpl::StdToChars
          ? "1111111111111111081984"
          : "1.1111111111111111E21");
  EXPECT_EQ(to<String>(1.123e10), "11230000000");
  EXPECT_EQ(to<String>(1E22), "1E22");

  EXPECT_EQ(
      to<String>(
          899999999999999918767229449717619953810131273674690656206848.0),
      "9E59");
  EXPECT_EQ(to<String>(std::numeric_limits<double>::quiet_NaN()), "NaN");
  EXPECT_EQ(to<String>(-std::numeric_limits<double>::quiet_NaN()), "NaN");
  EXPECT_EQ(to<String>(std::numeric_limits<double>::infinity()), "Infinity");
  EXPECT_EQ(to<String>(-std::numeric_limits<double>::infinity()), "-Infinity");
}

TEST(Conv, DoubleToString) {
  testDoubleToString<string>();
  testDoubleToString<fbstring>();
}

namespace {

#if defined(FOLLY_CONV_USE_TO_CHARS) && FOLLY_CONV_USE_TO_CHARS == 1
bool hasNoTrailingZero() {
  return true;
}
#else
/// NO_TRAILING_ZERO was added in double_conversion version 3.1.6
/// centos stream 9 uses double_conversion 3.1.5
template <typename T>
using detect_no_trailing_zero = decltype(T::NO_TRAILING_ZERO);

bool hasNoTrailingZero() {
  return is_detected_v<
      detect_no_trailing_zero,
      double_conversion::DoubleToStringConverter::Flags>;
}
#endif

} // namespace

/// Simple macro to test toAppend.
/// This is a macro so failures output the direct line that failed.
#define EXPECT_EQ_TO_APPEND(expected, value, mode, numDigits, flags) \
  {                                                                  \
    std::string actual;                                              \
    folly::toAppend(value, &actual, mode, numDigits, flags);         \
    EXPECT_EQ(actual, expected);                                     \
  }

/// Shared tests for DtoaMode::SHORTEST and DtoaMode::SHORTEST_SINGLE.
void testDoubleToStringShortest(DtoaMode mode) {
  ASSERT_TRUE(mode == DtoaMode::SHORTEST || mode == DtoaMode::SHORTEST_SINGLE)
      << static_cast<int>(mode);
  EXPECT_EQ_TO_APPEND("123.456", 123.456, mode, 0, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND("123", 123.0, mode, 0, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "123.", 123.0, mode, 0, DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "123.0",
      123.0,
      mode,
      0,
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);

  EXPECT_EQ_TO_APPEND(
      "123.0",
      123.0,
      mode,
      0,
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT |
          DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND("0", 0.0, mode, 0, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND("-0", -0.0, mode, 0, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND("0", -0.0, mode, 0, DtoaFlags::UNIQUE_ZERO);

  EXPECT_EQ_TO_APPEND(
      "0.",
      -0.0,
      mode,
      0,
      DtoaFlags::UNIQUE_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);
  EXPECT_EQ_TO_APPEND(
      "0.0",
      -0.0,
      mode,
      0,
      DtoaFlags::UNIQUE_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
}

/// Tests for DtoaMode::SHORTEST with various flags and numDigits.
TEST(Conv, DoubleToAppendShortestFlags) {
  testDoubleToStringShortest(DtoaMode::SHORTEST);
}

/// Tests for DtoaMode::SHORTEST_SINGLE with various flags and numDigits.
TEST(Conv, DoubleToAppendShortestSingleFlags) {
  testDoubleToStringShortest(DtoaMode::SHORTEST_SINGLE);
}

/// Tests for DtoaMode::FIXED with various flags and numDigits.
TEST(Conv, DoubleToAppendFixedFlags) {
  EXPECT_EQ_TO_APPEND(
      "-0.00000", -0.0, DtoaMode::FIXED, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "0.00000", -0.0, DtoaMode::FIXED, 5, DtoaFlags::UNIQUE_ZERO);

  EXPECT_EQ_TO_APPEND(
      "123456789.123456791043281555175781250000000000000000000000000000000000",
      123456789.123456789,
      DtoaMode::FIXED,
      60,
      DtoaFlags::NO_FLAGS);

  // the empty string is returned when numDigits is past the max.
  EXPECT_EQ_TO_APPEND(
      "",
      123456789.123456789,
      DtoaMode::FIXED,
      detail::kConvMaxFixedDigitsAfterPoint + 1,
      DtoaFlags::NO_FLAGS);
}

/// Tests for DtoaMode::FIXED with NO_TRAILING_ZERO.
/// This is in its own separate test because versions of double_conversion
/// < 3.1.6 do not have NO_TRAILING_ZERO.
TEST(Conv, DoubleToAppendFixedNoTrailingZero) {
  if (!hasNoTrailingZero()) {
    GTEST_SKIP()
        << "This version of double_conversion does not have NO_TRAILING_ZERO";
  }

  EXPECT_EQ_TO_APPEND(
      "0.00000", 0.0, DtoaMode::FIXED, 5, DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "0.00000",
      0.0,
      DtoaMode::FIXED,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "0.00000",
      0.0,
      DtoaMode::FIXED,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);

  EXPECT_EQ_TO_APPEND(
      "123456789.09877",
      123456789.0987654321,
      DtoaMode::FIXED,
      5,
      DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "123456789.09870",
      123456789.098705,
      DtoaMode::FIXED,
      5,
      DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "123456789.09871",
      123456789.098706,
      DtoaMode::FIXED,
      5,
      DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "123456789",
      123456789.123456789,
      DtoaMode::FIXED,
      0,
      DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "123456789.",
      123456789.123456789,
      DtoaMode::FIXED,
      0,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "123456789.0",
      123456789.123456789,
      DtoaMode::FIXED,
      0,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
}

/// Tests for DtoaMode::PRECISION with various flags and numDigits.
TEST(Conv, DoubleToAppendPrecisionFlags) {
  EXPECT_EQ_TO_APPEND(
      detail::kConvFloatToStringImpl == detail::FloatToStringImpl::StdToChars
          ? "1.2E-6"
          : "0.0000012",
      0.0000012345,
      DtoaMode::PRECISION,
      2,
      DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "1.2E9", 1234567890.0, DtoaMode::PRECISION, 2, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "9.000000000E59",
      899999999999999918767229449717619953810131273674690656206848.0,
      DtoaMode::PRECISION,
      10,
      DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "0.0000", 0.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "-0.0000", -0.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "0.0000", -0.0, DtoaMode::PRECISION, 5, DtoaFlags::UNIQUE_ZERO);

  EXPECT_EQ_TO_APPEND(
      "-0.0000", -0.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "0.12300", 0.123, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "1230.0", 1230.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "0.12300", 0.123, DtoaMode::PRECISION, 5, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "1E5", 123456.123456, DtoaMode::PRECISION, 1, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "", 123456.123456, DtoaMode::PRECISION, 0, DtoaFlags::NO_FLAGS);

  EXPECT_EQ_TO_APPEND(
      "123456.123456000001169741153717041015625000000000000000000000000000000000000000000000000000000000000000000000000000000000",
      123456.123456,
      DtoaMode::PRECISION,
      detail::kConvMaxPrecisionDigits,
      DtoaFlags::NO_FLAGS);

  // max past is 120, past that it outputs an empty string.
  EXPECT_EQ_TO_APPEND(
      "",
      123456.123456,
      DtoaMode::PRECISION,
      detail::kConvMaxPrecisionDigits + 1,
      DtoaFlags::NO_FLAGS);
}

/// Tests for DtoaMode::PRECISION with NO_TRAILING_ZERO.
/// NO_TRAILING_ZERO exists in versions of double_conversion >= 3.1.6
TEST(Conv, DoubleToAppendPrecisionNoTrailingZero) {
  if (!hasNoTrailingZero()) {
    GTEST_SKIP()
        << "This version of double_conversion does not have NO_TRAILING_ZERO";
  }

  EXPECT_EQ_TO_APPEND(
      "0", 0.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "0.",
      0.0,
      DtoaMode::PRECISION,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "0.0",
      0.0,
      DtoaMode::PRECISION,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);

  EXPECT_EQ_TO_APPEND(
      "-0", -0.0, DtoaMode::PRECISION, 5, DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "-0.",
      -0.0,
      DtoaMode::PRECISION,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "-0.0",
      -0.0,
      DtoaMode::PRECISION,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);

  EXPECT_EQ_TO_APPEND(
      detail::kConvFloatToStringImpl == detail::FloatToStringImpl::StdToChars
          ? "1.2E-6"
          : "0.0000012",
      0.0000012345,
      DtoaMode::PRECISION,
      2,
      DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "0.123", 0.123, DtoaMode::PRECISION, 5, DtoaFlags::NO_TRAILING_ZERO);

  EXPECT_EQ_TO_APPEND(
      "0.123",
      0.123,
      DtoaMode::PRECISION,
      5,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);

  EXPECT_EQ_TO_APPEND(
      "0.123",
      0.123,
      DtoaMode::PRECISION,
      8,
      DtoaFlags::NO_TRAILING_ZERO | DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
}

TEST(Conv, FBStringToString) {
  fbstring foo("foo");
  string ret = to<string>(foo);
  EXPECT_EQ(ret, "foo");
  string ret2 = to<string>(foo, 2);
  EXPECT_EQ(ret2, "foo2");
}

TEST(Conv, RoundTripInfinityBetweenFloatingPointTypes) {
  // float -> double -> float
  EXPECT_EQ(
      to<float>(to<double>(numeric_limits<float>::infinity())),
      numeric_limits<float>::infinity());
  EXPECT_EQ(
      to<float>(to<double>(-numeric_limits<float>::infinity())),
      -numeric_limits<float>::infinity());

  // float -> long double -> float
  EXPECT_EQ(
      to<float>(to<long double>(numeric_limits<float>::infinity())),
      numeric_limits<float>::infinity());
  EXPECT_EQ(
      to<float>(to<long double>(-numeric_limits<float>::infinity())),
      -numeric_limits<float>::infinity());

  // double -> long double -> double
  EXPECT_EQ(
      to<double>(to<long double>(numeric_limits<double>::infinity())),
      numeric_limits<double>::infinity());
  EXPECT_EQ(
      to<double>(to<long double>(-numeric_limits<double>::infinity())),
      -numeric_limits<double>::infinity());
}

TEST(Conv, StringPieceToDouble) {
  vector<tuple<const char*, const char*, double>> strs{
      make_tuple("2134123.125 zorro", " zorro", 2134123.125),
      make_tuple("  2134123.125 zorro", " zorro", 2134123.125),
      make_tuple(" 2134123.125  zorro", "  zorro", 2134123.125),
      make_tuple(" 2134123.125  zorro ", "  zorro ", 2134123.125),
      make_tuple("2134123.125zorro", "zorro", 2134123.125),
      make_tuple("0 zorro", " zorro", 0.0),
      make_tuple("  0 zorro", " zorro", 0.0),
      make_tuple(" 0  zorro", "  zorro", 0.0),
      make_tuple(" 0  zorro ", "  zorro ", 0.0),
      make_tuple("0zorro", "zorro", 0.0),
      make_tuple("0.0 zorro", " zorro", 0.0),
      make_tuple("  0.0 zorro", " zorro", 0.0),
      make_tuple(" 0.0  zorro", "  zorro", 0.0),
      make_tuple(" 0.0  zorro ", "  zorro ", 0.0),
      make_tuple("0.0zorro", "zorro", 0.0),
      make_tuple("0.0eb", "eb", 0.0),
      make_tuple("0.0EB", "EB", 0.0),
      make_tuple("0eb", "eb", 0.0),
      make_tuple("0EB", "EB", 0.0),
      make_tuple("12e", "e", 12.0),
      make_tuple("12e-", "e-", 12.0),
      make_tuple("12e+", "e+", 12.0),
      make_tuple("12e-f-g", "e-f-g", 12.0),
      make_tuple("12e+f+g", "e+f+g", 12.0),
      make_tuple("12euro", "euro", 12.0),
  };
  for (const auto& s : strs) {
    StringPiece pc(get<0>(s));
    EXPECT_EQ(get<2>(s), to<double>(&pc)) << "\"" << get<0>(s) << "\"";
    EXPECT_EQ(get<1>(s), pc);
    EXPECT_THROW(to<double>(StringPiece(get<0>(s))), std::range_error);
    EXPECT_EQ(get<2>(s), to<double>(StringPiece(get<0>(s), pc.data())));
  }

  // Test NaN conversion
  try {
    to<double>("not a number");
    ADD_FAILURE();
  } catch (const std::range_error&) {
  }

  EXPECT_TRUE(std::isnan(to<double>("nan")));
  EXPECT_TRUE(std::isnan(to<double>("NaN")));
  EXPECT_TRUE(std::isnan(to<double>("NAN")));
  EXPECT_TRUE(std::isnan(to<double>("-nan")));
  EXPECT_TRUE(std::isnan(to<double>("-NaN")));
  EXPECT_TRUE(std::isnan(to<double>("-NAN")));

  EXPECT_EQ(to<double>("inf"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("Inf"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("INF"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("inF"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("infinity"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("Infinity"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("INFINITY"), numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("iNfInItY"), numeric_limits<double>::infinity());
  EXPECT_THROW(to<double>("infinitX"), std::range_error);
  EXPECT_EQ(to<double>("-inf"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-Inf"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-INF"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-inF"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-infinity"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-Infinity"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-INFINITY"), -numeric_limits<double>::infinity());
  EXPECT_EQ(to<double>("-iNfInItY"), -numeric_limits<double>::infinity());
  EXPECT_THROW(to<double>("-infinitX"), std::range_error);
}

TEST(Conv, EmptyStringToInt) {
  string s = "";
  StringPiece pc(s);

  try {
    to<int>(pc);
    ADD_FAILURE();
  } catch (const std::range_error&) {
  }
}

TEST(Conv, CorruptedStringToInt) {
  string s = "-1";
  StringPiece pc(s.data(), s.data() + 1); // Only  "-"

  try {
    to<int64_t>(&pc);
    ADD_FAILURE();
  } catch (const std::range_error&) {
  }
}

TEST(Conv, EmptyStringToDouble) {
  string s = "";
  StringPiece pc(s);

  try {
    to<double>(pc);
    ADD_FAILURE();
  } catch (const std::range_error&) {
  }
}

TEST(Conv, IntToDouble) {
  auto d = to<double>(42);
  EXPECT_EQ(d, 42);
  try {
    (void)to<float>(957837589847);
    ADD_FAILURE();
  } catch (std::range_error&) {
    // LOG(INFO) << e.what();
  }
}

TEST(Conv, DoubleToInt) {
  auto i = to<int>(42.0);
  EXPECT_EQ(i, 42);
  try {
    auto i2 = to<int>(42.1);
    LOG(ERROR) << "to<int> returned " << i2 << " instead of throwing";
    ADD_FAILURE();
  } catch (std::range_error&) {
    // LOG(INFO) << e.what();
  }
}

namespace {

template <class From, class To>
void testNotFiniteToInt() {
  for (auto s : {"nan", "inf", "-inf"}) {
    auto v = to<From>(s);
    auto rv = folly::tryTo<To>(v);
    EXPECT_FALSE(rv.hasValue()) << s << " " << rv.value();
  }
}

} // namespace

TEST(Conv, NotFiniteToInt) {
  testNotFiniteToInt<float, int64_t>();
  testNotFiniteToInt<float, uint64_t>();
  testNotFiniteToInt<double, int64_t>();
  testNotFiniteToInt<double, uint64_t>();
}

TEST(Conv, EnumToInt) {
  enum A { x = 42, y = 420, z = 65 };
  auto i = to<int>(x);
  EXPECT_EQ(i, 42);
  auto j = to<char>(x);
  EXPECT_EQ(j, 42);
  try {
    auto i2 = to<char>(y);
    LOG(ERROR) << "to<char> returned " << static_cast<unsigned int>(i2)
               << " instead of throwing";
    ADD_FAILURE();
  } catch (std::range_error&) {
    // LOG(INFO) << e.what();
  }
}

TEST(Conv, EnumToString) {
  // task 813959
  enum A { x = 4, y = 420, z = 65 };
  EXPECT_EQ("foo.4", to<string>("foo.", x));
  EXPECT_EQ("foo.420", to<string>("foo.", y));
  EXPECT_EQ("foo.65", to<string>("foo.", z));
}

TEST(Conv, IntToEnum) {
  enum A { x = 42, y = 420 };
  auto i = to<A>(42);
  EXPECT_EQ(i, x);
  auto j = to<A>(100);
  EXPECT_EQ(j, 100);
  try {
    auto i2 = to<A>(5000000000LL);
    LOG(ERROR) << "to<A> returned " << static_cast<unsigned int>(i2)
               << " instead of throwing";
    ADD_FAILURE();
  } catch (std::range_error&) {
    // LOG(INFO) << e.what();
  }
}

TEST(Conv, UnsignedEnum) {
  enum E : uint32_t { x = 3000000000U };
  auto u = to<uint32_t>(x);
  EXPECT_EQ(u, 3000000000U);
  auto s = to<string>(x);
  EXPECT_EQ("3000000000", s);
  auto e = to<E>(3000000000U);
  EXPECT_EQ(e, x);
  try {
    auto i = to<int32_t>(x);
    LOG(ERROR) << "to<int32_t> returned " << i << " instead of throwing";
    ADD_FAILURE();
  } catch (std::range_error&) {
  }
}

TEST(Conv, UnsignedEnumClass) {
  enum class E : uint32_t { x = 3000000000U };
  auto u = to<uint32_t>(E::x);
  EXPECT_GT(u, 0);
  EXPECT_EQ(u, 3000000000U);
  EXPECT_EQ("3000000000", to<string>(E::x));
  EXPECT_EQ(E::x, to<E>(3000000000U));
  EXPECT_EQ(E::x, to<E>("3000000000"));
  E e;
  EXPECT_TRUE(parseTo("3000000000", e).hasValue());
  EXPECT_EQ(E::x, e);
  EXPECT_THROW(to<int32_t>(E::x), std::range_error);
}

// Multi-argument to<string> uses toAppend, a different code path than
// to<string>(enum).
TEST(Conv, EnumClassToString) {
  enum class A { x = 4, y = 420, z = 65 };
  EXPECT_EQ("foo.4", to<string>("foo.", A::x));
  EXPECT_EQ("foo.420", to<string>("foo.", A::y));
  EXPECT_EQ("foo.65", to<string>("foo.", A::z));
}

TEST(Conv, IntegralToBool) {
  EXPECT_FALSE(to<bool>(0));
  EXPECT_FALSE(to<bool>(0ul));

  EXPECT_TRUE(to<bool>(1));
  EXPECT_TRUE(to<bool>(1ul));

  EXPECT_TRUE(to<bool>(-42));
  EXPECT_TRUE(to<bool>(42ul));
}

template <typename Src>
void testStr2Bool() {
  EXPECT_FALSE(to<bool>(Src("0")));
  EXPECT_FALSE(to<bool>(Src("  000  ")));

  EXPECT_FALSE(to<bool>(Src("n")));
  EXPECT_FALSE(to<bool>(Src("no")));
  EXPECT_FALSE(to<bool>(Src("false")));
  EXPECT_FALSE(to<bool>(Src("False")));
  EXPECT_FALSE(to<bool>(Src("  fAlSe  ")));
  EXPECT_FALSE(to<bool>(Src("F")));
  EXPECT_FALSE(to<bool>(Src("off")));

  EXPECT_TRUE(to<bool>(Src("1")));
  EXPECT_TRUE(to<bool>(Src("  001 ")));
  EXPECT_TRUE(to<bool>(Src("y")));
  EXPECT_TRUE(to<bool>(Src("yes")));
  EXPECT_TRUE(to<bool>(Src("\nyEs\t")));
  EXPECT_TRUE(to<bool>(Src("true")));
  EXPECT_TRUE(to<bool>(Src("True")));
  EXPECT_TRUE(to<bool>(Src("T")));
  EXPECT_TRUE(to<bool>(Src("on")));

  EXPECT_THROW(to<bool>(Src("")), std::range_error);
  EXPECT_THROW(to<bool>(Src("2")), std::range_error);
  EXPECT_THROW(to<bool>(Src("11")), std::range_error);
  EXPECT_THROW(to<bool>(Src("19")), std::range_error);
  EXPECT_THROW(to<bool>(Src("o")), std::range_error);
  EXPECT_THROW(to<bool>(Src("fal")), std::range_error);
  EXPECT_THROW(to<bool>(Src("tru")), std::range_error);
  EXPECT_THROW(to<bool>(Src("ye")), std::range_error);
  EXPECT_THROW(to<bool>(Src("yes foo")), std::range_error);
  EXPECT_THROW(to<bool>(Src("bar no")), std::range_error);
  EXPECT_THROW(to<bool>(Src("one")), std::range_error);
  EXPECT_THROW(to<bool>(Src("true_")), std::range_error);
  EXPECT_THROW(to<bool>(Src("bogus_token_that_is_too_long")), std::range_error);
}

TEST(Conv, StringToBool) {
  // testStr2Bool<const char *>();
  testStr2Bool<std::string>();

  // Test with strings that are not NUL terminated.
  const char buf[] = "01234";
  EXPECT_FALSE(to<bool>(StringPiece(buf, buf + 1))); // "0"
  EXPECT_TRUE(to<bool>(StringPiece(buf + 1, buf + 2))); // "1"
  const char buf2[] = "one two three";
  EXPECT_TRUE(to<bool>(StringPiece(buf2, buf2 + 2))); // "on"
  const char buf3[] = "false";
  EXPECT_THROW(
      to<bool>(StringPiece(buf3, buf3 + 3)), // "fal"
      std::range_error);

  // Test the StringPiece* API
  const char buf4[] = "001foo";
  StringPiece sp4(buf4);
  EXPECT_TRUE(to<bool>(&sp4));
  EXPECT_EQ(buf4 + 3, sp4.begin());
  const char buf5[] = "0012";
  StringPiece sp5(buf5);
  EXPECT_THROW(to<bool>(&sp5), std::range_error);
  EXPECT_EQ(buf5, sp5.begin());
}

TEST(Conv, Transform) {
  const std::vector<int64_t> in{1, 2, 3};
  std::vector<std::string> out(in.size());
  std::transform(in.begin(), in.end(), out.begin(), to<std::string, int64_t>);
  const std::vector<std::string> ref{"1", "2", "3"};
  EXPECT_EQ(ref, out);
}

TEST(Conv, FloatToInt) {
  EXPECT_EQ(to<int>(42.0f), 42);
  EXPECT_EQ(to<int8_t>(-128.0f), int8_t(-128));
  EXPECT_THROW(to<int8_t>(-129.0), std::range_error);
  EXPECT_THROW(to<int8_t>(127.001), std::range_error);
  EXPECT_THROW(to<uint8_t>(-0.0001), std::range_error);
  EXPECT_THROW(
      to<uint64_t>(static_cast<float>(std::numeric_limits<uint64_t>::max())),
      std::range_error);
  EXPECT_THROW(to<uint64_t>(static_cast<float>(-1)), std::range_error);
}

TEST(Conv, IntToFloat) {
  EXPECT_EQ(to<float>(42ULL), 42.0);
  EXPECT_EQ(to<float>(int8_t(-128)), -128.0);
  EXPECT_THROW(
      to<float>(std::numeric_limits<uint64_t>::max()), std::range_error);
  EXPECT_THROW(
      to<float>(std::numeric_limits<int64_t>::max()), std::range_error);
  EXPECT_THROW(
      to<float>(std::numeric_limits<int64_t>::min() + 1), std::range_error);
#if FOLLY_HAVE_INT128_T
  EXPECT_THROW(
      to<double>(std::numeric_limits<unsigned __int128>::max()),
      std::range_error);
  EXPECT_THROW(
      to<double>(std::numeric_limits<__int128>::max()), std::range_error);
  EXPECT_THROW(
      to<double>(std::numeric_limits<__int128>::min() + 1), std::range_error);
#endif
}

TEST(Conv, BoolToString) {
  EXPECT_EQ(to<std::string>(true), "1");
  EXPECT_EQ(to<std::string>(false), "0");
}

TEST(Conv, BoolToFloat) {
  EXPECT_EQ(to<double>(true), 1.0);
  EXPECT_EQ(to<double>(false), 0.0);
}

TEST(Conv, FloatToBool) {
  EXPECT_EQ(to<bool>(1.0), true);
  EXPECT_EQ(to<bool>(0.0), false);
  EXPECT_EQ(to<bool>(2.7), true);
  EXPECT_EQ(to<bool>(std::numeric_limits<double>::max()), true);
  EXPECT_EQ(to<bool>(std::numeric_limits<double>::min()), true);
  EXPECT_EQ(to<bool>(std::numeric_limits<double>::lowest()), true);
  EXPECT_EQ(to<bool>(std::numeric_limits<double>::quiet_NaN()), true);
  EXPECT_EQ(to<bool>(std::numeric_limits<double>::infinity()), true);
  EXPECT_EQ(to<bool>(-std::numeric_limits<double>::infinity()), true);
}

TEST(Conv, RoundTripFloatToStringToFloat) {
  const std::array<float, 6> kTests{{
      3.14159f,
      12345678.f,
      numeric_limits<float>::lowest(),
      numeric_limits<float>::max(),
      numeric_limits<float>::infinity(),
      -numeric_limits<float>::infinity(),
  }};

  for (const auto& test : kTests) {
    SCOPED_TRACE(to<string>(test));
    EXPECT_EQ(to<float>(to<string>(test)), test);
  }

  EXPECT_TRUE(
      std::isnan(to<float>(to<string>(numeric_limits<float>::quiet_NaN()))));
}

namespace {

template <typename F>
void testConvError(
    F&& expr,
    const char* exprStr,
    ConversionCode code,
    const char* value,
    bool quotedValue,
    int line) {
  std::string where = to<std::string>(__FILE__, "(", line, "): ");
  try {
    auto res = expr();
    ADD_FAILURE() << where << exprStr << " -> " << res;
  } catch (const ConversionError& e) {
    EXPECT_EQ(code, e.errorCode()) << where << exprStr;
    std::string str(e.what());
    EXPECT_FALSE(str.empty()) << where << exprStr << " -> " << str;
    auto pos = str.find(':');
    if (value) {
      std::ostringstream exp;
      exp << str.substr(0, pos) + ": ";
      if (quotedValue) {
        exp << "\"" << value << "\"";
      } else {
        exp << value;
      }
      EXPECT_EQ(exp.str(), str) << where << exprStr << " -> " << str;
    } else {
      EXPECT_EQ(pos, std::string::npos) << where << exprStr << " -> " << str;
    }
  }
}
} // namespace

#define EXPECT_CONV_ERROR_QUOTE(expr, code, value, quoted) \
  testConvError(                                           \
      [&] { return expr; },                                \
      #expr,                                               \
      ConversionCode::code,                                \
      value,                                               \
      quoted,                                              \
      __LINE__)

#define EXPECT_CONV_ERROR(expr, code, value) \
  EXPECT_CONV_ERROR_QUOTE(expr, code, value, true)

#define EXPECT_CONV_ERROR_STR(type, str, code) \
  EXPECT_CONV_ERROR(to<type>(str), code, str)

#define EXPECT_CONV_ERROR_STR_NOVAL(type, str, code) \
  EXPECT_CONV_ERROR(to<type>(str), code, nullptr)

TEST(Conv, ConversionErrorStrToBool) {
  EXPECT_CONV_ERROR_STR_NOVAL(bool, StringPiece(), EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR_NOVAL(bool, "", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(bool, "  ", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(bool, " 11 ", BOOL_OVERFLOW);
  EXPECT_CONV_ERROR_STR(bool, "other ", BOOL_INVALID_VALUE);
  EXPECT_CONV_ERROR_STR(bool, " bla", BOOL_INVALID_VALUE);
  EXPECT_CONV_ERROR(to<bool>("  offbla"), NON_WHITESPACE_AFTER_END, "bla");
}

TEST(Conv, ConversionErrorStrToFloat) {
  EXPECT_CONV_ERROR_STR_NOVAL(float, StringPiece(), EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR_NOVAL(float, "", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(float, "  ", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(float, "\t", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(float, "  junk", STRING_TO_FLOAT_ERROR);
  EXPECT_CONV_ERROR(to<float>("  1bla"), NON_WHITESPACE_AFTER_END, "bla");

  EXPECT_CONV_ERROR_STR_NOVAL(double, StringPiece(), EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR_NOVAL(double, "", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(double, "  ", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(double, "\t", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(double, "  junk", STRING_TO_FLOAT_ERROR);
  EXPECT_CONV_ERROR(to<double>("  1bla"), NON_WHITESPACE_AFTER_END, "bla");
}

TEST(Conv, ConversionErrorStrToInt) {
  // empty string handling
  EXPECT_CONV_ERROR_STR_NOVAL(int, StringPiece(), EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR_NOVAL(int, "", EMPTY_INPUT_STRING);
  EXPECT_CONV_ERROR_STR(int, "  ", EMPTY_INPUT_STRING);

  // signed integers
  EXPECT_CONV_ERROR_STR(int, "  *", INVALID_LEADING_CHAR);
  EXPECT_CONV_ERROR_STR(int, "  +", NO_DIGITS);
  EXPECT_CONV_ERROR_STR(int, "  +*", NON_DIGIT_CHAR);
  EXPECT_CONV_ERROR_STR(int8_t, "  128", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_STR(int8_t, " -129", NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_STR(int8_t, " 1000", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_STR(int8_t, "-1000", NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR(to<int>(" -13bla"), NON_WHITESPACE_AFTER_END, "bla");

  // unsigned integers
  EXPECT_CONV_ERROR_STR(unsigned, "  -", NON_DIGIT_CHAR);
  EXPECT_CONV_ERROR_STR(uint8_t, " 256", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR(to<unsigned>("42bla"), NON_WHITESPACE_AFTER_END, "bla");
}

#define EXPECT_CONV_ERROR_PP_VAL(type, str, code, val)                  \
  do {                                                                  \
    StringPiece input(str);                                             \
    EXPECT_CONV_ERROR(to<type>(input.begin(), input.end()), code, val); \
  } while (0)

#define EXPECT_CONV_ERROR_PP(type, str, code) \
  EXPECT_CONV_ERROR_PP_VAL(type, str, code, str)

TEST(Conv, ConversionErrorPtrPairToInt) {
  // signed integers
  EXPECT_CONV_ERROR_PP(int, "", INVALID_LEADING_CHAR);
  EXPECT_CONV_ERROR_PP(int, " ", INVALID_LEADING_CHAR);
  EXPECT_CONV_ERROR_PP(int, "*", INVALID_LEADING_CHAR);
  EXPECT_CONV_ERROR_PP(int, "+", NO_DIGITS);
  EXPECT_CONV_ERROR_PP(int8_t, "128", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_PP(int8_t, "-129", NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_PP(int8_t, "1000", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_PP(int8_t, "-1000", NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_PP(int, "-junk", NON_DIGIT_CHAR);

  // unsigned integers
  EXPECT_CONV_ERROR_PP(unsigned, "", NO_DIGITS);
  EXPECT_CONV_ERROR_PP(uint8_t, "256", POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_PP(unsigned, "junk", NON_DIGIT_CHAR);
}

namespace {

template <typename T, typename V>
std::string prefixWithType(V value) {
  std::ostringstream oss;
  oss << "(" << pretty_name<T>() << ") ";
  oss << to<std::string>(value);
  return oss.str();
}
} // namespace

#define EXPECT_CONV_ERROR_ARITH(type, val, code) \
  EXPECT_CONV_ERROR_QUOTE(                       \
      to<type>(val), code, prefixWithType<type>(val).c_str(), false)

template <typename TUnsigned>
void unsignedUnderflow() {
  EXPECT_CONV_ERROR_ARITH(
      TUnsigned, std::numeric_limits<int8_t>::min(), ARITH_NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      TUnsigned, std::numeric_limits<int16_t>::min(), ARITH_NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      TUnsigned, std::numeric_limits<int32_t>::min(), ARITH_NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      TUnsigned, std::numeric_limits<int64_t>::min(), ARITH_NEGATIVE_OVERFLOW);
}

TEST(Conv, ConversionErrorIntToInt) {
  // Test overflow upper bound. First unsigned to signed.
  EXPECT_CONV_ERROR_ARITH(
      int8_t, std::numeric_limits<uint8_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int16_t, std::numeric_limits<uint16_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int32_t, std::numeric_limits<uint32_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int64_t, std::numeric_limits<uint64_t>::max(), ARITH_POSITIVE_OVERFLOW);

  // Signed to signed.
  EXPECT_CONV_ERROR_ARITH(
      int8_t, std::numeric_limits<int16_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int16_t, std::numeric_limits<int32_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int32_t, std::numeric_limits<int64_t>::max(), ARITH_POSITIVE_OVERFLOW);

  // Unsigned to unsigned.
  EXPECT_CONV_ERROR_ARITH(
      uint8_t, std::numeric_limits<uint16_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      uint16_t, std::numeric_limits<uint32_t>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      uint32_t, std::numeric_limits<uint64_t>::max(), ARITH_POSITIVE_OVERFLOW);

  // Test underflows from signed to unsigned data types. Make sure we test all
  // combinations.
  unsignedUnderflow<uint8_t>();
  unsignedUnderflow<uint16_t>();
  unsignedUnderflow<uint32_t>();
  unsignedUnderflow<uint64_t>();

  // Signed to signed.
  EXPECT_CONV_ERROR_ARITH(
      int8_t, std::numeric_limits<int16_t>::min(), ARITH_NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int16_t, std::numeric_limits<int32_t>::min(), ARITH_NEGATIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      int32_t, std::numeric_limits<int64_t>::min(), ARITH_NEGATIVE_OVERFLOW);
}

TEST(Conv, ConversionErrorFloatToFloat) {
  EXPECT_CONV_ERROR_ARITH(
      float, std::numeric_limits<double>::max(), ARITH_POSITIVE_OVERFLOW);
  EXPECT_CONV_ERROR_ARITH(
      float, std::numeric_limits<double>::lowest(), ARITH_NEGATIVE_OVERFLOW);
}

TEST(Conv, ConversionErrorIntToFloat) {
  EXPECT_CONV_ERROR_ARITH(
      float, std::numeric_limits<long long>::max(), ARITH_LOSS_OF_PRECISION);
}

TEST(Conv, ConversionErrorFloatToInt) {
  EXPECT_CONV_ERROR_ARITH(int8_t, 65.5, ARITH_LOSS_OF_PRECISION);
}

TEST(Conv, TryStringToBool) {
  for (const char* bad : {
           "fals",
           "tru",
           "false other string",
           "true other string",
           "0x1",
           "2",
           "10",
           "nu",
           "da",
           "of",
           "onn",
           "yep",
           "nope",
       }) {
    auto rv = folly::tryTo<bool>(bad);
    EXPECT_FALSE(rv.hasValue()) << bad;
  }

  for (const char* falsy : {
           "f",
           "F",
           "false",
           "False",
           "FALSE",
           " false ",
           "0",
           "00",
           "n",
           "N",
           "no",
           "No",
           "NO",
           "off",
           "Off",
           "OFF",
       }) {
    auto rv = folly::tryTo<bool>(falsy);
    EXPECT_TRUE(rv.hasValue()) << falsy;
    EXPECT_FALSE(rv.value()) << falsy;
  }

  for (const char* truthy : {
           "t",
           "T",
           "true",
           "True",
           "TRUE",
           " true ",
           "1",
           "01",
           "y",
           "Y",
           "yes",
           "Yes",
           "YES",
           "on",
           "On",
           "ON",
       }) {
    auto rv = folly::tryTo<bool>(truthy);
    EXPECT_TRUE(rv.hasValue()) << truthy;
    EXPECT_TRUE(rv.value()) << truthy;
  }
}

TEST(Conv, TryStringToInt) {
  auto rv1 = folly::tryTo<int>("1000000000000000000000000000000");
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<int>("4711");
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(rv2.value(), 4711);
}

TEST(Conv, TryStringToEnum) {
  enum class A { x = 42, y = 420, z = 65 };
  auto rv1 = folly::tryTo<A>("1000000000000000000000000000000");
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<A>("42");
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(A::x, rv2.value());
  auto rv3 = folly::tryTo<A>("50");
  EXPECT_TRUE(rv3.hasValue());
  EXPECT_EQ(static_cast<A>(50), rv3.value());
}

namespace {
/// Simple pure virtual class used by tests to change the function that converts
/// string to float.
template <class String>
class StrToFloat {
 public:
  virtual ~StrToFloat() = default;
  /// Converts a string to a float.
  /// The input string is expected to be a number in
  /// decimal or exponential notation (e.g., "3.14", "3.14e-2").
  virtual Expected<float, ConversionCode> operator()(String src) const = 0;

  /// Returns true if `operator()` returns an error when the input string has
  /// trailing junk.
  /// e.g., when the input string is "3.14junk", `operator()` returns an error.
  virtual bool returnsErrorOnTrailingJunk() const = 0;
};

/// Uses `folly::TryTo` to convert a string to a float.
template <class String>
class StrToFloatTryTo : public StrToFloat<String> {
 public:
  Expected<float, ConversionCode> operator()(String src) const override {
    return folly::tryTo<float>(src);
  }

  bool returnsErrorOnTrailingJunk() const override { return true; }
};
} // namespace

/// `strToFloat` is used to test out different implementations of string
/// to float conversions.
template <class String>
void tryStringToFloat(const StrToFloat<String>& strToFloat) {
  auto rv1 = strToFloat(String(""));
  EXPECT_FALSE(rv1.hasValue());

  const std::array<String, 9> kZero{{
      "0",
      "+0",
      "-0",
      ".0",
      "+.0",
      "-.0",
      "0.0",
      "+0.0",
      "-0.0",
  }};
  for (const auto& input : kZero) {
    auto rv = strToFloat(input);
    EXPECT_TRUE(rv.hasValue()) << input;
    EXPECT_EQ(rv.value(), 0.0f) << input;
  }

  auto rv2 = strToFloat(String("3.14"));
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_NEAR(rv2.value(), 3.14, 1e-5);

  auto rv2Positive = strToFloat(String("+3.14"));
  EXPECT_TRUE(rv2Positive.hasValue());
  EXPECT_NEAR(rv2Positive.value(), 3.14, 1e-5);

  auto rv2PositiveLessThan1 = strToFloat(String("+.14"));
  EXPECT_TRUE(rv2PositiveLessThan1.hasValue());
  EXPECT_NEAR(rv2PositiveLessThan1.value(), .14, 1e-5);

  const std::array<String, 6> kInvalidSigns{{
      "-",
      "+",
      "--3.14",
      "++3.14",
      "+-3.14",
      "-+3.14",
  }};
  for (const auto& input : kInvalidSigns) {
    auto rv = strToFloat(input);
    EXPECT_TRUE(rv.hasError()) << input;
    EXPECT_EQ(rv.error(), ConversionCode::STRING_TO_FLOAT_ERROR) << input;
  }

  auto rv2Negative = strToFloat(String("-3.14"));
  EXPECT_TRUE(rv2Negative.hasValue());
  EXPECT_NEAR(rv2Negative.value(), -3.14, 1e-5);

  auto rv2NegativeLessThan1 = strToFloat(String("-.14"));
  EXPECT_TRUE(rv2NegativeLessThan1.hasValue());
  EXPECT_NEAR(rv2NegativeLessThan1.value(), -.14, 1e-5);

  // No trailing '\0' to expose 1-byte buffer over-read
  char x = '-';
  auto rv3 = strToFloat(String(&x, 1));
  EXPECT_FALSE(rv3.hasValue());

  // Exact conversion at numeric limits (8+ decimal digits)
  auto rv4 = strToFloat(String("-3.4028235E38"));
  EXPECT_TRUE(rv4.hasValue());
  EXPECT_EQ(rv4.value(), numeric_limits<float>::lowest());
  auto rv5 = strToFloat(String("3.40282346E38"));
  EXPECT_TRUE(rv5.hasValue());
  EXPECT_EQ(rv5.value(), numeric_limits<float>::max());

  // Beyond numeric limits
  // numeric_limits<float>::lowest() ~= -3.402823466E38
  const std::array<String, 4> kOversizedInputs{{
      "-3.403E38",
      "-3.4029E38",
      "-3.402824E38",
      "-3.4028236E38",
  }};
  for (const auto& input : kOversizedInputs) {
    auto rv = strToFloat(input);
    EXPECT_EQ(rv.value(), -numeric_limits<float>::infinity()) << input;
  }

  // NaN
  const std::array<String, 6> kNanInputs{{
      "nan",
      "NaN",
      "NAN",
      "-nan",
      "-NaN",
      "-NAN",
  }};
  for (const auto& input : kNanInputs) {
    auto rv = strToFloat(input);
    EXPECT_TRUE(std::isnan(rv.value())) << input;
  }

  EXPECT_EQ(strToFloat("+nan").error(), ConversionCode::STRING_TO_FLOAT_ERROR);

  const std::array<String, 6> kInfinityInputs{{
      "-inf",
      "-INF",
      "-iNf",
      "-infinity",
      "-INFINITY",
      "-INFInITY",
  }};
  for (const auto& input : kInfinityInputs) {
    {
      auto rv = strToFloat(input);
      EXPECT_EQ(rv.value(), -numeric_limits<float>::infinity()) << input;
    }

    {
      auto positiveInput = input.substr(1);
      auto rv = strToFloat(positiveInput);
      EXPECT_EQ(rv.value(), numeric_limits<float>::infinity()) << positiveInput;
    }
  }

  EXPECT_EQ(
      strToFloat("+infinity").error(), ConversionCode::STRING_TO_FLOAT_ERROR);
  EXPECT_EQ(strToFloat("+inf").error(), ConversionCode::STRING_TO_FLOAT_ERROR);

  const std::array<String, 15> kScientificNotation{{
      "123.4560e0",
      "+123.4560e0",
      "123.4560e+0",
      "123.4560e-0",
      "123456.0e-3",
      "123456.0E-3",
      "+123456.0E-3",
      "0.123456e3",
      "0.123456e+3",
      "0.123456E+3",
      "+0.123456E+3",
      ".123456e3",
      ".123456e+3",
      ".123456E+3",
      "+.123456E+3",
  }};
  for (const auto& input : kScientificNotation) {
    auto rv = strToFloat(input);
    EXPECT_EQ(rv.value(), 123.456f) << input;
  }

  const std::array<String, 8> kSurroundingWhitespace{{
      " 123.456",
      "\n123.456",
      "\r123.456",
      "\t123.456",
      "\n123.456",
      "123.456 ",
      "123.456\n",
      " 123.456 ",
  }};
  for (const auto& input : kSurroundingWhitespace) {
    EXPECT_EQ(strToFloat(input).value(), 123.456f);
  }

  EXPECT_EQ(strToFloat("   ").error(), ConversionCode::EMPTY_INPUT_STRING);

  const std::array<String, 2> kJunkValues{{"junk", "a123.456"}};
  for (const auto& input : kJunkValues) {
    EXPECT_EQ(strToFloat(input).error(), ConversionCode::STRING_TO_FLOAT_ERROR);
  }

  const std::array<String, 8> kNonWhitespaceAfterEnd{{
      "123.456X",
      "123.456e",
      "123.456E",
      "123.456E-",
      "123.456E+",
      "123.456E-2f",
      "123.456E-f",
      "123.456E~2",
  }};
  for (const auto& input : kNonWhitespaceAfterEnd) {
    auto rv = strToFloat(input);
    EXPECT_EQ(strToFloat.returnsErrorOnTrailingJunk(), rv.hasError())
        << "input: " << input << " value " << rv.value();
    if (rv.hasError()) {
      EXPECT_EQ(rv.error(), ConversionCode::NON_WHITESPACE_AFTER_END)
          << "input: " << input;
    }
  }
}

TEST(Conv, TryStringToFloat) {
  tryStringToFloat<std::string>(StrToFloatTryTo<std::string>());
  tryStringToFloat<std::string_view>(StrToFloatTryTo<std::string_view>());
  tryStringToFloat<folly::StringPiece>(StrToFloatTryTo<folly::StringPiece>());
}

/// Uses `folly::detail::str_to_floating_fast_float_from_chars` to convert a
/// string to a float.
template <class String>
class StrToFloatFastFloatFromChars : public StrToFloat<String> {
 public:
  Expected<float, ConversionCode> operator()(String src) const override {
    StringPiece sp{src};
    return folly::detail::str_to_floating_fast_float_from_chars<float>(&sp);
  }

  bool returnsErrorOnTrailingJunk() const override { return false; }
};

TEST(Conv, TryStringToFloat_FastFloatFromChars) {
  tryStringToFloat<std::string>(StrToFloatFastFloatFromChars<std::string>());
  tryStringToFloat<std::string_view>(
      StrToFloatFastFloatFromChars<std::string_view>());
  tryStringToFloat<folly::StringPiece>(
      StrToFloatFastFloatFromChars<folly::StringPiece>());
}

template <class String>
void tryToDouble() {
  auto rv1 = folly::tryTo<double>(String(""));
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<double>(String("3.14"));
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_NEAR(rv2.value(), 3.14, 1e-10);
  // No trailing '\0' to expose 1-byte buffer over-read
  char y = '\t';
  auto rv4 = folly::tryTo<double>(folly::StringPiece(&y, 1));
  EXPECT_FALSE(rv4.hasValue());
}

TEST(Conv, TryStringToDouble) {
  tryToDouble<std::string>();
  tryToDouble<std::string_view>();
  tryToDouble<folly::StringPiece>();
}

TEST(Conv, TryIntToInt) {
  auto rv1 = folly::tryTo<uint8_t>(256);
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<uint8_t>(255);
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(rv2.value(), 255);
}

TEST(Conv, TryFloatToFloat) {
  auto rv1 = folly::tryTo<float>(1e100);
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<double>(25.5f);
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_NEAR(rv2.value(), 25.5, 1e-10);
}

TEST(Conv, TryFloatToInt) {
  auto rv1 = folly::tryTo<int>(100.001);
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<int>(100.0);
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(rv2.value(), 100);
}

TEST(Conv, TryIntToFloat) {
  auto rv1 = folly::tryTo<float>(std::numeric_limits<uint64_t>::max());
  EXPECT_FALSE(rv1.hasValue());
  auto rv2 = folly::tryTo<float>(1000ULL);
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(rv2.value(), 1000.0f);
}

template <class String>
void tryTo() noexcept {
  String sp1("1000000000000000000000000000000");
  auto rv1 = folly::tryTo<int>(sp1.data(), sp1.data() + sp1.size());
  EXPECT_FALSE(rv1.hasValue());
  String sp2("4711");
  auto rv2 = folly::tryTo<int>(sp2.data(), sp2.data() + sp2.size());
  EXPECT_TRUE(rv2.hasValue());
  EXPECT_EQ(rv2.value(), 4711);
  String sp3("-4711");
  auto rv3 = folly::tryTo<int>(sp3.data(), sp3.data() + sp3.size());
  EXPECT_TRUE(rv3.hasValue());
  EXPECT_EQ(rv3.value(), -4711);
  String sp4("4711");
  auto rv4 = folly::tryTo<uint16_t>(sp4.data(), sp4.data() + sp4.size());
  EXPECT_TRUE(rv4.hasValue());
  EXPECT_EQ(rv4.value(), 4711);
}

TEST(Conv, TryPtrPairToInt) {
  tryTo<string_view>();
  tryTo<StringPiece>();
}

TEST(Conv, allocateSize) {
  std::string str1 = "meh meh meh";
  std::string str2 = "zdech zdech zdech";

  auto res1 = folly::to<std::string>(str1, ".", str2);
  EXPECT_EQ(res1, str1 + "." + str2);

  std::string res2; // empty
  toAppendFit(str1, str2, 1, &res2);
  EXPECT_EQ(res2, str1 + str2 + "1");

  std::string res3;
  toAppendDelimFit(",", str1, str2, &res3);
  EXPECT_EQ(res3, str1 + "," + str2);
}

namespace my {
struct Dimensions {
  int w, h;
  std::tuple<const int&, const int&> tuple_view() const { return tie(w, h); }
  bool operator==(const Dimensions& other) const {
    return this->tuple_view() == other.tuple_view();
  }
};

Expected<StringPiece, ConversionCode> parseTo(
    folly::StringPiece in, Dimensions& out) {
  return parseTo(in, out.w)
      .then([](StringPiece sp) { return sp.removePrefix("x"), sp; })
      .then([&](StringPiece sp) { return parseTo(sp, out.h); });
}

template <class String>
void toAppend(const Dimensions& in, String* result) {
  folly::toAppend(in.w, 'x', in.h, result);
}

size_t estimateSpaceNeeded(const Dimensions& in) {
  return 2000 + folly::estimateSpaceNeeded(in.w) +
      folly::estimateSpaceNeeded(in.h);
}

enum class SmallEnum {};

Expected<StringPiece, ConversionCode> parseTo(StringPiece in, SmallEnum& out) {
  out = {};
  if (in == "SmallEnum") {
    return in.removePrefix(in), in;
  } else {
    return makeUnexpected(ConversionCode::STRING_TO_FLOAT_ERROR);
  }
}

template <class String>
void toAppend(SmallEnum, String* result) {
  folly::toAppend("SmallEnum", result);
}
} // namespace my

TEST(Conv, customKkproviders) {
  my::Dimensions expected{7, 8};
  EXPECT_EQ(expected, folly::to<my::Dimensions>("7x8"));
  auto str = folly::to<std::string>(expected);
  EXPECT_EQ("7x8", str);
  // make sure above implementation of estimateSpaceNeeded() is used.
  EXPECT_GT(str.capacity(), 2000);
  EXPECT_LT(str.capacity(), 2500);
  // toAppend with other arguments
  toAppend("|", expected, &str);
  EXPECT_EQ("7x8|7x8", str);
}

TEST(conv, customEnumclass) {
  EXPECT_EQ(my::SmallEnum{}, folly::to<my::SmallEnum>("SmallEnum"));
  EXPECT_EQ(my::SmallEnum{}, folly::tryTo<my::SmallEnum>("SmallEnum").value());
  auto str = to<string>(my::SmallEnum{});
  toAppend("|", my::SmallEnum{}, &str);
  EXPECT_EQ("SmallEnum|SmallEnum", str);
}

TEST(Conv, TryToThenWithVoid) {
  auto x = tryTo<int>("42").then([](int) {});
  EXPECT_TRUE(x.hasValue());
  Unit u = x.value();
  (void)u;
}

TEST(conv, TryIntToUnscopedEnumAndBack) {
  enum UnscopedEnum {
    First = 0,
    Second = 1,
  };
  EXPECT_EQ(UnscopedEnum::Second, folly::tryTo<UnscopedEnum>(1).value());
  EXPECT_EQ(1, folly::tryTo<int>(UnscopedEnum::Second).value());
}

TEST(conv, TryIntToScopedEnumAndBack) {
  enum class ScopedEnum {
    First = 0,
    Second = 1,
  };
  EXPECT_EQ(ScopedEnum::Second, folly::tryTo<ScopedEnum>(1).value());
  EXPECT_EQ(1, folly::tryTo<int>(ScopedEnum::Second).value());
}

#if defined(FOLLY_CONV_AVALIABILITY_TO_CHARS_FLOATING_POINT) && \
    FOLLY_CONV_AVALIABILITY_TO_CHARS_FLOATING_POINT == 1
TEST(Conv, DtoaFlagsSetSimple) {
  {
    detail::DtoaFlagsSet sut{DtoaFlags::NO_FLAGS};
    EXPECT_FALSE(sut.emitPositiveExponentSign());
    EXPECT_FALSE(sut.emitTrailingDecimalPoint());
    EXPECT_FALSE(sut.emitTrailingZeroAfterPoint());
    EXPECT_FALSE(sut.uniqueZero());
    EXPECT_FALSE(sut.noTrailingZero());
  }

  {
    detail::DtoaFlagsSet sut{
        DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
        DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT |
        DtoaFlags::NO_TRAILING_ZERO};
    EXPECT_FALSE(sut.emitPositiveExponentSign());
    EXPECT_TRUE(sut.emitTrailingDecimalPoint());
    EXPECT_TRUE(sut.emitTrailingZeroAfterPoint());
    EXPECT_FALSE(sut.uniqueZero());
    EXPECT_TRUE(sut.noTrailingZero());
  }
}

TEST(Conv, ParsedDecimalCtorOk) {
  {
    char input[] = "123";
    detail::ParsedDecimal sut{input, input + sizeof(input) - 1};
    EXPECT_EQ(sut.integerBegin, input);
    EXPECT_EQ(sut.integerEnd, input + sizeof(input) - 1);
    EXPECT_EQ(sut.decimalPoint, nullptr);
    EXPECT_EQ(sut.fractionalBegin, nullptr);
    EXPECT_EQ(sut.fractionalEnd, nullptr);
    EXPECT_EQ(sut.exponentSymbol, nullptr);
    EXPECT_EQ(sut.exponentSign, nullptr);
    EXPECT_EQ(sut.exponentBegin, nullptr);
    EXPECT_EQ(sut.exponentEnd, nullptr);
  }

  {
    char input[] = "123.";
    detail::ParsedDecimal sut{input, input + sizeof(input) - 1};
    EXPECT_EQ(sut.integerBegin, input);
    EXPECT_EQ(sut.integerEnd, input + 3);
    EXPECT_EQ(sut.decimalPoint, input + 3);
    EXPECT_EQ(sut.fractionalBegin, nullptr);
    EXPECT_EQ(sut.fractionalEnd, nullptr);
    EXPECT_EQ(sut.exponentSymbol, nullptr);
    EXPECT_EQ(sut.exponentSign, nullptr);
    EXPECT_EQ(sut.exponentBegin, nullptr);
    EXPECT_EQ(sut.exponentEnd, nullptr);
  }

  {
    char input[] = "123.456";
    detail::ParsedDecimal sut{input, input + sizeof(input) - 1};
    EXPECT_EQ(sut.integerBegin, input);
    EXPECT_EQ(sut.integerEnd, input + 3);
    EXPECT_EQ(sut.decimalPoint, input + 3);
    EXPECT_EQ(sut.fractionalBegin, input + 4);
    EXPECT_EQ(sut.fractionalEnd, input + 7);
    EXPECT_EQ(sut.exponentSymbol, nullptr);
    EXPECT_EQ(sut.exponentSign, nullptr);
    EXPECT_EQ(sut.exponentBegin, nullptr);
    EXPECT_EQ(sut.exponentEnd, nullptr);
  }

  {
    char input[] = "123.456e+07";
    detail::ParsedDecimal sut{input, input + sizeof(input) - 1};
    EXPECT_EQ(sut.integerBegin, input);
    EXPECT_EQ(sut.integerEnd, input + 3);
    EXPECT_EQ(sut.decimalPoint, input + 3);
    EXPECT_EQ(sut.fractionalBegin, input + 4);
    EXPECT_EQ(sut.fractionalEnd, input + 7);
    EXPECT_EQ(sut.exponentSymbol, input + 7);
    EXPECT_EQ(sut.exponentSign, input + 8);
    EXPECT_EQ(sut.exponentBegin, input + 9);
    EXPECT_EQ(sut.exponentEnd, input + 11);
  }
}

TEST(Conv, ParsedDecimalCtorErr) {
  EXPECT_THROW(
      { detail::ParsedDecimal sut(nullptr, nullptr); }, std::invalid_argument);
  {
    char input[] = "";
    EXPECT_THROW(detail::ParsedDecimal d(input, input), std::invalid_argument);
  }

  using namespace std::literals;

  std::string inputs[] = {
      " "s,
      "."s,
      "-"s,
      "1A"s,
      "A1"s,
      "-A"s,
      "1-"s,
      "1 "s,
      " 1"s,
      "1. 2"s,
      "1 .2"s,
      "1.2E"s,
      "1.2eX07"s,
  };

  for (std::string input : inputs) {
    EXPECT_THROW(
        {
          detail::ParsedDecimal d(input.data(), input.data() + input.length());
        },
        std::invalid_argument)
        << "input: '" << input << "'";
  }
}

/// Simple macro to test toAppendStdToChars.
/// This is a macro so failures output the direct line that failed.
#define EXPECT_EQ_TO_APPEND_STD_TO_CHARS(                                      \
    expected, value, mode, numDigits, flags)                                   \
  {                                                                            \
    std::string actual;                                                        \
    folly::detail::toAppendStdToChars(value, &actual, mode, numDigits, flags); \
    EXPECT_EQ(actual, expected);                                               \
  }

TEST(Conv, toAppendStdToChars) {
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "123.4", 123.4, DtoaMode::SHORTEST, 0, DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      // "1.23E9",
      "1230000000",
      1230000000.0,
      DtoaMode::SHORTEST,
      0,
      DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      // "1.23E+9",
      "1230000000",
      1230000000.0,
      DtoaMode::SHORTEST,
      0,
      DtoaFlags::EMIT_POSITIVE_EXPONENT_SIGN);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "0.1234", 0.1234, DtoaMode::SHORTEST, 0, DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      // "1.234E-6",
      "0.000001234",
      0.000001234,
      DtoaMode::SHORTEST,
      0,
      DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      // "-1.234E-6",
      "-0.000001234",
      -0.000001234,
      DtoaMode::SHORTEST,
      0,
      DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "0", -0.0, DtoaMode::SHORTEST, 0, DtoaFlags::UNIQUE_ZERO);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "123.4560000", 123.456, DtoaMode::FIXED, 7, DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "123.4560", 123.456, DtoaMode::PRECISION, 7, DtoaFlags::NO_FLAGS);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "123.",
      123.0,
      DtoaMode::PRECISION,
      3,
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);
  EXPECT_EQ_TO_APPEND_STD_TO_CHARS(
      "123.0",
      123.0,
      DtoaMode::PRECISION,
      3,
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
          DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
}
#endif // FOLLY_CONV_AVALIABILITY_TO_CHARS_FLOATING_POINT

#if !(defined(FOLLY_CONV_USE_TO_CHARS) && FOLLY_CONV_USE_TO_CHARS == 1)
TEST(Conv, DtoaModeConverter) {
  double_conversion::DoubleToStringConverter::DtoaMode shortest =
      detail::convert(DtoaMode::SHORTEST);
  EXPECT_EQ(shortest, double_conversion::DoubleToStringConverter::SHORTEST);

  double_conversion::DoubleToStringConverter::DtoaMode precision =
      detail::convert(DtoaMode::PRECISION);
  EXPECT_EQ(precision, double_conversion::DoubleToStringConverter::PRECISION);
}

TEST(Conv, DtoaFlagsConverter) {
  double_conversion::DoubleToStringConverter::Flags noFlags =
      detail::convert(DtoaFlags::NO_FLAGS);
  EXPECT_EQ(noFlags, double_conversion::DoubleToStringConverter::NO_FLAGS);

  double_conversion::DoubleToStringConverter::Flags uniqueZero =
      detail::convert(DtoaFlags::UNIQUE_ZERO);
  EXPECT_EQ(
      uniqueZero, double_conversion::DoubleToStringConverter::UNIQUE_ZERO);

  double_conversion::DoubleToStringConverter::Flags combo = detail::convert(
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
      DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
  EXPECT_EQ(
      combo,
      double_conversion::DoubleToStringConverter::EMIT_TRAILING_DECIMAL_POINT |
          double_conversion::DoubleToStringConverter::
              EMIT_TRAILING_ZERO_AFTER_POINT);
}
#endif // FOLLY_CONV_USE_TO_CHARS

TEST(Conv, DtoaFlags) {
  DtoaFlags combo = DtoaFlags::EMIT_TRAILING_DECIMAL_POINT |
      DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT;
  EXPECT_EQ(
      combo & DtoaFlags::EMIT_TRAILING_DECIMAL_POINT,
      DtoaFlags::EMIT_TRAILING_DECIMAL_POINT);
  EXPECT_EQ(
      combo & DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT,
      DtoaFlags::EMIT_TRAILING_ZERO_AFTER_POINT);
  EXPECT_EQ(combo & DtoaFlags::UNIQUE_ZERO, DtoaFlags::NO_FLAGS);
}
