FTL: Add find_if

/*

 * Copyright 2022 The Android Open Source Project

 *

 * 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.

 */

#pragma once

#include <algorithm>

#include <functional>

#include <utility>

#include <ftl/optional.h>

namespace android::ftl {

// Adapter for std::find_if that converts the return value from iterator to optional.

//

//   const ftl::StaticVector vector = {"upside"sv, "down"sv, "cake"sv};

//   assert(ftl::find_if(vector, [](const auto& str) { return str.front() == 'c'; }) == "cake"sv);

//

template <typename Container, typename Predicate, typename V = typename Container::value_type>

constexpr auto find_if(const Container& container, Predicate&& predicate)

    -> Optional<std::reference_wrapper<const V>> {

  const auto it = std::find_if(std::cbegin(container), std::cend(container),

                               std::forward<Predicate>(predicate));

  if (it == std::cend(container)) return {};

  return std::cref(*it);

}

// Transformers for ftl::find_if on a map-like `Container` that contains key-value pairs.

//

//   const ftl::SmallMap map = ftl::init::map<int, ftl::StaticVector<std::string_view, 3>>(

//       12, "snow"sv, "cone"sv)(13, "tiramisu"sv)(14, "upside"sv, "down"sv, "cake"sv);

//

//   using Map = decltype(map);

//

//   assert(14 == ftl::find_if(map, [](const auto& pair) {

//                  return pair.second.size() == 3;

//                }).transform(ftl::to_key<Map>));

//

//   const auto opt = ftl::find_if(map, [](const auto& pair) {

//                      return pair.second.size() == 1;

//                    }).transform(ftl::to_mapped_ref<Map>);

//

//   assert(opt);

//   assert(opt->get() == ftl::StaticVector("tiramisu"sv));

//

template <typename Map, typename Pair = typename Map::value_type,

          typename Key = typename Map::key_type>

constexpr auto to_key(const Pair& pair) -> Key {

  return pair.first;

}

template <typename Map, typename Pair = typename Map::value_type,

          typename Mapped = typename Map::mapped_type>

constexpr auto to_mapped_ref(const Pair& pair) -> std::reference_wrapper<const Mapped> {

  return std::cref(pair.second);

}

}  // namespace android::ftl

        address: true,

    },

    srcs: [

        "algorithm_test.cpp",

        "cast_test.cpp",

        "concat_test.cpp",

        "enum_test.cpp",

/*

 * Copyright 2022 The Android Open Source Project

 *

 * 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.

 */

#include <ftl/algorithm.h>

#include <ftl/small_map.h>

#include <ftl/static_vector.h>

#include <gtest/gtest.h>

#include <string_view>

namespace android::test {

// Keep in sync with example usage in header file.

TEST(Algorithm, FindIf) {

  using namespace std::string_view_literals;

  const ftl::StaticVector vector = {"upside"sv, "down"sv, "cake"sv};

  EXPECT_EQ(ftl::find_if(vector, [](const auto& str) { return str.front() == 'c'; }), "cake"sv);

  const ftl::SmallMap map = ftl::init::map<int, ftl::StaticVector<std::string_view, 3>>(

      12, "snow"sv, "cone"sv)(13, "tiramisu"sv)(14, "upside"sv, "down"sv, "cake"sv);

  using Map = decltype(map);

  EXPECT_EQ(14, ftl::find_if(map, [](const auto& pair) {

                  return pair.second.size() == 3;

                }).transform(ftl::to_key<Map>));

  const auto opt = ftl::find_if(map, [](const auto& pair) {

                     return pair.second.size() == 1;

                   }).transform(ftl::to_mapped_ref<Map>);

  ASSERT_TRUE(opt);

  EXPECT_EQ(opt->get(), ftl::StaticVector("tiramisu"sv));

}

}  // namespace android::test