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/*
* 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 <type_traits>
#include <variant>
namespace android::ftl::details {
template <typename... Ms>
struct Matcher : Ms... {
using Ms::operator()...;
};
// Deduction guide.
template <typename... Ms>
Matcher(Ms...) -> Matcher<Ms...>;
template <typename Matcher, typename... Ts>
constexpr bool is_exhaustive_match_v = (std::is_invocable_v<Matcher, Ts> && ...);
template <typename...>
struct Match;
template <typename T, typename U, typename... Ts>
struct Match<T, U, Ts...> {
template <typename Variant, typename Matcher>
static decltype(auto) match(Variant& variant, const Matcher& matcher) {
if (auto* const ptr = std::get_if<T>(&variant)) {
return matcher(*ptr);
} else {
return Match<U, Ts...>::match(variant, matcher);
}
}
};
template <typename T>
struct Match<T> {
template <typename Variant, typename Matcher>
static decltype(auto) match(Variant& variant, const Matcher& matcher) {
return matcher(std::get<T>(variant));
}
};
} // namespace android::ftl::details
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