// Copyright 2021 gRPC authors.
//
// 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 "src/core/lib/promise/seq.h"
#include <gtest/gtest.h>

namespace grpc_core {

TEST(PromiseTest, Immediate) {
  EXPECT_EQ(Seq([] { return 3; })(), 3);
}

TEST(PromiseTest, OneThen) {
  auto initial = [] { return 3; };
  auto then = [](int i) { return [i]() { return i + 4; }; };
  EXPECT_EQ(Seq(initial, then)(), Poll<int>(7));
}

TEST(PromiseTest, TwoTypedThens) {
  struct A {};
  struct B {};
  struct C {};
  auto initial = [] { return A{}; };
  auto next1 = [](A) { return []() { return B{}; }; };
  auto next2 = [](B) { return []() { return C{}; }; };
  EXPECT_FALSE(absl::holds_alternative<Pending>(Seq(initial, next1, next2)()));
}

/* This does not compile, but is useful for testing error messages generated
TEST(PromiseTest, MisTypedThen) {
  struct A {};
  struct B {};
  auto initial = [] { return A{}; };
  auto next = [](B) { return []() { return B{}; }; };
  Seq(initial, next)().take();
}
*/

TEST(PromiseTest, TwoThens) {
  auto initial = [] { return std::string("a"); };
  auto next1 = [](std::string i) { return [i]() { return i + "b"; }; };
  auto next2 = [](std::string i) { return [i]() { return i + "c"; }; };
  EXPECT_EQ(Seq(initial, next1, next2)(), Poll<std::string>("abc"));
}

TEST(PromiseTest, ThreeThens) {
  EXPECT_EQ(Seq([] { return std::string("a"); },
                [](std::string i) { return [i]() { return i + "b"; }; },
                [](std::string i) { return [i]() { return i + "c"; }; },
                [](std::string i) { return [i]() { return i + "d"; }; })(),
            Poll<std::string>("abcd"));
}

struct Big {
  int x[256];
  void YesItIsUnused() const {}
};

TEST(PromiseTest, SaneSizes) {
  auto x = Big();
  auto p1 = Seq(
      [x] {
        x.YesItIsUnused();
        return 1;
      },
      [](int) {
        auto y = Big();
        return [y]() {
          y.YesItIsUnused();
          return 2;
        };
      });
  EXPECT_GE(sizeof(p1), sizeof(Big));
  EXPECT_LT(sizeof(p1), 2 * sizeof(Big));
}

}  // namespace grpc_core

int main(int argc, char** argv) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}