// Copyright 2024 The Pigweed 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
//
//     https://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 "pw_channel/loopback_channel.h"

#include "pw_allocator/testing.h"
#include "pw_assert/check.h"
#include "pw_async2/dispatcher.h"
#include "pw_bytes/suffix.h"
#include "pw_channel/channel.h"
#include "pw_multibuf/simple_allocator.h"
#include "pw_status/status.h"

namespace {

using ::pw::allocator::test::AllocatorForTest;
using ::pw::async2::Context;
using ::pw::async2::Dispatcher;
using ::pw::async2::Pending;
using ::pw::async2::Poll;
using ::pw::async2::Ready;
using ::pw::async2::Task;
using ::pw::operator"" _b;
using ::pw::channel::ByteReader;
using ::pw::channel::DatagramReader;
using ::pw::channel::LoopbackByteChannel;
using ::pw::channel::LoopbackDatagramChannel;
using ::pw::multibuf::MultiBuf;
using ::pw::multibuf::MultiBufAllocator;
using ::pw::multibuf::SimpleAllocator;

class SimpleAllocatorForTest {
 public:
  SimpleAllocatorForTest() : simple_allocator_(data_area_, meta_alloc_) {}
  MultiBufAllocator& operator*() { return simple_allocator_; }
  MultiBufAllocator* operator->() { return &simple_allocator_; }

  MultiBuf BufWith(std::initializer_list<std::byte> data) {
    std::optional<MultiBuf> buffer = simple_allocator_.Allocate(data.size());
    PW_CHECK(buffer.has_value());
    std::copy(data.begin(), data.end(), buffer->begin());
    return std::move(*buffer);
  }

 private:
  static constexpr size_t kArbitraryDataSize = 256;
  static constexpr size_t kArbitraryMetaSize = 2048;
  std::array<std::byte, kArbitraryDataSize> data_area_;
  AllocatorForTest<kArbitraryMetaSize> meta_alloc_;
  SimpleAllocator simple_allocator_;
};

template <typename ChannelKind>
class ReaderTask : public Task {
 public:
  ReaderTask(ChannelKind& channel) : channel_(channel) {}

  int poll_count = 0;
  int read_count = 0;
  int bytes_read_count = 0;

 private:
  Poll<> DoPend(Context& cx) final {
    ++poll_count;
    while (true) {
      auto result = channel_.PendRead(cx);
      if (result.IsPending()) {
        return Pending();
      }
      if (!result->ok()) {
        // We hit an error-- call it quits.
        return Ready();
      }
      ++read_count;
      bytes_read_count += (**result).size();
    }
  }

  ChannelKind& channel_;
};

TEST(LoopbackDatagramChannel, LoopsEmptyDatagrams) {
  SimpleAllocatorForTest alloc;
  LoopbackDatagramChannel channel(*alloc);
  ReaderTask<DatagramReader> read_task(channel);

  Dispatcher dispatcher;
  dispatcher.Post(read_task);
  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 1);
  EXPECT_EQ(read_task.read_count, 0);
  EXPECT_EQ(read_task.bytes_read_count, 0);

  EXPECT_EQ(channel.Write(alloc.BufWith({})).status(), pw::OkStatus());

  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 2);
  EXPECT_EQ(read_task.read_count, 1);
  EXPECT_EQ(read_task.bytes_read_count, 0);
}

TEST(LoopbackDatagramChannel, LoopsDatagrams) {
  SimpleAllocatorForTest alloc;
  LoopbackDatagramChannel channel(*alloc);
  ReaderTask<DatagramReader> read_task(channel);

  Dispatcher dispatcher;
  dispatcher.Post(read_task);
  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 1);
  EXPECT_EQ(read_task.read_count, 0);
  EXPECT_EQ(read_task.bytes_read_count, 0);

  EXPECT_EQ(channel.Write(alloc.BufWith({1_b, 2_b, 3_b})).status(),
            pw::OkStatus());

  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 2);
  EXPECT_EQ(read_task.read_count, 1);
  EXPECT_EQ(read_task.bytes_read_count, 3);
}

TEST(LoopbackByteChannel, IgnoresEmptyWrites) {
  SimpleAllocatorForTest alloc;
  LoopbackByteChannel channel(*alloc);
  ReaderTask<ByteReader> read_task(channel);

  Dispatcher dispatcher;
  dispatcher.Post(read_task);
  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 1);
  EXPECT_EQ(read_task.read_count, 0);
  EXPECT_EQ(read_task.bytes_read_count, 0);

  EXPECT_EQ(channel.Write(alloc.BufWith({})).status(), pw::OkStatus());

  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 1);
  EXPECT_EQ(read_task.read_count, 0);
  EXPECT_EQ(read_task.bytes_read_count, 0);
}

TEST(LoopbackByteChannel, LoopsData) {
  SimpleAllocatorForTest alloc;
  LoopbackByteChannel channel(*alloc);
  ReaderTask<ByteReader> read_task(channel);

  Dispatcher dispatcher;
  dispatcher.Post(read_task);
  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 1);
  EXPECT_EQ(read_task.read_count, 0);
  EXPECT_EQ(read_task.bytes_read_count, 0);

  EXPECT_EQ(channel.Write(alloc.BufWith({1_b, 2_b, 3_b})).status(),
            pw::OkStatus());

  EXPECT_EQ(dispatcher.RunUntilStalled(), Pending());
  EXPECT_EQ(read_task.poll_count, 2);
  EXPECT_EQ(read_task.read_count, 1);
  EXPECT_EQ(read_task.bytes_read_count, 3);
}

}  // namespace