// Copyright 2021 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_transfer/transfer.h"

#include "gtest/gtest.h"
#include "pw_bytes/array.h"
#include "pw_rpc/raw/test_method_context.h"
#include "pw_transfer/transfer.pwpb.h"
#include "pw_transfer_private/chunk.h"

namespace pw::transfer {
namespace {

PW_MODIFY_DIAGNOSTICS_PUSH();
PW_MODIFY_DIAGNOSTIC(ignored, "-Wmissing-field-initializers");

using internal::Chunk;

Vector<std::byte, 64> EncodeChunk(const Chunk& chunk) {
  Vector<std::byte, 64> buffer(64);
  auto result = internal::EncodeChunk(chunk, buffer);
  EXPECT_EQ(result.status(), OkStatus());
  buffer.resize(result.value().size());
  return buffer;
}

Chunk DecodeChunk(ConstByteSpan buffer) {
  Chunk chunk = {};
  EXPECT_EQ(internal::DecodeChunk(buffer, chunk), OkStatus());
  return chunk;
}

class SimpleReadTransfer final : public ReadOnlyHandler {
 public:
  SimpleReadTransfer(uint32_t transfer_id, ConstByteSpan data)
      : ReadOnlyHandler(transfer_id),
        prepare_read_called(false),
        finalize_read_called(false),
        finalize_read_status(Status::Unknown()),
        reader_(data) {}

  Status PrepareRead() final {
    reader_.Seek(0);
    set_reader(reader_);
    prepare_read_called = true;
    return OkStatus();
  }

  void FinalizeRead(Status status) final {
    finalize_read_called = true;
    finalize_read_status = status;
  }

  bool prepare_read_called;
  bool finalize_read_called;
  Status finalize_read_status;

 private:
  stream::MemoryReader reader_;
};

constexpr auto kData = bytes::Initialized<32>([](size_t i) { return i; });

class ReadTransfer : public ::testing::Test {
 protected:
  ReadTransfer(size_t max_chunk_size_bytes = 64)
      : handler_(3, kData), ctx_(max_chunk_size_bytes, 64) {
    ctx_.service().RegisterHandler(handler_);

    ASSERT_FALSE(handler_.prepare_read_called);
    ASSERT_FALSE(handler_.finalize_read_called);

    ctx_.call();  // Open the read stream
  }

  SimpleReadTransfer handler_;
  PW_RAW_TEST_METHOD_CONTEXT(TransferService, Read, 5) ctx_;
};

TEST_F(ReadTransfer, SingleChunk) {
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 64, .offset = 0}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);

  ASSERT_EQ(ctx_.total_responses(), 2u);
  Chunk c0 = DecodeChunk(ctx_.responses()[0]);
  Chunk c1 = DecodeChunk(ctx_.responses()[1]);

  // First chunk should have all the read data.
  EXPECT_EQ(c0.transfer_id, 3u);
  EXPECT_EQ(c0.offset, 0u);
  ASSERT_EQ(c0.data.size(), kData.size());
  EXPECT_EQ(std::memcmp(c0.data.data(), kData.data(), c0.data.size()), 0);

  // Second chunk should be empty and set remaining_bytes = 0.
  EXPECT_EQ(c1.transfer_id, 3u);
  EXPECT_EQ(c1.data.size(), 0u);
  ASSERT_TRUE(c1.remaining_bytes.has_value());
  EXPECT_EQ(c1.remaining_bytes.value(), 0u);

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, OkStatus());
}

TEST_F(ReadTransfer, MultiChunk) {
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 0}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk c0 = DecodeChunk(ctx_.responses()[0]);

  EXPECT_EQ(c0.transfer_id, 3u);
  EXPECT_EQ(c0.offset, 0u);
  ASSERT_EQ(c0.data.size(), 16u);
  EXPECT_EQ(std::memcmp(c0.data.data(), kData.data(), c0.data.size()), 0);

  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 16}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  Chunk c1 = DecodeChunk(ctx_.responses()[1]);

  EXPECT_EQ(c1.transfer_id, 3u);
  EXPECT_EQ(c1.offset, 16u);
  ASSERT_EQ(c1.data.size(), 16u);
  EXPECT_EQ(std::memcmp(c1.data.data(), kData.data() + 16, c1.data.size()), 0);

  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 32}));
  ASSERT_EQ(ctx_.total_responses(), 3u);
  Chunk c2 = DecodeChunk(ctx_.responses()[2]);

  EXPECT_EQ(c2.transfer_id, 3u);
  EXPECT_EQ(c2.data.size(), 0u);
  ASSERT_TRUE(c2.remaining_bytes.has_value());
  EXPECT_EQ(c2.remaining_bytes.value(), 0u);

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, OkStatus());
}

TEST_F(ReadTransfer, MaxChunkSize_Client) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3,
                                     .pending_bytes = 64,
                                     .max_chunk_size_bytes = 8,
                                     .offset = 0}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);

  ASSERT_EQ(ctx_.total_responses(), 5u);
  Chunk c0 = DecodeChunk(ctx_.responses()[0]);
  Chunk c1 = DecodeChunk(ctx_.responses()[1]);
  Chunk c2 = DecodeChunk(ctx_.responses()[2]);
  Chunk c3 = DecodeChunk(ctx_.responses()[3]);
  Chunk c4 = DecodeChunk(ctx_.responses()[4]);

  EXPECT_EQ(c0.transfer_id, 3u);
  EXPECT_EQ(c0.offset, 0u);
  ASSERT_EQ(c0.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c0.data.data(), kData.data(), c0.data.size()), 0);

  EXPECT_EQ(c1.transfer_id, 3u);
  EXPECT_EQ(c1.offset, 8u);
  ASSERT_EQ(c1.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c1.data.data(), kData.data() + 8, c1.data.size()), 0);

  EXPECT_EQ(c2.transfer_id, 3u);
  EXPECT_EQ(c2.offset, 16u);
  ASSERT_EQ(c2.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c2.data.data(), kData.data() + 16, c2.data.size()), 0);

  EXPECT_EQ(c3.transfer_id, 3u);
  EXPECT_EQ(c3.offset, 24u);
  ASSERT_EQ(c3.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c3.data.data(), kData.data() + 24, c3.data.size()), 0);

  EXPECT_EQ(c4.transfer_id, 3u);
  EXPECT_EQ(c4.data.size(), 0u);
  ASSERT_TRUE(c4.remaining_bytes.has_value());
  EXPECT_EQ(c4.remaining_bytes.value(), 0u);

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, OkStatus());
}

class ReadTransferMaxChunkSize8 : public ReadTransfer {
 protected:
  ReadTransferMaxChunkSize8() : ReadTransfer(/*max_chunK_size_bytes=*/8) {}
};

TEST_F(ReadTransferMaxChunkSize8, MaxChunkSize_Server) {
  // Client asks for max 16-byte chunks, but service places a limit of 8 bytes.
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3,
                                     .pending_bytes = 64,
                                     .max_chunk_size_bytes = 16,
                                     .offset = 0}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);

  ASSERT_EQ(ctx_.total_responses(), 5u);
  Chunk c0 = DecodeChunk(ctx_.responses()[0]);
  Chunk c1 = DecodeChunk(ctx_.responses()[1]);
  Chunk c2 = DecodeChunk(ctx_.responses()[2]);
  Chunk c3 = DecodeChunk(ctx_.responses()[3]);
  Chunk c4 = DecodeChunk(ctx_.responses()[4]);

  EXPECT_EQ(c0.transfer_id, 3u);
  EXPECT_EQ(c0.offset, 0u);
  ASSERT_EQ(c0.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c0.data.data(), kData.data(), c0.data.size()), 0);

  EXPECT_EQ(c1.transfer_id, 3u);
  EXPECT_EQ(c1.offset, 8u);
  ASSERT_EQ(c1.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c1.data.data(), kData.data() + 8, c1.data.size()), 0);

  EXPECT_EQ(c2.transfer_id, 3u);
  EXPECT_EQ(c2.offset, 16u);
  ASSERT_EQ(c2.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c2.data.data(), kData.data() + 16, c2.data.size()), 0);

  EXPECT_EQ(c3.transfer_id, 3u);
  EXPECT_EQ(c3.offset, 24u);
  ASSERT_EQ(c3.data.size(), 8u);
  EXPECT_EQ(std::memcmp(c3.data.data(), kData.data() + 24, c3.data.size()), 0);

  EXPECT_EQ(c4.transfer_id, 3u);
  EXPECT_EQ(c4.data.size(), 0u);
  ASSERT_TRUE(c4.remaining_bytes.has_value());
  EXPECT_EQ(c4.remaining_bytes.value(), 0u);

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, OkStatus());
}

TEST_F(ReadTransfer, ClientError) {
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 0}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);
  ASSERT_EQ(ctx_.total_responses(), 1u);

  // Send client error.
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .status = Status::OutOfRange()}));
  ASSERT_EQ(ctx_.total_responses(), 1u);
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, Status::OutOfRange());
}

TEST_F(ReadTransfer, MalformedParametersChunk) {
  // pending_bytes is required in a parameters chunk.
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3}));
  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, Status::InvalidArgument());

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 3u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::InvalidArgument());
}

TEST_F(ReadTransfer, UnregisteredHandler) {
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 11, .pending_bytes = 32, .offset = 0}));

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 11u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::NotFound());
}

TEST_F(ReadTransfer, IgnoresNonPendingTransfers) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .offset = 3}));
  ctx_.SendClientStream(EncodeChunk(
      {.transfer_id = 3, .offset = 0, .data = std::span(kData).first(10)}));
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));

  // Only start transfer for initial packet.
  EXPECT_FALSE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);
}

TEST_F(ReadTransfer, AbortAndRestartIfInitialPacketIsReceived) {
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 0}));

  ASSERT_EQ(ctx_.total_responses(), 1u);

  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_FALSE(handler_.finalize_read_called);
  handler_.prepare_read_called = false;  // Reset so can check if called again.

  ctx_.SendClientStream(  // Resend starting chunk
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 0}));

  ASSERT_EQ(ctx_.total_responses(), 2u);

  EXPECT_TRUE(handler_.prepare_read_called);
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, Status::Aborted());
  handler_.finalize_read_called = false;  // Reset so can check later

  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 3, .pending_bytes = 16, .offset = 16}));
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .status = OkStatus()}));

  ASSERT_EQ(ctx_.total_responses(), 3u);
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, OkStatus());
}

TEST_F(ReadTransfer, AbortTransferIfZeroBytesAreRequested) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 3, .pending_bytes = 0}));

  ASSERT_EQ(ctx_.total_responses(), 1u);
  EXPECT_TRUE(handler_.finalize_read_called);
  EXPECT_EQ(handler_.finalize_read_status, Status::Internal());

  Chunk chunk = DecodeChunk(ctx_.responses().back());
  EXPECT_TRUE(chunk.status.has_value());
  EXPECT_EQ(*chunk.status, Status::Internal());
}

class SimpleWriteTransfer final : public WriteOnlyHandler {
 public:
  SimpleWriteTransfer(uint32_t transfer_id, ByteSpan data)
      : WriteOnlyHandler(transfer_id),
        prepare_write_called(false),
        finalize_write_called(false),
        finalize_write_status(Status::Unknown()),
        writer_(data) {}

  Status PrepareWrite() final {
    writer_.Seek(0);
    set_writer(writer_);
    prepare_write_called = true;
    return OkStatus();
  }

  Status FinalizeWrite(Status status) final {
    finalize_write_called = true;
    finalize_write_status = status;
    return finalize_write_return_status_;
  }

  void set_finalize_write_return(Status status) {
    finalize_write_return_status_ = status;
  }

  bool prepare_write_called;
  bool finalize_write_called;
  Status finalize_write_status;

 private:
  Status finalize_write_return_status_;
  stream::MemoryWriter writer_;
};

class WriteTransfer : public ::testing::Test {
 protected:
  WriteTransfer(size_t max_bytes_to_receive = 64)
      : buffer{}, handler_(7, buffer), ctx_(64, max_bytes_to_receive) {
    ctx_.service().RegisterHandler(handler_);

    ASSERT_FALSE(handler_.prepare_write_called);
    ASSERT_FALSE(handler_.finalize_write_called);

    ctx_.call();  // Open the write stream
  }

  std::array<std::byte, kData.size()> buffer;
  SimpleWriteTransfer handler_;

  PW_RAW_TEST_METHOD_CONTEXT(TransferService, Write) ctx_;
};

TEST_F(WriteTransfer, SingleChunk) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 32u);
  ASSERT_TRUE(chunk.max_chunk_size_bytes.has_value());
  EXPECT_EQ(chunk.max_chunk_size_bytes.value(), 42u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 0,
                                         .data = std::span(kData),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), OkStatus());

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
  EXPECT_EQ(std::memcmp(buffer.data(), kData.data(), kData.size()), 0);
}

TEST_F(WriteTransfer, FinalizeFails) {
  // Return an error when FinalizeWrite is called.
  handler_.set_finalize_write_return(Status::FailedPrecondition());

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));
  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 0,
                                         .data = std::span(kData),
                                         .remaining_bytes = 0}));

  Chunk chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::DataLoss());

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
}

TEST_F(WriteTransfer, MultiChunk) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 32u);

  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(16)}));
  ASSERT_EQ(ctx_.total_responses(), 1u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 16,
                                         .data = std::span(kData).subspan(16),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), OkStatus());

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
  EXPECT_EQ(std::memcmp(buffer.data(), kData.data(), kData.size()), 0);
}

class WriteTransferMaxBytes16 : public WriteTransfer {
 protected:
  WriteTransferMaxBytes16()
      : WriteTransfer(/*default_max_bytes_to_receive=*/16) {}
};

TEST_F(WriteTransferMaxBytes16, MultipleParameters) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 16u);

  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(8)}));
  ASSERT_EQ(ctx_.total_responses(), 1u);

  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 8, .data = std::span(kData).subspan(8, 8)}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 16u);

  ctx_.SendClientStream<64>(
      EncodeChunk({.transfer_id = 7,
                   .offset = 16,
                   .data = std::span(kData).subspan(16, 8)}));
  ASSERT_EQ(ctx_.total_responses(), 2u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 24,
                                         .data = std::span(kData).subspan(24),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 3u);
  chunk = DecodeChunk(ctx_.responses()[2]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), OkStatus());

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
  EXPECT_EQ(std::memcmp(buffer.data(), kData.data(), kData.size()), 0);
}

TEST_F(WriteTransferMaxBytes16, SetsDefaultPendingBytes) {
  // Default max bytes is smaller than buffer.
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  EXPECT_EQ(chunk.pending_bytes.value(), 16u);
}

TEST_F(WriteTransfer, SetsWriterPendingBytes) {
  // Buffer is smaller than constructor's default max bytes.
  std::array<std::byte, 8> small_buffer = {};

  SimpleWriteTransfer handler_(987, small_buffer);
  ctx_.service().RegisterHandler(handler_);

  ctx_.SendClientStream(EncodeChunk({.transfer_id = 987}));
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 987u);
  EXPECT_EQ(chunk.pending_bytes.value(), 8u);
}

TEST_F(WriteTransfer, UnexpectedOffset) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  EXPECT_EQ(chunk.offset, 0u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 32u);

  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(16)}));
  ASSERT_EQ(ctx_.total_responses(), 1u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 8,  // incorrect
                                         .data = std::span(kData).subspan(16),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  EXPECT_EQ(chunk.offset, 16u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 16u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 16,  // incorrect
                                         .data = std::span(kData).subspan(16),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 3u);
  chunk = DecodeChunk(ctx_.responses()[2]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), OkStatus());

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
  EXPECT_EQ(std::memcmp(buffer.data(), kData.data(), kData.size()), 0);
}

TEST_F(WriteTransferMaxBytes16, TooMuchData) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 16u);

  // pending_bytes = 16
  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(8)}));
  ASSERT_EQ(ctx_.total_responses(), 1u);

  // pending_bytes = 8
  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 8, .data = std::span(kData).subspan(8, 4)}));
  ASSERT_EQ(ctx_.total_responses(), 1u);

  // pending_bytes = 4 but send 8 instead
  ctx_.SendClientStream<64>(
      EncodeChunk({.transfer_id = 7,
                   .offset = 12,
                   .data = std::span(kData).subspan(12, 8)}));
  ASSERT_EQ(ctx_.total_responses(), 2u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::Internal());
}

TEST_F(WriteTransfer, UnregisteredHandler) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 999}));

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 999u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::NotFound());
}

TEST_F(WriteTransfer, ClientError) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 7u);
  ASSERT_TRUE(chunk.pending_bytes.has_value());
  EXPECT_EQ(chunk.pending_bytes.value(), 32u);

  ctx_.SendClientStream<64>(
      EncodeChunk({.transfer_id = 7, .status = Status::DataLoss()}));
  EXPECT_EQ(ctx_.total_responses(), 1u);

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, Status::DataLoss());
}

TEST_F(WriteTransfer, OnlySendParametersUpdateOnceAfterDrop) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  ASSERT_EQ(ctx_.total_responses(), 1u);

  constexpr std::span data(kData);
  ctx_.SendClientStream<64>(
      EncodeChunk({.transfer_id = 7, .offset = 0, .data = data.first(1)}));

  // Drop offset 1, then send the rest of the data.
  for (uint32_t i = 2; i < kData.size(); ++i) {
    ctx_.SendClientStream<64>(EncodeChunk(
        {.transfer_id = 7, .offset = i, .data = data.subspan(i, 1)}));
  }

  ASSERT_EQ(ctx_.total_responses(), 2u);
  Chunk chunk = DecodeChunk(ctx_.responses().back());
  EXPECT_EQ(chunk.transfer_id, 7u);
  EXPECT_EQ(chunk.offset, 1u);

  // Send the remaining data and the final status.
  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 1,
                                         .data = data.subspan(1, 31),
                                         .status = OkStatus()}));

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
}

TEST_F(WriteTransfer, ResendParametersIfSentRepeatedChunkDuringRecovery) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  ASSERT_EQ(ctx_.total_responses(), 1u);

  constexpr std::span data(kData);

  // Skip offset 0, then send the rest of the data.
  for (uint32_t i = 1; i < kData.size(); ++i) {
    ctx_.SendClientStream<64>(EncodeChunk(
        {.transfer_id = 7, .offset = i, .data = data.subspan(i, 1)}));
  }

  ASSERT_EQ(ctx_.total_responses(), 2u);  // Resent transfer parameters once.

  const auto last_chunk = EncodeChunk(
      {.transfer_id = 7, .offset = kData.size() - 1, .data = data.last(1)});
  ctx_.SendClientStream<64>(last_chunk);

  // Resent transfer parameters since the packet is repeated
  ASSERT_EQ(ctx_.total_responses(), 3u);

  ctx_.SendClientStream<64>(last_chunk);
  ASSERT_EQ(ctx_.total_responses(), 4u);

  Chunk chunk = DecodeChunk(ctx_.responses().back());
  EXPECT_EQ(chunk.transfer_id, 7u);
  EXPECT_EQ(chunk.offset, 0u);
  EXPECT_TRUE(chunk.pending_bytes.has_value());

  // Resumes normal operation when correct offset is sent.
  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = kData, .status = OkStatus()}));

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
}

TEST_F(WriteTransfer, IgnoresNonPendingTransfers) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7, .offset = 3}));
  ctx_.SendClientStream(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(10)}));
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7, .status = OkStatus()}));

  // Only start transfer for initial packet.
  EXPECT_FALSE(handler_.prepare_write_called);
  EXPECT_FALSE(handler_.finalize_write_called);
}

TEST_F(WriteTransfer, AbortAndRestartIfInitialPacketIsReceived) {
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  ASSERT_EQ(ctx_.total_responses(), 1u);

  ctx_.SendClientStream<64>(EncodeChunk(
      {.transfer_id = 7, .offset = 0, .data = std::span(kData).first(16)}));

  ASSERT_EQ(ctx_.total_responses(), 1u);

  ASSERT_TRUE(handler_.prepare_write_called);
  ASSERT_FALSE(handler_.finalize_write_called);
  handler_.prepare_write_called = false;  // Reset to check it's called again.

  // Simulate client disappearing then restarting the transfer.
  ctx_.SendClientStream(EncodeChunk({.transfer_id = 7}));

  EXPECT_TRUE(handler_.prepare_write_called);
  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, Status::Aborted());

  handler_.finalize_write_called = false;  // Reset to check it's called again.

  ASSERT_EQ(ctx_.total_responses(), 2u);

  ctx_.SendClientStream<64>(EncodeChunk({.transfer_id = 7,
                                         .offset = 0,
                                         .data = std::span(kData),
                                         .remaining_bytes = 0}));
  ASSERT_EQ(ctx_.total_responses(), 3u);

  EXPECT_TRUE(handler_.finalize_write_called);
  EXPECT_EQ(handler_.finalize_write_status, OkStatus());
  EXPECT_EQ(std::memcmp(buffer.data(), kData.data(), kData.size()), 0);
}

class SometimesUnavailableReadHandler final : public ReadOnlyHandler {
 public:
  SometimesUnavailableReadHandler(uint32_t transfer_id, ConstByteSpan data)
      : ReadOnlyHandler(transfer_id), reader_(data), call_count_(0) {}

  Status PrepareRead() final {
    if ((call_count_++ % 2) == 0) {
      return Status::Unavailable();
    }

    set_reader(reader_);
    return OkStatus();
  }

 private:
  stream::MemoryReader reader_;
  int call_count_;
};

TEST_F(ReadTransfer, PrepareError) {
  SometimesUnavailableReadHandler unavailable_handler(88, kData);
  ctx_.service().RegisterHandler(unavailable_handler);

  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 88, .pending_bytes = 128, .offset = 0}));

  ASSERT_EQ(ctx_.total_responses(), 1u);
  Chunk chunk = DecodeChunk(ctx_.responses()[0]);
  EXPECT_EQ(chunk.transfer_id, 88u);
  ASSERT_TRUE(chunk.status.has_value());
  EXPECT_EQ(chunk.status.value(), Status::Unavailable());

  // Try starting the transfer again. It should work this time.
  ctx_.SendClientStream(
      EncodeChunk({.transfer_id = 88, .pending_bytes = 128, .offset = 0}));
  ASSERT_EQ(ctx_.total_responses(), 3u);
  chunk = DecodeChunk(ctx_.responses()[1]);
  EXPECT_EQ(chunk.transfer_id, 88u);
  ASSERT_EQ(chunk.data.size(), kData.size());
  EXPECT_EQ(std::memcmp(chunk.data.data(), kData.data(), chunk.data.size()), 0);
}

PW_MODIFY_DIAGNOSTICS_POP();

}  // namespace
}  // namespace pw::transfer