//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#include "db/db_test_util.h"
#include "test_util/sync_point.h"

namespace ROCKSDB_NAMESPACE {

class MockFS;

class MockRandomAccessFile : public FSRandomAccessFileWrapper {
 public:
  MockRandomAccessFile(std::unique_ptr<FSRandomAccessFile>& file,
                       bool support_prefetch, std::atomic_int& prefetch_count)
      : FSRandomAccessFileWrapper(file.get()),
        file_(std::move(file)),
        support_prefetch_(support_prefetch),
        prefetch_count_(prefetch_count) {}

  IOStatus Prefetch(uint64_t offset, size_t n, const IOOptions& options,
                    IODebugContext* dbg) override {
    if (support_prefetch_) {
      prefetch_count_.fetch_add(1);
      return target()->Prefetch(offset, n, options, dbg);
    } else {
      return IOStatus::NotSupported("Prefetch not supported");
    }
  }

 private:
  std::unique_ptr<FSRandomAccessFile> file_;
  const bool support_prefetch_;
  std::atomic_int& prefetch_count_;
};

class MockFS : public FileSystemWrapper {
 public:
  explicit MockFS(const std::shared_ptr<FileSystem>& wrapped,
                  bool support_prefetch)
      : FileSystemWrapper(wrapped), support_prefetch_(support_prefetch) {}

  IOStatus NewRandomAccessFile(const std::string& fname,
                               const FileOptions& opts,
                               std::unique_ptr<FSRandomAccessFile>* result,
                               IODebugContext* dbg) override {
    std::unique_ptr<FSRandomAccessFile> file;
    IOStatus s;
    s = target()->NewRandomAccessFile(fname, opts, &file, dbg);
    result->reset(
        new MockRandomAccessFile(file, support_prefetch_, prefetch_count_));
    return s;
  }

  void ClearPrefetchCount() { prefetch_count_ = 0; }

  bool IsPrefetchCalled() { return prefetch_count_ > 0; }

 private:
  const bool support_prefetch_;
  std::atomic_int prefetch_count_{0};
};

class PrefetchTest
    : public DBTestBase,
      public ::testing::WithParamInterface<std::tuple<bool, bool>> {
 public:
  PrefetchTest() : DBTestBase("/prefetch_test", true) {}
};

std::string BuildKey(int num, std::string postfix = "") {
  return "my_key_" + std::to_string(num) + postfix;
}

TEST_P(PrefetchTest, Basic) {
  // First param is if the mockFS support_prefetch or not
  bool support_prefetch = std::get<0>(GetParam());

  // Second param is if directIO is enabled or not
  bool use_direct_io = std::get<1>(GetParam());
  const int kNumKeys = 1100;
  std::shared_ptr<MockFS> fs =
      std::make_shared<MockFS>(env_->GetFileSystem(), support_prefetch);
  std::unique_ptr<Env> env(new CompositeEnvWrapper(env_, fs));
  Options options = CurrentOptions();
  options.write_buffer_size = 1024;
  options.create_if_missing = true;
  options.compression = kNoCompression;
  options.env = env.get();
  if (use_direct_io) {
    options.use_direct_reads = true;
    options.use_direct_io_for_flush_and_compaction = true;
  }

  int buff_prefetch_count = 0;
  SyncPoint::GetInstance()->SetCallBack("FilePrefetchBuffer::Prefetch:Start",
                                        [&](void*) { buff_prefetch_count++; });
  SyncPoint::GetInstance()->EnableProcessing();

  Status s = TryReopen(options);
  if (use_direct_io && (s.IsNotSupported() || s.IsInvalidArgument())) {
    // If direct IO is not supported, skip the test
    return;
  } else {
    ASSERT_OK(s);
  }

  // create first key range
  WriteBatch batch;
  for (int i = 0; i < kNumKeys; i++) {
    batch.Put(BuildKey(i), "value for range 1 key");
  }
  ASSERT_OK(db_->Write(WriteOptions(), &batch));

  // create second key range
  batch.Clear();
  for (int i = 0; i < kNumKeys; i++) {
    batch.Put(BuildKey(i, "key2"), "value for range 2 key");
  }
  ASSERT_OK(db_->Write(WriteOptions(), &batch));

  // delete second key range
  batch.Clear();
  for (int i = 0; i < kNumKeys; i++) {
    batch.Delete(BuildKey(i, "key2"));
  }
  ASSERT_OK(db_->Write(WriteOptions(), &batch));

  // compact database
  std::string start_key = BuildKey(0);
  std::string end_key = BuildKey(kNumKeys - 1);
  Slice least(start_key.data(), start_key.size());
  Slice greatest(end_key.data(), end_key.size());

  // commenting out the line below causes the example to work correctly
  db_->CompactRange(CompactRangeOptions(), &least, &greatest);

  if (support_prefetch && !use_direct_io) {
    // If underline file system supports prefetch, and directIO is not enabled
    // make sure prefetch() is called and FilePrefetchBuffer is not used.
    ASSERT_TRUE(fs->IsPrefetchCalled());
    fs->ClearPrefetchCount();
    ASSERT_EQ(0, buff_prefetch_count);
  } else {
    // If underline file system doesn't support prefetch, or directIO is
    // enabled, make sure prefetch() is not called and FilePrefetchBuffer is
    // used.
    ASSERT_FALSE(fs->IsPrefetchCalled());
    ASSERT_GT(buff_prefetch_count, 0);
    buff_prefetch_count = 0;
  }

  // count the keys
  {
    auto iter = std::unique_ptr<Iterator>(db_->NewIterator(ReadOptions()));
    int num_keys = 0;
    for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
      num_keys++;
    }
  }

  // Make sure prefetch is called only if file system support prefetch.
  if (support_prefetch && !use_direct_io) {
    ASSERT_TRUE(fs->IsPrefetchCalled());
    fs->ClearPrefetchCount();
    ASSERT_EQ(0, buff_prefetch_count);
  } else {
    ASSERT_FALSE(fs->IsPrefetchCalled());
    ASSERT_GT(buff_prefetch_count, 0);
    buff_prefetch_count = 0;
  }
  Close();
}

INSTANTIATE_TEST_CASE_P(PrefetchTest, PrefetchTest,
                        ::testing::Combine(::testing::Bool(),
                                           ::testing::Bool()));

}  // namespace ROCKSDB_NAMESPACE

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

  return RUN_ALL_TESTS();
}
