//  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 "port/port.h"
#include "port/stack_trace.h"
#include "rocksdb/file_system.h"
#include "file/random_access_file_reader.h"
#include "test_util/testharness.h"
#include "test_util/testutil.h"

namespace ROCKSDB_NAMESPACE {

class RandomAccessFileReaderTest : public testing::Test {
 public:
  void SetUp() override {
    test::ResetTmpDirForDirectIO();
    env_ = Env::Default();
    fs_ = FileSystem::Default();
    test_dir_ = test::PerThreadDBPath("random_access_file_reader_test");
    ASSERT_OK(fs_->CreateDir(test_dir_, IOOptions(), nullptr));
    alignment_ = GetAlignment();
  }

  void TearDown() override {
    EXPECT_OK(test::DestroyDir(env_, test_dir_));
  }

  bool IsDirectIOSupported() {
    Write(".direct", "");
    FileOptions opt;
    opt.use_direct_reads = true;
    std::unique_ptr<FSRandomAccessFile> f;
    auto s = fs_->NewRandomAccessFile(Path(".direct"), opt, &f, nullptr);
    return s.ok();
  }

  void Write(const std::string& fname, const std::string& content) {
    std::unique_ptr<FSWritableFile> f;
    ASSERT_OK(fs_->NewWritableFile(Path(fname), FileOptions(), &f, nullptr));
    ASSERT_OK(f->Append(content, IOOptions(), nullptr));
    ASSERT_OK(f->Close(IOOptions(), nullptr));
  }

  void Read(const std::string& fname, const FileOptions& opts,
                std::unique_ptr<RandomAccessFileReader>* reader) {
    std::string fpath = Path(fname);
    std::unique_ptr<FSRandomAccessFile> f;
    ASSERT_OK(fs_->NewRandomAccessFile(fpath, opts, &f, nullptr));
    (*reader).reset(new RandomAccessFileReader(std::move(f), fpath, env_));
  }

  void AssertResult(const std::string& content,
                    const std::vector<FSReadRequest>& reqs) {
    for (const auto& r : reqs) {
      ASSERT_OK(r.status);
      ASSERT_EQ(r.len, r.result.size());
      ASSERT_EQ(content.substr(r.offset, r.len), r.result.ToString());
    }
  }

  size_t alignment() const { return alignment_; }

 private:
  Env* env_;
  std::shared_ptr<FileSystem> fs_;
  std::string test_dir_;
  size_t alignment_;

  std::string Path(const std::string& fname) {
    return test_dir_ + "/" + fname;
  }

  size_t GetAlignment() {
    std::string f = "get_alignment";
    Write(f, "");
    std::unique_ptr<RandomAccessFileReader> r;
    Read(f, FileOptions(), &r);
    size_t alignment = r->file()->GetRequiredBufferAlignment();
    EXPECT_OK(fs_->DeleteFile(Path(f), IOOptions(), nullptr));
    return alignment;
  }
};

TEST_F(RandomAccessFileReaderTest, ReadDirectIO) {
  if (!IsDirectIOSupported()) {
    printf("Direct IO is not supported, skip this test\n");
    return;
  }

  std::string fname = "read-direct-io";
  Random rand(0);
  std::string content;
  test::RandomString(&rand, static_cast<int>(alignment()), &content);
  Write(fname, content);

  FileOptions opts;
  opts.use_direct_reads = true;
  std::unique_ptr<RandomAccessFileReader> r;
  Read(fname, opts, &r);
  ASSERT_TRUE(r->use_direct_io());

  size_t offset = alignment() / 2;
  size_t len = alignment() / 3;
  Slice result;
  AlignedBuf buf;
  for (bool for_compaction : {true, false}) {
    ASSERT_OK(r->Read(IOOptions(), offset, len, &result, nullptr, &buf,
                      for_compaction));
    ASSERT_EQ(result.ToString(), content.substr(offset, len));
  }
}

TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
  if (!IsDirectIOSupported()) {
    printf("Direct IO is not supported, skip this test\n");
    return;
  }

  // Creates a file with 3 pages.
  std::string fname = "multi-read-direct-io";
  Random rand(0);
  std::string content;
  test::RandomString(&rand, 3 * static_cast<int>(alignment()), &content);
  Write(fname, content);

  FileOptions opts;
  opts.use_direct_reads = true;
  std::unique_ptr<RandomAccessFileReader> r;
  Read(fname, opts, &r);
  ASSERT_TRUE(r->use_direct_io());

  {
    // Reads 2 blocks in the 1st page.
    // The results should be SharedSlices of the same underlying buffer.
    //
    // Illustration (each x is a 1/4 page)
    // First page: xxxx
    // 1st block:  x
    // 2nd block:    xx
    FSReadRequest r0;
    r0.offset = 0;
    r0.len = alignment() / 4;
    r0.scratch = nullptr;

    FSReadRequest r1;
    r1.offset = alignment() / 2;
    r1.len = alignment() / 2;
    r1.scratch = nullptr;

    std::vector<FSReadRequest> reqs;
    reqs.push_back(std::move(r0));
    reqs.push_back(std::move(r1));
    AlignedBuf aligned_buf;
    ASSERT_OK(
        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));

    AssertResult(content, reqs);
  }

  {
    // Reads 3 blocks:
    // 1st block in the 1st page;
    // 2nd block from the middle of the 1st page to the middle of the 2nd page;
    // 3rd block in the 2nd page.
    // The results should be SharedSlices of the same underlying buffer.
    //
    // Illustration (each x is a 1/4 page)
    // 2 pages:   xxxxxxxx
    // 1st block: x
    // 2nd block:   xxxx
    // 3rd block:        x
    FSReadRequest r0;
    r0.offset = 0;
    r0.len = alignment() / 4;
    r0.scratch = nullptr;

    FSReadRequest r1;
    r1.offset = alignment() / 2;
    r1.len = alignment();
    r1.scratch = nullptr;

    FSReadRequest r2;
    r2.offset = 2 * alignment() - alignment() / 4;
    r2.len = alignment() / 4;
    r2.scratch = nullptr;

    std::vector<FSReadRequest> reqs;
    reqs.push_back(std::move(r0));
    reqs.push_back(std::move(r1));
    reqs.push_back(std::move(r2));
    AlignedBuf aligned_buf;
    ASSERT_OK(
        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));

    AssertResult(content, reqs);
  }

  {
    // Reads 3 blocks:
    // 1st block in the middle of the 1st page;
    // 2nd block in the middle of the 2nd page;
    // 3rd block in the middle of the 3rd page.
    // The results should be SharedSlices of the same underlying buffer.
    //
    // Illustration (each x is a 1/4 page)
    // 3 pages:   xxxxxxxxxxxx
    // 1st block:  xx
    // 2nd block:      xx
    // 3rd block:          xx
    FSReadRequest r0;
    r0.offset = alignment() / 4;
    r0.len = alignment() / 2;
    r0.scratch = nullptr;

    FSReadRequest r1;
    r1.offset = alignment() + alignment() / 4;
    r1.len = alignment() / 2;
    r1.scratch = nullptr;

    FSReadRequest r2;
    r2.offset = 2 * alignment() + alignment() / 4;
    r2.len = alignment() / 2;
    r2.scratch = nullptr;

    std::vector<FSReadRequest> reqs;
    reqs.push_back(std::move(r0));
    reqs.push_back(std::move(r1));
    reqs.push_back(std::move(r2));
    AlignedBuf aligned_buf;
    ASSERT_OK(
        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));

    AssertResult(content, reqs);
  }

  {
    // Reads 2 blocks:
    // 1st block in the middle of the 1st page;
    // 2nd block in the middle of the 3rd page.
    // The results are two different buffers.
    //
    // Illustration (each x is a 1/4 page)
    // 3 pages:   xxxxxxxxxxxx
    // 1st block:  xx
    // 2nd block:          xx
    FSReadRequest r0;
    r0.offset = alignment() / 4;
    r0.len = alignment() / 2;
    r0.scratch = nullptr;

    FSReadRequest r1;
    r1.offset = 2 * alignment() + alignment() / 4;
    r1.len = alignment() / 2;
    r1.scratch = nullptr;

    std::vector<FSReadRequest> reqs;
    reqs.push_back(std::move(r0));
    reqs.push_back(std::move(r1));
    AlignedBuf aligned_buf;
    ASSERT_OK(
        r->MultiRead(IOOptions(), reqs.data(), reqs.size(), &aligned_buf));

    AssertResult(content, reqs);
  }
}

}  // namespace ROCKSDB_NAMESPACE

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