#include "tensorflow/core/lib/io/record_reader.h"
#include <gtest/gtest.h>
#include "tensorflow/core/lib/core/coding.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/status_test_util.h"
#include "tensorflow/core/lib/hash/crc32c.h"
#include "tensorflow/core/lib/io/record_writer.h"
#include "tensorflow/core/lib/random/simple_philox.h"
#include "tensorflow/core/public/env.h"

namespace tensorflow {
namespace io {

// Construct a string of the specified length made out of the supplied
// partial string.
static string BigString(const string& partial_string, size_t n) {
  string result;
  while (result.size() < n) {
    result.append(partial_string);
  }
  result.resize(n);
  return result;
}

// Construct a string from a number
static string NumberString(int n) {
  char buf[50];
  snprintf(buf, sizeof(buf), "%d.", n);
  return string(buf);
}

// Return a skewed potentially long string
static string RandomSkewedString(int i, random::SimplePhilox* rnd) {
  return BigString(NumberString(i), rnd->Skewed(17));
}

class RecordioTest : public testing::Test {
 private:
  class StringDest : public WritableFile {
   public:
    string contents_;

    Status Close() override { return Status::OK(); }
    Status Flush() override { return Status::OK(); }
    Status Sync() override { return Status::OK(); }
    Status Append(const StringPiece& slice) override {
      contents_.append(slice.data(), slice.size());
      return Status::OK();
    }
  };

  class StringSource : public RandomAccessFile {
   public:
    StringPiece contents_;
    mutable bool force_error_;
    mutable bool returned_partial_;
    StringSource() : force_error_(false), returned_partial_(false) {}

    Status Read(uint64 offset, size_t n, StringPiece* result,
                     char* scratch) const override {
      EXPECT_FALSE(returned_partial_) << "must not Read() after eof/error";

      if (force_error_) {
        force_error_ = false;
        returned_partial_ = true;
        return errors::DataLoss("read error");
      }

      if (offset >= contents_.size()) {
        return errors::OutOfRange("end of file");
      }

      if (contents_.size() < offset + n) {
        n = contents_.size() - offset;
        returned_partial_ = true;
      }
      *result = StringPiece(contents_.data() + offset, n);
      return Status::OK();
    }
  };

  StringDest dest_;
  StringSource source_;
  bool reading_;
  uint64 readpos_;
  RecordWriter* writer_;
  RecordReader* reader_;

 public:
  RecordioTest()
      : reading_(false),
        readpos_(0),
        writer_(new RecordWriter(&dest_)),
        reader_(new RecordReader(&source_)) {}

  ~RecordioTest() override {
    delete writer_;
    delete reader_;
  }

  void Write(const string& msg) {
    ASSERT_TRUE(!reading_) << "Write() after starting to read";
    ASSERT_OK(writer_->WriteRecord(StringPiece(msg)));
  }

  size_t WrittenBytes() const { return dest_.contents_.size(); }

  string Read() {
    if (!reading_) {
      reading_ = true;
      source_.contents_ = StringPiece(dest_.contents_);
    }
    string record;
    Status s = reader_->ReadRecord(&readpos_, &record);
    if (s.ok()) {
      return record;
    } else if (errors::IsOutOfRange(s)) {
      return "EOF";
    } else {
      return s.ToString();
    }
  }

  void IncrementByte(int offset, int delta) {
    dest_.contents_[offset] += delta;
  }

  void SetByte(int offset, char new_byte) {
    dest_.contents_[offset] = new_byte;
  }

  void ShrinkSize(int bytes) {
    dest_.contents_.resize(dest_.contents_.size() - bytes);
  }

  void FixChecksum(int header_offset, int len) {
    // Compute crc of type/len/data
    uint32_t crc = crc32c::Value(&dest_.contents_[header_offset + 6], 1 + len);
    crc = crc32c::Mask(crc);
    core::EncodeFixed32(&dest_.contents_[header_offset], crc);
  }

  void ForceError() { source_.force_error_ = true; }

  void StartReadingAt(uint64_t initial_offset) { readpos_ = initial_offset; }

  void CheckOffsetPastEndReturnsNoRecords(uint64_t offset_past_end) {
    Write("foo");
    Write("bar");
    Write(BigString("x", 10000));
    reading_ = true;
    source_.contents_ = StringPiece(dest_.contents_);
    uint64 offset = WrittenBytes() + offset_past_end;
    string record;
    Status s = reader_->ReadRecord(&offset, &record);
    ASSERT_TRUE(errors::IsOutOfRange(s)) << s;
  }
};

TEST_F(RecordioTest, Empty) { ASSERT_EQ("EOF", Read()); }

TEST_F(RecordioTest, ReadWrite) {
  Write("foo");
  Write("bar");
  Write("");
  Write("xxxx");
  ASSERT_EQ("foo", Read());
  ASSERT_EQ("bar", Read());
  ASSERT_EQ("", Read());
  ASSERT_EQ("xxxx", Read());
  ASSERT_EQ("EOF", Read());
  ASSERT_EQ("EOF", Read());  // Make sure reads at eof work
}

TEST_F(RecordioTest, ManyRecords) {
  for (int i = 0; i < 100000; i++) {
    Write(NumberString(i));
  }
  for (int i = 0; i < 100000; i++) {
    ASSERT_EQ(NumberString(i), Read());
  }
  ASSERT_EQ("EOF", Read());
}

TEST_F(RecordioTest, RandomRead) {
  const int N = 500;
  {
    random::PhiloxRandom philox(301, 17);
    random::SimplePhilox rnd(&philox);
    for (int i = 0; i < N; i++) {
      Write(RandomSkewedString(i, &rnd));
    }
  }
  {
    random::PhiloxRandom philox(301, 17);
    random::SimplePhilox rnd(&philox);
    for (int i = 0; i < N; i++) {
      ASSERT_EQ(RandomSkewedString(i, &rnd), Read());
    }
  }
  ASSERT_EQ("EOF", Read());
}

// Tests of all the error paths in log_reader.cc follow:
static void AssertHasSubstr(StringPiece s, StringPiece expected) {
  EXPECT_TRUE(StringPiece(s).contains(expected)) << s << " does not contain "
                                                 << expected;
}

TEST_F(RecordioTest, ReadError) {
  Write("foo");
  ForceError();
  AssertHasSubstr(Read(), "Data loss");
}

TEST_F(RecordioTest, CorruptLength) {
  Write("foo");
  IncrementByte(6, 100);
  AssertHasSubstr(Read(), "Data loss");
}

TEST_F(RecordioTest, CorruptLengthCrc) {
  Write("foo");
  IncrementByte(10, 100);
  AssertHasSubstr(Read(), "Data loss");
}

TEST_F(RecordioTest, CorruptData) {
  Write("foo");
  IncrementByte(14, 10);
  AssertHasSubstr(Read(), "Data loss");
}

TEST_F(RecordioTest, CorruptDataCrc) {
  Write("foo");
  IncrementByte(WrittenBytes() - 1, 10);
  AssertHasSubstr(Read(), "Data loss");
}

TEST_F(RecordioTest, ReadEnd) { CheckOffsetPastEndReturnsNoRecords(0); }

TEST_F(RecordioTest, ReadPastEnd) { CheckOffsetPastEndReturnsNoRecords(5); }

}  // namespace io
}  // namespace tensorflow