// Copyright 2017 The Nomulus Authors. All Rights Reserved.
//
// 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
//
//     http://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.

package google.registry.tools;

import static com.google.common.truth.Truth.assertThat;
import static google.registry.tools.LevelDbLogReader.ChunkType;

import com.google.common.collect.ImmutableList;
import com.google.common.primitives.Bytes;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** LevelDbLogReader tests. */
@RunWith(JUnit4.class)
public final class LevelDbLogReaderTest {

  private static final int MAX_RECORD = LevelDbLogReader.BLOCK_SIZE - LevelDbLogReader.HEADER_SIZE;

  // Size of the test record.  Any value < 256 will do.
  private static final int TEST_RECORD_SIZE = 231;

  // The maximum offset at which a test record can be inserted, measured in bytes from the beginning
  // of the block.
  private static final int MAX_TEST_RECORD_OFFSET =
      LevelDbLogReader.BLOCK_SIZE - (LevelDbLogReader.HEADER_SIZE + TEST_RECORD_SIZE);

  /**
   * Adds a record of bytes of 'val' of the given size to bytes.
   *
   * <p>This currently doesn't write a real checksum since we're not doing anything with that in the
   * leveldb reader.
   *
   * <p>Returns the new offset for the next block.
   */
  private static int addRecord(
      byte[] bytes, int pos, ChunkType type, int size, int val) {

    // Write a bogus checksum.
    for (int i = 0; i < 4; ++i) {
      bytes[pos++] = -1;
    }

    // Write size and type.
    bytes[pos++] = (byte) size;
    bytes[pos++] = (byte) (size >> 8);
    bytes[pos++] = (byte) type.getCode();

    // Write "size" bytes of data.
    for (int i = 0; i < size; ++i) {
      bytes[pos + i] = (byte) val;

      // Swap the least significant bytes in val so we can have more than 256 different same-sized
      // records.
      val = (val >> 8) | ((val & 0xff) << 8);
    }

    return pos + size;
  }

  private TestBlock makeBlockOfRepeatingBytes(int startVal) {
    byte[] block = new byte[LevelDbLogReader.BLOCK_SIZE];
    int pos = 0;
    int recordCount = 0;
    while (pos < MAX_TEST_RECORD_OFFSET) {
      pos =
          addRecord(
              block,
              pos,
              ChunkType.FULL,
              TEST_RECORD_SIZE,
              0xffff & (pos + startVal));
      ++recordCount;
    }
    return new TestBlock(block, recordCount);
  }

  @Test
  public void testSimpleBlock() throws IOException {
    TestBlock block = makeBlockOfRepeatingBytes(0);
    LevelDbLogReader reader = new LevelDbLogReader();
    reader.readFrom(new ByteArrayInputStream(block.data));
    ImmutableList<byte[]> records = reader.getRecords();
    assertThat(records).hasSize(block.recordCount);
  }

  @Test
  public void testLargeRecord() throws IOException {
    byte[] block = new byte[LevelDbLogReader.BLOCK_SIZE];
    addRecord(block, 0, ChunkType.FIRST, MAX_RECORD, (byte) 1);
    LevelDbLogReader reader = new LevelDbLogReader();
    reader.readFrom(new ByteArrayInputStream(block));
    assertThat(reader.getRecords()).isEmpty();

    addRecord(block, 0, ChunkType.MIDDLE, MAX_RECORD, (byte) 2);
    reader.readFrom(new ByteArrayInputStream(block));
    assertThat(reader.getRecords()).isEmpty();

    addRecord(block, 0, ChunkType.LAST, MAX_RECORD, (byte) 3);
    reader.readFrom(new ByteArrayInputStream(block));

    List<byte[]> records = reader.getRecords();
    assertThat(records).hasSize(1);
    byte[] record = records.get(0);

    for (int i = 0; i < MAX_RECORD; ++i) {
      assertThat(record[i]).isEqualTo((i % 2 == 1) ? 0 : 1);
    }
    for (int i = MAX_RECORD; i < MAX_RECORD * 2; ++i) {
      // Note that we have to invert the byte check here because MAX_RECORD is not divisible by two.
      assertThat(record[i]).isEqualTo((i % 2 == 0) ? 0 : 2);
    }
    for (int i = MAX_RECORD * 2; i < MAX_RECORD * 3; ++i) {
      assertThat(record[i]).isEqualTo((i % 2 == 1) ? 0 : 3);
    }
  }

  @Test
  public void readFromMultiBlockStream() throws IOException {
    TestBlock block0 = makeBlockOfRepeatingBytes(0);
    TestBlock block1 = makeBlockOfRepeatingBytes(138);
    ByteArrayInputStream source = new ByteArrayInputStream(Bytes.concat(block0.data, block1.data));

    LevelDbLogReader reader = new LevelDbLogReader();
    reader.readFrom(source);
    assertThat(reader.getRecords()).hasSize(block0.recordCount + block1.recordCount);
  }

  @Test
  public void testChunkTypesToCode() {
    // Verify that we're translating chunk types to code values correctly.z
    assertThat(ChunkType.fromCode(ChunkType.END.getCode())).isEqualTo(ChunkType.END);
    assertThat(ChunkType.fromCode(ChunkType.FULL.getCode())).isEqualTo(ChunkType.FULL);
    assertThat(ChunkType.fromCode(ChunkType.FIRST.getCode())).isEqualTo(ChunkType.FIRST);
    assertThat(ChunkType.fromCode(ChunkType.MIDDLE.getCode())).isEqualTo(ChunkType.MIDDLE);
    assertThat(ChunkType.fromCode(ChunkType.LAST.getCode())).isEqualTo(ChunkType.LAST);
  }

  /** Aggregates the bytes of a test block with the record count. */
  private static final class TestBlock {
    final byte[] data;
    final int recordCount;

    TestBlock(byte[] data, int recordCount) {
      this.data = data;
      this.recordCount = recordCount;
    }
  }
}