/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.drill.exec.vector.complex;

import java.util.Collections;
import java.util.Iterator;
import java.util.Set;

import org.apache.drill.common.types.TypeProtos;
import org.apache.drill.common.types.Types;
import org.apache.drill.exec.exception.SchemaChangeRuntimeException;
import org.apache.drill.exec.expr.BasicTypeHelper;
import org.apache.drill.exec.memory.AllocationManager.BufferLedger;
import org.apache.drill.exec.memory.BufferAllocator;
import org.apache.drill.exec.proto.UserBitShared;
import org.apache.drill.exec.record.MaterializedField;
import org.apache.drill.exec.record.TransferPair;
import org.apache.drill.exec.vector.AddOrGetResult;
import org.apache.drill.exec.vector.BaseValueVector;
import org.apache.drill.exec.vector.UInt4Vector;
import org.apache.drill.exec.vector.ValueVector;
import org.apache.drill.exec.vector.VectorDescriptor;
import org.apache.drill.exec.vector.ZeroVector;
import org.apache.drill.shaded.guava.com.google.common.base.Preconditions;
import org.apache.drill.shaded.guava.com.google.common.collect.ObjectArrays;

import io.netty.buffer.DrillBuf;

public abstract class BaseRepeatedValueVector extends BaseValueVector implements RepeatedValueVector {

  public final static ValueVector DEFAULT_DATA_VECTOR = ZeroVector.INSTANCE;
  public final static String OFFSETS_VECTOR_NAME = "$offsets$";
  public final static String DATA_VECTOR_NAME = "$data$";

  public final static MaterializedField OFFSETS_FIELD =
      MaterializedField.create(OFFSETS_VECTOR_NAME, Types.required(TypeProtos.MinorType.UINT4));

  protected final UInt4Vector offsets;
  protected ValueVector vector;

  protected BaseRepeatedValueVector(MaterializedField field, BufferAllocator allocator) {
    this(field, allocator, DEFAULT_DATA_VECTOR);
  }

  protected BaseRepeatedValueVector(MaterializedField field, BufferAllocator allocator, ValueVector vector) {
    super(field, allocator);
    this.offsets = new UInt4Vector(OFFSETS_FIELD, allocator);
    this.vector = Preconditions.checkNotNull(vector, "data vector cannot be null");
  }

  @Override
  public boolean allocateNewSafe() {
    /* boolean to keep track if all the memory allocation were successful
     * Used in the case of composite vectors when we need to allocate multiple
     * buffers for multiple vectors. If one of the allocations failed we need to
     * clear all the memory that we allocated
     */
    boolean success = false;
    try {
      if (!offsets.allocateNewSafe()) {
        return false;
      }
      success = vector.allocateNewSafe();
    } finally {
      if (!success) {
        clear();
      }
    }
    offsets.zeroVector();
    return success;
  }

  @Override
  public UInt4Vector getOffsetVector() { return offsets; }

  @Override
  public ValueVector getDataVector() { return vector; }

  @Override
  public void setInitialCapacity(int numRecords) {
    offsets.setInitialCapacity(numRecords + 1);
    vector.setInitialCapacity(numRecords * RepeatedValueVector.DEFAULT_REPEAT_PER_RECORD);
  }

  @Override
  public int getValueCapacity() {
    final int offsetValueCapacity = Math.max(offsets.getValueCapacity() - 1, 0);
    if (vector == DEFAULT_DATA_VECTOR) {
      return offsetValueCapacity;
    }
    return Math.min(vector.getValueCapacity(), offsetValueCapacity);
  }

  @Override
  protected UserBitShared.SerializedField.Builder getMetadataBuilder() {
    return super.getMetadataBuilder()
        .addChild(offsets.getMetadata())
        .addChild(vector.getMetadata());
  }

  @Override
  public int getBufferSize() {
    if (getAccessor().getValueCount() == 0) {
      return 0;
    }
    return offsets.getBufferSize() + vector.getBufferSize();
  }

  @Override
  public int getAllocatedSize() {
    return offsets.getAllocatedSize() + vector.getAllocatedSize();
  }

  @Override
  public int getBufferSizeFor(int valueCount) {
    if (valueCount == 0) {
      return 0;
    }

    return offsets.getBufferSizeFor(valueCount + 1) + vector.getBufferSizeFor(valueCount);
  }

  @Override
  public Iterator<ValueVector> iterator() {
    return Collections.singleton(getDataVector()).iterator();
  }

  @Override
  public void clear() {
    offsets.clear();
    vector.clear();
    super.clear();
  }

  @Override
  public DrillBuf[] getBuffers(boolean clear) {
    final DrillBuf[] buffers = ObjectArrays.concat(offsets.getBuffers(false), vector.getBuffers(false), DrillBuf.class);
    if (clear) {
      for (final DrillBuf buffer:buffers) {
        buffer.retain();
      }
      clear();
    }
    return buffers;
  }

  @Override
  public void load(UserBitShared.SerializedField metadata, DrillBuf buffer) {
    final UserBitShared.SerializedField offsetMetadata = metadata.getChild(0);
    offsets.load(offsetMetadata, buffer);

    final UserBitShared.SerializedField vectorMetadata = metadata.getChild(1);
    if (getDataVector() == DEFAULT_DATA_VECTOR) {
      addOrGetVector(VectorDescriptor.create(vectorMetadata.getMajorType()));
    }

    final int offsetLength = offsetMetadata.getBufferLength();
    final int vectorLength = vectorMetadata.getBufferLength();
    vector.load(vectorMetadata, buffer.slice(offsetLength, vectorLength));
  }

  /**
   * Returns 1 if inner vector is explicitly set via #addOrGetVector else 0
   *
   * @see org.apache.drill.exec.vector.complex.ContainerVectorLike#size()
   */
  @Override
  public int size() {
    return vector == DEFAULT_DATA_VECTOR ? 0:1;
  }

  @SuppressWarnings("unchecked")
  @Override
  public <T extends ValueVector> AddOrGetResult<T> addOrGetVector(VectorDescriptor descriptor) {
    boolean created = false;
    if (vector == DEFAULT_DATA_VECTOR && descriptor.getType().getMinorType() != TypeProtos.MinorType.LATE) {
      final MaterializedField field = descriptor.withName(DATA_VECTOR_NAME).getField();
      vector = BasicTypeHelper.getNewVector(field, allocator);
      // returned vector must have the same field
      assert field.equals(vector.getField());
      getField().addChild(field);
      created = true;
    }

    final TypeProtos.MajorType actual = vector.getField().getType();
    if (!actual.equals(descriptor.getType())) {
      final String msg = String.format("Inner vector type mismatch. Requested type: [%s], actual type: [%s]",
          descriptor.getType(), actual);
      throw new SchemaChangeRuntimeException(msg);
    }

    return new AddOrGetResult<>((T)vector, created);
  }

  protected void replaceDataVector(ValueVector v) {
    vector.clear();
    vector = v;
  }

  public void setChildVector(ValueVector childVector) {

    // When created, the list uses the default vector of type LATE.
    // That entry appears as a child vector. Remove it and add the
    // new type instead.
    //
    // Here we are simply asserting that the client is following the basic protocol:
    // that the child vector can be set only once, to change the original LATE vector
    // to something else.

    assert vector == DEFAULT_DATA_VECTOR;
    replaceDataVector(childVector);
    field.addChild(childVector.getField());
    assert field.getChildren().size() == 1;
  }

  @Override
  public void collectLedgers(Set<BufferLedger> ledgers) {
    offsets.collectLedgers(ledgers);
    vector.collectLedgers(ledgers);
  }

  @Override
  public int getPayloadByteCount(int valueCount) {
    if (valueCount == 0) {
      return 0;
    }
    final int entryCount = offsets.getAccessor().get(valueCount);
    return offsets.getPayloadByteCount(valueCount) + vector.getPayloadByteCount(entryCount);
  }

  @Override
  public void exchange(ValueVector other) {
    final BaseRepeatedValueVector target = (BaseRepeatedValueVector) other;
    vector.exchange(target.vector);
    offsets.exchange(target.offsets);
  }

  protected abstract class BaseRepeatedValueVectorTransferPair<T extends BaseRepeatedValueVector> implements TransferPair {

    protected final T target;
    protected final TransferPair[] children;

    protected BaseRepeatedValueVectorTransferPair(T target) {
      this.target = Preconditions.checkNotNull(target);
      if (target.getDataVector() == DEFAULT_DATA_VECTOR) {
        target.addOrGetVector(VectorDescriptor.create(getDataVector().getField()));
        target.getDataVector().allocateNew();
      }
      this.children = new TransferPair[] {
          getOffsetVector().makeTransferPair(target.getOffsetVector()),
          getDataVector().makeTransferPair(target.getDataVector())
      };
    }

    @Override
    public void transfer() {
      for (TransferPair child : children) {
        child.transfer();
      }
    }

    @Override
    public ValueVector getTo() {
      return target;
    }

    @Override
    public void splitAndTransfer(int startIndex, int length) {
      target.allocateNew();
      for (int i = 0; i < length; i++) {
        copyValueSafe(startIndex + i, i);
      }
    }

    protected void copyValueSafe(int destIndex, int start, int end) {
      TransferPair vectorTransfer = children[1];
      int newIndex = target.getOffsetVector().getAccessor().get(destIndex);
      // TODO: make this a bulk copy.
      for (int i = start; i < end; i++, newIndex++) {
        vectorTransfer.copyValueSafe(i, newIndex);
      }
      target.getOffsetVector().getMutator().setSafe(destIndex + 1, newIndex);
    }
  }

  public abstract class BaseRepeatedAccessor extends BaseValueVector.BaseAccessor implements RepeatedAccessor {

    @Override
    public int getValueCount() {
      return Math.max(offsets.getAccessor().getValueCount() - 1, 0);
    }

    @Override
    public int getInnerValueCount() {
      return vector.getAccessor().getValueCount();
    }

    @Override
    public int getInnerValueCountAt(int index) {
      return offsets.getAccessor().get(index+1) - offsets.getAccessor().get(index);
    }

    @Override
    public boolean isNull(int index) {
      return false;
    }

    @Override
    public boolean isEmpty(int index) {
      return false;
    }
  }

  public abstract class BaseRepeatedMutator extends BaseValueVector.BaseMutator implements RepeatedMutator {

    @Override
    public void startNewValue(int index) {
      while (offsets.getValueCapacity() <= index) {
        offsets.reAlloc();
      }
      offsets.getMutator().setSafe(index + 1, offsets.getAccessor().get(index));
      setValueCount(index + 1);
    }

    @Override
    public void setValueCount(int valueCount) {
      // TODO: populate offset end points
      // Convention seems to be that if the "outer" value count
      // is zero, then the offset vector can also be zero-length:
      // the normal initial zero position is omitted. While this
      // saves a bit of memory, it greatly complicates code that
      // works with vectors because of the special case for zero-length
      // vectors.
      offsets.getMutator().setValueCount(valueCount == 0 ? 0 : valueCount + 1);
      final int childValueCount = valueCount == 0 ? 0 : offsets.getAccessor().get(valueCount);
      vector.getMutator().setValueCount(childValueCount);
    }

    public int getInnerValueCountAt(int index) {
      return offsets.getAccessor().get(index + 1) - offsets.getAccessor().get(index);
    }
  }
}