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/*
 * 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.parquet.pig.convert;

import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.parquet.io.api.Binary;
import org.apache.parquet.io.api.Converter;
import org.apache.parquet.io.api.GroupConverter;
import org.apache.parquet.io.api.PrimitiveConverter;
import org.apache.parquet.pig.PigSchemaConverter;
import org.apache.parquet.pig.SchemaConversionException;
import org.apache.parquet.schema.GroupType;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.FrontendException;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.impl.logicalLayer.schema.Schema.FieldSchema;

/**
 * Converts groups into Pig Maps
 */
final class MapConverter extends GroupConverter {

  private final MapKeyValueConverter keyValue;
  private final ParentValueContainer parent;

  private Map buffer = new BufferMap();

  private Object currentKey;
  private Object currentValue;

  MapConverter(
      GroupType parquetSchema,
      FieldSchema pigSchema,
      ParentValueContainer parent,
      boolean numbersDefaultToZero,
      boolean columnIndexAccess)
      throws FrontendException {
    if (parquetSchema.getFieldCount() != 1) {
      throw new IllegalArgumentException("maps have only one field. " + parquetSchema);
    }
    this.parent = parent;
    keyValue = new MapKeyValueConverter(
        parquetSchema.getType(0).asGroupType(),
        pigSchema.schema.getField(0),
        numbersDefaultToZero,
        columnIndexAccess);
  }

  @Override
  public Converter getConverter(int fieldIndex) {
    if (fieldIndex != 0) {
      throw new IllegalArgumentException("maps have only one field. can't reach " + fieldIndex);
    }
    return keyValue;
  }

  /**
   * runtime methods
   */
  @Override
  public final void start() {
    buffer.clear();
  }

  @Override
  public void end() {
    parent.add(new LinkedHashMap(buffer));
  }

  /**
   * to contain the values of the Map until we read them all
   */
  private static final class BufferMap extends AbstractMap {
    private List> entries = new ArrayList>();
    private Set> entrySet = new AbstractSet>() {
      @Override
      public Iterator> iterator() {
        return entries.iterator();
      }

      @Override
      public int size() {
        return entries.size();
      }
    };

    @Override
    public Tuple put(String key, Object value) {
      entries.add(new SimpleImmutableEntry(key, value));
      return null;
    }

    @Override
    public void clear() {
      entries.clear();
    }

    @Override
    public Set> entrySet() {
      return entrySet;
    }
  }

  /**
   * convert Key/Value groups into map entries
   */
  final class MapKeyValueConverter extends GroupConverter {

    private final Converter keyConverter;
    private final Converter valueConverter;

    MapKeyValueConverter(
        GroupType parquetSchema,
        Schema.FieldSchema pigSchema,
        boolean numbersDefaultToZero,
        boolean columnIndexAccess) {
      if (parquetSchema.getFieldCount() != 2
          || !parquetSchema.getType(0).getName().equals("key")
          || !parquetSchema.getType(1).getName().equals("value")) {
        throw new IllegalArgumentException("schema does not match map key/value " + parquetSchema);
      }
      try {
        keyConverter = TupleConverter.newConverter(
            new PigSchemaConverter()
                .convertField(parquetSchema.getType(0))
                .getField(0),
            parquetSchema.getType(0),
            new ParentValueContainer() {
              void add(Object value) {
                currentKey = value;
              }
            },
            numbersDefaultToZero,
            columnIndexAccess);
      } catch (FrontendException fe) {
        throw new SchemaConversionException("can't convert keytype " + parquetSchema.getType(0), fe);
      }
      valueConverter = TupleConverter.newConverter(
          pigSchema,
          parquetSchema.getType(1),
          new ParentValueContainer() {
            void add(Object value) {
              currentValue = value;
            }
          },
          numbersDefaultToZero,
          columnIndexAccess);
    }

    @Override
    public Converter getConverter(int fieldIndex) {
      if (fieldIndex == 0) {
        return keyConverter;
      } else if (fieldIndex == 1) {
        return valueConverter;
      }
      throw new IllegalArgumentException("only the key (0) and value (1) fields expected: " + fieldIndex);
    }

    /**
     * runtime methods
     */
    @Override
    public final void start() {
      currentKey = null;
      currentValue = null;
    }

    @Override
    public void end() {
      buffer.put(currentKey.toString(), currentValue);
      currentKey = null;
      currentValue = null;
    }
  }

  /**
   * convert the key into a string
   */
  final class StringKeyConverter extends PrimitiveConverter {

    @Override
    public final void addBinary(Binary value) {
      currentKey = value.toStringUsingUTF8();
    }
  }
}