/* 
 * 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 parquet.hadoop.api;

import static parquet.Preconditions.checkNotNull;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.apache.hadoop.conf.Configuration;

import parquet.io.api.RecordConsumer;
import parquet.schema.MessageType;


/**
 * Abstraction to use with {@link parquet.hadoop.ParquetOutputFormat} to convert incoming records
 *
 * @param <T> the type of the incoming records
 * @author Julien Le Dem
 */
abstract public class WriteSupport<T> {

    /**
     * information to be persisted in the file
     *
     * @author Julien Le Dem
     */
    public static final class WriteContext {
        private final MessageType schema;
        private final Map<String, String> extraMetaData;

        /**
         * @param schema        the schema of the data
         * @param extraMetaData application specific metadata to add in the file
         */
        public WriteContext(MessageType schema, Map<String, String> extraMetaData) {
            super();
            this.schema = checkNotNull(schema, "schema");
            this.extraMetaData = Collections.unmodifiableMap(checkNotNull(extraMetaData, "extraMetaData"));
        }

        /**
         * @return the schema of the file
         */
        public MessageType getSchema() {
            return schema;
        }

        /**
         * @return application specific metadata
         */
        public Map<String, String> getExtraMetaData() {
            return extraMetaData;
        }

    }

    /**
     * Information to be added in the file once all the records have been written
     *
     * @author Julien Le Dem
     */
    public static final class FinalizedWriteContext {
        private final Map<String, String> extraMetaData;
        // this class exists to facilitate evolution of the API
        // we can add more fields later

        /**
         * @param extraMetaData application specific metadata to add in the file
         */
        public FinalizedWriteContext(Map<String, String> extraMetaData) {
            super();
            this.extraMetaData = Collections.unmodifiableMap(checkNotNull(extraMetaData, "extraMetaData"));
        }

        /**
         * @return application specific metadata
         */
        public Map<String, String> getExtraMetaData() {
            return extraMetaData;
        }

    }

    /**
     * called first in the task
     *
     * @param configuration the job's configuration
     * @return the information needed to write the file
     */
    public abstract WriteContext init(Configuration configuration);

    /**
     * This will be called once per row group
     *
     * @param recordConsumer the recordConsumer to write to
     */
    public abstract void prepareForWrite(RecordConsumer recordConsumer);

    /**
     * called once per record
     *
     * @param record one record to write to the previously provided record consumer
     */
    public abstract void write(T record);

    /**
     * called once in the end after the last record was written
     *
     * @return information to be added in the file
     */
    public FinalizedWriteContext finalizeWrite() {
        return new FinalizedWriteContext(new HashMap<String, String>());
    }

}