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Extended functionality for the Java driver.
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/*
 * Copyright DataStax, Inc.
 *
 * 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 com.datastax.driver.extras.codecs;

import com.datastax.driver.core.ProtocolVersion;
import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.core.exceptions.InvalidTypeException;
import com.google.common.reflect.TypeToken;
import java.nio.ByteBuffer;

/**
 * An abstract {@link TypeCodec} that stores JAVA objects as serialized strings. This can serve as a
 * base for codecs dealing with XML or JSON formats.
 *
 * This codec can be seen as a convenience base class to help implementing Java-to-XML or
 * Java-to-JSON mappings, but it comes with a performance penalty: each Java object is serialized in
 * two steps: first to a String, and then to a {@link ByteBuffer}, which means that each
 * serialization actually incurs in two potentially expensive operations being carried.
 *
 * If you are using an XML or JSON library that supports writing Java objects directly to {@link
 * ByteBuffer}s, consider writing your own codec instead of using this one.
 *
 * @param  The Java type this codec serializes from and deserializes to.
 */
public abstract class ParsingCodec extends TypeCodec {

  private final TypeCodec innerCodec;

  public ParsingCodec(Class javaType) {
    this(TypeToken.of(javaType));
  }

  public ParsingCodec(TypeToken javaType) {
    this(TypeCodec.varchar(), javaType);
  }

  public ParsingCodec(TypeCodec innerCodec, Class javaType) {
    this(innerCodec, TypeToken.of(javaType));
  }

  public ParsingCodec(TypeCodec innerCodec, TypeToken javaType) {
    super(innerCodec.getCqlType(), javaType);
    this.innerCodec = innerCodec;
  }

  @Override
  public ByteBuffer serialize(T value, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    return value == null ? null : innerCodec.serialize(toString(value), protocolVersion);
  }

  @Override
  public T deserialize(ByteBuffer bytes, ProtocolVersion protocolVersion)
      throws InvalidTypeException {
    String value = innerCodec.deserialize(bytes, protocolVersion);
    return value == null ? null : fromString(value);
  }

  @Override
  public String format(T value) throws InvalidTypeException {
    return value == null ? null : innerCodec.format(toString(value));
  }

  @Override
  public T parse(String value) throws InvalidTypeException {
    return value == null || value.isEmpty() || value.equalsIgnoreCase("NULL")
        ? null
        : fromString(innerCodec.parse(value));
  }

  /**
   * Return the String representation of the given object; no special CQL quoting should be applied
   * here. Null values should be accepted; in most cases, implementors should return null for null
   * inputs.
   *
   * @param value the value to convert into a string
   * @return the String representation of the given object
   */
  protected abstract String toString(T value);

  /**
   * Parse the given string into an object; no special CQL unquoting should be applied here. Null
   * values should be accepted; in most cases, implementors should return null for null inputs.
   *
   * @param value the string to parse
   * @return the parsed object.
   */
  protected abstract T fromString(String value);
}