/*
 * 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.guava;

import com.datastax.driver.core.TypeCodec;
import com.datastax.driver.extras.codecs.MappingCodec;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
import com.google.common.reflect.TypeParameter;
import com.google.common.reflect.TypeToken;

import java.util.Collection;
import java.util.Map;

/**
 * A codec that wraps other codecs around Guava's {@link Optional} API.
 *
 * @param <T> The wrapped Java type
 */
public class OptionalCodec<T> extends MappingCodec<Optional<T>, T> {

    private final Predicate<T> isAbsent;

    public OptionalCodec(TypeCodec<T> codec) {
        this(codec, new Predicate<T>() {
            @Override
            public boolean apply(T input) {
                return input == null
                        || input instanceof Collection && ((Collection) input).isEmpty()
                        || input instanceof Map && ((Map) input).isEmpty();
            }
        });
    }

    public OptionalCodec(TypeCodec<T> codec, Predicate<T> isAbsent) {
        // @formatter:off
        super(codec, new TypeToken<Optional<T>>() {}.where(new TypeParameter<T>() {}, codec.getJavaType()));
        // @formatter:on
        this.isAbsent = isAbsent;
    }

    @Override
    protected Optional<T> deserialize(T value) {
        return isAbsent(value) ? Optional.<T>absent() : Optional.fromNullable(value);
    }

    @Override
    protected T serialize(Optional<T> value) {
        return value.isPresent() ? value.get() : absentValue();
    }

    protected T absentValue() {
        return null;
    }

    protected boolean isAbsent(T value) {
        return isAbsent.apply(value);
    }

}
