/*
 * 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.flink.api.java.typeutils;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.common.typeutils.base.ListSerializer;

import java.util.List;

import static org.apache.flink.util.Preconditions.checkNotNull;

/**
 * A {@link TypeInformation} for the list types of the Java API.
 *
 * @param <T> The type of the elements in the list.
 */
@PublicEvolving
public final class ListTypeInfo<T> extends TypeInformation<List<T>> {

	private static final long serialVersionUID = 1L;

	private final TypeInformation<T> elementTypeInfo;


	public ListTypeInfo(Class<T> elementTypeClass) {
		this.elementTypeInfo = of(checkNotNull(elementTypeClass, "elementTypeClass"));
	}

	public ListTypeInfo(TypeInformation<T> elementTypeInfo) {
		this.elementTypeInfo = checkNotNull(elementTypeInfo, "elementTypeInfo");
	}

	// ------------------------------------------------------------------------
	//  ListTypeInfo specific properties
	// ------------------------------------------------------------------------

	/**
	 * Gets the type information for the elements contained in the list
	 */
	public TypeInformation<T> getElementTypeInfo() {
		return elementTypeInfo;
	}

	// ------------------------------------------------------------------------
	//  TypeInformation implementation
	// ------------------------------------------------------------------------

	@Override
	public boolean isBasicType() {
		return false;
	}

	@Override
	public boolean isTupleType() {
		return false;
	}

	@Override
	public int getArity() {
		return 0;
	}

	@Override
	public int getTotalFields() {
		// similar as arrays, the lists are "opaque" to the direct field addressing logic
		// since the list's elements are not addressable, we do not expose them
		return 1;
	}

	@SuppressWarnings("unchecked")
	@Override
	public Class<List<T>> getTypeClass() {
		return (Class<List<T>>)(Class<?>)List.class;
	}

	@Override
	public boolean isKeyType() {
		return false;
	}

	@Override
	public TypeSerializer<List<T>> createSerializer(ExecutionConfig config) {
		TypeSerializer<T> elementTypeSerializer = elementTypeInfo.createSerializer(config);
		return new ListSerializer<>(elementTypeSerializer);
	}

	// ------------------------------------------------------------------------

	@Override
	public String toString() {
		return "List<" + elementTypeInfo + '>';
	}

	@Override
	public boolean equals(Object obj) {
		if (obj == this) {
			return true;
		}
		else if (obj instanceof ListTypeInfo) {
			final ListTypeInfo<?> other = (ListTypeInfo<?>) obj;
			return other.canEqual(this) && elementTypeInfo.equals(other.elementTypeInfo);
		} else {
			return false;
		}
	}

	@Override
	public int hashCode() {
		return 31 * elementTypeInfo.hashCode() + 1;
	}

	@Override
	public boolean canEqual(Object obj) {
		return obj != null && obj.getClass() == getClass();
	}
}