/*
 *  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.isis.applib.util;

import java.util.List;
import java.util.Objects;
import java.util.function.Function;

import org.apache.isis.commons.internal.base._Casts;
import org.apache.isis.commons.internal.collections._Lists;

/**
 * Fluent Object Equality Composition.
 *
 * @param <T>
 * @since 2.0.0
 */
public class Equality<T> {

    public static <T> Equality<T> checkEquals(Function<? super T, ?> getter) {
        Objects.requireNonNull(getter);
        return new Equality<>(getter);
    }

    private final List<Function<? super T, ?>> getters = _Lists.newArrayList();

    private Equality(Function<? super T, ?> getter) {
        getters.add(getter);
    }

    public Equality<T> thenCheckEquals(Function<? super T, ?> getter){
        Objects.requireNonNull(getter);
        getters.add(getter);
        return this;
    }

    public boolean equals(T target, Object other){
        if(target==null && other==null) {
            return true;
        }
        if(target==null || other==null) {
            return false;
        }
        if(target.getClass() != other.getClass()) {
            return false;
        }
        final T o = _Casts.uncheckedCast(other);

        for(Function<? super T, ?> getter : getters) {
            if(!Objects.equals(getter.apply(target), getter.apply(o)))
                return false;
        }

        return true;
    }



}
