/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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.querydsl.core.support;

import java.util.List;

import javax.annotation.Nullable;

import com.mysema.commons.lang.CloseableIterator;
import com.mysema.commons.lang.IteratorAdapter;
import com.querydsl.core.Fetchable;
import com.querydsl.core.FetchableQuery;
import com.querydsl.core.NonUniqueResultException;
import com.querydsl.core.ResultTransformer;
import com.querydsl.core.types.SubQueryExpression;

/**
 * {@code FetchableQueryBase} extends the {@link QueryBase} class to provide default
 * implementations of the methods of the {@link com.querydsl.core.Fetchable} interface
 *
 * @param <T> result type
 * @param <Q> concrete subtype
 *
 * @author tiwe
 */
public abstract class FetchableQueryBase<T, Q extends FetchableQueryBase<T, Q>>
        extends QueryBase<Q> implements Fetchable<T> {

    public FetchableQueryBase(QueryMixin<Q> queryMixin) {
        super(queryMixin);
    }

    @Override
    public List<T> fetch() {
        return IteratorAdapter.asList(iterate());
    }

    @Override
    public final T fetchFirst() {
        return limit(1).fetchOne();
    }

    public <T> T transform(ResultTransformer<T> transformer) {
        return transformer.transform((FetchableQuery<?,?>) this);
    }

    @Nullable
    protected <T> T uniqueResult(CloseableIterator<T> it) {
        try {
            if (it.hasNext()) {
                T rv = it.next();
                if (it.hasNext()) {
                    throw new NonUniqueResultException();
                }
                return rv;
            } else {
                return null;
            }
        } finally {
            it.close();
        }
    }

    @Override
    public final boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (o instanceof SubQueryExpression) {
            SubQueryExpression<?> s = (SubQueryExpression<?>) o;
            return s.getMetadata().equals(queryMixin.getMetadata());
        } else {
            return false;
        }
    }

}