api/applib/src/main/java/org/apache/causeway/applib/query/QueryRange.java

/*
 *  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.causeway.applib.query;

import java.io.Serializable;

/**
 * To support paging of query results, specifies an offset/start instance and limits
 * the number of instances to be retrieved.
 *
 * <p>
 *     Used by {@link NamedQuery#withRange(QueryRange)} and
 *     {@link AllInstancesQuery#withRange(QueryRange)}.
 * </p>
 *
 * @since 2.0 {@index}
 */
public interface QueryRange extends Serializable {

    // -- INTERFACE

    /**
     * Whether this range is unconstrained, meaning that there is
     * {@link #hasOffset() no offset} and {@link #hasLimit() no limit} has
     * been specified.
     */
    boolean isUnconstrained();

    /**
     * Whether this range has had a non-zero offset specified using
     * {@link #withStart(long)}.
     */
    boolean hasOffset();

    /**
     * Whether this range has a limit to the number of instances to be returned
     * using {@link #withLimit(long)}.
     */
    boolean hasLimit();

    /**
     * The start index into the set table.
     * (non-negative)
     */
    long getStart();

    /**
     * The maximum number of items to return, starting at {@link #getStart()}
     * (non-negative).
     */
    long getLimit();

    /**
     * The end index into the set table. Overflow is ignored.
     * (non-negative)
     */
    long getEnd();

    // -- TO INT

    /**
     * The start index into the set table (as java int primitive)
     * @throws ArithmeticException - if {@code start} overflows an int
     */
    default int getStartAsInt() {
        return Math.toIntExact(getStart());
    }

    /**
     * The maximum number of items to return (as java int primitive)
     * if {@code limit} overflows an int, {@link Integer#MAX_VALUE} is returned.
     */
    default int getLimitAsInt() {
        final long limit = getLimit();
        return limit<=((long)Integer.MAX_VALUE)
                ? Math.toIntExact(limit)
                : Integer.MAX_VALUE;
    }

    /**
     * The end index into the set table. Overflow is ignored. (as java int primitive)
     * if {@code end} overflows an int, {@link Integer#MAX_VALUE} is returned.
     */
    default int getEndAsInt() {
        final long end = getEnd();
        return end<=((long)Integer.MAX_VALUE)
                ? Math.toIntExact(end)
                : Integer.MAX_VALUE;
    }

    // -- FACTORIES

    static QueryRange unconstrained() {
        return of(0L, 0L);
    }

    static QueryRange start(long start) {
        return of(start, 0L);
    }

    static QueryRange limit(long limit) {
        return of(0L, limit);
    }

    static QueryRange of(long... range) {
        return new _QueryRangeDefault(range);
    }

    // -- WITHERS

    default QueryRange withStart(long start) {
        return of(start, getLimit());
    }

    default QueryRange withLimit(long limit) {
        return of(getStart(), limit);
    }


}