/*
 * Copyright 2008-present MongoDB, 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.mongodb.internal.operation;

import org.bson.BsonDocument;
import org.bson.BsonInt32;

final class CursorHelper {

    
Gets the limit of the number of documents in the OP_REPLY response to the get more request. A value of zero tells the server to
use the default size. A negative value tells the server to return no more than that number and immediately close the cursor.
Otherwise, the server will return no more than that number and return the same cursorId to allow the rest of the documents to be
fetched, if it turns out there are more documents.
The value returned by this method is based on the limit, the batch size, both of which can be positive, negative, or zero, and the
number of documents fetched so far.
Params:
limit – the user-specified limit on the number of results returned
batchSize – the user-specified batch size
numReturnedSoFar – the number of results returned so far
Returns:
the value for numberToReturn in the OP_GET_MORE wire protocol message.
@mongodb.driver.manual
../meta-driver/latest/legacy/mongodb-wire-protocol/#op-get-more OP_GET_MORE/**
     * <p>Gets the limit of the number of documents in the OP_REPLY response to the get more request. A value of zero tells the server to
     * use the default size. A negative value tells the server to return no more than that number and immediately close the cursor.
     * Otherwise, the server will return no more than that number and return the same cursorId to allow the rest of the documents to be
     * fetched, if it turns out there are more documents.</p>
     *
     * <p>The value returned by this method is based on the limit, the batch size, both of which can be positive, negative, or zero, and the
     * number of documents fetched so far.</p>
     *
     * @return the value for numberToReturn in the OP_GET_MORE wire protocol message.
     * @mongodb.driver.manual ../meta-driver/latest/legacy/mongodb-wire-protocol/#op-get-more OP_GET_MORE
     * @param limit the user-specified limit on the number of results returned
     * @param batchSize the user-specified batch size
     * @param numReturnedSoFar the number of results returned so far
     */
    static int getNumberToReturn(final int limit, final int batchSize, final int numReturnedSoFar) {
        int numberToReturn;
        if (Math.abs(limit) != 0) {
            numberToReturn = Math.abs(limit) - numReturnedSoFar;
            if (batchSize != 0 && numberToReturn > Math.abs(batchSize)) {
                numberToReturn = batchSize;
            }
        } else {
            numberToReturn = batchSize;
        }
        return numberToReturn;
    }

    static BsonDocument getCursorDocumentFromBatchSize(final Integer batchSize) {
        return batchSize == null ? new BsonDocument() : new BsonDocument("batchSize", new BsonInt32(batchSize));
    }

    private CursorHelper() {
    }
}