/**
 *    Copyright (C) 2015 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#include "mongo/bson/bsonobj.h"
#include "mongo/db/operation_context.h"
#include "mongo/util/fail_point_service.h"

namespace mongo {

/**
 * The state associated with tailable cursors.
 */
struct AwaitDataState {
    /**
     * The deadline for how long we wait on the tail of capped collection before returning IS_EOF.
     */
    Date_t waitForInsertsDeadline;

    /**
     * If true, when no results are available from a plan, then instead of returning immediately,
     * the system should wait up to the length of the operation deadline for data to be inserted
     * which causes results to become available.
     */
    bool shouldWaitForInserts;
};

extern const OperationContext::Decoration<AwaitDataState> awaitDataState;

class BSONObj;
class QueryRequest;

// Enabling this fail point will cause the getMore command to busy wait after pinning the cursor,
// until the fail point is disabled.
MONGO_FP_FORWARD_DECLARE(keepCursorPinnedDuringGetMore);

// Failpoint for making getMore not wait for an awaitdata cursor. Allows us to avoid waiting during
// tests.
MONGO_FP_FORWARD_DECLARE(disableAwaitDataForGetMoreCmd);

/**
 * Suite of find/getMore related functions used in both the mongod and mongos query paths.
 */
class FindCommon {
public:
    // The maximum amount of user data to return to a client in a single batch.
    //
    // This max may be exceeded by epsilon for output documents that approach the maximum user
    // document size. That is, if we must return a BSONObjMaxUserSize document, then the total
    // response size will be BSONObjMaxUserSize plus the amount of size required for the message
    // header and the cursor response "envelope". (The envolope contains namespace and cursor id
    // info.)
    static const int kMaxBytesToReturnToClientAtOnce = BSONObjMaxUserSize;

    // The initial size of the query response buffer.
    static const int kInitReplyBufferSize = 32768;

    /**
     * Returns true if the batchSize for the initial find has been satisfied.
     *
     * If 'qr' does not have a batchSize, the default batchSize is respected.
     */
    static bool enoughForFirstBatch(const QueryRequest& qr, long long numDocs);

    /**
     * Returns true if the batchSize for the getMore has been satisfied.
     *
     * An 'effectiveBatchSize' value of zero is interpreted as the absence of a batchSize, in which
     * case this method returns false.
     */
    static bool enoughForGetMore(long long effectiveBatchSize, long long numDocs) {
        return effectiveBatchSize && numDocs >= effectiveBatchSize;
    }

    /**
     * Given the number of docs ('numDocs') and bytes ('bytesBuffered') currently buffered as a
     * response to a cursor-generating command, returns true if there are enough remaining bytes in
     * our budget to fit 'nextDoc'.
     */
    static bool haveSpaceForNext(const BSONObj& nextDoc, long long numDocs, int bytesBuffered);

    /**
     * Transforms the raw sort spec into one suitable for use as the ordering specification in
     * BSONObj::woCompare().
     *
     * In particular, eliminates text score meta-sort from 'sortSpec'.
     *
     * The input must be validated (each BSON element must be either a number or text score
     * meta-sort specification).
     */
    static BSONObj transformSortSpec(const BSONObj& sortSpec);
};

}  // namespace mongo