/**
 * Copyright (C) 2017 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.
 */

#pragma once

#include "mongo/bson/mutable/document.h"
#include "mongo/bson/mutable/element.h"
#include "mongo/db/bson/dotted_path_support.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/query/collation/collator_interface.h"

namespace mongo {

// Extracts the value for 'pattern' for both 'lhs' and 'rhs' and return true if 'lhs' <
// 'rhs'. We expect that both 'lhs' and 'rhs' be key patterns.
struct PatternElementCmp {
    PatternElementCmp() = default;

    PatternElementCmp(const BSONObj& pattern, const CollatorInterface* collator)
        : sortPattern(pattern), useWholeValue(pattern.hasField("")), collator(collator) {}

    bool operator()(const mutablebson::Element& lhs, const mutablebson::Element& rhs) const {
        namespace dps = ::mongo::dotted_path_support;
        if (useWholeValue) {
            const int comparedValue = lhs.compareWithElement(rhs, collator, false);

            const bool reversed = (sortPattern.firstElement().number() < 0);

            return (reversed ? comparedValue > 0 : comparedValue < 0);
        } else {
            // TODO: Push on to mutable in the future, and to support non-contiguous Elements.
            BSONObj lhsObj =
                lhs.getType() == Object ? lhs.getValueObject() : lhs.getValue().wrap("");
            BSONObj rhsObj =
                rhs.getType() == Object ? rhs.getValueObject() : rhs.getValue().wrap("");

            BSONObj lhsKey = dps::extractElementsBasedOnTemplate(lhsObj, sortPattern, true);
            BSONObj rhsKey = dps::extractElementsBasedOnTemplate(rhsObj, sortPattern, true);

            return lhsKey.woCompare(rhsKey, sortPattern, false, collator) < 0;
        }
    }

    BSONObj sortPattern;
    bool useWholeValue = true;
    const CollatorInterface* collator = nullptr;
};

}  // namespace mongo