/**
 * Copyright (c) 2011 10gen 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/platform/basic.h"

#include "mongo/db/pipeline/accumulator.h"

#include "mongo/db/pipeline/accumulation_statement.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/value.h"

namespace mongo {

using boost::intrusive_ptr;

REGISTER_ACCUMULATOR(max, AccumulatorMax::create);
REGISTER_ACCUMULATOR(min, AccumulatorMin::create);
REGISTER_EXPRESSION(max, ExpressionFromAccumulator<AccumulatorMax>::parse);
REGISTER_EXPRESSION(min, ExpressionFromAccumulator<AccumulatorMin>::parse);

const char* AccumulatorMinMax::getOpName() const {
    if (_sense == 1)
        return "$min";
    return "$max";
}

void AccumulatorMinMax::processInternal(const Value& input, bool merging) {
    // nullish values should have no impact on result
    if (!input.nullish()) {
        /* compare with the current value; swap if appropriate */
        int cmp = getExpressionContext()->getValueComparator().compare(_val, input) * _sense;
        if (cmp > 0 || _val.missing()) {  // missing is lower than all other values
            _val = input;
            _memUsageBytes = sizeof(*this) + input.getApproximateSize() - sizeof(Value);
        }
    }
}

Value AccumulatorMinMax::getValue(bool toBeMerged) const {
    if (_val.missing()) {
        return Value(BSONNULL);
    }
    return _val;
}

AccumulatorMinMax::AccumulatorMinMax(const boost::intrusive_ptr<ExpressionContext>& expCtx,
                                     Sense sense)
    : Accumulator(expCtx), _sense(sense) {
    _memUsageBytes = sizeof(*this);
}

void AccumulatorMinMax::reset() {
    _val = Value();
    _memUsageBytes = sizeof(*this);
}

intrusive_ptr<Accumulator> AccumulatorMin::create(
    const boost::intrusive_ptr<ExpressionContext>& expCtx) {
    return new AccumulatorMin(expCtx);
}

intrusive_ptr<Accumulator> AccumulatorMax::create(
    const boost::intrusive_ptr<ExpressionContext>& expCtx) {
    return new AccumulatorMax(expCtx);
}
}
