/**
 *    Copyright (C) 2015 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/query/plan_cache_indexability.h"

#include <memory>
#include "mongo/base/init.h"
#include "mongo/base/owned_pointer_vector.h"
#include "mongo/db/query/index_entry.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/matcher/expression_algo.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/stdx/memory.h"

namespace mongo {

    void PlanCacheIndexabilityState::processSparseIndex(const BSONObj& keyPattern) {
        for (BSONElement elem : keyPattern) {
            _pathDiscriminatorsMap[elem.fieldNameStringData()].push_back(
                [] (const MatchExpression* queryExpr) {
                    if (queryExpr->matchType() != MatchExpression::EQ) {
                        return true;
                    }
                    const auto* queryExprEquality =
                        static_cast<const EqualityMatchExpression*>(queryExpr);
                    return !queryExprEquality->getData().isNull();
                }
            );
        }
    }

    void PlanCacheIndexabilityState::processPartialIndex(const MatchExpression* filterExpr) {
        invariant(filterExpr);
        for (size_t i = 0; i < filterExpr->numChildren(); ++i) {
            processPartialIndex(filterExpr->getChild(i));
        }
        if (!filterExpr->isLogical()) {
            _pathDiscriminatorsMap[filterExpr->path()].push_back(
                [filterExpr] (const MatchExpression* queryExpr) {
                    return expression::isSubsetOf(queryExpr, filterExpr);
                }
            );
        }
    }

namespace {
    const IndexabilityDiscriminators emptyDiscriminators;
}  // namespace

    const IndexabilityDiscriminators& PlanCacheIndexabilityState::getDiscriminators(
            StringData path) const {
        PathDiscriminatorsMap::const_iterator it = _pathDiscriminatorsMap.find(path);
        if (it == _pathDiscriminatorsMap.end()) {
            return emptyDiscriminators;
        }
        return it->second;
    }

    void PlanCacheIndexabilityState::updateDiscriminators(
            const std::vector<IndexEntry>& indexEntries) {
        _pathDiscriminatorsMap = PathDiscriminatorsMap();

        for (const IndexEntry& idx : indexEntries) {
            if (idx.sparse) {
                processSparseIndex(idx.keyPattern);
            }
            if (idx.filterExpr) {
                processPartialIndex(idx.filterExpr);
            }
        }
    }

}  // namespace mongo