/**
*    Copyright (C) 2014 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/db/catalog/index_key_validate.h"

#include "mongo/db/field_ref.h"
#include "mongo/db/index_names.h"
#include "mongo/db/jsobj.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {
    Status validateKeyPattern(const BSONObj& key) {
        const ErrorCodes::Error code = ErrorCodes::CannotCreateIndex;

        if ( key.objsize() > 2048 )
            return Status(code, "Index key pattern too large.");

        if ( key.isEmpty() )
            return Status(code, "Index keys cannot be empty.");

        string pluginName = IndexNames::findPluginName( key );
        if ( pluginName.size() ) {
            if ( !IndexNames::isKnownName( pluginName ) )
                return Status(code,
                              mongoutils::str::stream() << "Unknown index plugin '"
                                                        << pluginName << '\'');
        }

        BSONObjIterator it( key );
        while ( it.more() ) {
            BSONElement keyElement = it.next();

            if( keyElement.type() == Object || keyElement.type() == Array )
                return Status(code, "Index keys cannot be Objects or Arrays.");

            if ( keyElement.type() == String && pluginName != keyElement.str() ) {
                return Status(code, "Can't use more than one index plugin for a single index.");
            }

            // Ensure that the fields on which we are building the index are valid: a field must not
            // begin with a '$' unless it is part of a DBRef or text index, and a field path cannot
            // contain an empty field. If a field cannot be created or updated, it should not be
            // indexable.

            FieldRef keyField( keyElement.fieldName() );

            const size_t numParts = keyField.numParts();
            if ( numParts == 0 ) {
                return Status(code, "Index keys cannot be an empty field.");
            }

            // "$**" is acceptable for a text index.
            if ( mongoutils::str::equals( keyElement.fieldName(), "$**" ) &&
                 keyElement.valuestrsafe() == IndexNames::TEXT )
                continue;


            for ( size_t i = 0; i != numParts; ++i ) {
                const StringData part = keyField.getPart(i);

                // Check if the index key path contains an empty field.
                if ( part.empty() ) {
                    return Status(code, "Index keys cannot contain an empty field.");
                }

                if ( part[0] != '$' )
                    continue;

                // Check if the '$'-prefixed field is part of a DBRef: since we don't have the
                // necessary context to validate whether this is a proper DBRef, we allow index
                // creation on '$'-prefixed names that match those used in a DBRef.
                const bool mightBePartOfDbRef = (i != 0) &&
                                                (part == "$db" ||
                                                 part == "$id" ||
                                                 part == "$ref");

                if ( !mightBePartOfDbRef ) {
                    return Status(code, "Index key contains an illegal field name: "
                                        "field name starts with '$'.");
                }
            }
        }

        return Status::OK();
    }
} // namespace mongo
