/**
 *    Copyright (C) 2013 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/db/ops/modifier_compare.h"

#include "mongo/base/error_codes.h"
#include "mongo/bson/mutable/document.h"
#include "mongo/db/ops/field_checker.h"
#include "mongo/db/ops/log_builder.h"
#include "mongo/db/ops/path_support.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {

    namespace str = mongoutils::str;

    struct ModifierCompare::PreparedState {

        PreparedState(mutablebson::Document& targetDoc)
            : doc(targetDoc)
            , idxFound(0)
            , elemFound(doc.end()) {
        }

        // Document that is going to be changed.
        mutablebson::Document& doc;

        // Index in _fieldRef for which an Element exist in the document.
        size_t idxFound;

        // Element corresponding to _fieldRef[0.._idxFound].
        mutablebson::Element elemFound;
    };

    ModifierCompare::ModifierCompare(ModifierCompare::ModifierCompareMode mode)
        : _mode(mode)
        , _pathReplacementPosition(0) {
    }

    ModifierCompare::~ModifierCompare() {
    }

    Status ModifierCompare::init(const BSONElement& modExpr, const Options& opts,
                                 bool* positional) {

        _updatePath.parse(modExpr.fieldName());
        Status status = fieldchecker::isUpdatable(_updatePath);
        if (!status.isOK()) {
            return status;
        }

        // If a $-positional operator was used, get the index in which it occurred
        // and ensure only one occurrence.
        size_t foundCount;
        bool foundDollar = fieldchecker::isPositional(
            _updatePath, &_pathReplacementPosition, &foundCount);

        if (positional)
            *positional = foundDollar;

        if (foundDollar && foundCount > 1) {
            return Status(ErrorCodes::BadValue,
                          str::stream() << "Too many positional (i.e. '$') elements found in path '"
                                        << _updatePath.dottedField() << "'");
        }

        // Store value for later.
        _val = modExpr;
        return Status::OK();
    }

    Status ModifierCompare::prepare(mutablebson::Element root,
                                const StringData& matchedField,
                                ExecInfo* execInfo) {

        _preparedState.reset(new PreparedState(root.getDocument()));

        // If we have a $-positional field, it is time to bind it to an actual field part.
        if (_pathReplacementPosition) {
            if (matchedField.empty()) {
                return Status(ErrorCodes::BadValue,
                              str::stream() << "The positional operator did not find the match "
                                               "needed from the query. Unexpanded update: "
                                            << _updatePath.dottedField());
            }
            _updatePath.setPart(_pathReplacementPosition, matchedField);
        }

        // Locate the field name in 'root'. Note that we may not have all the parts in the path
        // in the doc -- which is fine. Our goal now is merely to reason about whether this mod
        // apply is a noOp or whether is can be in place. The remaining path, if missing, will
        // be created during the apply.
        Status status = pathsupport::findLongestPrefix(_updatePath,
                                                       root,
                                                       &_preparedState->idxFound,
                                                       &_preparedState->elemFound);

        // FindLongestPrefix may say the path does not exist at all, which is fine here, or
        // that the path was not viable or otherwise wrong, in which case, the mod cannot
        // proceed.
        if (status.code() == ErrorCodes::NonExistentPath) {
            _preparedState->elemFound = root.getDocument().end();
        }
        else if (!status.isOK()) {
            return status;
        }

        // We register interest in the field name. The driver needs this info to sort out if
        // there is any conflict among mods.
        execInfo->fieldRef[0] = &_updatePath;

        const bool destExists = (_preparedState->elemFound.ok() &&
                                 _preparedState->idxFound == (_updatePath.numParts() - 1));
        if (!destExists) {
            execInfo->noOp = false;
        }
        else {
            const int compareVal = _preparedState->elemFound.compareWithBSONElement(_val, false);
            execInfo->noOp = (compareVal == 0) ||
                             ((_mode == ModifierCompare::MAX) ?
                                     (compareVal > 0) : (compareVal < 0));
        }

        return Status::OK();
    }

    Status ModifierCompare::apply() const {

        const bool destExists = (_preparedState->elemFound.ok() &&
                                 _preparedState->idxFound == (_updatePath.numParts() - 1));
        // If there's no need to create any further field part, the $set is simply a value
        // assignment.
        if (destExists) {
            return _preparedState->elemFound.setValueBSONElement(_val);
        }

        mutablebson::Document& doc = _preparedState->doc;
        StringData lastPart = _updatePath.getPart(_updatePath.numParts() - 1);
        // If the element exists and is the same type, then that is what we want to work with
        mutablebson::Element elemToSet = doc.makeElementWithNewFieldName(lastPart, _val);
        if (!elemToSet.ok()) {
            return Status(ErrorCodes::InternalError, "can't create new element");
        }

        // Now, we can be in two cases here, as far as attaching the element being set goes:
        // (a) none of the parts in the element's path exist, or (b) some parts of the path
        // exist but not all.
        if (!_preparedState->elemFound.ok()) {
            _preparedState->elemFound = doc.root();
            _preparedState->idxFound = 0;
        }
        else {
            _preparedState->idxFound++;
        }

        // createPathAt() will complete the path and attach 'elemToSet' at the end of it.
        return pathsupport::createPathAt(_updatePath,
                                         _preparedState->idxFound,
                                         _preparedState->elemFound,
                                         elemToSet);
    }

    Status ModifierCompare::log(LogBuilder* logBuilder) const {
        return logBuilder->addToSetsWithNewFieldName(_updatePath.dottedField(), _val);
    }

} // namespace mongo
