/**
 *    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_set.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 ModifierSet::PreparedState {

        PreparedState(mutablebson::Document* targetDoc)
            : doc(*targetDoc)
            , idxFound(0)
            , elemFound(doc.end())
            , noOp(false)
            , elemIsBlocking(false) {
        }

        // 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;

        // This $set is a no-op?
        bool noOp;

        // The element we find during a replication operation that blocks our update path
        bool elemIsBlocking;

    };

    ModifierSet::ModifierSet(ModifierSet::ModifierSetMode mode)
        : _fieldRef()
        , _posDollar(0)
        , _setMode(mode)
        , _val()
        , _modOptions() {
    }

    ModifierSet::~ModifierSet() {
    }

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

        //
        // field name analysis
        //

        // Break down the field name into its 'dotted' components (aka parts) and check that
        // the field is fit for updates
        _fieldRef.parse(modExpr.fieldName());
        Status status = fieldchecker::isUpdatable(_fieldRef);
        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(_fieldRef, &_posDollar, &foundCount);

        if (positional)
            *positional = foundDollar;

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

        //
        // value analysis
        //

        if (!modExpr.ok())
            return Status(ErrorCodes::BadValue, "cannot $set an empty value");

        _val = modExpr;
        _modOptions = opts;

        return Status::OK();
    }

    Status ModifierSet::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 (_posDollar) {
            if (matchedField.empty()) {
                return Status(ErrorCodes::BadValue,
                              str::stream() << "The positional operator did not find the match "
                                               "needed from the query. Unexpanded update: "
                                            << _fieldRef.dottedField());
            }
            _fieldRef.setPart(_posDollar, 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 remainin path, if missing, will
        // be created during the apply.
        Status status = pathsupport::findLongestPrefix(_fieldRef,
                                                       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 (_modOptions.fromReplication && status.code() == ErrorCodes::PathNotViable) {
            // If we are coming from replication and it is an invalid path,
            // then push on indicating that we had a blocking element, which we stopped at
            _preparedState->elemIsBlocking = true;
        }
        else if (!status.isOK()) {
            return status;
        }

        if (_setMode == SET_ON_INSERT) {
            execInfo->context = ModifierInterface::ExecInfo::INSERT_CONTEXT;
        }

        // 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] = &_fieldRef;

        //
        // in-place and no-op logic
        //

        // If the field path is not fully present, then this mod cannot be in place, nor is a
        // noOp.
        if (!_preparedState->elemFound.ok() ||
            _preparedState->idxFound < (_fieldRef.numParts()-1)) {
            return Status::OK();
        }

        // If the value being $set is the same as the one already in the doc, than this is a
        // noOp.
        if (_preparedState->elemFound.ok() &&
            _preparedState->idxFound == (_fieldRef.numParts()-1) &&
            _preparedState->elemFound.compareWithBSONElement(_val, false /*ignore field*/) == 0) {
            execInfo->noOp = _preparedState->noOp = true;
        }

        return Status::OK();
    }

    Status ModifierSet::apply() const {
        dassert(!_preparedState->noOp);

        const bool destExists = _preparedState->elemFound.ok() &&
                                _preparedState->idxFound == (_fieldRef.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);
        }

        //
        // Complete document path logic
        //

        // Creates the final element that's going to be $set in 'doc'.
        mutablebson::Document& doc = _preparedState->doc;
        StringData lastPart = _fieldRef.getPart(_fieldRef.numParts()-1);
        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++;
        }

        // Remove the blocking element, if we are from replication applier. See comment below.
        if (_modOptions.fromReplication && !destExists && _preparedState->elemFound.ok() &&
            _preparedState->elemIsBlocking &&
            (!(_preparedState->elemFound.isType(Array)) ||
             !(_preparedState->elemFound.isType(Object)))
           ) {

            /**
             * With replication we want to be able to remove blocking elements for $set (only).
             * The reason they are blocking elements is that they are not embedded documents
             * (objects) nor an array (a special type of an embedded doc) and we cannot
             * add children to them (because the $set path requires adding children past
             * the blocking element).
             *
             * Imagine that we started with this:
             * {_id:1, a:1} + {$set : {"a.b.c" : 1}} -> {_id:1, a: {b: {c:1}}}
             * Above we found that element (a:1) is blocking at position 1. We now will replace
             * it with an empty object so the normal logic below can be
             * applied from the root (in this example case).
             *
             * Here is an array example:
             * {_id:1, a:[1, 2]} + {$set : {"a.0.c" : 1}} -> {_id:1, a: [ {c:1}, 2]}
             * The blocking element is "a.0" since it is a number, non-object, and we must
             * then replace it with an empty object so we can add c:1 to that empty object
             */

            mutablebson::Element blockingElem = _preparedState->elemFound;
            BSONObj newObj;
            // Replace blocking non-object with an empty object
            Status status = blockingElem.setValueObject(newObj);
            if (!status.isOK()) {
                return status;
            }
        }

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

    Status ModifierSet::log(LogBuilder* logBuilder) const {

        // We'd like to create an entry such as {$set: {<fieldname>: <value>}} under 'logRoot'.
        // We start by creating the {$set: ...} Element.
        mutablebson::Document& doc = logBuilder->getDocument();

        // Create the {<fieldname>: <value>} Element. Note that we log the mod with a
        // dotted field, if it was applied over a dotted field. The rationale is that the
        // secondary may be in a different state than the primary and thus make different
        // decisions about creating the intermediate path in _fieldRef or not.
        mutablebson::Element logElement = doc.makeElementWithNewFieldName(
            _fieldRef.dottedField(), _val);

        if (!logElement.ok()) {
            return Status(ErrorCodes::InternalError, "cannot create details for $set mod");
        }

        return logBuilder->addToSets(logElement);
    }

} // namespace mongo
