/**
 *    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_inc.h"

#include "mongo/base/error_codes.h"
#include "mongo/bson/mutable/algorithm.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 mb = mutablebson;
    namespace str = mongoutils::str;

    struct ModifierInc::PreparedState {

        PreparedState(mutablebson::Document& doc)
            : doc(doc)
            , idxFound(0)
            , elemFound(doc.end())
            , newValue()
            , noOp(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;

        // Value to be applied
        SafeNum newValue;

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

    ModifierInc::ModifierInc(ModifierIncMode mode)
        : ModifierInterface ()
        , _mode(mode)
        , _fieldRef()
        , _posDollar(0)
        , _val() {
    }

    ModifierInc::~ModifierInc() {
    }

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

        //
        // field name analysis
        //

        // Perform standard field name and updateable checks.
        _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.isNumber()) {
            // TODO: Context for mod error messages would be helpful
            // include mod code, etc.
            return Status(ErrorCodes::TypeMismatch,
                          str::stream() << "Cannot "
                                        << (_mode == MODE_INC ? "increment" : "multiply")
                                        << " with non-numeric argument: {"
                                        << modExpr << "}");
        }

        _val = modExpr;
        dassert(_val.isValid());

        return Status::OK();
    }

    Status ModifierInc::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 remaining 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 (!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] = &_fieldRef;

        // Capture the value we are going to write. At this point, there may not be a value
        // against which to operate, so the result will be simply _val.
        _preparedState->newValue = _val;

        //
        // 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)) {

            // For multiplication, we treat ops against missing as yielding zero. We take
            // advantage here of the promotion rules for SafeNum; the expression below will
            // always yield a zero of the same type of operand that the user provided
            // (e.g. double).
            if (_mode == MODE_MUL)
                _preparedState->newValue *= SafeNum(static_cast<int>(0));

            return Status::OK();
        }

        // If the value being $inc'ed is the same as the one already in the doc, than this is a
        // noOp.
        if (!_preparedState->elemFound.isNumeric()) {
            mb::Element idElem = mb::findFirstChildNamed(root, "_id");
            return Status(
                ErrorCodes::TypeMismatch,
                str::stream() << "Cannot apply "
                              << (_mode == MODE_INC ? "$inc" : "$mul")
                              << " to a value of non-numeric type. {"
                              << idElem.toString()
                              << "} has the field '" <<  _preparedState->elemFound.getFieldName()
                              << "' of non-numeric type "
                              << typeName(_preparedState->elemFound.getType()));
        }
        const SafeNum currentValue = _preparedState->elemFound.getValueSafeNum();

        // Update newValue w.r.t to the current value of the found element.
        if (_mode == MODE_INC)
            _preparedState->newValue += currentValue;
        else
            _preparedState->newValue *= currentValue;

        // If the result of the addition is invalid, we must return an error.
        if (!_preparedState->newValue.isValid()) {
            mb::Element idElem = mb::findFirstChildNamed(root, "_id");
            return Status(ErrorCodes::BadValue,
                          str::stream() << "Failed to apply $inc operations to current value ("
                                        << currentValue.debugString() << ") for document {"
                                        << idElem.toString() << "}");
        }

        // If the values are identical (same type, same value), then this is a no-op.
        if (_preparedState->newValue.isIdentical(currentValue)) {
            _preparedState->noOp = execInfo->noOp = true;
            return Status::OK();
        }

        return Status::OK();
    }

    Status ModifierInc::apply() const {
        dassert(_preparedState->noOp == false);

        // If there's no need to create any further field part, the $inc is simply a value
        // assignment.
        if (_preparedState->elemFound.ok() &&
            _preparedState->idxFound == (_fieldRef.numParts() - 1)) {
            return _preparedState->elemFound.setValueSafeNum(_preparedState->newValue);
        }

        //
        // 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.makeElementSafeNum(lastPart, _preparedState->newValue);
        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(_fieldRef,
                                         _preparedState->idxFound,
                                         _preparedState->elemFound,
                                         elemToSet);
    }

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

        dassert(_preparedState->newValue.isValid());

        // 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();

        // Then we create the {<fieldname>: <value>} Element.
        mutablebson::Element logElement = doc.makeElementSafeNum(
            _fieldRef.dottedField(),
            _preparedState->newValue);

        if (!logElement.ok()) {
            return Status(ErrorCodes::InternalError,
                          str::stream() << "Could not append entry to "
                                        << (_mode == MODE_INC ? "$inc" : "$mul")
                                        << " oplog entry: "
                                        << "set '" << _fieldRef.dottedField() << "' -> "
                                        << _preparedState->newValue.debugString() );
        }

        // Now, we attach the {<fieldname>: <value>} Element under the {$set: ...} segment.
        return logBuilder->addToSets(logElement);
    }

} // namespace mongo
