/**
 *    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.
 */

#pragma once

#include <string>

#include "mongo/base/disallow_copying.h"
#include "mongo/bson/mutable/element.h"
#include "mongo/db/field_ref.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/ops/modifier_interface.h"
#include "mongo/db/ops/modifier_push_sorter.h"

namespace mongo {

class LogBuilder;

class ModifierPush : public ModifierInterface {
    MONGO_DISALLOW_COPYING(ModifierPush);

public:
    enum ModifierPushMode { PUSH_NORMAL, PUSH_ALL };
    explicit ModifierPush(ModifierPushMode mode = PUSH_NORMAL);

    //
    // Modifier interface implementation
    //

    virtual ~ModifierPush();

    /**
     * A 'modExpr' here is a BSONElement {<fieldname>: <each clause>, <slice clause>, <sort
     * clause>} coming from a $push mod such as {$set: {x: $each[{a:1}], $slice:3,
     * $sort{b:1}}}. init() extracts and validates the field name and the clauses. It
     * returns OK if successful or a status describing the error.
     *
     * There are currently a few restrictions concerning the clauses (but all can be
     * lifted):
     *   + $slice can be negative only (ie, slicing from the recent end)
     *   + $sort requires $slice to be present
     *   + $sort can only sort objects (as opposed to basic types), so it only takes
     *     object as patterns
     *   + Because of the previous, $sort requires that the array being pushed to be made
     *     of objects
     */
    virtual Status init(const BSONElement& modExpr, const Options& opts, bool* positional = NULL);

    /**
     * Locates the array to be pushed into in the 'root', if it exists, and fills in
     * execInfo accordingly. Returns true if $push would succeed in 'root', otherwise
     * return a status describing the error.
     *
     * Note that a $push is never in-place. The cost of checking if it is a no-op makes it
     * so that we don't do such check either. As such, execInfo is always filled with
     * 'false' for those two options.
     */
    virtual Status prepare(mutablebson::Element root, StringData matchedField, ExecInfo* execInfo);

    /**
     * Pushes the array into the prepared position and "sort/slice"s the resulting array
     * according to that call's instructions.
     */
    virtual Status apply() const;

    /**
     * $push currently logs the entire resulting array as a $set.
     *
     * TODO Log a positional $set in the array, whenever possible.
     */
    virtual Status log(LogBuilder* logBuilder) const;

private:
    // Access to each component of fieldName that's the target of this mod.
    FieldRef _fieldRef;

    // 0 or index for $-positional in _fieldRef.
    size_t _posDollar;

    // Clauses for the $push that are filled when the $each variation of the command is used.
    bool _eachMode;
    BSONElement _eachElem;
    bool _slicePresent;
    int64_t _slice;
    bool _sortPresent;
    size_t _startPosition;

    PatternElementCmp _sort;

    // Whether this mod is supposed to be parsed as a $pushAll.
    const ModifierPushMode _pushMode;

    // Simple (old style) push value when the $each variation of the command is not
    // used. The _eachMode flag would be off if we're this mode.
    BSONElement _val;

    // The instance of the field in the provided doc. This state is valid after a
    // prepare() was issued and until a log() is issued. The document this mod is
    // being prepared against must be live throughout all the calls.
    struct PreparedState;
    std::unique_ptr<PreparedState> _preparedState;
};

}  // namespace mongo