/**
 *    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/platform/basic.h"

#include "mongo/db/exec/pipeline_proxy.h"

#include <boost/shared_ptr.hpp>

#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/expression_context.h"

namespace mongo {

    using boost::intrusive_ptr;
    using boost::shared_ptr;
    using std::vector;

    PipelineProxyStage::PipelineProxyStage(intrusive_ptr<Pipeline> pipeline,
                                           const boost::shared_ptr<PlanExecutor>& child,
                                           WorkingSet* ws)
        : _pipeline(pipeline)
        , _includeMetaData(_pipeline->getContext()->inShard) // send metadata to merger
        , _childExec(child)
        , _ws(ws)
    {}

    PlanStage::StageState PipelineProxyStage::work(WorkingSetID* out) {
        if (!out) {
            return PlanStage::FAILURE;
        }

        if (!_stash.empty()) {
            *out = _ws->allocate();
            WorkingSetMember* member = _ws->get(*out);
            member->obj = _stash.back();
            _stash.pop_back();
            member->state = WorkingSetMember::OWNED_OBJ;
            return PlanStage::ADVANCED;
        }

        if (boost::optional<BSONObj> next = getNextBson()) {
            *out = _ws->allocate();
            WorkingSetMember* member = _ws->get(*out);
            member->obj = *next;
            member->state = WorkingSetMember::OWNED_OBJ;
            return PlanStage::ADVANCED;
        }

        return PlanStage::IS_EOF;
    }

    bool PipelineProxyStage::isEOF() {
        if (!_stash.empty())
            return false;

        if (boost::optional<BSONObj> next = getNextBson()) {
            _stash.push_back(*next);
            return false;
        }

        return true;
    }

    void PipelineProxyStage::invalidate(OperationContext* txn,
                                        const RecordId& dl,
                                        InvalidationType type) {
        // propagate to child executor if still in use
        if (boost::shared_ptr<PlanExecutor> exec = _childExec.lock()) {
            exec->invalidate(txn, dl, type);
        }
    }

    void PipelineProxyStage::saveState() {
        _pipeline->getContext()->opCtx = NULL;
    }

    void PipelineProxyStage::restoreState(OperationContext* opCtx) {
        invariant(_pipeline->getContext()->opCtx == NULL);
        _pipeline->getContext()->opCtx = opCtx;
    }

    void PipelineProxyStage::pushBack(const BSONObj& obj) {
        _stash.push_back(obj);
    }

    vector<PlanStage*> PipelineProxyStage::getChildren() const {
        vector<PlanStage*> empty;
        return empty;
    }

    boost::optional<BSONObj> PipelineProxyStage::getNextBson() {
        if (boost::optional<Document> next = _pipeline->output()->getNext()) {
            if (_includeMetaData) {
                return next->toBsonWithMetaData();
            }
            else {
                return next->toBson();
            }
        }

        return boost::none;
    }

    shared_ptr<PlanExecutor> PipelineProxyStage::getChildExecutor() {
        return _childExec.lock();
    }

} // namespace mongo