/**
 *    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.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kWrite

#include "mongo/platform/basic.h"

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

#include "mongo/db/catalog/collection.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/service_context.h"
#include "mongo/db/op_observer.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/repl/replication_coordinator_global.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"

namespace mongo {

using std::unique_ptr;
using std::vector;

// static
const char* DeleteStage::kStageType = "DELETE";

DeleteStage::DeleteStage(OperationContext* txn,
                         const DeleteStageParams& params,
                         WorkingSet* ws,
                         Collection* collection,
                         PlanStage* child)
    : _txn(txn),
      _params(params),
      _ws(ws),
      _collection(collection),
      _child(child),
      _idRetrying(WorkingSet::INVALID_ID),
      _idReturning(WorkingSet::INVALID_ID),
      _commonStats(kStageType) {}

DeleteStage::~DeleteStage() {}

bool DeleteStage::isEOF() {
    if (!_collection) {
        return true;
    }
    if (!_params.isMulti && _specificStats.docsDeleted > 0) {
        return true;
    }
    return _idRetrying == WorkingSet::INVALID_ID && _idReturning == WorkingSet::INVALID_ID &&
        _child->isEOF();
}

PlanStage::StageState DeleteStage::work(WorkingSetID* out) {
    ++_commonStats.works;

    // Adds the amount of time taken by work() to executionTimeMillis.
    ScopedTimer timer(&_commonStats.executionTimeMillis);

    if (isEOF()) {
        return PlanStage::IS_EOF;
    }
    invariant(_collection);  // If isEOF() returns false, we must have a collection.

    // It is possible that after a delete was executed, a WriteConflictException occurred
    // and prevented us from returning ADVANCED with the old version of the document.
    if (_idReturning != WorkingSet::INVALID_ID) {
        // We should only get here if we were trying to return something before.
        invariant(_params.returnDeleted);

        WorkingSetMember* member = _ws->get(_idReturning);
        invariant(member->state == WorkingSetMember::OWNED_OBJ);

        *out = _idReturning;
        _idReturning = WorkingSet::INVALID_ID;
        ++_commonStats.advanced;
        return PlanStage::ADVANCED;
    }

    // Either retry the last WSM we worked on or get a new one from our child.
    WorkingSetID id;
    StageState status;
    if (_idRetrying == WorkingSet::INVALID_ID) {
        status = _child->work(&id);
    } else {
        status = ADVANCED;
        id = _idRetrying;
        _idRetrying = WorkingSet::INVALID_ID;
    }

    if (PlanStage::ADVANCED == status) {
        WorkingSetMember* member = _ws->get(id);

        // We want to free this member when we return, unless we need to retry it.
        ScopeGuard memberFreer = MakeGuard(&WorkingSet::free, _ws, id);

        if (!member->hasLoc()) {
            // We expect to be here because of an invalidation causing a force-fetch, and
            // doc-locking storage engines do not issue invalidations.
            ++_specificStats.nInvalidateSkips;
            ++_commonStats.needTime;
            return PlanStage::NEED_TIME;
        }
        RecordId rloc = member->loc;
        // Deletes can't have projections. This means that covering analysis will always add
        // a fetch. We should always get fetched data, and never just key data.
        invariant(member->hasObj());

        try {
            // If the snapshot changed, then we have to make sure we have the latest copy of the
            // doc and that it still matches.
            std::unique_ptr<RecordCursor> cursor;
            if (_txn->recoveryUnit()->getSnapshotId() != member->obj.snapshotId()) {
                cursor = _collection->getCursor(_txn);
                if (!WorkingSetCommon::fetch(_txn, member, cursor)) {
                    // Doc is already deleted. Nothing more to do.
                    ++_commonStats.needTime;
                    return PlanStage::NEED_TIME;
                }

                // Make sure the re-fetched doc still matches the predicate.
                if (_params.canonicalQuery &&
                    !_params.canonicalQuery->root()->matchesBSON(member->obj.value(), NULL)) {
                    // Doesn't match.
                    ++_commonStats.needTime;
                    return PlanStage::NEED_TIME;
                }
            }

            // TODO: Do we want to buffer docs and delete them in a group rather than
            // saving/restoring state repeatedly?

            try {
                _child->saveState();
                if (supportsDocLocking()) {
                    // Doc-locking engines require this after saveState() since they don't use
                    // invalidations.
                    WorkingSetCommon::prepareForSnapshotChange(_ws);
                }
            } catch (const WriteConflictException& wce) {
                std::terminate();
            }

            if (_params.returnDeleted) {
                // Save a copy of the document that is about to get deleted.
                BSONObj deletedDoc = member->obj.value();
                member->obj.setValue(deletedDoc.getOwned());
                member->loc = RecordId();
                member->state = WorkingSetMember::OWNED_OBJ;
            }

            // Do the write, unless this is an explain.
            if (!_params.isExplain) {
                WriteUnitOfWork wunit(_txn);

                const bool deleteCappedOK = false;
                const bool deleteNoWarn = false;
                BSONObj deletedId;

                _collection->deleteDocument(_txn,
                                            rloc,
                                            deleteCappedOK,
                                            deleteNoWarn,
                                            _params.shouldCallLogOp ? &deletedId : NULL);

                wunit.commit();
            }

            ++_specificStats.docsDeleted;
        } catch (const WriteConflictException& wce) {
            _idRetrying = id;
            memberFreer.Dismiss();  // Keep this member around so we can retry deleting it.
            *out = WorkingSet::INVALID_ID;
            _commonStats.needYield++;
            return NEED_YIELD;
        }

        //  As restoreState may restore (recreate) cursors, cursors are tied to the
        //  transaction in which they are created, and a WriteUnitOfWork is a
        //  transaction, make sure to restore the state outside of the WritUnitOfWork.
        try {
            _child->restoreState(_txn);
        } catch (const WriteConflictException& wce) {
            // Note we don't need to retry anything in this case since the delete already
            // was committed. However, we still need to return the deleted document
            // (if it was requested).
            if (_params.returnDeleted) {
                // member->obj should refer to the deleted document.
                invariant(member->state == WorkingSetMember::OWNED_OBJ);

                _idReturning = id;
                // Keep this member around so that we can return it on the next work() call.
                memberFreer.Dismiss();
            }
            *out = WorkingSet::INVALID_ID;
            _commonStats.needYield++;
            return NEED_YIELD;
        }

        if (_params.returnDeleted) {
            // member->obj should refer to the deleted document.
            invariant(member->state == WorkingSetMember::OWNED_OBJ);

            memberFreer.Dismiss();  // Keep this member around so we can return it.
            *out = id;
            ++_commonStats.advanced;
            return PlanStage::ADVANCED;
        }

        ++_commonStats.needTime;
        return PlanStage::NEED_TIME;
    } else if (PlanStage::FAILURE == status || PlanStage::DEAD == status) {
        *out = id;
        // If a stage fails, it may create a status WSM to indicate why it failed, in which case
        // 'id' is valid.  If ID is invalid, we create our own error message.
        if (WorkingSet::INVALID_ID == id) {
            const std::string errmsg = "delete stage failed to read in results from child";
            *out = WorkingSetCommon::allocateStatusMember(
                _ws, Status(ErrorCodes::InternalError, errmsg));
        }
        return status;
    } else if (PlanStage::NEED_TIME == status) {
        ++_commonStats.needTime;
    } else if (PlanStage::NEED_YIELD == status) {
        *out = id;
        ++_commonStats.needYield;
    }

    return status;
}

void DeleteStage::saveState() {
    _txn = NULL;
    ++_commonStats.yields;
    _child->saveState();
}

void DeleteStage::restoreState(OperationContext* opCtx) {
    invariant(_txn == NULL);
    _txn = opCtx;
    ++_commonStats.unyields;
    _child->restoreState(opCtx);

    const NamespaceString& ns(_collection->ns());
    massert(28537,
            str::stream() << "Demoted from primary while removing from " << ns.ns(),
            !_params.shouldCallLogOp ||
                repl::getGlobalReplicationCoordinator()->canAcceptWritesFor(ns));
}

void DeleteStage::invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) {
    ++_commonStats.invalidates;
    _child->invalidate(txn, dl, type);
}

vector<PlanStage*> DeleteStage::getChildren() const {
    vector<PlanStage*> children;
    children.push_back(_child.get());
    return children;
}

PlanStageStats* DeleteStage::getStats() {
    _commonStats.isEOF = isEOF();
    unique_ptr<PlanStageStats> ret(new PlanStageStats(_commonStats, STAGE_DELETE));
    ret->specific.reset(new DeleteStats(_specificStats));
    ret->children.push_back(_child->getStats());
    return ret.release();
}

const CommonStats* DeleteStage::getCommonStats() const {
    return &_commonStats;
}

const SpecificStats* DeleteStage::getSpecificStats() const {
    return &_specificStats;
}

// static
long long DeleteStage::getNumDeleted(PlanExecutor* exec) {
    invariant(exec->getRootStage()->isEOF());
    invariant(exec->getRootStage()->stageType() == STAGE_DELETE);
    DeleteStage* deleteStage = static_cast<DeleteStage*>(exec->getRootStage());
    const DeleteStats* deleteStats =
        static_cast<const DeleteStats*>(deleteStage->getSpecificStats());
    return deleteStats->docsDeleted;
}

}  // namespace mongo