/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kCommand

#include "mongo/platform/basic.h"

#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/collection_validation.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/query/internal_plans.h"
#include "mongo/db/storage/durable_catalog.h"
#include "mongo/db/storage/record_store.h"
#include "mongo/logv2/log.h"
#include "mongo/util/fail_point.h"
#include "mongo/util/scopeguard.h"

namespace mongo {

// Sets the 'valid' result field to false and returns immediately.
MONGO_FAIL_POINT_DEFINE(validateCmdCollectionNotValid);

namespace {

// Protects the state below.
Mutex _validationMutex;

// Holds the set of full `databaseName.collectionName` namespace strings in progress. Validation
// commands register themselves in this data structure so that subsequent commands on the same
// namespace will wait rather than run in parallel.
std::set<std::string> _validationsInProgress;

// This is waited upon if there is found to already be a validation command running on the targeted
// namespace, as _validationsInProgress would indicate. This is signaled when a validation command
// finishes on any namespace.
stdx::condition_variable _validationNotifier;

}  // namespace

/**
 * Example validate command:
 *   {
 *       validate: "collectionNameWithoutTheDBPart",
 *       full: <bool>  // If true, a more thorough (and slower) collection validation is performed.
 *       background: <bool>  // If true, performs validation on the checkpoint of the collection.
 *   }
 */
class ValidateCmd : public BasicCommand {
public:
    ValidateCmd() : BasicCommand("validate") {}

    AllowedOnSecondary secondaryAllowed(ServiceContext*) const override {
        return AllowedOnSecondary::kAlways;
    }

    std::string help() const override {
        return str::stream() << "Validate contents of a namespace by scanning its data structures "
                             << "for correctness.\nThis is a slow operation.\n"
                             << "\tAdd {full: true} option to do a more thorough check.\n"
                             << "\tAdd {background: true} to validate in the background.\n"
                             << "\tAdd {repair: true} to run repair mode.\n"
                             << "Cannot specify both {full: true, background: true}.";
    }

    virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
        return false;
    }

    bool allowsAfterClusterTime(const BSONObj& cmd) const override {
        return false;
    }

    bool canIgnorePrepareConflicts() const override {
        return false;
    }

    bool maintenanceOk() const override {
        return false;
    }

    virtual void addRequiredPrivileges(const std::string& dbname,
                                       const BSONObj& cmdObj,
                                       std::vector<Privilege>* out) const {
        ActionSet actions;
        actions.addAction(ActionType::validate);
        out->push_back(Privilege(parseResourcePattern(dbname, cmdObj), actions));
    }

    bool run(OperationContext* opCtx,
             const std::string& dbname,
             const BSONObj& cmdObj,
             BSONObjBuilder& result) {
        if (MONGO_unlikely(validateCmdCollectionNotValid.shouldFail())) {
            result.appendBool("valid", false);
            return true;
        }

        const NamespaceString nss(CommandHelpers::parseNsCollectionRequired(dbname, cmdObj));
        bool background = cmdObj["background"].trueValue();

        // Background validation is not supported on the ephemeralForTest storage engine due to its
        // lack of support for timestamps. Switch the mode to foreground validation instead.
        if (background && storageGlobalParams.engine == "ephemeralForTest") {
            LOGV2(4775400,
                  "ephemeralForTest does not support background validation, switching to "
                  "foreground validation");
            background = false;
        }

        const bool fullValidate = cmdObj["full"].trueValue();
        if (background && fullValidate) {
            uasserted(ErrorCodes::CommandNotSupported,
                      str::stream() << "Running the validate command with both { background: true }"
                                    << " and { full: true } is not supported.");
        }

        const bool enforceFastCount = cmdObj["enforceFastCount"].trueValue();
        if (background && enforceFastCount) {
            uasserted(ErrorCodes::CommandNotSupported,
                      str::stream() << "Running the validate command with both { background: true }"
                                    << " and { enforceFastCount: true } is not supported.");
        }

        const bool repair = cmdObj["repair"].trueValue();
        if (background && repair) {
            uasserted(ErrorCodes::CommandNotSupported,
                      str::stream() << "Running the validate command with both {background: true }"
                                    << " and { repair: true } is not supported.");
        }
        if (enforceFastCount && repair) {
            uasserted(ErrorCodes::CommandNotSupported,
                      str::stream()
                          << "Running the validate command with both {enforceFastCount: true }"
                          << " and { repair: true } is not supported.");
        }
        repl::ReplicationCoordinator* replCoord = repl::ReplicationCoordinator::get(opCtx);
        if (repair && replCoord->isReplEnabled()) {
            uasserted(ErrorCodes::CommandNotSupported,
                      str::stream()
                          << "Running the validate command with { repair: true } can only be"
                          << " performed in standalone mode.");
        }

        if (!serverGlobalParams.quiet.load()) {
            LOGV2(20514,
                  "CMD: validate",
                  "namespace"_attr = nss,
                  "background"_attr = background,
                  "full"_attr = fullValidate,
                  "enforceFastCount"_attr = enforceFastCount,
                  "repair"_attr = repair);
        }

        // Only one validation per collection can be in progress, the rest wait.
        {
            stdx::unique_lock<Latch> lock(_validationMutex);
            try {
                opCtx->waitForConditionOrInterrupt(_validationNotifier, lock, [&] {
                    return _validationsInProgress.find(nss.ns()) == _validationsInProgress.end();
                });
            } catch (AssertionException& e) {
                CommandHelpers::appendCommandStatusNoThrow(
                    result,
                    {ErrorCodes::CommandFailed,
                     str::stream() << "Exception thrown during validation: " << e.toString()});
                return false;
            }

            _validationsInProgress.insert(nss.ns());
        }

        ON_BLOCK_EXIT([&] {
            stdx::lock_guard<Latch> lock(_validationMutex);
            _validationsInProgress.erase(nss.ns());
            _validationNotifier.notify_all();
        });

        auto mode = [&] {
            if (background)
                return CollectionValidation::ValidateMode::kBackground;
            if (enforceFastCount)
                return CollectionValidation::ValidateMode::kForegroundFullEnforceFastCount;
            if (fullValidate)
                return CollectionValidation::ValidateMode::kForegroundFull;
            return CollectionValidation::ValidateMode::kForeground;
        }();

        auto repairMode = [&] {
            switch (mode) {
                case CollectionValidation::ValidateMode::kForeground:
                case CollectionValidation::ValidateMode::kForegroundFull:
                case CollectionValidation::ValidateMode::kForegroundFullIndexOnly:
                    // Foreground validation may not repair data while running as a replica set node
                    // because we do not have timestamps that are required to perform writes.
                    if (replCoord->isReplEnabled()) {
                        return CollectionValidation::RepairMode::kNone;
                    }
                    if (repair) {
                        return CollectionValidation::RepairMode::kFixErrors;
                    }
                    // Foreground validation will adjust multikey metadata by default.
                    return CollectionValidation::RepairMode::kAdjustMultikey;
                default:
                    return CollectionValidation::RepairMode::kNone;
            }
        }();

        if (repair) {
            opCtx->recoveryUnit()->setPrepareConflictBehavior(
                PrepareConflictBehavior::kIgnoreConflictsAllowWrites);
        }

        ValidateResults validateResults;
        Status status =
            CollectionValidation::validate(opCtx, nss, mode, repairMode, &validateResults, &result);
        if (!status.isOK()) {
            return CommandHelpers::appendCommandStatusNoThrow(result, status);
        }

        validateResults.appendToResultObj(&result, /*debugging=*/false);

        if (!validateResults.valid) {
            result.append("advice",
                          "A corrupt namespace has been detected. See "
                          "http://dochub.mongodb.org/core/data-recovery for recovery steps.");
        }

        return true;
    }

} validateCmd;
}  // namespace mongo