/**
 *    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.
 */

#pragma once

#include <memory>
#include <vector>

#include "mongo/base/disallow_copying.h"
#include "mongo/db/storage/storage_engine.h"
#include "mongo/platform/unordered_set.h"
#include "mongo/stdx/functional.h"
#include "mongo/util/decorable.h"

namespace mongo {

    class AbstractMessagingPort;
    class Client;
    class OperationContext;
    class OpObserver;

    /**
     * Classes that implement this interface can receive notification on killOp.
     *
     * See GlobalEnvironmentExperiment::registerKillOpListener() for more information, including
     * limitations on the lifetime of registered listeners.
     */
    class KillOpListenerInterface {
    public:
        /**
         * Will be called *after* ops have been told they should die.
         * Callback must not fail.
         */
        virtual void interrupt(unsigned opId) = 0;
        virtual void interruptAll() = 0;

    protected:
        // Should not delete through a pointer of this type
        virtual ~KillOpListenerInterface() {}
    };

    class StorageFactoriesIterator {
        MONGO_DISALLOW_COPYING(StorageFactoriesIterator);
    public:
        virtual ~StorageFactoriesIterator() { }
        virtual bool more() const = 0;
        virtual const StorageEngine::Factory* next() = 0;
    protected:
        StorageFactoriesIterator() { }
    };

    /**
     * Class representing the context of a service, such as a MongoD database service or
     * a MongoS routing service.
     *
     * A ServiceContext is the root of a hierarchy of contexts.  A ServiceContext owns
     * zero or more Clients, which in turn each own OperationContexts.
     */
    class ServiceContext : public Decorable<ServiceContext> {
        MONGO_DISALLOW_COPYING(ServiceContext);
    public:
        /**
         * Special deleter used for cleaning up Client objects owned by a ServiceContext.
         * See UniqueClient, below.
         */
        class ClientDeleter {
        public:
            void operator()(Client* client) const;
        };

        /**
         * Observer interface implemented to hook client creation and destruction.
         */
        class ClientObserver {
        public:
            virtual ~ClientObserver() = default;

            /**
             * Hook called after a new client "client" is created on "service" by
             * service->makeClient().
             *
             * For a given client and registered instance of ClientObserver, if onCreateClient
             * returns without throwing an exception, onDestroyClient will be called when "client"
             * is deleted.
             */
            virtual void onCreateClient(ServiceContext* service, Client* client) = 0;

            /**
             * Hook called on a "client" created by "service" before deleting "client".
             *
             * Like a destructor, must not throw exceptions.
             */
            virtual void onDestroyClient(ServiceContext* service, Client* client) = 0;
        };

        using ClientSet = unordered_set<Client*>;

        /**
         * Cursor for enumerating the live Client objects belonging to a ServiceContext.
         *
         * Lifetimes of this type are synchronized with client creation and destruction.
         */
        class LockedClientsCursor {
        public:
            /**
             * Constructs a cursor for enumerating the clients of "service", blocking "service" from
             * creating or destroying Client objects until this instance is destroyed.
             */
            explicit LockedClientsCursor(ServiceContext* service);

            /**
             * Returns the next client in the enumeration, or nullptr if there are no more clients.
             */
            Client* next();

        private:
            boost::unique_lock<boost::mutex> _lock;
            ClientSet::const_iterator _curr;
            ClientSet::const_iterator _end;
        };

        /**
         * This is the unique handle type for Clients created by a ServiceContext.
         */
        using UniqueClient = std::unique_ptr<Client, ClientDeleter>;

        virtual ~ServiceContext();

        /**
         * Registers an observer of lifecycle events on Clients created by this ServiceContext.
         *
         * See the ClientObserver type, above, for details.
         *
         * All calls to registerClientObserver must complete before ServiceContext
         * is used in multi-threaded operation, or is used to create clients via calls
         * to makeClient.
         */
        void registerClientObserver(std::unique_ptr<ClientObserver> observer);

        /**
         * Creates a new Client object representing a client session associated with this
         * ServiceContext.
         *
         * The "desc" string is used to set a descriptive name for the client, used in logging.
         *
         * If supplied, "p" is the communication channel used for communicating with the client.
         */
        UniqueClient makeClient(std::string desc, AbstractMessagingPort* p = nullptr);

        //
        // Storage
        //

        /**
         * Register a storage engine.  Called from a MONGO_INIT that depends on initializiation of
         * the global environment.
         * Ownership of 'factory' is transferred to global environment upon registration.
         */
        virtual void registerStorageEngine(const std::string& name,
                                           const StorageEngine::Factory* factory) = 0;

        /**
         * Returns true if "name" refers to a registered storage engine.
         */
        virtual bool isRegisteredStorageEngine(const std::string& name) = 0;

        /**
         * Produce an iterator over all registered storage engine factories.
         * Caller owns the returned object and is responsible for deleting when finished.
         *
         * Never returns nullptr.
         */
        virtual StorageFactoriesIterator* makeStorageFactoriesIterator() = 0;

        /**
         * Set the storage engine.  The engine must have been registered via registerStorageEngine.
         */
        virtual void setGlobalStorageEngine(const std::string& name) = 0;

        /**
         * Shuts down storage engine cleanly and releases any locks on mongod.lock.
         */
        virtual void shutdownGlobalStorageEngineCleanly() = 0;

        /**
         * Return the storage engine instance we're using.
         */
        virtual StorageEngine* getGlobalStorageEngine() = 0;

        //
        // Global operation management.  This may not belong here and there may be too many methods
        // here.
        //

        /**
         * Signal all OperationContext(s) that they have been killed.
         */
        virtual void setKillAllOperations() = 0;

        /**
         * Reset the operation kill state after a killAllOperations.
         * Used for testing.
         */
        virtual void unsetKillAllOperations() = 0;

        /**
         * Get the state for killing all operations.
         */
        virtual bool getKillAllOperations() = 0;

        /**
         * @param i opid of operation to kill
         * @return if operation was found 
         **/
        virtual bool killOperation(unsigned int opId) = 0;

        /**
         * Kills all operations that have a Client that is associated with an incoming user
         * connection, except for the one associated with txn.
         */
        virtual void killAllUserOperations(const OperationContext* txn) = 0;

        /**
         * Registers a listener to be notified each time an op is killed.
         *
         * listener does not become owned by the environment. As there is currently no way to
         * unregister, the listener object must outlive this ServiceContext object.
         */
        virtual void registerKillOpListener(KillOpListenerInterface* listener) = 0;

        /**
         * Returns a new OperationContext.  Caller owns pointer.
         */
        virtual OperationContext* newOpCtx() = 0;

        //
        // Global OpObserver.
        //

        /**
         * Set the OpObserver.
         */
        virtual void setOpObserver(std::unique_ptr<OpObserver> opObserver) = 0;

        /**
         * Return the OpObserver instance we're using.
         */
        virtual OpObserver* getOpObserver() = 0;

    protected:
        ServiceContext() = default;

        /**
         * Mutex used to synchronize access to mutable state of this ServiceContext instance,
         * including possibly by its subclasses.
         */
        boost::mutex _mutex;

    private:
        /**
         * Vector of registered observers.
         */
        std::vector<std::unique_ptr<ClientObserver>> _clientObservers;
        ClientSet _clients;
    };

    /**
     * Returns true if there is a global ServiceContext.
     */
    bool hasGlobalServiceContext();

    /**
     * Returns the singleton ServiceContext for this server process.
     *
     * Fatal if there is currently no global ServiceContext.
     *
     * Caller does not own pointer.
     */
    ServiceContext* getGlobalServiceContext();

    /**
     * Sets the global ServiceContext.  If 'serviceContext' is NULL, un-sets and deletes
     * the current global ServiceContext.
     *
     * Takes ownership of 'serviceContext'.
     */
    void setGlobalServiceContext(std::unique_ptr<ServiceContext>&& serviceContext);

    /**
     * Shortcut for querying the storage engine about whether it supports document-level locking.
     * If this call becomes too expensive, we could cache the value somewhere so we don't have to
     * fetch the storage engine every time.
     */
    bool supportsDocLocking();

    /**
     * Returns true if the storage engine in use is MMAPV1.
     */
    bool isMMAPV1();

    /*
     * Extracts the storageEngine bson from the CollectionOptions provided.  Loops through each
     * provided storageEngine and asks the matching registered storage engine if the
     * collection/index options are valid.  Returns an error if the collection/index options are
     * invalid.
     * If no matching registered storage engine is found, return an error.
     * Validation function 'func' must be either:
     * - &StorageEngine::Factory::validateCollectionStorageOptions; or
     * - &StorageEngine::Factory::validateIndexStorageOptions
     */
    Status validateStorageOptions(const BSONObj& storageEngineOptions,
        stdx::function<Status (const StorageEngine::Factory* const, const BSONObj&)> validateFunc);

    /*
     * Returns a BSONArray containing the names of available storage engines, or an empty
     * array if there is no global ServiceContext
     */
    BSONArray storageEngineList();

    /*
     * Appends a the list of available storage engines to a BSONObjBuilder for reporting purposes.
     */
    void appendStorageEngineList(BSONObjBuilder* result);

}  // namespace mongo