/*
 *    Copyright (C) 2010 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <string>

#include <boost/shared_ptr.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>
#include <pcrecpp.h>

#include "mongo/bson/util/atomic_int.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/jsobj.h"
#include "mongo/util/timer.h"

namespace mongo {

    /**
     * Configuration object describing a bench run activity.
     */
    class BenchRunConfig : private boost::noncopyable {
    public:

        /**
         * Create a new BenchRunConfig object, and initialize it from the BSON
         * document, "args".
         *
         * Caller owns the returned object, and is responsible for its deletion.
         */
        static BenchRunConfig *createFromBson( const BSONObj &args );

        BenchRunConfig();

        void initializeFromBson( const BSONObj &args );

        // Create a new connection to the mongo instance specified by this configuration.
        DBClientBase *createConnection() const;

        /**
         * Connection string describing the host to which to connect.
         */
        std::string host;

        /**
         * Name of the database on which to operate.
         */
        std::string db;

        /**
         * Optional username for authenticating to the database.
         */
        std::string username;

        /**
         * Optional password for authenticating to the database.
         *
         * Only useful if username is non-empty.
         */
        std::string password;

        /**
         * Number of parallel threads to perform the bench run activity.
         */
        unsigned parallel;

        /**
         * Desired duration of the bench run activity, in seconds.
         *
         * NOTE: Only used by the javascript benchRun() and benchRunSync() functions.
         */
        double seconds;

        bool hideResults;
        bool handleErrors;
        bool hideErrors;

        boost::shared_ptr< pcrecpp::RE > trapPattern;
        boost::shared_ptr< pcrecpp::RE > noTrapPattern;
        boost::shared_ptr< pcrecpp::RE > watchPattern;
        boost::shared_ptr< pcrecpp::RE > noWatchPattern;

        /**
         * Operation description.  A BSON array of objects, each describing a single
         * operation.
         *
         * Every thread in a benchRun job will perform these operations in sequence, restarting at
         * the beginning when the end is reached, until the job is stopped.
         *
         * TODO: Document the operation objects.
         *
         * TODO: Introduce support for performing each operation exactly N times.
         */
        BSONObj ops;

        bool throwGLE;
        bool breakOnTrap;

    private:
        /// Initialize a config object to its default values.
        void initializeToDefaults();
    };

    /**
     * An event counter for events that have an associated duration.
     *
     * Not thread safe.  Expected use is one instance per thread during parallel execution.
     */
    class BenchRunEventCounter : private boost::noncopyable {
    public:
        /// Constructs a zeroed out counter.
        BenchRunEventCounter();
        ~BenchRunEventCounter();

        /**
         * Zero out the counter.
         */
        void reset();

        /**
         * Conceptually the equivalent of "+=".  Adds "other" into this.
         */
        void updateFrom( const BenchRunEventCounter &other );

        /**
         * Count one instance of the event, which took "timeMicros" microseconds.
         */
        void countOne(unsigned long long timeMicros) {
            ++_numEvents;
            _totalTimeMicros += timeMicros;
        }

        /**
         * Get the total number of microseconds ellapsed during all observed events.
         */
        unsigned long long getTotalTimeMicros() const { return _totalTimeMicros; }

        /**
         * Get the number of observed events.
         */
        unsigned long long getNumEvents() const { return _numEvents; }

    private:
        unsigned long long _numEvents;
        unsigned long long _totalTimeMicros;
    };

    /**
     * RAII object for tracing an event.
     *
     * Construct an instance of this at the beginning of an event, and have it go out of scope at
     * the end, to facilitate tracking events.
     *
     * This type can be used to separately count failures and successes by passing two event
     * counters to the BenchRunEventCounter constructor, and calling "succeed()" on the object at
     * the end of a successful event.  If an exception is thrown, the fail counter will receive the
     * event, and otherwise, the succes counter will.
     *
     * In all cases, the counter objects must outlive the trace object.
     */
    class BenchRunEventTrace : private boost::noncopyable {
    public:
        explicit BenchRunEventTrace(BenchRunEventCounter *eventCounter) {
            initialize(eventCounter, eventCounter, false);
        }

        BenchRunEventTrace(BenchRunEventCounter *successCounter,
                           BenchRunEventCounter *failCounter,
                           bool defaultToFailure=true) {
            initialize(successCounter, failCounter, defaultToFailure);
        }

        ~BenchRunEventTrace() {
            (_succeeded ? _successCounter : _failCounter)->countOne(_timer.micros());
        }

        void succeed() { _succeeded = true; }
        void fail() { _succeeded = false; }

    private:
        void initialize(BenchRunEventCounter *successCounter,
                        BenchRunEventCounter *failCounter,
                        bool defaultToFailure) {
            _successCounter = successCounter;
            _failCounter = failCounter;
            _succeeded = !defaultToFailure;
        }

        Timer _timer;
        BenchRunEventCounter *_successCounter;
        BenchRunEventCounter *_failCounter;
        bool _succeeded;
    };

    /**
     * Statistics object representing the result of a bench run activity.
     */
    class BenchRunStats : private boost::noncopyable {
    public:
        BenchRunStats();
        ~BenchRunStats();

        void reset();

        void updateFrom( const BenchRunStats &other );

        bool error;
        unsigned long long errCount;

        BenchRunEventCounter findOneCounter;
        BenchRunEventCounter updateCounter;
        BenchRunEventCounter insertCounter;
        BenchRunEventCounter deleteCounter;
        BenchRunEventCounter queryCounter;

        std::map<std::string, long long> opcounters;
        std::vector<BSONObj> trappedErrors;
    };

    /**
     * State of a BenchRun activity.
     *
     * Logically, the states are "starting up", "running" and "finished."
     */
    class BenchRunState : private boost::noncopyable {
    public:
        enum State { BRS_STARTING_UP, BRS_RUNNING, BRS_FINISHED };

        explicit BenchRunState(unsigned numWorkers);
        ~BenchRunState();

        //
        // Functions called by the job-controlling thread, through an instance of BenchRunner.
        //

        /**
         * Block until the current state is "awaitedState."
         *
         * massert() (uassert()?) if "awaitedState" is unreachable from
         * the current state.
         */
        void waitForState(State awaitedState);

        /**
         * Notify the worker threads to wrap up.  Does not block.
         */
        void tellWorkersToFinish();

        /// Check that the current state is BRS_FINISHED.
        void assertFinished();

        //
        // Functions called by the worker threads, through instances of BenchRunWorker.
        //

        /**
         * Predicate that workers call to see if they should finish (as a result of a call
         * to tellWorkersToFinish()).
         */
        bool shouldWorkerFinish();

        /**
         * Called by each BenchRunWorker from within its thread context, immediately before it
         * starts sending requests to the configured mongo instance.
         */
        void onWorkerStarted();

        /**
         * Called by each BenchRunWorker from within its thread context, shortly after it finishes
         * sending requests to the configured mongo instance.
         */
        void onWorkerFinished();

    private:
        boost::mutex _mutex;
        boost::condition _stateChangeCondition;
        unsigned _numUnstartedWorkers;
        unsigned _numActiveWorkers;
        AtomicUInt _isShuttingDown;
    };

    /**
     * A single worker in the bench run activity.
     *
     * Represents the behavior of one thread working in a bench run activity.
     */
    class BenchRunWorker : private boost::noncopyable {
    public:

        /**
         * Create a new worker, performing one thread's worth of the activity described in
         * "config", and part of the larger activity with state "brState".  Both "config"
         * and "brState" must exist for the life of this object.
         *
         * "id" is a positive integer which should uniquely identify the worker.
         */
        BenchRunWorker(size_t id, const BenchRunConfig *config, BenchRunState *brState);
        ~BenchRunWorker();

        /**
         * Start performing the "work" behavior in a new thread.
         */
        void start();

        /**
         * Get the run statistics for a worker.
         *
         * Should only be observed _after_ the worker has signaled its completion by calling
         * onWorkerFinished() on the BenchRunState passed into its constructor.
         */
        const BenchRunStats &stats() const { return _stats; }

    private:
        /// The main method of the worker, executed inside the thread launched by start().
        void run();

        /// The function that actually sets about generating the load described in "_config".
        void generateLoadOnConnection( DBClientBase *conn );

        /// Predicate, used to decide whether or not it's time to terminate the worker.
        bool shouldStop() const;

        size_t _id;
        const BenchRunConfig *_config;
        BenchRunState *_brState;
        BenchRunStats _stats;
    };

    /**
     * Object representing a "bench run" activity.
     */
    class BenchRunner : private boost::noncopyable {
    public:
        /**
         * Utility method to create a new bench runner from a BSONObj representation
         * of a configuration.
         *
         * TODO: This is only really for the use of the javascript benchRun() methods,
         * and should probably move out of the BenchRunner class.
         */
        static BenchRunner* createWithConfig( const BSONObj &configArgs );

        /**
         * Look up a bench runner object by OID.
         *
         * TODO: Same todo as for "createWithConfig".
         */
        static BenchRunner* get( OID oid );

        /**
         * Stop a running "runner", and return a BSON representation of its resultant
         * BenchRunStats.
         *
         * TODO: Same as for "createWithConfig".
         */
        static BSONObj finish( BenchRunner* runner );

        /**
         * Create a new bench runner, to perform the activity described by "*config."
         *
         * Takes ownership of "config", and will delete it.
         */
        explicit BenchRunner( BenchRunConfig *config );
        ~BenchRunner();

        /**
         * Start the activity.  Only call once per instance of BenchRunner.
         */
        void start();

        /**
         * Stop the activity.  Block until the activitiy has stopped.
         */
        void stop();

        /**
         * Store the collected event data from a completed bench run activity into "stats."
         *
         * Illegal to call until after stop() returns.
         */
        void populateStats(BenchRunStats *stats);

        OID oid() const { return _oid; }

        const BenchRunConfig &config() const { return *_config; } // TODO: Remove this function.

        // JS bindings
        static BSONObj benchFinish(const BSONObj& argsFake, void* data);
        static BSONObj benchStart(const BSONObj& argsFake, void* data);
        static BSONObj benchRunSync(const BSONObj& argsFake, void* data);

    private:
        // TODO: Same as for createWithConfig.
        static boost::mutex _staticMutex;
        static map< OID, BenchRunner* > _activeRuns;

        OID _oid;
        BenchRunState _brState;
        boost::scoped_ptr<BenchRunConfig> _config;
        vector<BenchRunWorker *> _workers;

        BSONObj before;
        BSONObj after;
    };

}  // namespace mongo
