/*
 *    Copyright (C) 2012 10gen 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::kControl

#include "mongo/util/fail_point.h"

#include "mongo/platform/random.h"
#include "mongo/stdx/thread.h"
#include "mongo/util/concurrency/threadlocal.h"
#include "mongo/util/log.h"
#include "mongo/util/mongoutils/str.h"
#include "mongo/util/time_support.h"

namespace mongo {
namespace {

/**
 * Type representing the per-thread PRNG used by fail-points.  Required because TSP_* macros,
 * below, only let you create one thread-specific object per type.
 */
class FailPointPRNG {
public:
    FailPointPRNG() : _prng(std::unique_ptr<SecureRandom>(SecureRandom::create())->nextInt64()) {}

    void resetSeed(int32_t seed) {
        _prng = PseudoRandom(seed);
    }

    int32_t nextPositiveInt32() {
        return _prng.nextInt32() & ~(1 << 31);
    }

private:
    PseudoRandom _prng;
};

}  // namespace


TSP_DECLARE(FailPointPRNG, failPointPrng);
TSP_DEFINE(FailPointPRNG, failPointPrng);

namespace {

int32_t prngNextPositiveInt32() {
    return failPointPrng.getMake()->nextPositiveInt32();
}

}  // namespace

void FailPoint::setThreadPRNGSeed(int32_t seed) {
    failPointPrng.getMake()->resetSeed(seed);
}

FailPoint::FailPoint() : _fpInfo(0), _mode(off), _timesOrPeriod(0) {}

void FailPoint::shouldFailCloseBlock() {
    _fpInfo.subtractAndFetch(1);
}

void FailPoint::setMode(Mode mode, ValType val, const BSONObj& extra) {
    /**
     * Outline:
     *
     * 1. Deactivates fail point to enter write-only mode
     * 2. Waits for all current readers of the fail point to finish
     * 3. Sets the new mode.
     */

    stdx::lock_guard<stdx::mutex> scoped(_modMutex);

    // Step 1
    disableFailPoint();

    // Step 2
    while (_fpInfo.load() != 0) {
        sleepmillis(50);
    }

    _mode = mode;
    _timesOrPeriod.store(val);

    _data = extra.copy();

    if (_mode != off) {
        enableFailPoint();
    }
}

const BSONObj& FailPoint::getData() const {
    return _data;
}

void FailPoint::enableFailPoint() {
    // TODO: Better to replace with a bitwise OR, once available for AU32
    ValType currentVal = _fpInfo.load();
    ValType expectedCurrentVal;
    ValType newVal;

    do {
        expectedCurrentVal = currentVal;
        newVal = expectedCurrentVal | ACTIVE_BIT;
        currentVal = _fpInfo.compareAndSwap(expectedCurrentVal, newVal);
    } while (expectedCurrentVal != currentVal);
}

void FailPoint::disableFailPoint() {
    // TODO: Better to replace with a bitwise AND, once available for AU32
    ValType currentVal = _fpInfo.load();
    ValType expectedCurrentVal;
    ValType newVal;

    do {
        expectedCurrentVal = currentVal;
        newVal = expectedCurrentVal & REF_COUNTER_MASK;
        currentVal = _fpInfo.compareAndSwap(expectedCurrentVal, newVal);
    } while (expectedCurrentVal != currentVal);
}

FailPoint::RetCode FailPoint::slowShouldFailOpenBlock() {
    ValType localFpInfo = _fpInfo.addAndFetch(1);

    if ((localFpInfo & ACTIVE_BIT) == 0) {
        return slowOff;
    }

    switch (_mode) {
        case alwaysOn:
            return slowOn;

        case random: {
            const AtomicInt32::WordType maxActivationValue = _timesOrPeriod.load();
            if (prngNextPositiveInt32() < maxActivationValue) {
                return slowOn;
            }
            return slowOff;
        }
        case nTimes: {
            AtomicInt32::WordType newVal = _timesOrPeriod.subtractAndFetch(1);

            if (newVal <= 0) {
                disableFailPoint();
            }

            return slowOn;
        }

        default:
            error() << "FailPoint Mode not supported: " << static_cast<int>(_mode);
            fassertFailed(16444);
    }
}

BSONObj FailPoint::toBSON() const {
    BSONObjBuilder builder;

    stdx::lock_guard<stdx::mutex> scoped(_modMutex);
    builder.append("mode", _mode);
    builder.append("data", _data);

    return builder.obj();
}
}