// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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.

// Date 2014/09/25 17:50:21

#ifndef  BVAR_RECORDER_H

#define  BVAR_RECORDER_H

#include <stdint.h>                              // int64_t uint64_t

#include "butil/macros.h"                         // BAIDU_CASSERT

#include "butil/logging.h"                        // LOG

#include "bvar/detail/combiner.h"                // detail::AgentCombiner

#include "bvar/variable.h"

#include "bvar/window.h"

#include "bvar/detail/sampler.h"

namespace bvar {

struct Stat {

    Stat() : sum(0), num(0) {}

    Stat(int64_t sum2, int64_t num2) : sum(sum2), num(num2) {}

    int64_t sum;

    int64_t num;

    int64_t get_average_int() const {

        //num can be changed by sampling thread, use tmp_num

        int64_t tmp_num = num;

        if (tmp_num == 0) {

            return 0;

        }

        return sum / (int64_t)tmp_num;

    }

    double get_average_double() const {

        int64_t tmp_num = num;

        if (tmp_num == 0) {

            return 0.0;

        }

        return (double)sum / (double)tmp_num;

    }

    Stat operator-(const Stat& rhs) const {

        return Stat(sum - rhs.sum, num - rhs.num);

    }

    void operator-=(const Stat& rhs) {

        sum -= rhs.sum;

        num -= rhs.num;

    }

    Stat operator+(const Stat& rhs) const {

        return Stat(sum + rhs.sum, num + rhs.num);

    }

    void operator+=(const Stat& rhs) {

        sum += rhs.sum;

        num += rhs.num;

    }

};

inline std::ostream& operator<<(std::ostream& os, const Stat& s) {

    const int64_t v = s.get_average_int();

    if (v != 0) {

        return os << v;

    } else {

        return os << s.get_average_double();

    }

}

// For calculating average of numbers.

// Example:

//   IntRecorder latency;

//   latency << 1 << 3 << 5;

//   CHECK_EQ(3, latency.average());

class IntRecorder : public Variable {

public:

    // Compressing format:

    // | 20 bits (unsigned) | sign bit | 43 bits |

    //       num                   sum

    const static size_t SUM_BIT_WIDTH=44;

    const static uint64_t MAX_SUM_PER_THREAD = (1ul << SUM_BIT_WIDTH) - 1;

    const static uint64_t MAX_NUM_PER_THREAD = (1ul << (64ul - SUM_BIT_WIDTH)) - 1;

    BAIDU_CASSERT(SUM_BIT_WIDTH > 32 && SUM_BIT_WIDTH < 64, 

                  SUM_BIT_WIDTH_must_be_between_33_and_63);

    struct AddStat {

        void operator()(Stat& s1, const Stat& s2) const { s1 += s2; }

    };

    struct MinusStat {

        void operator()(Stat& s1, const Stat& s2) const { s1 -= s2; }

    };    

    typedef Stat value_type;

    typedef detail::ReducerSampler<IntRecorder, Stat,

                                   AddStat, MinusStat> sampler_type;

    typedef Stat SampleSet;

    struct AddToStat {

        void operator()(Stat& lhs, uint64_t rhs) const {

            lhs.sum += _extend_sign_bit(_get_sum(rhs));

            lhs.num += _get_num(rhs);

        }

    };

    typedef detail::AgentCombiner<Stat, uint64_t, AddToStat> combiner_type;

    typedef combiner_type::Agent agent_type;

    IntRecorder() : _sampler(NULL) {}

    explicit IntRecorder(const butil::StringPiece& name) : _sampler(NULL) {

        expose(name);

    }

    IntRecorder(const butil::StringPiece& prefix, const butil::StringPiece& name)

        : _sampler(NULL) {

        expose_as(prefix, name);

    }

    ~IntRecorder() {

        hide();

        if (_sampler) {

            _sampler->destroy();

            _sampler = NULL;

        }

    }

    // Note: The input type is acutally int. Use int64_t to check overflow.

    IntRecorder& operator<<(int64_t/*note*/ sample);

    int64_t average() const {

        return _combiner.combine_agents().get_average_int();

    }

    double average(double) const {

        return _combiner.combine_agents().get_average_double();

    }

    Stat get_value() const {

        return _combiner.combine_agents();

    }

    Stat reset() {

        return _combiner.reset_all_agents();

    }

    AddStat op() const { return AddStat(); }

    MinusStat inv_op() const { return MinusStat(); }

    void describe(std::ostream& os, bool /*quote_string*/) const override {

        os << get_value();

    }

    bool valid() const { return _combiner.valid(); }

    sampler_type* get_sampler() {

        if (NULL == _sampler) {

            _sampler = new sampler_type(this);

            _sampler->schedule();

        }

        return _sampler;

    }

    // This name is useful for printing overflow log in operator<< since

    // IntRecorder is often used as the source of data and not exposed.

    void set_debug_name(const butil::StringPiece& name) {

        _debug_name.assign(name.data(), name.size());

    }

private:

    // TODO: The following numeric functions should be independent utils

    static uint64_t _get_sum(const uint64_t n) {

        return (n & MAX_SUM_PER_THREAD);

    }

    static uint64_t _get_num(const uint64_t n) {

        return n >> SUM_BIT_WIDTH;

    }

    // Fill all the first (64 - SUM_BIT_WIDTH + 1) bits with 1 if the sign bit is 1 

    // to represent a complete 64-bit negative number

    // Check out http://en.wikipedia.org/wiki/Signed_number_representations if

    // you are confused

    static int64_t _extend_sign_bit(const uint64_t sum) {

        return (((1ul << (64ul - SUM_BIT_WIDTH + 1)) - 1) 

               * ((1ul << (SUM_BIT_WIDTH - 1) & sum)))

               | (int64_t)sum;

    }

    // Convert complement into a |SUM_BIT_WIDTH|-bit unsigned integer

    static uint64_t _get_complement(int64_t n) {

        return n & (MAX_SUM_PER_THREAD);

    }

    static uint64_t _compress(const uint64_t num, const uint64_t sum) {

        return (num << SUM_BIT_WIDTH) 

               // There is a redundant '1' in the front of sum which was

               // combined with two negative number, so truncation has to be 

               // done here

               | (sum & MAX_SUM_PER_THREAD)

               ;

    }

    // Check whether the sum of the two integer overflows the range of signed

    // integer with the width of SUM_BIT_WIDTH, which is 

    // [-2^(SUM_BIT_WIDTH -1), 2^(SUM_BIT_WIDTH -1) - 1) (eg. [-128, 127) for

    // signed 8-bit integer)

    static bool _will_overflow(const int64_t lhs, const int rhs) {

        return 

            // Both integers are positive and the sum is larger than the largest

            // number

            ((lhs > 0) && (rhs > 0) 

                && (lhs + rhs > ((int64_t)MAX_SUM_PER_THREAD >> 1)))

            // Or both integers are negative and the sum is less than the lowest

            // number

            || ((lhs < 0) && (rhs < 0) 

                    && (lhs + rhs < (-((int64_t)MAX_SUM_PER_THREAD >> 1)) - 1))

            // otherwise the sum cannot overflow iff lhs does not overflow

            // because |sum| < |lhs| 

            ;

    }

private:

    combiner_type           _combiner;

    sampler_type*           _sampler;

    std::string             _debug_name;

};

inline IntRecorder& IntRecorder::operator<<(int64_t sample) {

    if (BAIDU_UNLIKELY((int64_t)(int)sample != sample)) {

        const char* reason = NULL;

        if (sample > std::numeric_limits<int>::max()) {

            reason = "overflows";

            sample = std::numeric_limits<int>::max();

        } else {

            reason = "underflows";

            sample = std::numeric_limits<int>::min();

        }

        // Truncate to be max or min of int. We're using 44 bits to store the

        // sum thus following aggregations are not likely to be over/underflow.

        if (!name().empty()) {

            LOG(WARNING) << "Input=" << sample << " to `" << name()

                       << "\' " << reason;

        } else if (!_debug_name.empty()) {

            LOG(WARNING) << "Input=" << sample << " to `" << _debug_name

                       << "\' " << reason;

        } else {

            LOG(WARNING) << "Input=" << sample << " to IntRecorder("

                       << (void*)this << ") " << reason;

        }

    }

    agent_type* agent = _combiner.get_or_create_tls_agent();

    if (BAIDU_UNLIKELY(!agent)) {

        LOG(FATAL) << "Fail to create agent";

        return *this;

    }

    uint64_t n;

    agent->element.load(&n);

    const uint64_t complement = _get_complement(sample);

    uint64_t num;

    uint64_t sum;

    do {

        num = _get_num(n);

        sum = _get_sum(n);

        if (BAIDU_UNLIKELY((num + 1 > MAX_NUM_PER_THREAD) ||

                           _will_overflow(_extend_sign_bit(sum), sample))) {

            // Although agent->element might have been cleared at this 

            // point, it is just OK because the very value is 0 in

            // this case

            agent->combiner->commit_and_clear(agent);

            sum = 0;

            num = 0;

            n = 0;

        }

    } while (!agent->element.compare_exchange_weak(

                 n, _compress(num + 1, sum + complement)));

    return *this;

}

}  // namespace bvar

#endif  //BVAR_RECORDER_H