/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

#include "squid.h"
#include "StatHist.h"

#include <cmath>

/* Local functions */
static StatHistBinDumper statHistBinDumper;

namespace Math
{
hbase_f Log;
hbase_f Exp;
hbase_f Null;
};

/* low level init, higher level functions has less params */
void
StatHist::init(unsigned int newCapacity, hbase_f * val_in_, hbase_f * val_out_, double newMin, double newMax)
{
    /* check before we divide to get scale_ */
    assert(val_in_(newMax - newMin) > 0);
    min_ = newMin;
    max_ = newMax;
    capacity_ = newCapacity;
    val_in = val_in_;
    val_out = val_out_;
    bins = static_cast<bins_type *>(xcalloc(capacity_, sizeof(bins_type)));
    scale_ = capacity_ / val_in(max_ - min_);
}

StatHist::StatHist(const StatHist &src) :
    bins(nullptr),
    capacity_(src.capacity_),
    min_(src.min_),
    max_(src.max_),
    scale_(src.scale_),
    val_in(src.val_in),
    val_out(src.val_out)
{
    if (src.bins!=nullptr) {
        bins = static_cast<bins_type *>(xcalloc(src.capacity_, sizeof(bins_type)));
        memcpy(bins,src.bins,capacity_*sizeof(*bins));
    }
}

void
StatHist::count(double v)
{
    if (bins==nullptr) //do not count before initialization or after destruction
        return;
    const unsigned int bin = findBin(v);
    ++bins[bin];
}

unsigned int
StatHist::findBin(double v)
{
    v -= min_;      /* offset */

    if (v <= 0.0)       /* too small */
        return 0;

    unsigned int bin;
    double tmp_bin=floor(scale_ * val_in(v) + 0.5);

    if (tmp_bin < 0.0) // should not happen
        return 0;
    bin = static_cast <unsigned int>(tmp_bin);

    if (bin >= capacity_)   /* too big */
        bin = capacity_ - 1;

    return bin;
}

double
StatHist::val(unsigned int bin) const
{
    return val_out((double) bin / scale_) + min_;
}

double
statHistDeltaMedian(const StatHist & A, const StatHist & B)
{
    return statHistDeltaPctile(A, B, 0.5);
}

double
statHistDeltaPctile(const StatHist & A, const StatHist & B, double pctile)
{
    return A.deltaPctile(B, pctile);
}

double
StatHist::deltaPctile(const StatHist & B, double pctile) const
{
    unsigned int i;
    bins_type s1 = 0;
    bins_type h = 0;
    bins_type a = 0;
    bins_type b = 0;
    unsigned int I = 0;
    unsigned int J = capacity_;
    unsigned int K;
    double f;

    assert(capacity_ == B.capacity_);

    int *D = static_cast<int *>(xcalloc(capacity_, sizeof(int)));

    for (i = 0; i < capacity_; ++i) {
        D[i] = B.bins[i] - bins[i];
        assert(D[i] >= 0);
    }

    for (i = 0; i < capacity_; ++i)
        s1 += D[i];

    h = int(s1 * pctile);

    for (i = 0; i < capacity_; ++i) {
        J = i;
        b += D[J];

        if (a <= h && h <= b)
            break;

        I = i;

        a += D[I];
    }

    xfree(D);

    if (s1 == 0)
        return 0.0;

    if (a > h)
        return 0.0;

    if (a >= b)
        return 0.0;

    if (I >= J)
        return 0.0;

    f = (h - a) / (b - a);

    K = (unsigned int) floor(f * (double) (J - I) + I);

    return val(K);
}

static void
statHistBinDumper(StoreEntry * sentry, int idx, double val, double size, int count)
{
    if (count)
        storeAppendPrintf(sentry, "\t%3d/%f\t%d\t%f\n",
                          idx, val, count, count / size);
}

void
StatHist::dump(StoreEntry * sentry, StatHistBinDumper * bd) const
{
    double left_border = min_;

    if (!bd)
        bd = statHistBinDumper;

    for (unsigned int i = 0; i < capacity_; ++i) {
        const double right_border = val(i + 1);
        assert(right_border - left_border > 0.0);
        bd(sentry, i, left_border, right_border - left_border, bins[i]);
        left_border = right_border;
    }
}

StatHist &
StatHist::operator += (const StatHist &B)
{
    Must(capacity_ == B.capacity_);
    Must(min_ == B.min_);
    Must(max_ == B.max_);

    if (B.bins == nullptr) { // B was not yet initializted
        return *this;
    }
    if (bins == nullptr) { // this histogram was not yet initialized
        *this = B;
        return *this;
    }
    for (unsigned int i = 0; i < capacity_; ++i) {
        bins[i] += B.bins[i];
    }
    return *this;
}

/* log based histogram */
double
Math::Log(double x)
{
    assert((x + 1.0) >= 0.0);
    return log(x + 1.0);
}

double
Math::Exp(double x)
{
    return exp(x) - 1.0;
}

void
StatHist::logInit(unsigned int capacity, double min, double max)
{
    init(capacity, Math::Log, Math::Exp, min, max);
}

/* linear histogram for enums */
/* we want to be have [-1,last_enum+1] range to track out of range enums */
double
Math::Null(double x)
{
    return x;
}

void
StatHist::enumInit(unsigned int last_enum)
{
    init(last_enum + 3, Math::Null, Math::Null, -1.0, (2.0 + last_enum));
}

void
statHistEnumDumper(StoreEntry * sentry, int idx, double val, double, int count)
{
    if (count)
        storeAppendPrintf(sentry, "%2d\t %5d\t %5d\n",
                          idx, (int) val, count);
}

void
statHistIntDumper(StoreEntry * sentry, int, double val, double, int count)
{
    if (count)
        storeAppendPrintf(sentry, "%9d\t%9d\n", (int) val, count);
}

