/******************************************************************************
 * This program demonstrates a significant digits rounding function.
 * 
 * Copyright © 2017 Richard Lesh.  All rights reserved.
 *****************************************************************************/

#undef NDEBUG

#include "Utils.hpp"
#include <clocale>
#include <cmath>
#include <codecvt>
#include <fmt/format.h>
#include <fmt/xchar.h>
#include <iostream>
#include <string>

std::locale utf8loc(std::locale(), new std::codecvt_utf8<wchar_t>);
using namespace Utils;
using namespace std;

double round_sig_dig(double value, int sigdigits) noexcept {
    if (value == 0.0) {
        return 0.0;
    }
    double const p = pow(10.0, sigdigits - int(floor(log10(abs(value)))) - 1);
    return floor(value * p + 0.5) / p;
}

int main(int argc, char **argv) {
    setlocale(LC_ALL, "en_US.UTF-8");
    wcout.imbue(utf8loc);
    wcin.imbue(utf8loc);

// Test with π
    for (int sd = 1; sd <= 16; ++sd) {
        wcout << fmt::format(L"π to {0:d} significant digits: {1:.16f}", sd, round_sig_dig(M_PI, sd)) << endl;
    }

// Test with ℯ
    for (int sd = 1; sd <= 16; ++sd) {
        wcout << fmt::format(L"ℯ to {0:d} significant digits: {1:.16f}", sd, round_sig_dig(M_E, sd)) << endl;
    }

// Test with 1/π
    for (int sd = 1; sd <= 16; ++sd) {
        wcout << fmt::format(L"1/π to {0:d} significant digits: {1:.16e}", sd, round_sig_dig(1.0 / M_PI, sd)) << endl;
    }

// Test with 1e-6/e
    for (int sd = 1; sd <= 16; ++sd) {
        wcout << fmt::format(L"1e-6/e to {0:d} significant digits: {1:.16e}", sd, round_sig_dig(1e-6 / M_E, sd)) << endl;
    }
    return 0;
}