cpuspark

#if 0
g++ -std=c++11 -o bin/cpuspark $0
exit
#endif

// #include <unicode/utf8.h>
#include <sys/sysinfo.h>
#include <sys/stat.h>
#include <unistd.h>
#include <cstring>
#include <thread>
#include <vector>
#include <fstream>
#include <iostream>
#include <algorithm>

const std::vector<const char*> bars = { "▁", "▂", "▃", "▄", "▅", "▆", "▇", "█" };

const std::size_t HISTORY_LEN = 6;

int main()
{
    auto term = getenv("TERM");
    if ( term && !strcmp(term, "linux") && (!getenv("DISPLAY") || !getenv("WINDOWID")) )
        return 0;
    const auto file = std::string("/tmp/") + std::to_string(getppid()) + ".cpuspark";
    std::ifstream i{ file };
    std::vector<std::string> history;
    std::string l;
    while ( std::getline(i, l).good() )
    {
        std::cout << l;
        history.push_back(l);
    }
    i.close();
    double load;
    if ( getloadavg(&load, 1) == 1 )
    {
        std::size_t index = bars.size() * load / ( std::thread::hardware_concurrency() + 1 );
        auto bar = index < bars.size() ? bars[index] : bars[bars.size()-1];
        std::cout << bar;
        struct stat st;
        if ( stat(file.c_str(), &st) || time(NULL) - st.st_mtime >= 30 )
        {
            while ( history.size() > HISTORY_LEN )
                history.erase( history.begin() );
            std::ofstream o{ file };
            for ( auto&& h : history )
                o << h << '\n';
            o << bar << '\n';
        }
    }
}