/* -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

#include <config.h>

#include "cgroups.h"

#include "util.h"

#include <map>

#include <unordered_map>

#include <utility>

bool

cgroups_enabled(void)

{

    static bool initialized = false;

    static bool has_cgroups;

    if (not initialized) {

        initialized = true;

        has_cgroups = Glib::file_test("/proc/cgroups", Glib::FileTest::FILE_TEST_EXISTS);

    }

    return has_cgroups;

}

static const std::pair<std::string, std::string> &

parse_cgroup_line(const std::string& line) {

    static std::unordered_map<std::string, std::pair<std::string, std::string>> line_cache;

    auto it = line_cache.insert({line, {"", ""} });

    if (it.second) { // inserted new

        std::string::size_type cat_start, name_start;

        if ((cat_start = line.find(':')) != std::string::npos

            && (name_start = line.find(':', cat_start + 1)) != std::string::npos) {

            // printf("%s %lu %lu\n", line.c_str(), cat_start, name_start);

            auto cat = line.substr(cat_start + 1, name_start - cat_start - 1);

            auto name = line.substr(name_start + 1);

            // strip the name= prefix

            if (cat.find("name=") == 0) {

                cat.erase(0, 5);

            }

            if (!name.empty() && name != "/") {

                it.first->second = {name, cat};

            }

        }

    }

    return it.first->second;

}

static const std::string&

get_process_cgroup_string(pid_t pid) {

    static std::unordered_map<std::string, std::string> file_cache{ {"", ""} };

    /* read out of /proc/pid/cgroup */

    auto path = "/proc/" + std::to_string(pid) + "/cgroup";

    std::string text;

    try {

        text = Glib::file_get_contents(path);

    } catch (...) {

        return file_cache[""];

    }

    auto it = file_cache.insert({ text, "" });

    if (it.second) { // inserted new

        // name -> [cat...], sorted by name;

        std::map<std::string, std::vector<std::string>> names;

        std::string::size_type last = 0, eol;

        // for each line in the file

        while ((eol = text.find('\n', last)) != std::string::npos) {

            auto line = text.substr(last, eol - last);

            last = eol + 1;

            const auto& p = parse_cgroup_line(line);

            if (!p.first.empty()) {

                names[p.first].push_back(p.second);

            }

        }

        // name (cat1, cat2), ...

        // sorted by name, categories

        std::vector<std::string> groups;

        for (auto& i : names) {

            std::sort(begin(i.second), end(i.second));

            std::string cats = procman::join(i.second, ", ");

            groups.push_back(i.first + " (" + cats + ')');

        }

        it.first->second = procman::join(groups, ", ");

    }

    return it.first->second;

}

void get_process_cgroup_info(ProcInfo& info) {

    if (not cgroups_enabled())

        return;

    const auto& cgroup_string = get_process_cgroup_string(info.pid);

    info.cgroup_name = cgroup_string;

}