// Software Name : cppuprofile
// SPDX-FileCopyrightText: Copyright (c) 2022 Orange
// SPDX-License-Identifier: BSD-3-Clause
//
// This software is distributed under the BSD License;
// see the LICENSE file for more details.
//
// Author: Cédric CHEDALEUX <cedric.chedaleux@orange.com> et al.

#include "cpumonitor.h"
#include <fstream>
#include <sstream>

using namespace std;

uprofile::CpuMonitor::CpuMonitor() :
    m_nbCpus(getNumberOfCPUCores())
{
    m_lastIdleTimes.resize(m_nbCpus, 0);
    m_lastTotalTimes.resize(m_nbCpus, 0);
}

uprofile::CpuMonitor::~CpuMonitor()
{
}

size_t uprofile::CpuMonitor::getNumberOfCPUCores()
{
    size_t nbCores = 0;
#if defined(__linux__)
    ifstream meminfo("/proc/cpuinfo");
    string str;
    while (getline(meminfo, str)) {
        if (str.rfind("processor", 0) == 0) {
            nbCores++;
        }
    }
#endif
    return nbCores;
}

void uprofile::CpuMonitor::extractCpuTimes(const string& cpuInfo, size_t& idleTime, size_t& totalTime)
{
    // Remove 'cpu<index' word and
    // extract the idle time and sum all other times
    size_t spacePos = cpuInfo.find(' ');
    if (spacePos == string::npos) {
        return;
    }

    stringstream times(cpuInfo.substr(spacePos + 1));
    int index = 0;
    for (size_t time; times >> time; ++index) {
        if (index == 3) { // idle time i s the 4th param
            idleTime = time;
        }
        totalTime += time;
    }
}

vector<float> uprofile::CpuMonitor::getUsage()
{
    vector<float> usages;
#if defined(__linux__)
    ifstream procStat("/proc/stat");
    // /proc/stat dumps the following info:
    //      user nice system idle iowait irq softirq
    // cpu  2255 34 2290 22625563 6290 127 456
    // cpu0 1132 34 1441 11311718 3675 127 438
    // cpu1 1123 0 849 11313845 2614 0 18
    // ...
    // Each numbers represents the amount of time the CPU has spent performing
    // different kind of work

    for (size_t cpuIndex = 0; cpuIndex < m_nbCpus; ++cpuIndex) {
        string cpuName("cpu");
        cpuName += to_string(cpuIndex);

        // Look in /proc/stack the CPU info
        string line;
        while (getline(procStat, line)) {
            if (line.find(cpuName) != std::string::npos) {
                size_t idleTime = 0, totalTime = 0;
                extractCpuTimes(line, idleTime, totalTime);

                // To compute CPU load, we compute the time the CPU has been idle since the last read.
                float cpuLoad = 100.0 * (1.0 - (float)(idleTime - m_lastIdleTimes[cpuIndex]) / (totalTime - m_lastTotalTimes[cpuIndex]));
                usages.push_back(cpuLoad);

                // Save the times value for the next read
                m_lastIdleTimes[cpuIndex] = idleTime;
                m_lastTotalTimes[cpuIndex] = totalTime;
                break;
            }
        }
    }
#endif

    return usages;
}