#include <iostream>
#include <thread>
#include <string>
#include <vector>
#include <unistd.h>
#include <time.h>
#include <stdlib.h>
#include <sys/stat.h>

#include <opencv4/opencv2/opencv.hpp>
#include <opencv4/opencv2/video/tracking.hpp>
#include <opencv4/opencv2/core/ocl.hpp>
#include <opencv4/opencv2/videoio.hpp>

using namespace cv;
using namespace std;

struct shared_t
{
    vector<Mat>    buff;
    vector<thread> writers;
    TermCriteria   criteria;
    string         detectUrl;
    string         recordUrl;
    string         outDir;
    string         postMoCmd;
    string         postNoMoCmd;
    string         secsStr;
    bool           wrRunning;
    bool           ffRunning;
    int            motion;
    int            gap;
    int            secs;

} sharedRes;

string cleanDir(const string &path)
{
    if (path[path.size() - 1] == '/')
    {
        return path.substr(0, path.size() - 1);
    }
    else
    {
        return path;
    }
}

bool createDir(const string &dir)
{
    auto ret = mkdir(dir.c_str(), 0777);

    if (ret == -1)
    {
        return errno == EEXIST;
    }
    else
    {
        return true;
    }
}

bool createDirTree(const string &full_path)
{
    size_t pos = 0;
    auto   ret = true;

    while (ret == true && pos != string::npos)
    {
        pos = full_path.find('/', pos + 1);
        ret = createDir(full_path.substr(0, pos));
    }

    return ret;
}

void vidCap(shared_t *share)
{
    if (share->buff.size() >= 100)
    {
        share->wrRunning = true;

        time_t rawtime;

        time(&rawtime);

        auto timeinfo = localtime(&rawtime);

        char dirName[20];
        char fileName[20];

        strftime(dirName, 20, "%Y%m%d", timeinfo);
        strftime(fileName, 20, "%H%M%S.avi", timeinfo);

        createDirTree(cleanDir(share->outDir) + string("/") + string(dirName));

        auto dstPath = cleanDir(share->outDir) + string("/") + string(dirName) + string("/") + string(fileName);
        auto codec   = VideoWriter::fourcc('M', 'J', 'P', 'G');
        auto fps     = 25.0;

        VideoWriter writer;

        writer.open(dstPath, codec, fps, share->buff[0].size(), true);

        if (!writer.isOpened())
        {
            cerr << "could not open the output video file for writing: " << dstPath;
        }
        else
        {
            for (; !share->buff.empty(); share->buff.erase(share->buff.begin()))
            {
                writer.write(share->buff[0]);
            }
        }

        share->wrRunning = false;
    }
}

void detectDiff(Mat prev, Mat next, shared_t *share)
{
    // optical flow calculations are used to detect motion.
    // reference: https://docs.opencv.org/3.4/d4/dee/tutorial_optical_flow.html
    vector<Point2f> p0, p1;
    vector<uchar>   status;
    vector<float>   err;

    goodFeaturesToTrack(prev, p0, 50, 0.5, 3, Mat(), 3, false, 0.04);
    calcOpticalFlowPyrLK(prev, next, p0, p1, status, err, Size(10, 10), 2, share->criteria);

    for(uint i = 0; i < p0.size(); i++)
    {
        if (norm(p0[i] - p1[i]) > share->gap)
        {
            share->motion += 150;

            break;
        }
        else if (share->motion != 0)
        {
            share->motion -= 1;
        }
    }
}

void timer(shared_t *share)
{
    sleep(share->secs);

    if (share->motion == 0)
    {
        share->ffRunning = false;
    }

    if (!share->wrRunning)
    {
        new thread(vidCap, share);
    }
}

void addFramesToBuffer(const vector<Mat> &newFrames, shared_t *share)
{
    for (auto &&frame : newFrames)
    {
        share->buff.push_back(frame);
    }
}

Mat toGray(const Mat &src)
{
    Mat ret;

    cvtColor(src, ret, COLOR_BGR2GRAY);

    return ret;
}

void moDetect(shared_t *share)
{
    auto dCap = VideoCapture(share->detectUrl, CAP_FFMPEG);
    auto rCap = VideoCapture(share->recordUrl, CAP_FFMPEG);

    vector<Mat> dFrames, rFrames;
    Mat         dFrame, rFrame;

    while (share->ffRunning)
    {
        dCap >> dFrame;
        rCap >> rFrame;

        if (dFrame.empty())
        {
            // broken frames returned from the cameras i've tested this with would cause
            // the entire capture connection to drop, hence why this bit of code is here
            // to detect empty frames (signs of a dropped connection) and attempt
            // re-connect to the cammera.
            dCap.open(share->detectUrl, CAP_FFMPEG);
        }
        else if (rFrame.empty())
        {
            rCap.open(share->recordUrl, CAP_FFMPEG);
        }
        else if ((dFrames.size() < 2) || (rFrames.size() < 2))
        {
            rFrames.push_back(rFrame.clone());
            dFrames.push_back(toGray(dFrame));
        }
        else
        {
            if (share->gap == 0)
            {
                // share->gap is used in detectDiff() to compare how far a
                // point in the optical flow has moved. it is calculated by a
                // certain percentage of the total pixel area of the frames.

                // as of right now it is hard coded to 0.00579% of the total
                // pixel area of the frames and only needs to be calculated
                // once hence why share->gap == 0 is checked.
                share->gap = ((double) 0.00579 / (double) 100) * (dFrame.size().height * dFrame.size().width);
            }

            if (share->motion != 0)
            {
                addFramesToBuffer(rFrames, share);
            }

            detectDiff(dFrames[0], dFrames[1], share);

            rFrames.clear();
            dFrames.clear();
        }
    }

    if (share->motion != 0)
    {
        system(share->postMoCmd.c_str());
    }
    else
    {
        system(share->postNoMoCmd.c_str());
    }
}

string parseForParam(const string &arg, int argc, char** argv)
{
    for (int i = 0; i < argc; ++i)
    {
        auto argInParams = string(argv[i]);

        if (arg.compare(argInParams) == 0)
        {
            // check ahead, make sure i + 1 won't cause out-of-range exception
            if ((i + 1) <= (argc - 1))
            {
                return string(argv[i + 1]);
            }
        }
    }

    return string();
}

int main(int argc, char** argv)
{
    auto vidRet  = 0;
    auto moRet   = 0;
    auto secsStr = parseForParam("-sec", argc, argv);
    auto highUrl = parseForParam("-rs", argc, argv);
    auto lowUrl  = parseForParam("-ds", argc, argv);
    auto outDir  = parseForParam("-dir", argc, argv);
    auto moCmd   = parseForParam("-mc", argc, argv);
    auto noMocmd = parseForParam("-nmc", argc, argv);
    auto secs    = strtol(secsStr.c_str(), NULL, 10);

    if (lowUrl.empty())
    {
        cerr << "the detection-stream camera url is empty." << endl;
    }
    else if (highUrl.empty())
    {
        cerr << "the recording-stream camera url is empty." << endl;
    }
    else if (outDir.empty())
    {
        cerr << "the output directory is empty." << endl;
    }
    else if (secs == 0)
    {
        cerr << "the amount of seconds in -sec cannot be 0 or an invalid number was given." << endl;
    }
    else
    {
        sharedRes.criteria  = TermCriteria((TermCriteria::COUNT) + (TermCriteria::EPS), 10, 0.03);
        sharedRes.wrRunning = false;
        sharedRes.motion    = 0;
        sharedRes.gap       = 0;

        while (true)
        {
            sharedRes.recordUrl   = highUrl;
            sharedRes.detectUrl   = lowUrl;
            sharedRes.postMoCmd   = moCmd;
            sharedRes.postNoMoCmd = noMocmd;
            sharedRes.secsStr     = secsStr;
            sharedRes.secs        = secs;
            sharedRes.outDir      = outDir;
            sharedRes.ffRunning   = true;

            thread th1(timer, &sharedRes);
            thread th2(moDetect, &sharedRes);

            // Wait for the threads to finish
            // Wait for thread t1 to finish
            th1.join();
            // Wait for thread t2 to finish
            th2.join();
        }

        return 0;
    }

    return 1;
}