/**
 * stream_server.c:
 * OpenCV video streaming server
 *
 * Author  Nash <me_at_nashruddin.com>
 *
 * See the tutorial at
 * http://nashruddin.com/StrEAMinG_oPENcv_vIdEos_ovER_tHe_nEtWoRk
 */

#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include "cv.h"
#include "highgui.h"

#define PORT 8888

CvCapture*  capture;
IplImage*   img0;
IplImage*   img1;
int         is_data_ready = 0;
int         serversock, clientsock;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

void* streamServer(void* arg);
void  quit(char* msg, int retval);

int main(int argc, char** argv)
{
    pthread_t   thread_s;
    int         key;
    
    if (argc == 2) {
        capture = cvCaptureFromFile(argv[1]);
    } else {
        capture = cvCaptureFromCAM(0);
    }
    
    if (!capture) {
        quit("cvCapture failed", 1);
    }
    
    img0 = cvQueryFrame(capture);
    img1 = cvCreateImage(cvGetSize(img0), IPL_DEPTH_8U, 1);
    
    cvZero(img1);
    cvNamedWindow("stream_server", CV_WINDOW_AUTOSIZE);
    
    /* print the width and height of the frame, needed by the client */
    fprintf(stdout, "width:  %d\nheight: %d\n\n", img0->width, img0->height);
    fprintf(stdout, "Press 'q' to quit.\n\n");
    
    /* run the streaming server as a separate thread */
    if (pthread_create(&thread_s, NULL, streamServer, NULL)) {
        quit("pthread_create failed.", 1);
    }
    
    while(key != 'q') {
        /* get a frame from camera */
        img0 = cvQueryFrame(capture);
        if (!img0) break;
        
        img0->origin = 0;
        cvFlip(img0, img0, 1); //-1);
        
        /**
         * convert to grayscale
         * note that the grayscaled image is the image to be sent to the client
         * so we enclose it with pthread_mutex_lock to make it thread safe
         */
        pthread_mutex_lock(&mutex);
        cvCvtColor(img0, img1, CV_BGR2GRAY);
        is_data_ready = 1;
        pthread_mutex_unlock(&mutex);
        
        /* also display the video here on server */
        cvShowImage("stream_server", img0);
        key = cvWaitKey(30);
    }
    
    /* user has pressed 'q', terminate the streaming server */
    if (pthread_cancel(thread_s)) {
        quit("pthread_cancel failed.", 1);
    }
    
    /* free memory */
    cvDestroyWindow("stream_server");
    quit(NULL, 0);
}

/**
 * This is the streaming server, run as a separate thread
 * This function waits for a client to connect, and send the grayscaled images
 */
void* streamServer(void* arg)
{
    struct sockaddr_in server;
    
    /* make this thread cancellable using pthread_cancel() */
    pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
    pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL);
    
    /* open socket */
    if ((serversock = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
        quit("socket() failed", 1);
    }
    
    /* setup server's IP and port */
    memset(&server, 0, sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(PORT);
    server.sin_addr.s_addr = INADDR_ANY;
    
    /* bind the socket */
    if (bind(serversock, (const void*)&server, sizeof(server)) == -1) {
        quit("bind() failed", 1);
    }
    
    /* wait for connection */
    if (listen(serversock, 10) == -1) {
        quit("listen() failed.", 1);
    }
    
    /* accept a client */
    if ((clientsock = accept(serversock, NULL, NULL)) == -1) {
        quit("accept() failed", 1);
    }
    
    /* the size of the data to be sent */
    int imgsize = img1->imageSize;
    int bytes, i;
    
    /* start sending images */
    while(1)
    {
        /* send the grayscaled frame, thread safe */
        pthread_mutex_lock(&mutex);
        if (is_data_ready) {
            bytes = send(clientsock, img1->imageData, imgsize, 0);
            is_data_ready = 0;
        }
        pthread_mutex_unlock(&mutex);
        
        /* if something went wrong, restart the connection */
        if (bytes != imgsize) {
            fprintf(stderr, "Connection closed.\n");
            close(clientsock);
            
            if ((clientsock = accept(serversock, NULL, NULL)) == -1) {
                quit("accept() failed", 1);
            }
        }
        
        /* have we terminated yet? */
        pthread_testcancel();
        
        /* no, take a rest for a while */
        usleep(1000);
    }
}

/**
 * this function provides a way to exit nicely from the system
 */
void quit(char* msg, int retval)
{
    if (retval == 0) {
        fprintf(stdout, (msg == NULL ? "" : msg));
        fprintf(stdout, "\n");
    } else {
        fprintf(stderr, (msg == NULL ? "" : msg));
        fprintf(stderr, "\n");
    }
    
    if (clientsock) close(clientsock);
    if (serversock) close(serversock);
    if (capture) cvReleaseCapture(&capture);
    if (img1) cvReleaseImage(&img1);
    
    pthread_mutex_destroy(&mutex);
    
    exit(retval);
}