#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#include <pthread.h>

#define NUM_THREADS 2

void* threadSpawnRecv(void* args);
int selectThenRecvFrom();
int sendData();

int sock;

int main() {
	struct sockaddr_in addr;
	pthread_t threads[NUM_THREADS];
	int i;

	//create a new socket
	sock = socket(PF_INET, SOCK_DGRAM, 0);
	if (sock < 0 ) {
		printf("socket() failed\n");
		return -1;
	}
	addr.sin_family = AF_INET;
	if( (addr.sin_addr.s_addr = inet_addr("0.0.0.0")) == INADDR_NONE) {
		printf("converting bind() IP failed\n");
		return -1;
	}
	addr.sin_port = htons(1337);
	if(bind(sock, (struct sockaddr*) &addr, sizeof(addr) ) < 0 ) {
		printf("converting bind() IP failed %s\n", strerror(errno));
		return -1;
	}
	for(i = 0; i < NUM_THREADS; ++i) {
		if(pthread_create(&threads[i], NULL, threadSpawnRecv, NULL) != 0) {
			return -1;
		}
	}
	while(sendData() == 0) {} //send data in a loop
	return 0;
}

void* threadSpawnRecv(void* args) { //try to receive data in a loop
	while(selectThenRecvFrom() == 0) {}
	exit(-1); //if any of the receiver threads exists out we terminate the programme
}

int selectThenRecvFrom() { //check to see if there is data avaliable at the socket via select, and use recvfrom if there is to receive it
	static int count = 0;
	fd_set readSet; //build new set
	FD_ZERO(&readSet);
	FD_SET(sock, &readSet); //adds the socket to our readSet

	struct timeval selectTimeout;
	selectTimeout.tv_sec  = 0;
	selectTimeout.tv_usec = 10000;
	if (select(sock + 1, &readSet, NULL, NULL, &selectTimeout) < 0) { //select to find if sock has new data
		printf("select() failed, %s\n", strerror(errno));
		return -1;
	}
	if(FD_ISSET(sock, &readSet)) {
		unsigned char buffer[4*1024];
		struct sockaddr from;
		socklen_t fromLen = sizeof(from);
		if (recvfrom(sock, buffer, sizeof(buffer), MSG_DONTWAIT, &from, &fromLen) < 0) { //receive data
			//printf("Failed during recvfrom, %s\n", strerror(errno));
			return 0; //try again
		}
		if(++count % 100 == 0) printf("received %d\n", count);
	}
	return 0;
}

int sendData() { //send one packet of data to ourself
	struct sockaddr_in m_sendto;
	m_sendto.sin_family = AF_INET;
	if((m_sendto.sin_addr.s_addr = inet_addr("127.0.0.1")) == INADDR_NONE) {
		printf("Failed to convert sendto IP\n");
		return -1;
	}
	m_sendto.sin_port   = htons(1337);
	int tolen = sizeof(m_sendto);

	if(sendto(sock, "1234567890", 10, 0, (struct sockaddr*)&m_sendto, tolen) == -1) {
		printf("Failed to \'sendto\': %s\n", strerror(errno));
		return -1;
	}
	return 0;
}