#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/ip.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdio.h>
#include<set>
using namespace std;

bool operator<(const struct sockaddr_in &a, const struct sockaddr_in &b){
	if(a.sin_addr.s_addr == b.sin_addr.s_addr)
		return a.sin_port < b.sin_port;
	return a.sin_addr.s_addr < b.sin_addr.s_addr;
}

set<struct sockaddr_in> clients;

int main(){
	int skt = socket(AF_INET, SOCK_DGRAM, 0);

	struct sockaddr_in sad;
	sad.sin_port = htons(5141);
	sad.sin_addr.s_addr = INADDR_ANY;
	sad.sin_family = AF_INET;
	if( bind(skt, (struct sockaddr *)(&sad), sizeof(struct sockaddr_in)) ){ // step 2
		perror("bind");
		return 1;
	}

	char buffer[1024];
	struct sockaddr_in sender_address;
	socklen_t sad_len = sizeof(sender_address);
	while(1){
		/* When we get a message:
 		 * 	Relay to all other clients
 		 * 	If the message is from somebody we haven't heard of
 		 * 		Add them to the list of clients
 		 */
		sender_address.sin_addr.s_addr = 0;
		sender_address.sin_port = 0;
		ssize_t reclen = recvfrom(skt, buffer, 1024, 0, (struct sockaddr *)&sender_address, &sad_len);
		buffer[reclen] = 0;
		printf("Received \"%s\" from %s on port %d\n", buffer, inet_ntoa(sender_address.sin_addr), ntohs(sender_address.sin_port));
		if(!clients.contains(sender_address)) // O(log(n))
			clients.insert(sender_address);
		for(const struct sockaddr_in &addr : clients)
			sendto(skt, buffer, reclen, 0, (struct sockaddr *)&addr, sad_len);
		
	}
	return 0;
}