#include<signal.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/ip.h>
#include<netdb.h>
#include<arpa/inet.h>
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
#include<pthread.h>

short from_inside_port = 6000;
short from_ouside_port = 5115;

struct pt_param {
	int in_fd;
	int out_fd;
};

void* pass_through(void *p){
	struct pt_param *ptp = p;
	char buffer[2048];
	size_t readlen;
	while(1){
		readlen = read(ptp->in_fd, buffer, 2048); 
		if(readlen < 1)
			break;
		if(write(ptp->out_fd, buffer, readlen) != readlen)
			break;
	}
	printf("Terminating forward from fd %d to fd %d\n", ptp->in_fd, ptp->out_fd);
}

int main(int argc, char ** argv){
	struct sockaddr_in sad;
	sad.sin_port = htons(from_inside_port);
	sad.sin_addr.s_addr = INADDR_ANY;
	sad.sin_family = AF_INET;

	int skt = socket(AF_INET, SOCK_STREAM, 0); // Step 1
	if(skt == -1){
		perror("socket");
		return 1;
	}
	while( bind(skt, (struct sockaddr*)(&sad), sizeof(struct sockaddr_in)) ){ // step 2
		if(from_inside_port < 6005){
			from_inside_port++;
			sad.sin_port = htons(from_inside_port);
		} else {
			perror("bind");
			return 1;
		}
	}
	printf("Listening on port %d\n", from_inside_port);
	if( listen(skt, 5) ){ // step 3
		perror("listen");
		return 1;
	}	
	int inside_fd;
	struct sockaddr_in inside_address;
	socklen_t address_size = sizeof(struct sockaddr_in);
	inside_fd = accept(skt, (struct sockaddr *)(&inside_address), &address_size); // step 4
	printf("Inside connection is ready!\n");

	// After this, accept connections from outside and forward the traffic in

	sad.sin_port = htons(from_ouside_port);
	sad.sin_family = AF_INET;

	int oskt = socket(AF_INET, SOCK_STREAM, 0);
	if(oskt == -1){
		perror("socket");
		return 1;
	}
	if( bind(oskt, (struct sockaddr*)(&sad), sizeof(struct sockaddr_in)) ){ // step 2
		perror("bind");
		return 1;
	}
	if( listen(oskt, 5) ){ // step 3
		perror("listen");
		return 1;
	}	

	int client_fd;
	struct sockaddr_in client_address;
	while(1){
		client_fd = accept(oskt, (struct sockaddr*)(&client_address), &address_size);

		// Pass to inside loop
		// But it should go both directions!
		pthread_t threads[2];
		struct pt_param outside_to_inside = {client_fd, inside_fd};
		struct pt_param inside_to_outside = {inside_fd, client_fd};

		pthread_create(&threads[0], 0, pass_through, &outside_to_inside);
		pthread_create(&threads[1], 0, pass_through, &inside_to_outside);

		for(int i = 0; i < 2; i++)
			pthread_join(threads[i], 0);


	}
	close(skt);
	close(oskt);
	return 0;
}