#include <stdio.h>
#include <netdb.h>
#include <sys/socket.h>

#include "postgres.h"
#include "fmgr.h"
#include "utils/palloc.h"


text *create_text(char *data) {
	unsigned long r_size;
	text *result;
	
	r_size = strlen(data);
	result = palloc(r_size + VARHDRSZ);
	VARATT_SIZEP(result) = r_size + VARHDRSZ;
	memcpy(VARDATA(result), data, r_size);
	return(result);
}


PG_FUNCTION_INFO_V1(resolveip);

Datum resolveip(PG_FUNCTION_ARGS) {
	struct hostent *host;
	struct in_addr addr;
	text *ipaddress = (text *)PG_GETARG_TEXT_P(0);
	const char *bad_ip_txt = "Bad IP address: '";
	char *message;
	
	unsigned long r_size, a_size = VARSIZE(ipaddress) - VARHDRSZ;
	char *saddress = (char *)palloc(a_size + 1);
	
	memcpy(saddress, VARDATA(ipaddress), a_size);
	saddress[a_size] = 0;		/* terminate string */
	
	if (! inet_aton(saddress, &addr)) {
		message = palloc(strlen(bad_ip_txt) + a_size + 2);
		message[0] = 0;
		strcat(message, bad_ip_txt);
		strcat(message, saddress);
		strcat(message, "'");
		
		PG_RETURN_TEXT_P(create_text(message));
	}
	host = gethostbyaddr(&addr, sizeof addr, AF_INET);
	
	if (! host) {
		PG_RETURN_NULL();
	}

	PG_RETURN_TEXT_P(create_text(host->h_name));
}