#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <errno.h>
#include <limits.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include "proxy.h"

static int parse_host(const char *host, const char *port, struct addrinfo **addr)
{
	struct addrinfo hints = {
		.ai_family   = AF_UNSPEC,
		.ai_socktype = SOCK_STREAM,
		.ai_flags    = AI_PASSIVE,
	};

	int err;
	if ((err = getaddrinfo(host, port, &hints, addr))) {
		fprintf(stderr, "getaddrinfo failed: %s\n", gai_strerror(err));
		return -1;
	}

	return 0;
}

static int listen_source(struct addrinfo *source)
{
	int fd = -1;
	for (struct addrinfo *a = source; a; a = a->ai_next) {
		if ((fd = socket(a->ai_family, a->ai_socktype, a->ai_protocol)) == -1)
			continue;
		if (!bind(fd, a->ai_addr, a->ai_addrlen) && !listen(fd, 1))
			break;
		close(fd);
		fd = -1;
	}
	return fd;
}

static int connect_target(struct addrinfo *target)
{
	int fd = -1;
	for (struct addrinfo *a = target; a; a = a->ai_next) {
		if ((fd = socket(a->ai_family, a->ai_socktype, a->ai_protocol)) == -1)
			continue;
		if (connect(fd, a->ai_addr, a->ai_addrlen) != -1)
			break;
		close(fd);
		fd = -1;
	}
	return fd;
}

struct args {
	struct addrinfo *source;
	struct addrinfo *target;
	unsigned delay;
};

static void usage(const char *progname)
{
	int width = 20;
	const char *args[] = {
		"-d DELAY",     "millisecond delay to add (default: 500ms)",
		"-p LOCALPORT", "port to listen on (default: 1234)",
		NULL
	};
	fprintf(stderr, "usage: %s [-d DELAY] [-p LOCALPORT] HOST PORT\n\n", progname);
	for (const char **a = args; *a; a += 2)
		fprintf(stderr, "\t%-*s %s\n", width, a[0], a[1]);
}

static int parse_unsigned(const char *arg, unsigned *out)
{
	char *end;
	errno = 0;
	unsigned long val = strtoul(arg, &end, 10);
	if (*end) return -1;
	if (errno && !val) return -1;
	if (val == ULONG_MAX && errno == ERANGE) return -1;
	if (val > UINT_MAX) return -1;
	*out = val;
	return 0;
}

static int parse_args(struct args *args, int argc, char **argv)
{
	args->delay = 500;

	const char *localport = "1234";
	const char *host = NULL, *port = NULL;

	extern char *optarg;
	extern int optind;
	int opt, error = 0;

	while ((opt = getopt(argc, argv, "+d:p:")) != -1) {
		switch (opt) {
		case 'd':
			if (parse_unsigned(optarg, &args->delay)) {
				fprintf(stderr, "invalid delay\n");
				error = 1;
			}
			break;

		case 'p':
			localport = optarg;
			break;

		default:
			error = 1;
		}
	}

	if (optind <= argc - 2) {
		host = argv[optind++];
		port = argv[optind++];
	} else error = 1;

	if (error) {
		usage(argv[0]);
		return -1;
	}
	if (parse_host(NULL, localport, &args->source))
		return -1;
	if (parse_host(host, port, &args->target))
		return -1;

	return 0;
}

int main(int argc, char **argv)
{
	struct args args;
	if (parse_args(&args, argc, argv))
		return -1;

	int listenfd = listen_source(args.source);
	if (listenfd < 0) {
		perror("listen_source");
		return -1;
	}

	for (;;) {
		int sourcefd = accept(listenfd, NULL, NULL);
		if (sourcefd == -1) break;

		int targetfd = connect_target(args.target);
		if (targetfd == -1) {
			perror("connect_target");
			close(sourcefd);
			break;
		}

		proxy(sourcefd, targetfd, args.delay);

		close(targetfd);
		close(sourcefd);
	}

	close(listenfd);
	return 0;
}