/* Copyright (c) 2017, Curtis McEnroe <programble@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <arpa/inet.h>
#include <err.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <unistd.h>

#define UNUSED __attribute__((unused))

static void spawn(const char *cmd, int dest, int src) {
	pid_t pid = fork();
	if (pid < 0) err(EX_OSERR, "fork");

	if (pid) {
		int status;
		pid_t dead = waitpid(pid, &status, 0);
		if (dead < 0) err(EX_OSERR, "waitpid(%d)", pid);
		if (status) warnx("%s: status %d", cmd, status);

	} else {
		int fd = dup2(src, dest);
		if (fd < 0) err(EX_OSERR, "dup2");

		execlp(cmd, cmd, NULL);
		err(EX_UNAVAILABLE, "%s", cmd);
	}
}

static int pbd(void) {
	int error;

	int server = socket(PF_INET, SOCK_STREAM, 0);
	if (server < 0) err(EX_OSERR, "socket");

	error = fcntl(server, F_SETFD, FD_CLOEXEC);
	if (error) err(EX_IOERR, "fcntl");

	struct sockaddr_in addr = {
		.sin_family = AF_INET,
		.sin_port = htons(7062),
		.sin_addr = { .s_addr = htonl(0x7F000001) },
	};
	error = bind(server, (struct sockaddr *)&addr, sizeof(addr));
	if (error) err(EX_UNAVAILABLE, "bind");

	error = listen(server, 0);
	if (error) err(EX_UNAVAILABLE, "listen");

	for (;;) {
		int client = accept(server, NULL, NULL);
		if (client < 0) err(EX_IOERR, "accept");

		error = fcntl(client, F_SETFD, FD_CLOEXEC);
		if (error) err(EX_IOERR, "fcntl");

		spawn("pbpaste", STDOUT_FILENO, client);

		char p;
		ssize_t peek = recv(client, &p, 1, MSG_PEEK);
		if (peek < 0) err(EX_IOERR, "recv");

		if (peek) spawn("pbcopy", STDIN_FILENO, client);

		close(client);
	}
}

static int pbdClient(void) {
	int client = socket(PF_INET, SOCK_STREAM, 0);
	if (client < 0) err(EX_OSERR, "socket");

	struct sockaddr_in addr = {
		.sin_family = AF_INET,
		.sin_port = htons(7062),
		.sin_addr = { .s_addr = htonl(0x7F000001) },
	};
	int error = connect(client, (struct sockaddr *)&addr, sizeof(addr));
	if (error) err(EX_UNAVAILABLE, "connect");

	return client;
}

static void copy(int out, int in) {
	char buf[4096];
	ssize_t readSize;
	while (0 < (readSize = read(in, buf, sizeof(buf)))) {
		ssize_t writeSize = write(out, buf, readSize);
		if (writeSize < 0) err(EX_IOERR, "write(%d)", out);
		if (writeSize < readSize) errx(EX_IOERR, "short write(%d)", out);
	}
	if (readSize < 0) err(EX_IOERR, "read(%d)", in);
}

static int pbcopy(void) {
	int client = pbdClient();
	copy(client, STDIN_FILENO);
	return EX_OK;
}

static int pbpaste(void) {
	int client = pbdClient();
	shutdown(client, SHUT_WR);
	copy(STDOUT_FILENO, client);
	return EX_OK;
}

int main(int argc UNUSED, char *argv[]) {
	if (!argv[0][0] || !argv[0][1]) return EX_USAGE;
	switch (argv[0][2]) {
		case 'd': return pbd();
		case 'c': return pbcopy();
		case 'p': return pbpaste();
		default:  return EX_USAGE;
	}
}