#include <fcntl.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>


void
copyfile(char *path, char *text, FILE *fp)
{
	FILE *in;
	char *cp;
	char buf[BUFSIZ];

	if ((in = fopen(path, "r"))) {
		fprintf(fp, "%s:\r\n", text);
		while (fgets(buf, sizeof buf - 1, in)) {
			if ((cp = strchr(buf, '\n'))) {
				*cp++ = '\r';
				*cp++ = '\n';
				*cp = '\0';
			}
			fputs(buf, fp);
		}
	} else {
		fprintf(fp, "No %s.\r\n", text);
	}
}


void
reply(int fd)
{
	struct passwd *pw;
	char buf[BUFSIZ];
	char *cp;
	FILE *fp;

	if (!(fp = fdopen(fd, "r+"))) {
		perror("fdopen");
		exit(1);
	}
	fgets(buf, sizeof(buf), fp);
	for (cp=buf; *cp; cp++) {
		if (*cp=='\r' || *cp=='\n') {
			*cp = '\0';
			break;
		}
	}

	/* Refuse {C} queries */
	if (*buf == '\0') {
		fprintf(fp, "Finger online user list denied.\r\n");
		exit(1);
	}

	/* Ignore and skip `/W' */
	cp = buf;
	if (strncmp(buf, "/W ", 3)==0) {
		for (cp=buf+3; *cp && *cp==' '; cp++) {
			;
		}
	}

	/* Refuse {Q2} queries */
	if (strchr(cp, '@')) {
		fprintf(fp, "Finger forwarding service denied.\r\n");
		exit(1);
	}

	pw = getpwnam(cp);
	if (!pw) {
		fprintf(fp, "No such user.\r\n");
		exit(1);
	}

	/*
	** Refuse queries for users who don't want to get fingered
	** This is senseless in our setup, because home directories have mode 0700.
	** We would refuse all queries to users other than oneself.
	**
	snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir, ".nofinger");
	struct stat sb;
	int ret = stat(buf, &sb);
	if (ret != -1 || (ret == -1 && errno != ENOENT)) {
		fprintf(fp, "User does not want to be fingered.\r\n");
		exit(1);
	}
	*/

	/* Eventually, reply. */
	fprintf(fp, "login: %s\t\trealname: %s\r\n", pw->pw_name, pw->pw_gecos);
	fprintf(fp, "home: %s\t\tshell: %s\r\n", pw->pw_dir, pw->pw_shell);
	snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir, ".project");
	copyfile(buf, "project", fp);
	snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir, ".plan");
	copyfile(buf, "plan", fp);
	snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir, ".pubkey");
	copyfile(buf, "public key", fp);
}


int
main(int argc, char *argv[])
{
	int sd, fd;
	pid_t pid;
	short port = 7979;

	if (argc == 2) {
		if ((port = atoi(argv[1])) <= 0) {
			fprintf(stderr, "port must be a positive number\n");
			exit(1);
		}
	}

	if ((sd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
		perror("socket");
		exit(1);
	}

	int optval = 1;
	if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof optval) == -1) {
		perror("setsockopt");
		exit(1);
	}

	struct sockaddr_in address = {0};
	address.sin_family = AF_INET;
	address.sin_addr.s_addr = htonl(INADDR_ANY);
	address.sin_port = htons(port);
	if (bind(sd, (struct sockaddr *)&address, sizeof address) == -1) {
		perror("bind");
		exit(1);
	}

	if (listen(sd, SOMAXCONN) == -1) {
		perror("listen");
		exit(1);
	}

	/* don't create zombies */
	signal(SIGCHLD, SIG_IGN);

	/* Now, wait for incoming connections */
	while ((fd = accept(sd, 0, 0)) != -1) {
		/* we have a connection */
		if ((pid = fork()) == -1) {
			perror("fork");
			exit(1);
		} else if (pid == 0) {
			/* child */
			reply(fd);
			exit(0);
		}
		/* parent */
		close(fd);
	}

	return 0;
}