#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <pthread.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <errno.h>
#include <signal.h>

#include "packet.h"
#include "netascii.h"
#include "handlers.h"

int nbtpd_stop = 0;

void stop_handler(int i) {
	syslog(LOG_ERR, "caught shutdown signal, cleaning up.");
	if (i != 0) {
		nbtpd_stop = i;
	} else {
		nbtpd_stop = 1;
	}
	return;
}

void usage(char *name) {
	printf("USAGE: %s -d -u nobody -g nobody -a 127.0.0.1 -p 69\n", name);
	printf("\td: daemonize.\n");
	printf("\tu: username to run as (default: nobody).  Must be specified after -d.\n");
	printf("\tg: group to run as (default: nobody).  Must be specified after -d.\n");
	printf("\ta: address to bind to (default: 127.0.0.1)\n");
	printf("\tp: port to bind to (default: 69)\n");
}

int main(int argc, char **argv) {
	int daemonize = 0;
	char addr[16], user[32], group[32];
	memset(addr, '\0', sizeof(addr));
	memset(user, '\0', sizeof(user));
	memset(group, '\0', sizeof(group));
	strcpy(addr, "127.0.0.1");
	strcpy(user, "nobody");
	strcpy(group, "nobody");
	int port = 69;
	
	int ch = 0;
	while ((ch = getopt(argc, argv, "da:p:u:g:h")) != -1) {
		switch (ch) {
			case 'a':
				//TODO: this is unsafe
				strcpy(addr, optarg);
				break;
			case 'p':
				port = atoi(optarg);
				if ((port <= 0) || (port >= 65536)) {
					fprintf(stderr, "invalid port specified.\n");
					return -1;
				}
				break;
			case 'd':
				daemonize = 1;
				break;
			case 'g':
				if (daemonize) {
					//TODO: this is unsafe
					strcpy(group, optarg);
				} else {
					fprintf(stderr, "-g requires -d\n");
					return -1;
				}
				break;
			case 'u':
				if (daemonize) {
					//TODO: this is unsafe
					strcpy(user, optarg);
				} else {
					fprintf(stderr, "-u requires -d\n");
					return -1;
				}
				break;
			 case 'h': case '?':
				usage(argv[0]);
				return -1;
		}
	}

	setlogmask(LOG_UPTO(LOG_INFO));
	openlog(argv[0], LOG_PID | LOG_PERROR | LOG_NDELAY, LOG_FTP);
	syslog(LOG_INFO, "starting up...");
	signal(SIGTERM, &stop_handler);
	signal(SIGINT, &stop_handler);

	if (daemonize) {
		if (daemon(1, 0)) {
			syslog(LOG_ERR, "failed to daemonize as requested!");
			return -1;
		} else {
			syslog(LOG_INFO, "daemonized");
		}
	}

	int s = socket(AF_INET, SOCK_DGRAM, 0);
	if (s <= 0) {
		syslog(LOG_ERR, "unable to bind socket!");
		return -1;
	}
	struct sockaddr_in saddr;
	saddr.sin_family = AF_INET;
	saddr.sin_port = htons(port);
	saddr.sin_addr.s_addr = inet_addr(addr);

	if (bind(s, (struct sockaddr*)&saddr, sizeof(saddr)) < 0) {
		switch (errno) {
			case EACCES:
				syslog(LOG_ERR, "socket bind failed: permission denied");
				break;
			case EADDRINUSE:
				syslog(LOG_ERR, "socket bind failed: address already in use");
				break;
			case EADDRNOTAVAIL:
				syslog(LOG_ERR, "socket bind failed: address not available");
				break;
			default:
				syslog(LOG_ERR, "socket bind failed");
		}
		return -1;
	}
	syslog(LOG_INFO, "socket bind success");

	if (daemonize) {
		//TODO: use getpwnam_r() and getgrnam_r()
		struct group *g = getgrnam((const char *)&group);
		if (setgid((*g).gr_gid) == -1) {
			syslog(LOG_ERR, "failed to drop group privileges");
			return -1;
		}
		struct passwd *u = getpwnam((const char *)&user);
		if (setuid((*u).pw_uid) == -1) {
			syslog(LOG_ERR, "failed to drop user privileges");
			return -1;
		}
	}

	// create persistent buffer
	char *buf;
	buf = malloc(1024);
	if (buf == NULL) {
		syslog(LOG_CRIT, "unable to allocate memory!");
		close(s);
		return -1;
	}
	while (!nbtpd_stop) {
		struct sockaddr_in caddr;
		unsigned int clen = sizeof(caddr);
		memset(buf, '\0', 1024);
		ssize_t recvd_bytes = 0;
		if ((recvd_bytes = recvfrom(s, buf, 1024, 0, 
				(struct sockaddr *)&caddr, &clen)) < 0) {
			syslog(
				LOG_ERR,
				"got a client connection, but unable to receive data!"
			);
			continue;
		}
		if (recvd_bytes < 4) {
			syslog(LOG_ERR, "ignoring invalid packet.");
			continue;
		}
		nbd_nbtpd_args *args = malloc(sizeof(nbd_nbtpd_args));
		if (args == NULL) {
			syslog(LOG_CRIT, "unable to allocate memory");
			continue;
		}
		nbd_tftp_opcode oc = ntohs(((uint16_t)buf[0] << 8) + buf[1]);
		(*args).client = caddr;
		(*args).err = 0;
		memset((*args).path, '\0', 768);
		memset((*args).mode, '\0', 32);
		int i;
		for(i = 2; buf[i] != 0 && i < recvd_bytes && (i - 2) < 768; i++) {
			(*args).path[i - 2] = buf[i];
		}
		int s = i + 1;
		if (s >= recvd_bytes) {
			oc = 0;
		} else {
			for(i = s; buf[i] != 0 && i < recvd_bytes && (i - s) < 32; i++) {
				(*args).mode[i - s] = buf[i];
			}
		}
		pthread_t *_thread = malloc(sizeof(pthread_t));
		if (_thread == NULL) {
			syslog(LOG_CRIT, "unable to allocate memory");
			free(args);
			continue;
		}
		void *(*func)(void *);
		switch (oc) {
			case RRQ:
				func = &read_req_resp;
				break;
			case WRQ:
				func = &write_req_resp;
				break;
			default:
				(*args).err = 4;
				func = &nbd_nbtpd_resp_error;
		}
		if (pthread_create(_thread, 0, func, (void *)args) != 0) {
			syslog(
				LOG_CRIT,
				"unable to handle request: cannot create thread!"
			);
			free(args);
		}
	}

	// free our persistent buffer
	free(buf);
	// close socket
	close(s);
	// wait for threads to exit
	pthread_exit(NULL);
	// exit program
	return 0;
}