/*
 * LimoX - The Linux on mobile XMPP chat client
 * Copyright (C) 2022  xengineering
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */


#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdbool.h>


/*
 * Get the domainpart of the Jabber ID (JID)
 *
 * See https://datatracker.ietf.org/doc/html/rfc7622#section-3.2 for details.
 */
char *get_domainpart(char *jid)
{
	int start = 0;           // inclusive index
	int stop = strlen(jid);  // exclusive index

	for(int i=0; i<strlen(jid); i++) {
		if (jid[i] == '/') {
			stop = i;
			break;
		}
	}

	for(int i=0; i<strlen(jid); i++) {
		if (jid[i] == '@') {
			start = i + 1;
			break;
		}
	}

	char *retval = (char *)malloc((stop-start+1) * sizeof(char));
	memcpy(retval, jid+start, (stop-start) * sizeof(char));
	retval[stop] = '\0';

	return retval;
}

/*
 * Return the preferred struct addrinfo * or NULL
 *
 * This handles DNS resolution. It returns the first valid addrinfo which is
 * returned by getaddrinfo. Mind that the addrinfo could use IPv6 instead of
 * IPv4.
 *
 * FIXME this just takes the first received IPv4 address (by far not compliant
 *       to RFC 6120!)
 * FIXME This function contains a memory leak! Free the linked list servinfo!
 */
struct addrinfo *resolve_dns(char *domain)
{
	struct addrinfo hints;
	struct addrinfo *servinfo;
	void *addr;
	char ipstr[INET6_ADDRSTRLEN];
	memset(&hints, 0, sizeof hints);
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	if (getaddrinfo(domain, "xmpp-client", &hints, &servinfo) != 0) {
		printf("Failed to resolve hostname '%s'.\n", domain);
		return NULL;
	}
	struct addrinfo *p;
	for(p=servinfo; p!=NULL; p=p->ai_next) {
		if (p->ai_family == AF_INET) {
			struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
			addr = &(ipv4->sin_addr);
			inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
			printf("Got compatible IPv4 address %s from DNS.\n", ipstr);
			return p;
		} else if (p->ai_family == AF_INET6) {
			printf("Ignored IPv6 DNS entry which is not supported.\n");
		} else {
			printf("Ignored unknown addrinfo address type.\n");
		}
	}
	printf("No suitable IP address found via DNS!\n");
	return NULL;
}

/*
 * Start XMPP stream via the given socket filedescriptor
 *
 * Returns 0 in case of success and -1 otherwise.
 */
int start_stream(int sock_fd, char *jid, char *domainpart)
{
	const char *tmpl = "<stream:stream\
 from='%s'\
 to='%s'\
 version='1.0'\
 xml:lang='en'\
 xmlns='jabber:client'\
 xmlns:stream='http://etherx.jabber.org/streams'>";

	char *msg;
	asprintf(&msg, tmpl, jid, domainpart);
	int len = strlen(msg);

	int sent = send(sock_fd, msg, len, 0);
	if (sent == len) {
		printf(">>> %s\n", msg);
		return 0;
	} else if (sent == 0) {
		printf("Failed to send any bytes to server!\n");
		return -1;
	} else {
		printf("Could just send %d bytes of %d bytes to server!\n", sent, len);
		return -1;
	}
}

/*
 * Get JID and password and return true on success
 */
bool get_credentials(char **jid, char **pwd)
{
	if (getenv("LIMOX_USER") == NULL || getenv("LIMOX_PWD") == NULL) {
		printf("Failed to connect.\n");
		printf("Please set the LIMOX_USER and LIMOX_PWD shell variables.\n");
		return false;
	}

	*jid = getenv("LIMOX_USER");
	*pwd = getenv("LIMOX_PWD");

	return true;
}

/*
 * Initialize the network connection to the XMPP server and return socket fd
 *
 * TODO: Error handling is missing.
 */
int xmpp_connect(void)
{
	printf("net_init()\n");

	int sock = -1;

	char *jid;
	char *pwd;
	if (!get_credentials(&jid, &pwd)) {
		return sock;
	}
	printf("Trying to connect as '%s' with '%s'.\n", jid, pwd);

	char *domain = get_domainpart(jid);
	printf("Domainpart is '%s'.\n", domain);

	struct addrinfo *addr = resolve_dns(domain);

	sock = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
	if (sock == -1) {
		printf("Failed to get socket from OS!.");
		return sock;
	} else {
		printf("Got socket number %d from OS.\n", sock);
	}

	if (connect(sock, addr->ai_addr, addr->ai_addrlen) == -1) {
		printf("Failed to connect!\n");
		return sock;
	} else {
		printf("Successfully connected.\n");
	}

	if (start_stream(sock, jid, domain) == -1) {
		printf("Failed to init stream!\n");
		return sock;
	}
	printf("Stream init sent.\n");

	return sock;
}