/*
 * Copyright (C) 2010-2015 Mamadou DIOP.
 *
 * This file is part of Open Source Doubango Framework.
 *
 * DOUBANGO 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.
 *	
 * DOUBANGO 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 DOUBANGO.
 *
 */
 /**@file tnet_dns_resolvconf.c
  * @brief Parser for "/etc/resolv.conf" file to retrive DNS servers.
  */
 #include "tnet_dns_resolvconf.h"
 
 #include "tnet_utils.h"
 
 #include "dns/tnet_dns.h"
 
 #include "tsk_string.h"
 #include "tsk_memory.h"
 #include "tsk_ragel_state.h"
 #include "tsk_debug.h"
 
 #include <string.h>
 
 
 /* ===	Ragel state machine === */
 %%{
 	machine tdns_machine_resolvconf;
 
 	action tag{
 		tag_start = p;
 	}
 
 	action add_dns{
 		int len = (int)(p  - tag_start);
 		if(len && len<=sizeof(ip)){
 			tnet_address_t *address;
 			memset(ip, '\0', sizeof(ip));
 			memcpy(ip, tag_start, len);
 			TSK_DEBUG_INFO("Adding DNS server = %s:%d", ip, TNET_DNS_SERVER_PORT_DEFAULT);
 			
 			address = tnet_address_create(ip);
 			address->family = tnet_get_family(ip, TNET_DNS_SERVER_PORT_DEFAULT);
 			address->dnsserver = 1;
 			tsk_list_push_ascending_data(servers, (void**)&address);
 		}
 	}
 
 	SP = " ";
 	LF = "\n";
 	CR = "\r";
 	CRLF = CR LF;
 	ENDL = (LF | CR | CRLF);
 
 	o_name = any+;
 	o_value = any+;
 	
 	COMMENT = SP*<: ("#" | ";") any*;
 	OPTION_ANY = SP*<: o_name :>SP+<: o_value :>SP*;
 	OPTION_DNS = SP*<: "nameserver"i :>SP+<: o_value>tag %add_dns :>SP*;
 	LINE = (OPTION_DNS)@100 | (OPTION_ANY)@0 | (COMMENT)@50;
 	
 	main := ((LINE :>ENDL) | ENDL)* %3  any* %2;
 }%%
 
 /** Gets list of DNS servers from a conf file.
 * @param path Path of the conf file from which to retrieve the DNS servers.
 * should be @a "/etc/resolv.conf". You can adjust the value by modifying @ref TNET_RESOLV_CONF_PATH.<br>
 * If you are using <b>Android</b> and the resolv.conf file is missing, then run the following line in a command window: <br>
 * <i>ln -s /private/var/run/resolv.conf /etc/resolv.conf</i><br> If this fails, then try to manually add the file.
 * @retval List of DNS servers.
 */
 tnet_addresses_L_t * tnet_dns_resolvconf_parse(const char* path)
 {
 	tnet_addresses_L_t* servers = tsk_null;
 	tnet_ip_t ip;
 	const char* fullpath = path;
 	const char* tag_start = tsk_null;
 	FILE* fd;
 	char* buf = tsk_null;
 	
 	// Ragel
 	int cs = 0;
 	const char *p;
 	const char *pe;
 	const char *eof;
 
 	TSK_RAGEL_DISABLE_WARNINGS_BEGIN()
 	%%write data;
 	TSK_RAGEL_DISABLE_WARNINGS_END()
 	(void)(eof);
 	(void)(tdns_machine_resolvconf_first_final);
 	(void)(tdns_machine_resolvconf_error);
 	(void)(tdns_machine_resolvconf_en_main);
 
 	if(tsk_strnullORempty(fullpath)){
 		fullpath = TNET_RESOLV_CONF_PATH;
 	}
 
 	/* Open the file and read all data */
 	if((fd = fopen(fullpath, "r"))){
 		long len;
 		fseek(fd, 0L, SEEK_END);
 		len = ftell(fd);
 		fseek(fd, 0L, SEEK_SET);
 		#if HAVE_CRT //Debug memory
 		if (!(buf = (char*)tsk_calloc(len + 1, 1))) {
 		
 	#else
 		if (!(buf = (char*)calloc(len + 1, 1))) {
 	#endif //HAVE_CRT
 			TSK_DEBUG_ERROR("Failed to allocate buffer with size = %ld", (len + 1));
 			goto bail;
 		}
 		fread(buf, 1, len, fd);
 		p = &buf[0];
 		pe = p + len + 1/*hack*/;
 		eof = pe;
 		fclose(fd);
 		
 		buf[len] = '\n'; // hack to have perfect lines
 
 		servers = tsk_list_create();
 	}
 	else {
 #if ANDROID || defined(__APPLE__) /* TARGET_OS_IPHONE not defined for bsd libraries */
 		TSK_DEBUG_INFO("Failed to open [%s]. But don't panic, we have detected that you are using Google Android/iOS Systems.\n"
 			"You should look at the Progammer's Guide for more information.\n If you are not using DNS functions, don't worry about this warning.", 
 			fullpath);
 #else
 		TSK_DEBUG_ERROR("Failed to open %s.", fullpath);
 #endif
 		goto bail;
 	}
 
 	TSK_RAGEL_DISABLE_WARNINGS_BEGIN()
 	%%write init;
 	%%write exec;
 	TSK_RAGEL_DISABLE_WARNINGS_END()
 	
 	if (cs < %%{ write first_final; }%% ) {
 		TSK_DEBUG_ERROR("Failed to parse %s.", fullpath);
 		TSK_OBJECT_SAFE_FREE(servers);
 	}
 
 bail:
 	TSK_FREE(buf);
 	return servers;
 }