/*
* Copyright (C) 2009 Mamadou Diop.
*
* Contact: Mamadou Diop <diopmamadou(at)doubango.org>
*	
* 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.
 *
 * @author Mamadou Diop <diopmamadou(at)doubango.org>
 *
 * @date Created: Sat Nov 8 16:54:58 2009 mdiop
 */
#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);
			
			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;
	FILE* fd;
	char buf[4092];
	
	// Ragel
	int cs = 0;
	const char *p;
	const char *pe;
	const char *eof;

	%%write data;

	if(tsk_strnullORempty(fullpath)){
		fullpath = TNET_RESOLV_CONF_PATH;
	}

	/* Open the file and read all data */
	if((fd = fopen(fullpath, "r"))){
		int len = fread(buf, sizeof(uint8_t), sizeof(buf)-2, 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
		TSK_DEBUG_INFO("Failed to open [%s]. But don't panic, we have detected that you are using Google Android System.\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;
	}

	%%write init;
	%%write exec;
	
	if( cs < %%{ write first_final; }%% ){
		TSK_DEBUG_ERROR("Failed to parse %s.", fullpath);
		TSK_OBJECT_SAFE_FREE(servers);
	}

bail:
	return servers;
}


