/*
robotsParser.java
-------------------------------------
part of YACY
(C) 2005, 2006 by Alexander Schier
Martin Thelian
last change: $LastChangedDate$LastChangedBy: orbiter $
Revision: $LastChangedRevision$
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 2 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 private License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
extended to return structured objects instead of a Object[] and
extended to return a Allow-List by Michael Christen, 21.07.2008
extended to allow multiple user agents given by definition and
returning the used user agent my Michael Christen 3.4.2011
*/
package net.yacy.crawler.robots;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Set;
import java.util.regex.Pattern;
import net.yacy.cora.document.UTF8;
/*
* A class for Parsing robots.txt files.
* It only parses the Deny Part, yet.
*
* Robots RFC
* http://www.robotstxt.org/wc/norobots-rfc.html
*
* TODO:
* - On the request attempt resulted in temporary failure a robot
* should defer visits to the site until such time as the resource
* can be retrieved.
*
* - Extended Standard for Robot Exclusion
* See: http://www.conman.org/people/spc/robots2.html
*
* - Robot Exclusion Standard Revisited
* See: http://www.kollar.com/robots.html
*/
public final class RobotsTxtParser {
private static final Pattern patternTab = Pattern.compile("\t");
private static final String ROBOTS_USER_AGENT = "User-agent:".toUpperCase();
private static final String ROBOTS_DISALLOW = "Disallow:".toUpperCase();
private static final String ROBOTS_ALLOW = "Allow:".toUpperCase();
private static final String ROBOTS_COMMENT = "#";
private static final String ROBOTS_SITEMAP = "Sitemap:".toUpperCase();
private static final String ROBOTS_CRAWL_DELAY = "Crawl-delay:".toUpperCase();
private final ArrayList<String> allowList;
private final ArrayList<String> denyList;
private String sitemap;
private long crawlDelayMillis;
private final Set<String> myNames; // a list of own name lists
private String agentName; // the name of the agent that was used to return the result
protected RobotsTxtParser(final Set<String> myNames) {
this.allowList = new ArrayList<String>(0);
this.denyList = new ArrayList<String>(0);
this.sitemap = "";
this.crawlDelayMillis = 0;
this.myNames = myNames;
this.agentName = null;
}
protected RobotsTxtParser(final Set<String> myNames, final byte[] robotsTxt) {
this(myNames);
if (robotsTxt != null && robotsTxt.length != 0) {
final ByteArrayInputStream bin = new ByteArrayInputStream(robotsTxt);
final BufferedReader reader = new BufferedReader(new InputStreamReader(bin));
parse(reader);
}
}
private void parse(final BufferedReader reader) {
final ArrayList<String> deny4AllAgents = new ArrayList<String>();
final ArrayList<String> deny4ThisAgents = new ArrayList<String>();
final ArrayList<String> allow4AllAgents = new ArrayList<String>();
final ArrayList<String> allow4ThisAgents = new ArrayList<String>();
int pos;
String line = null, lineUpper = null;
boolean isRule4AllAgents = false,
isRule4ThisAgents = false,
rule4ThisAgentsFound = false,
inBlock = false;
try {
lineparser: while ((line = reader.readLine()) != null) {
// replacing all tabs with spaces
line = patternTab.matcher(line).replaceAll(" ").trim();
lineUpper = line.toUpperCase();
// parse empty line
if (line.isEmpty()) {
// we have reached the end of the rule block
if (rule4ThisAgentsFound) {
// stop here because other robot blocks are either not for YaCy
// or global settings which shall not overwrite YaCys settings.
break lineparser;
}
continue lineparser;
}
// parse comment
if (line.startsWith(ROBOTS_COMMENT)) {
// we can ignore this. Just a comment line
continue lineparser;
}
// parse sitemap; if there are several sitemaps then take the first url
// TODO: support for multiple sitemaps
if (lineUpper.startsWith(ROBOTS_SITEMAP) && (this.sitemap == null || this.sitemap.isEmpty())) {
pos = line.indexOf(' ');
if (pos != -1) {
this.sitemap = line.substring(pos).trim();
}
continue lineparser;
}
// parse user agent
if (lineUpper.startsWith(ROBOTS_USER_AGENT)) {
if (inBlock) {
// we have detected the start of a new block
if (rule4ThisAgentsFound) {
// stop here because other robot blocks are either not for YaCy
// or global settings which shall not overwrite YaCys settings.
break lineparser;
}
inBlock = false;
isRule4AllAgents = false;
isRule4ThisAgents = false;
this.crawlDelayMillis = 0; // each block has a separate delay
}
// cutting off comments at the line end
pos = line.indexOf(ROBOTS_COMMENT);
if (pos != -1) line = line.substring(0,pos).trim();
// getting out the robots name
pos = line.indexOf(' ');
if (pos != -1) {
final String userAgent = line.substring(pos).trim();
isRule4AllAgents |= userAgent.equals("*");
for (final String agent: this.myNames) {
if (userAgent.toLowerCase().equals(agent)) {
this.agentName = agent;
isRule4ThisAgents = true;
break;
}
}
if (isRule4ThisAgents) rule4ThisAgentsFound = true;
}
continue lineparser;
}
// parse crawl delay
if (lineUpper.startsWith(ROBOTS_CRAWL_DELAY)) {
inBlock = true;
if (isRule4ThisAgents || isRule4AllAgents) {
pos = line.indexOf(' ');
if (pos != -1) {
try {
// the crawl delay can be a float number and means number of seconds
this.crawlDelayMillis = (long) (1000.0 * Float.parseFloat(line.substring(pos).trim()));
} catch (final NumberFormatException e) {
// invalid crawling delay
}
}
}
continue lineparser;
}
// parse disallow
if (lineUpper.startsWith(ROBOTS_DISALLOW) || lineUpper.startsWith(ROBOTS_ALLOW)) {
inBlock = true;
final boolean isDisallowRule = lineUpper.startsWith(ROBOTS_DISALLOW);
if (isRule4ThisAgents || isRule4AllAgents) {
// cutting off comments at the line end
pos = line.indexOf(ROBOTS_COMMENT);
if (pos != -1) line = line.substring(0,pos).trim();
// cut off tailing *
if (line.endsWith("*")) line = line.substring(0,line.length()-1);
// parse the path
pos = line.indexOf(' ');
if (pos >= 0) {
// getting the path
String path = line.substring(pos).trim();
// unencoding all special charsx
try {
path = UTF8.decodeURL(path);
} catch (final Exception e) {
/*
* url decoding failed. E.g. because of
* "Incomplete trailing escape (%) pattern"
*/
}
// escaping all occurences of ; because this char is used as special char in the Robots DB
path = RobotsTxt.ROBOTS_DB_PATH_SEPARATOR_MATCHER.matcher(path).replaceAll("%3B");
// adding it to the pathlist
if (isDisallowRule) {
if (isRule4AllAgents) deny4AllAgents.add(path);
if (isRule4ThisAgents) deny4ThisAgents.add(path);
} else {
if (isRule4AllAgents) allow4AllAgents.add(path);
if (isRule4ThisAgents) allow4ThisAgents.add(path);
}
}
}
continue lineparser;
}
}
} catch (final IOException e) {}
this.allowList.addAll(rule4ThisAgentsFound ? allow4ThisAgents : allow4AllAgents);
this.denyList.addAll(rule4ThisAgentsFound ? deny4ThisAgents : deny4AllAgents);
}
/**
* a crawl delay can be assigned to every agent or for all agents
* a special case is where the user agent of this yacy peer is given explicitely
* using the peer name and then if the crawl delay is given as '0' the crawler
* does not make any no-DOS-forced crawl pause.
* @return the crawl delay between two crawl access times in milliseconds
*/
protected long crawlDelayMillis() {
return this.crawlDelayMillis;
}
/**
* the user agent that was applied to get the crawl properties is recorded
* because it is possible that this robots.txt parser applies to several user agents
* which may be i.e. 'yacy', 'yacybot', <peer-name>'.yacy' or <peer-hash>'.yacyh'
* Effects: see also comment to crawlDelayMillis()
* @return the name of the user agent that was used for the result properties or null if no user agent name was used to identify the agent
*/
protected String agentName() {
return this.agentName;
}
protected String sitemap() {
return this.sitemap;
}
protected ArrayList<String> allowList() {
return this.allowList;
}
protected ArrayList<String> denyList() {
return this.denyList;
}
}