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CommonMarkRenderer.java
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CommonMarkRenderer.java
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/*
* Copyright 2015, Red Hat, Inc. and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.zanata.util;
import com.google.common.base.Throwables;
import lombok.extern.slf4j.Slf4j;
import org.jboss.seam.ScopeType;
import org.jboss.seam.annotations.AutoCreate;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.Scope;
import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
/**
* @author Sean Flanigan <a href="mailto:sflaniga@redhat.com">sflaniga@redhat.com</a>
*/
@AutoCreate
@Name("commonMarkRenderer")
@Scope(ScopeType.APPLICATION)
@Slf4j
public class CommonMarkRenderer {
// TODO when upgrading, use org.webjars.bower:commonmark Maven artifact
// instead, plus org.apache.servicemix.tooling:depends-maven-plugin to
// generate dependencies.properties and get the correct version.
private static final String commonMarkImpl = "commonmark-0.18.1.min.js";
// ScriptEngine is expensive, but not really threadsafe (even in Rhino).
// However, they are quite large, so it's probably not worth keeping
// one for every thread. Instead, we keep one around, and synchronise
// access to it.
// Please ensure any methods which use this Invocable are synchronized!
private Invocable invocable = getInvocable();
/**
* Return the name of the implementation script, available under "/script/"
* (ie under web resource "$zanata/script/" or under classpath resource
* "META-INF/resources/script/".
*
* NB also used in JSF as
* <code><h:outputScript target="body" library="script" name="${commonMarkRenderer.scriptName}"/></code>
* @return
*/
public String getScriptName() {
return commonMarkImpl;
}
/**
* Render CommonMark text to HTML and sanitise it.
* @param commonMark
* @return
*/
public String renderToHtmlSafe(String commonMark) {
String unsafeHtml = renderToHtmlUnsafe(commonMark);
return HtmlUtil.SANITIZER.sanitize(unsafeHtml);
}
public synchronized String renderToHtmlUnsafe(String commonMark) {
try {
return (String) invocable.invokeFunction("mdRender", commonMark);
} catch (ScriptException | NoSuchMethodException e) {
throw Throwables.propagate(e);
}
}
private Invocable getInvocable() {
try (BufferedReader reader = new BufferedReader(new InputStreamReader(
getScriptAsStream(getScriptName()), StandardCharsets.UTF_8))) {
ScriptEngine engine = newEngine();
engine.eval("window = this;");
engine.eval(reader);
// Create a javascript function 'mdRender' which takes CommonMark
// as a string and returns a rendered HTML string:
String initScript =
"var reader = new commonmark.Parser();" +
"var writer = new commonmark.HtmlRenderer();" +
"function mdRender(src) {" +
" return writer.render(reader.parse(src));" +
"};";
engine.eval(initScript);
return (Invocable) engine;
} catch (IOException | ScriptException e) {
throw Throwables.propagate(e);
}
}
protected InputStream getScriptAsStream(String scriptName) {
return getClass().getClassLoader().getResourceAsStream(
"META-INF/resources/script/" + scriptName);
}
private ScriptEngine newEngine() {
ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
ScriptEngine engine =
scriptEngineManager.getEngineByName("rhino17R5");
if (engine == null) {
log.warn("Falling back on generic JavaScript engine");
engine = scriptEngineManager.getEngineByName("JavaScript");
}
return engine;
}
}