StandardBindings.java

/*
 * RHQ Management Platform
 * Copyright (C) 2005-2011 Red Hat, Inc.
 * All rights reserved.
 *
 * 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 version 2 of the License.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

package org.rhq.bindings;

import java.io.PrintWriter;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import javax.script.ScriptEngine;

import org.rhq.bindings.client.ResourceClientFactory;
import org.rhq.bindings.client.RhqFacade;
import org.rhq.bindings.client.RhqManager;
import org.rhq.bindings.export.Exporter;
import org.rhq.bindings.output.TabularWriter;
import org.rhq.bindings.util.ScriptAssert;
import org.rhq.bindings.util.ScriptUtil;
import org.rhq.core.domain.auth.Subject;
import org.rhq.core.domain.util.PageControl;

/**
 * This class encapsulates the standard set of data inserted in the {@link ScriptContext#ENGINE_SCOPE} of the
 * script engines.
 * <p>
 * Upon instantiation this class has all the properties initialized with the default values so that a common base
 * is available for all the users of this class. The user is however able to later modify these defaults to provide
 * use-case specific overrides (for example the CLI might want to supply impls that hook into the console to provide
 * interactivity with user in some workflows, which, generically, is not possible in a common case).
 * <p>
 * *NOTE*: any change in what is exposed to the scripting clients needs to be reflected in the API check configuration
 * in the pom.xml of the corresponding modules, because any class that gets exposed in the script context essentially
 * becomes a public API.
 *
 * @author Lukas Krejci
 */
public class StandardBindings extends HashMap<String, Object> {

    /**
     * A listener interface for objects that need to be aware of the fact that the
     * RHQ facade associated with the bidings has changed.
     */
    public interface RhqFacadeChangeListener {
        void rhqFacadeChanged(StandardBindings bindings);
    }

    private static final long serialVersionUID = 1L;

    public static final String UNLIMITED_PC = "unlimitedPC";
    public static final String PAGE_CONTROL = "pageControl";
    public static final String EXPORTER = "exporter";
    public static final String SUBJECT = "subject";
    public static final String PRETTY = "pretty";
    public static final String SCRIPT_UTIL = "scriptUtil";
    public static final String PROXY_FACTORY = "ProxyFactory";
    public static final String ASSERT = "Assert";

    private Map<RhqManager, Object> managers;
    private Set<RhqFacadeChangeListener> facadeChangeListeners;
    private RhqFacade rhqFacade;

    private static class CastingEntry<T> implements Map.Entry<String, T> {

        private Map.Entry<String, Object> inner;
        private Class<T> clazz;

        public CastingEntry(Map.Entry<String, Object> inner, Class<T> clazz) {
            this.inner = inner;
            this.clazz = clazz;
        }

        @Override
        public String getKey() {
            return inner.getKey();
        }

        @Override
        public T getValue() {
            return clazz.cast(inner.getValue());
        }

        @Override
        public T setValue(T value) {
            return clazz.cast(inner.setValue(value));
        }

    }

    public StandardBindings(PrintWriter output, RhqFacade rhqFacade) {
        facadeChangeListeners = new HashSet<RhqFacadeChangeListener>();
        PageControl pc = new PageControl();
        pc.setPageNumber(-1);

        //these are generic and don't require an RHQ facade...
        put(UNLIMITED_PC, pc);
        put(PAGE_CONTROL, PageControl.getUnlimitedInstance());
        put(EXPORTER, new Exporter());
        put(PRETTY, new TabularWriter(output));
        put(ASSERT, new ScriptAssert());

        setFacade(output, rhqFacade);
    }

    /**
     * If you want to preserve non-client-dependent bindings when the facade changes, call this as opposed to
     * constructing new StandardBindings.
     */
    public void setFacade(PrintWriter output, RhqFacade rhqFacade) {
        // remove any existing managers
        if (null != managers) {
            for (RhqManager manager : managers.keySet()) {
                remove(manager.name());
            }
            managers.clear();
        }

        //script utils can handle a null facade
        put(SCRIPT_UTIL, new ScriptUtil(rhqFacade));

        if (rhqFacade != null) {
            managers = rhqFacade.getScriptingAPI();

            put(SUBJECT, rhqFacade.getSubject());
            put(PROXY_FACTORY, new ResourceClientFactory(rhqFacade, output));
        } else {
            managers = Collections.emptyMap();
            put(SUBJECT, null);
            put(PROXY_FACTORY, null);
        }

        for (Map.Entry<RhqManager, Object> entry : managers.entrySet()) {
            put(entry.getKey().name(), entry.getValue());
        }

        this.rhqFacade = rhqFacade;

        notifyFacadeChanged();
    }

    public RhqFacade getAssociatedRhqFacade() {
        return rhqFacade;
    }

    public void addRhqFacadeChangeListener(RhqFacadeChangeListener listener) {
        this.facadeChangeListeners.add(listener);
        listener.rhqFacadeChanged(this);
    }

    public void removeRhqFacadeChangeListere(RhqFacadeChangeListener listener) {
        this.facadeChangeListeners.remove(listener);
    }

    public void preInject(ScriptEngine scriptEngine) {
        ((ScriptUtil) get(SCRIPT_UTIL)).init(scriptEngine);
        ((ScriptAssert) get(ASSERT)).init(scriptEngine);
    }

    public void postInject(ScriptEngine scriptEngine) {
        ScriptEngineFactory.bindIndirectionMethods(scriptEngine, SCRIPT_UTIL);
        ScriptEngineFactory.bindIndirectionMethods(scriptEngine, ASSERT);
    }

    public Map.Entry<String, PageControl> getUnlimitedPC() {
        return castEntry(UNLIMITED_PC, PageControl.class);
    }

    public Map.Entry<String, PageControl> getPageControl() {
        return castEntry(PAGE_CONTROL, PageControl.class);
    }

    public Map.Entry<String, Exporter> getExporter() {
        return castEntry(EXPORTER, Exporter.class);
    }

    public Map.Entry<String, Subject> getSubject() {
        return castEntry(SUBJECT, Subject.class);
    }

    public Map.Entry<String, TabularWriter> getPretty() {
        return castEntry(PRETTY, TabularWriter.class);
    }

    public Map.Entry<String, ScriptUtil> getScriptUtil() {
        return castEntry(SCRIPT_UTIL, ScriptUtil.class);
    }

    public Map.Entry<String, ResourceClientFactory> getProxyFactory() {
        return castEntry(PROXY_FACTORY, ResourceClientFactory.class);
    }

    public Map<RhqManager, Object> getManagers() {
        //XXX ideally this should be a projection into our map
        return (null == managers) ? managers = Collections.emptyMap() : managers;
    }

    private Map.Entry<String, Object> getEntry(String key) {
        for (Map.Entry<String, Object> entry : entrySet()) {
            if (key == null && entry.getKey() == null) {
                return entry;
            } else if (key.equals(entry.getKey())) {
                return entry;
            }
        }

        return null;
    }

    private <T> Map.Entry<String, T> castEntry(String key, Class<T> clazz) {
        Map.Entry<String, Object> entry = getEntry(key);
        if (entry == null) {
            return null;
        }

        return new CastingEntry<T>(entry, clazz);
    }

    private void notifyFacadeChanged() {
        for (RhqFacadeChangeListener listener : facadeChangeListeners) {
            listener.rhqFacadeChanged(this);
        }
    }
}