/**
 * Copyright 2010 JBoss Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.drools.guvnor.server.selector;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.drools.repository.AssetItem;


public class SelectorManager {

	private static final Logger log = LoggerFactory.getLogger( SelectorManager.class );
	public static String SELECTOR_CONFIG_PROPERTIES = "/selectors.properties";
	private static final SelectorManager INSTANCE = new SelectorManager(SELECTOR_CONFIG_PROPERTIES);

    /**
     * This is a map of the selectors to use.
     */
	public final Map<String, AssetSelector> selectors = new HashMap<String, AssetSelector>();

	SelectorManager(String configPath) {
		log.debug("Loading selectors");
		Properties props = new Properties();
		try {
			props.load(this.getClass().getResourceAsStream(configPath));
		    props.put("BuiltInSelector", "org.drools.guvnor.server.selector.BuiltInSelector");
			for (Iterator iter = props.keySet().iterator(); iter.hasNext();) {
				String selectorName = (String) iter.next();
				String val = props.getProperty(selectorName);
                try {
                    if (val.endsWith("drl")) {
                        selectors.put(selectorName ,loadRuleSelector( val) );
                    } else {
                        selectors.put(selectorName, loadSelectorImplementation( val ));
                    }
                } catch (Exception e) {
                    log.error("Unable to load a selector [" + val + "]", e);
                }
			}
		} catch (IOException e) {
			log.error("Unable to load selectors.", e);
		}
	}

    /**
     * Return a selector. If the name is null or empty it will return a nil/default selector
     * (one that lets everything through). If the selector is not found, it will return null;
     */
    public AssetSelector getSelector(String name) {
        if (name == null || "".equals(name.trim())) {
            return nilSelector();
        } else {
            if (this.selectors.containsKey( name )) {
                return this.selectors.get( name );
            } else {
                log.debug( "No selector found by the name of " + name );
                return null;
            }
        }
    }
    
    public String[] getCustomSelectors() {
    	 Set<String> s = selectors.keySet();    	 
    	 List<String> selectorList = new ArrayList<String>();
    	 selectorList.addAll(s);    	 
    	 selectorList.remove("BuiltInSelector");
    	 String[] result = new String[selectorList.size()];
    	 return selectorList.toArray(result);
    }

	private AssetSelector nilSelector() {
        return new AssetSelector() {
            public boolean isAssetAllowed(AssetItem asset) {
                return true;
            }
        };
    }

    private AssetSelector loadSelectorImplementation(String val) throws Exception {
        return (AssetSelector) Thread.currentThread().getContextClassLoader().loadClass( val ).newInstance();
 	}

	private AssetSelector loadRuleSelector(String val) {

		return new RuleBasedSelector(val);
	}

	public static SelectorManager getInstance() {
		return INSTANCE;
	}
}