package at.knowcenter.wag.egov.egiz.ldap.api;

import java.util.Hashtable;

import org.apache.log4j.Logger;

import at.knowcenter.wag.egov.egiz.sig.LDAPAPI;

/**
 * @author <a href="mailto:thomas.knall@iaik.tugraz.at">Thomas Knall</a>
 */
public class LDAPAPIFactoryImpl extends LDAPAPIFactory {

	private static final Logger log = Logger.getLogger(LDAPAPIFactoryImpl.class);

	private Hashtable<String, LDAPAPI> ldapImpls;
	
	protected LDAPAPIFactoryImpl() {
		ldapImpls = new Hashtable<String, LDAPAPI>();
	}

	private static LDAPAPI instantiatelAPIImpl(String implClassURI) throws LDAPAPIException {
		if (implClassURI == null) {
			throw new NullPointerException("URI of implementing class must not be null.");
		}
		if (implClassURI.length() == 0) {
			throw new IllegalArgumentException("URI of implementing class must not be empty.");
		}
		log.info("Trying to instantiate \"" + LDAPAPI.class.getName() + "\" implementation \"" + implClassURI + "\"...");
		LDAPAPI ldapAPIImpl = null;
		try {
			Class clazz = Class.forName(implClassURI);
			Object ldapAPIImplObj = clazz.newInstance();
			if (!(ldapAPIImplObj instanceof LDAPAPI)) {
				throw new LDAPAPIException("Declared class does not implement \""	+ LDAPAPI.class.getName() + "\".");
			}
			ldapAPIImpl = (LDAPAPI) ldapAPIImplObj;
			log.info("LDAPAPI implementation successfully instantiated.");
		} catch (InstantiationException e) {
			throw new LDAPAPIException("Declared implementation of \"" + LDAPAPI.class.getName() + "\" cannot be instantiated.");
		} catch (IllegalAccessException e) {
			throw new LDAPAPIException("Declared implementation of \"" + LDAPAPI.class.getName() + "\" cannot be instantiated (illegal access).");
		} catch (ClassNotFoundException e) {
			throw new LDAPAPIException("Unable to find class \"" + implClassURI + "\" as implementation of \"" + LDAPAPI.class.getName() + "\".");
		}
		return ldapAPIImpl;
	}
	
	public synchronized LDAPAPI createLDAPAPI(String implClassURI) throws LDAPAPIException {
		if (implClassURI == null || implClassURI.length() == 0) {
			// use internal implementation
			implClassURI = LDAPAPIImpl.class.getName();
		}
		LDAPAPI impl = ldapImpls.get(implClassURI);
		if (impl == null) {
			impl = instantiatelAPIImpl(implClassURI);
			ldapImpls.put(implClassURI, impl);
		}
		return impl;
	}

}