package org.argeo.cms.e4;
   
   import org.argeo.cms.CmsException;
   import org.eclipse.e4.core.contexts.ContextFunction;
   import org.eclipse.e4.core.contexts.IEclipseContext;
   import org.eclipse.e4.core.di.IInjector;
   import org.osgi.framework.BundleContext;
   import org.osgi.framework.FrameworkUtil;
   import org.osgi.framework.InvalidSyntaxException;
  import org.osgi.framework.ServiceReference;
  
  /** An Eclipse 4 {@link ContextFunction} based on an OSGi filter. */
  public class OsgiFilterContextFunction extends ContextFunction {
  
  	private BundleContext bc = FrameworkUtil.getBundle(OsgiFilterContextFunction.class).getBundleContext();
  
  	@Override
  	public Object compute(IEclipseContext context, String contextKey) {
  		ServiceReference<?>[] srs;
  		try {
  			srs = bc.getServiceReferences((String) null, contextKey);
  		} catch (InvalidSyntaxException e) {
  			throw new CmsException("Context key " + contextKey + " must be a valid osgi filter", e);
  		}
  		if (srs == null || srs.length == 0) {
  			return IInjector.NOT_A_VALUE;
  		} else {
  			// return the first one
  			return bc.getService(srs[0]);
  		}
  	}
  
  }