/**
 * 
 */
package org.gcube.informationsystem.discovery;

import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.gcube.informationsystem.base.reference.Element;
import org.gcube.informationsystem.base.reference.properties.PropertyElement;
import org.gcube.informationsystem.types.annotations.ISProperty;
import org.gcube.informationsystem.utils.ReflectionUtility;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Luca Frosini (ISTI - CNR)
 */
public class Discovery<E extends Element> {
	
	public static Logger logger = LoggerFactory.getLogger(Discovery.class);
	
	protected final Class<E> root;
	protected final Set<Package> packages;
	protected final List<Class<E>> discoveredElement;
	protected final List<DiscoveredElementAction<Element>> discoveredElementActions;
	
	protected boolean discovered;
	
	public Discovery(Class<E> root) throws Exception {
		this.root = root;
		this.packages = new HashSet<>();
		this.discovered = false;
		this.discoveredElement = new ArrayList<>();
		this.discoveredElementActions = new ArrayList<>();
		add(root);
	}
	
	public List<Class<E>> getDiscoveredElement() {
		return discoveredElement;
	}
	
	@SuppressWarnings("unchecked")
	public synchronized void addDiscoveredElementActions(DiscoveredElementAction<Element> discoveredElementAction) throws Exception {
		discoveredElementActions.add(discoveredElementAction);
		if(discovered) {
			for(Class<E> clz : discoveredElement) {
				discoveredElementAction.analizeElement((Class<Element>) clz);
			}
		}
	}
	
	public void addPackage(Package p) {
		packages.add(p);
	}
	
	public void addPackages(Collection<Package> packages) {
		for(Package p : packages) {
			addPackage(p);
		}
	}

	@SuppressWarnings("unchecked")
	protected void add(Class<E> clz) throws Exception {
		if(!discoveredElement.contains(clz)) {
			discoveredElement.add(clz);
			for(DiscoveredElementAction<Element> discoveredElementAction : discoveredElementActions) {
				discoveredElementAction.analizeElement((Class<Element>) clz);
			}
			logger.info("+ Added {}.", clz);
		}
	}
	
	protected void analizeElement(Class<E> clz) throws Exception {
		logger.trace("Analizyng {}", clz);
		
		if(!clz.isInterface()) {
			logger.trace("- Discarding {} because is not an interface", clz);
			return;
		}
		
		if(!root.isAssignableFrom(clz)) {
			logger.trace("- Discarding {} because is not a {}", clz, root.getSimpleName());
			return;
		}
		
		if(discoveredElement.contains(clz)) {
			logger.trace("- Discarding {} because was already managed", clz);
			return;
		}
		
		Class<?>[] interfaces = clz.getInterfaces();
		
		for(Class<?> interfaceClass : interfaces) {
			@SuppressWarnings("unchecked")
			Class<E> parent = (Class<E>) interfaceClass;
			analizeElement(parent);
		}
		
		if(root == PropertyElement.class) {
			
			for(Method m : clz.getDeclaredMethods()) {
				m.setAccessible(true);
				if(m.isAnnotationPresent(ISProperty.class)) {
					if(Map.class.isAssignableFrom(m.getReturnType()) || Set.class.isAssignableFrom(m.getReturnType())
							|| List.class.isAssignableFrom(m.getReturnType())) {
						
						Type[] typeArguments = ((ParameterizedType) m.getGenericReturnType()).getActualTypeArguments();
						for(Type t : typeArguments) {
							@SuppressWarnings("unchecked")
							Class<? extends PropertyElement> tClass = (Class<? extends PropertyElement>) t;
							if(root.isAssignableFrom(tClass)) {
								@SuppressWarnings("unchecked")
								Class<E> type = (Class<E>) tClass;
								analizeElement(type);
							}
						}
						
					} else if(root.isAssignableFrom(m.getReturnType())) {
						@SuppressWarnings("unchecked")
						Class<E> eClz = (Class<E>) m.getReturnType();
						analizeElement(eClz);
					}
				}
				
			}
		}
		add(clz);
	}
	
	public synchronized void discover() throws Exception {
		this.discovered = false;
		for(Package p : packages) {
			List<Class<?>> classes = ReflectionUtility.getClassesForPackage(p);
			for(Class<?> clz : classes) {
				@SuppressWarnings("unchecked")
				Class<E> eClz = (Class<E>) clz;
				analizeElement(eClz);
			}
		}
		this.discovered = true;
	}
	
}