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A Presentation Model(MVVM) framework for the Android platform

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package org.robobinding.function;

import java.lang.reflect.Method;
import java.text.MessageFormat;
import java.util.Map;
import java.util.Set;

import org.robobinding.Bug;
import org.robobinding.util.MethodUtils;

import com.google.common.collect.Maps;

/**
 * @since 1.0
 * @author Cheng Wei
 *
 */
public class LazyFunctions implements Functions {
	private final Class beanClass;
	private final Map functions;
	private final FunctionSupply supply;

	public LazyFunctions(Class beanClass, Set methods, FunctionSupply supply) {
		this.beanClass = beanClass;
		this.functions = Maps.newHashMap();
		this.supply = supply;
		
		initializeFunctions(methods);
	}

	private void initializeFunctions(Set methods) {
		for(MethodDescriptor method : methods) {
			functions.put(method, null);
		}
	}

	@Override
	public Function find(String functionName, Class... parameterTypes) {
		Method method = MethodUtils.getMatchingAccessibleMethod(beanClass, functionName, parameterTypes);
		
		if(method == null) {
			return null;
		}
		
		MethodDescriptor methodDescriptor = new MethodDescriptor(method.getName(), method.getParameterTypes());
		if(!functions.containsKey(methodDescriptor)) {
			throw new RuntimeException("No such method '"+new MethodDescription(beanClass, method)+"'");
		}
		
		Function function = functions.get(methodDescriptor);
		
		if (function == null) {
			function = supply.tryToCreateFunction(methodDescriptor);
			if(function == null) {
				throw new Bug(MessageFormat.format("The method '{0}' is not generated",  new MethodDescription(beanClass, method)));
			}

			functions.put(methodDescriptor, function);
		}

		return function;
	}
}