package org.apache.commons.chain.generic;

import org.apache.commons.chain.Command;
import org.apache.commons.chain.Context;
import java.lang.reflect.Method;
import java.util.WeakHashMap;
import java.lang.reflect.InvocationTargetException;

/**
 * An abstract base command which uses introspection to look up a method to execute.  
 * For use by developers who prefer to group related functionality into a single class
 * rather than an inheritance family.
 */

public abstract class DispatchCommand implements Command {

    protected WeakHashMap methods = new WeakHashMap();

    protected String method = null;

    protected String methodKey = null;

    protected static final Class[] DEFAULT_SIGNATURE = new Class[] { Context.class };

    public boolean execute(Context context) throws Exception {

        if (this.getMethod() == null && this.getMethodKey() == null) {
            throw new IllegalStateException("Neither 'method' nor 'methodKey' properties are defined ");
        }

        Method methodObject = extractMethod(context);

        return invokeMethod(methodObject, context);
    }

    protected Method extractMethod(Context context) throws NoSuchMethodException {

        String methodName = this.getMethod();

        if (methodName == null) {
            methodName = context.get(this.getMethodKey()).toString();
        }

        Method theMethod = null;

        synchronized (methods) {
            theMethod = (Method) methods.get(methodName);

            if (theMethod == null) {
                theMethod = getClass().getMethod(methodName, getSignature());
                methods.put(methodName, theMethod);
            }
        }

        return theMethod;
    }


    protected boolean invokeMethod(Method methodObject, Context context) throws InvocationTargetException, IllegalAccessException {
        
        Boolean result = (Boolean) methodObject.invoke(this, getArguments(context));

        return (result != null && result.booleanValue());
        
    }

    protected Class[] getSignature() {
        return DEFAULT_SIGNATURE;
    }

    protected Object[] getArguments(Context context) {
        return new Object[] { context };
    }

    public String getMethod() {
        return method;
    }
    public String getMethodKey() {
        return methodKey;
    }
    public void setMethod(String method) {
        this.method = method;
    }
    public void setMethodKey(String methodKey) {
        this.methodKey = methodKey;
    }

    

}