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Groovy: A powerful, dynamic language for the JVM
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/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package groovy.lang;

import org.codehaus.groovy.ast.expr.ArgumentListExpression;
import org.codehaus.groovy.control.CompilationFailedException;
import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.codehaus.groovy.runtime.InvokerHelper;

import java.io.File;
import java.io.IOException;

/**
 * This object represents a Groovy script
 *
 * @author James Strachan
 * @author Guillaume Laforge
 * @version $Revision: 7222 $
 */
public abstract class Script extends GroovyObjectSupport {
    private Binding binding;

    protected Script() {
        this(new Binding());
    }

    protected Script(Binding binding) {
        this.binding = binding;
    }

    public Binding getBinding() {
        return binding;
    }

    public void setBinding(Binding binding) {
        this.binding = binding;
    }

    public Object getProperty(String property) {
        try {
            return binding.getVariable(property);
        } catch (MissingPropertyException e) {
            return super.getProperty(property);
        }
    }

    public void setProperty(String property, Object newValue) {
        if ("binding".equals(property))
            setBinding((Binding) newValue);
        else if("metaClass".equals(property))
            setMetaClass((MetaClass)newValue);
        else
            binding.setVariable(property, newValue);
    }

    /**
     * Invoke a method (or closure in the binding) defined.
     *
     * @param name method to call
     * @param args arguments to pass to the method
     * @return value
     */
    public Object invokeMethod(String name, Object args) {
        try {
            return super.invokeMethod(name, args);
        }
        // if the method was not found in the current scope (the script's methods)
        // let's try to see if there's a method closure with the same name in the binding
        catch (MissingMethodException mme) {
            try {
                if (name.equals(mme.getMethod())) {
                    Object boundClosure = binding.getVariable(name);
                    if (boundClosure != null && boundClosure instanceof Closure) {
                        return ((Closure) boundClosure).call((Object[])args);
                    } else {
                        throw mme;
                    }
                } else {
                    throw mme;
                }
            } catch (MissingPropertyException mpe) {
                throw mme;
            }
        }
    }

    /**
     * The main instance method of a script which has variables in scope
     * as defined by the current {@link Binding} instance.
     */
    public abstract Object run();

    // println helper methods

    /**
     * Prints a newline to the current 'out' variable which should be a PrintWriter
     * or at least have a println() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void println() {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            System.out.println();
            return;
        }

        InvokerHelper.invokeMethod(object, "println", ArgumentListExpression.EMPTY_ARRAY);
    }

    /**
     * Prints the value to the current 'out' variable which should be a PrintWriter
     * or at least have a print() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void print(Object value) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.print(System.out,value);
            return;
        }

        InvokerHelper.invokeMethod(object, "print", new Object[]{value});
    }

    /**
     * Prints the value and a newline to the current 'out' variable which should be a PrintWriter
     * or at least have a println() method defined on it.
     * If there is no 'out' property then print to standard out.
     */
    public void println(Object value) {
        Object object;

        try {
            object = getProperty("out");
        } catch (MissingPropertyException e) {
            DefaultGroovyMethods.println(System.out,value);
            return;
        }

        InvokerHelper.invokeMethod(object, "println", new Object[]{value});
    }

    /**
     * A helper method to allow the dynamic evaluation of groovy expressions using this
     * scripts binding as the variable scope
     *
     * @param expression is the Groovy script expression to evaluate
     */
    public Object evaluate(String expression) throws CompilationFailedException, IOException {
        GroovyShell shell = new GroovyShell(binding);
        return shell.evaluate(expression);
    }

    /**
     * A helper method to allow the dynamic evaluation of groovy expressions using this
     * scripts binding as the variable scope
     *
     * @param file is the Groovy script to evaluate
     */
    public Object evaluate(File file) throws CompilationFailedException, IOException {
        GroovyShell shell = new GroovyShell(binding);
        return shell.evaluate(file);
    }

    /**
     * A helper method to allow scripts to be run taking command line arguments
     */
    public void run(File file, String[] arguments) throws CompilationFailedException, IOException {
        GroovyShell shell = new GroovyShell(binding);
        shell.run(file, arguments);
    }
}