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/*
 * Copyright 2003-2013 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 org.codehaus.groovy.runtime;

import groovy.lang.Closure;

import java.util.List;

/**
 * A wrapper for Closure to support composition.
 * Normally used only internally through the rightShift() and
 * leftShift() methods on Closure.
 * 
 * Typical usages:
 * 
 * def twice = { a -> a * 2 }
 * def inc = { b -> b + 1 }
 * def f = { x -> twice(inc(x)) } // longhand
 * def g = inc >> twice
 * def h = twice << inc
 * assert f(10) == 22
 * assert g(10) == 22
 * assert h(10) == 22
 *
 * def s2c = { it.chars[0] }
 * def p = Integer.&toHexString >> s2c >> Character.&toUpperCase
 * assert p(15) == 'F'
 *
 * def multiply = { a, b -> a * b }
 * def identity = { a -> [a, a] }
 * def sq = identity >> multiply
 * assert (1..5).collect{ sq(it) } == [1, 4, 9, 16, 25]
 *
 * def add3 = { a, b, c -> a + b + c }
 * def add2plus10 = add3.curry(10)
 * def multBoth = { a, b, c -> [a*c, b*c] }
 * def twiceBoth = multBoth.rcurry(2)
 * def twiceBothPlus10 = twiceBoth >> add2plus10
 * assert twiceBothPlus10(5, 10) == 40
 * 
 *
 * @author Paul King
 */
public final class ComposedClosure extends Closure {

    private Closure first;
    private Closure second;

    public ComposedClosure(Closure first, Closure second) {
        super(first.clone());
        this.first = (Closure) getOwner();
        this.second = (Closure) second.clone();
        maximumNumberOfParameters = first.getMaximumNumberOfParameters();
    }

    public void setDelegate(Object delegate) {
        ((Closure) getOwner()).setDelegate(delegate);
        second.setDelegate(delegate);
    }

    public Object getDelegate() {
        return ((Closure) getOwner()).getDelegate();
    }

    public void setResolveStrategy(int resolveStrategy) {
        ((Closure) getOwner()).setResolveStrategy(resolveStrategy);
        second.setResolveStrategy(resolveStrategy);
    }

    public int getResolveStrategy() {
        return ((Closure) getOwner()).getResolveStrategy();
    }

    public Object clone() {
        return new ComposedClosure(first, second);
    }

    public Class[] getParameterTypes() {
        return first.getParameterTypes();
    }

    public Object doCall(Object... args) {
        return call(args);
    }

    @Override
    public V call(Object... args) {
        Object temp = first.call(args);
        if (temp instanceof List && second.getParameterTypes().length > 1) temp = ((List) temp).toArray();
        return temp instanceof Object[] ? second.call((Object[]) temp) : second.call(temp);
    }
}