/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.commons.lang.reflect;

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import org.apache.commons.lang.ArrayUtils;
import org.apache.commons.lang.ClassUtils;
import org.apache.commons.lang.SystemUtils;

/**
 * Contains common code for working with Methods/Constructors, extracted and
 * refactored from <code>MethodUtils</code> when it was imported from Commons
 * BeanUtils.
 *
 * @author Apache Software Foundation
 * @author Steve Cohen
 * @author Matt Benson
 * @since 2.5
 * @version $Id$
 */
abstract class MemberUtils {
    // TODO extract an interface to implement compareParameterSets(...)?

    private static final int ACCESS_TEST = Modifier.PUBLIC | Modifier.PROTECTED | Modifier.PRIVATE;

    private static final Method IS_SYNTHETIC;
    static {
        Method isSynthetic = null;
        if (SystemUtils.isJavaVersionAtLeast(1.5f)) {
            // cannot call synthetic methods:
            try {
                isSynthetic = Member.class.getMethod("isSynthetic",
                        ArrayUtils.EMPTY_CLASS_ARRAY);
            } catch (Exception e) {
            }
        }
        IS_SYNTHETIC = isSynthetic;
    }

    /** Array of primitive number types ordered by "promotability" */
    private static final Class[] ORDERED_PRIMITIVE_TYPES = { Byte.TYPE, Short.TYPE,
            Character.TYPE, Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE };

    /**
     * XXX Default access superclass workaround
     *
     * When a public class has a default access superclass with public members,
     * these members are accessible. Calling them from compiled code works fine.
     * Unfortunately, on some JVMs, using reflection to invoke these members
     * seems to (wrongly) to prevent access even when the modifer is public.
     * Calling setAccessible(true) solves the problem but will only work from
     * sufficiently privileged code. Better workarounds would be gratefully
     * accepted.
     * @param o the AccessibleObject to set as accessible
     */
    static void setAccessibleWorkaround(AccessibleObject o) {
        if (o == null || o.isAccessible()) {
            return;
        }
        Member m = (Member) o;
        if (Modifier.isPublic(m.getModifiers())
                && isPackageAccess(m.getDeclaringClass().getModifiers())) {
            try {
                o.setAccessible(true);
            } catch (SecurityException e) {
                // ignore in favor of subsequent IllegalAccessException
            }
        }
    }

    /**
     * Learn whether a given set of modifiers implies package access.
     * @param modifiers to test
     * @return true unless package/protected/private modifier detected
     */
    static boolean isPackageAccess(int modifiers) {
        return (modifiers & ACCESS_TEST) == 0;
    }

    /**
     * Check a Member for basic accessibility.
     * @param m Member to check
     * @return true if <code>m</code> is accessible
     */
    static boolean isAccessible(Member m) {
        return m != null && Modifier.isPublic(m.getModifiers()) && !isSynthetic(m);
    }

    /**
     * Try to learn whether a given member, on JDK >= 1.5, is synthetic.
     * @param m Member to check
     * @return true if <code>m</code> was introduced by the compiler.
     */
    static boolean isSynthetic(Member m) {
        if (IS_SYNTHETIC != null) {
            try {
                return ((Boolean) IS_SYNTHETIC.invoke(m, null)).booleanValue();
            } catch (Exception e) {
            }
        }
        return false;
    }

    /**
     * Compare the relative fitness of two sets of parameter types in terms of
     * matching a third set of runtime parameter types, such that a list ordered
     * by the results of the comparison would return the best match first
     * (least).
     *
     * @param left the "left" parameter set
     * @param right the "right" parameter set
     * @param actual the runtime parameter types to match against
     * <code>left</code>/<code>right</code>
     * @return int consistent with <code>compare</code> semantics
     */
    static int compareParameterTypes(Class[] left, Class[] right, Class[] actual) {
        float leftCost = getTotalTransformationCost(actual, left);
        float rightCost = getTotalTransformationCost(actual, right);
        return leftCost < rightCost ? -1 : rightCost < leftCost ? 1 : 0;
    }

    /**
     * Returns the sum of the object transformation cost for each class in the
     * source argument list.
     * @param srcArgs The source arguments
     * @param destArgs The destination arguments
     * @return The total transformation cost
     */
    private static float getTotalTransformationCost(Class[] srcArgs, Class[] destArgs) {
        float totalCost = 0.0f;
        for (int i = 0; i < srcArgs.length; i++) {
            Class srcClass, destClass;
            srcClass = srcArgs[i];
            destClass = destArgs[i];
            totalCost += getObjectTransformationCost(srcClass, destClass);
        }
        return totalCost;
    }

    /**
     * Gets the number of steps required needed to turn the source class into
     * the destination class. This represents the number of steps in the object
     * hierarchy graph.
     * @param srcClass The source class
     * @param destClass The destination class
     * @return The cost of transforming an object
     */
    private static float getObjectTransformationCost(Class srcClass, Class destClass) {
        if (destClass.isPrimitive()) {
            return getPrimitivePromotionCost(srcClass, destClass);
        }
        float cost = 0.0f;
        while (srcClass != null && !destClass.equals(srcClass)) {
            if (destClass.isInterface() && ClassUtils.isAssignable(srcClass, destClass)) {
                // slight penalty for interface match.
                // we still want an exact match to override an interface match,
                // but
                // an interface match should override anything where we have to
                // get a superclass.
                cost += 0.25f;
                break;
            }
            cost++;
            srcClass = srcClass.getSuperclass();
        }
        /*
         * If the destination class is null, we've travelled all the way up to
         * an Object match. We'll penalize this by adding 1.5 to the cost.
         */
        if (srcClass == null) {
            cost += 1.5f;
        }
        return cost;
    }

    /**
     * Get the number of steps required to promote a primitive number to another
     * type.
     * @param srcClass the (primitive) source class
     * @param destClass the (primitive) destination class
     * @return The cost of promoting the primitive
     */
    private static float getPrimitivePromotionCost(final Class srcClass, final Class destClass) {
        float cost = 0.0f;
        Class cls = srcClass;
        if (!cls.isPrimitive()) {
            // slight unwrapping penalty
            cost += 0.1f;
            cls = ClassUtils.wrapperToPrimitive(cls);
        }
        for (int i = 0; cls != destClass && i < ORDERED_PRIMITIVE_TYPES.length; i++) {
            if (cls == ORDERED_PRIMITIVE_TYPES[i]) {
                cost += 0.1f;
                if (i < ORDERED_PRIMITIVE_TYPES.length - 1) {
                    cls = ORDERED_PRIMITIVE_TYPES[i + 1];
                }
            }
        }
        return cost;
    }

}