/*
 * Copyright 2011 The Apache Software Foundation
 *
 *  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 net.sf.cglib.proxy;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import net.sf.cglib.core.Constants;
import net.sf.cglib.core.Signature;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

Uses bytecode reflection to figure out the targets of all bridge methods that use invokespecial
and invokeinterface, so that we can later rewrite them to use invokevirtual.
For interface bridges, using invokesuper will fail since the method being bridged to is in a
superinterface, not a superclass. Starting in Java 8, javac emits default bridge methods in
interfaces, which use invokeinterface to bridge to the target method.
Author:
sberlin@gmail.com (Sam Berlin)/**
 * Uses bytecode reflection to figure out the targets of all bridge methods that use invokespecial
 * and invokeinterface, so that we can later rewrite them to use invokevirtual.
 *
 * <p>For interface bridges, using invokesuper will fail since the method being bridged to is in a
 * superinterface, not a superclass. Starting in Java 8, javac emits default bridge methods in
 * interfaces, which use invokeinterface to bridge to the target method.
 *
 * @author sberlin@gmail.com (Sam Berlin)
 */
class BridgeMethodResolver {

    private final Map/* <Class, Set<Signature> */declToBridge;
    private final ClassLoader classLoader;

    public BridgeMethodResolver(Map declToBridge, ClassLoader classLoader) {
        this.declToBridge = declToBridge;
        this.classLoader = classLoader;
    }

    
Finds all bridge methods that are being called with invokespecial &
returns them.
/**
     * Finds all bridge methods that are being called with invokespecial &
     * returns them.
     */
    public Map/*<Signature, Signature>*/resolveAll() {
        Map resolved = new HashMap();
        for (Iterator entryIter = declToBridge.entrySet().iterator(); entryIter.hasNext(); ) {
            Map.Entry entry = (Map.Entry) entryIter.next();
            Class owner = (Class) entry.getKey();
            Set bridges = (Set) entry.getValue();
            try {
                InputStream is = classLoader.getResourceAsStream(owner.getName().replace('.', '/') + ".class");
                if (is == null) {
                    return resolved;
                }
                try {
                    new ClassReader(is)
                            .accept(new BridgedFinder(bridges, resolved),
                                    ClassReader.SKIP_FRAMES | ClassReader.SKIP_DEBUG);
                } finally {
                    is.close();
                }
            } catch (IOException ignored) {}
        }
        return resolved;
    }

    private static class BridgedFinder extends ClassVisitor {
        private Map/*<Signature, Signature>*/ resolved;
        private Set/*<Signature>*/ eligibleMethods;
        
        private Signature currentMethod = null;

        BridgedFinder(Set eligibleMethods, Map resolved) {
            super(Constants.ASM_API);
            this.resolved = resolved;
            this.eligibleMethods = eligibleMethods;
        }

        public void visit(int version, int access, String name,
                String signature, String superName, String[] interfaces) {
        }

        public MethodVisitor visitMethod(int access, String name, String desc,
                String signature, String[] exceptions) {
            Signature sig = new Signature(name, desc);
            if (eligibleMethods.remove(sig)) {
                currentMethod = sig;
                return new MethodVisitor(Constants.ASM_API) {
                    public void visitMethodInsn(
                            int opcode, String owner, String name, String desc, boolean itf) {
                        if ((opcode == Opcodes.INVOKESPECIAL
                                        || (itf && opcode == Opcodes.INVOKEINTERFACE))
                                && currentMethod != null) {
                            Signature target = new Signature(name, desc);
                            // If the target signature is the same as the current,
                            // we shouldn't change our bridge becaues invokespecial
                            // is the only way to make progress (otherwise we'll
                            // get infinite recursion).  This would typically
                            // only happen when a bridge method is created to widen
                            // the visibility of a superclass' method.
                            if (!target.equals(currentMethod)) {
                                resolved.put(currentMethod, target);
                            }
                            currentMethod = null;
                        }
                    }
                };
            } else {
                return null;
            }
        }
    }

}