package com.infomancers.collections.yield.asmbase;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.commons.EmptyVisitor;
import org.objectweb.asm.util.CheckClassAdapter;
import org.objectweb.asm.util.TraceClassVisitor;

import java.io.PrintWriter;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

/**
 * Copyright (c) 2007, Aviad Ben Dov
 * <p/>
 * All rights reserved.
 * <p/>
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * <p/>
 * 1. Redistributions of source code must retain the above copyright notice, this list
 * of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice, this
 * list of conditions and the following disclaimer in the documentation and/or other
 * materials provided with the distribution.
 * 3. Neither the name of Infomancers, Ltd. nor the names of its contributors may be
 * used to endorse or promote products derived from this software without specific
 * prior written permission.
 * <p/>
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
public abstract class AbstractYielderTransformer implements ClassFileTransformer {
    private final boolean debug;

    public AbstractYielderTransformer(boolean debug) {
        this.debug = debug;
    }

    public final byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
        byte[] result = classfileBuffer;

        if (classBeingRedefined == null) {
            try {
                // first pass - gather statistics
                ClassReader reader = new ClassReader(classfileBuffer);
                final YieldReturnCounter counter = new YieldReturnCounter(new EmptyVisitor());
                final LocalVariableMapper mapper = new LocalVariableMapper(counter);
                YielderChecker checker = new YielderChecker(mapper);

                reader.accept(checker, 0);

                if (checker.isYielder()) {
                    // second pass - write new code
                    trace("Before", result);

                    YielderInformationContainer info = new DelegatingInformationContainer(counter, mapper);

                    if (debug) {
                        System.out.println("info: [" + info + "]");
                    }

                    result = enhanceClass(reader, info);

                    trace("After", result);
                    check(result);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return result;
    }

    protected abstract byte[] enhanceClass(ClassReader reader, YielderInformationContainer info);

    private void trace(String title, byte[] classfileBytes) {
        if (debug) {
            TraceClassVisitor traceClassVisitor = new TraceClassVisitor(new PrintWriter(System.out));

            System.out.println();
            System.out.println("<------------- " + title + " ---------------> ");
            new ClassReader(classfileBytes).accept(traceClassVisitor, 0);
        }
    }

    private void check(byte[] bytes) {
        if (debug) {
            CheckClassAdapter.verify(new ClassReader(bytes), true, new PrintWriter(System.out));
        }
    }

}