/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2005 Dave Brosius <dbrosius@users.sourceforge.net>
 * Copyright (C) 2005 University of Maryland
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package edu.umd.cs.findbugs.detect;

import org.apache.bcel.classfile.Code;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.BytecodeScanningDetector;
import edu.umd.cs.findbugs.StatelessDetector;
import edu.umd.cs.findbugs.ba.ClassContext;

/**
 * finds public classes that use 'this' as a semaphore, which can cause
 * conflicts if clients of this class use an instance of this class as their own
 * synchronization point. Frankly, Just calling synchronized on this, or
 * defining synchronized methods is bad, but since that is so prevalent, don't
 * warn on that.
 */
public class PublicSemaphores extends BytecodeScanningDetector implements StatelessDetector {
    private static final int SEEN_NOTHING = 0;

    private static final int SEEN_ALOAD_0 = 1;

    private final BugReporter bugReporter;

    private int state;

    private boolean alreadyReported;

    public PublicSemaphores(BugReporter bugReporter) {
        this.bugReporter = bugReporter;
    }

    @Override
    public void visitClassContext(ClassContext classContext) {
        JavaClass cls = classContext.getJavaClass();
        if ((!cls.isPublic()) || (cls.getClassName().indexOf('$') >= 0)) {
            return;
        }

        alreadyReported = false;
        super.visitClassContext(classContext);
    }

    @Override
    public void visit(Code obj) {
        Method m = getMethod();
        if (m.isStatic() || alreadyReported) {
            return;
        }

        state = SEEN_NOTHING;
        super.visit(obj);
    }

    @Override
    public void sawOpcode(int seen) {
        if (alreadyReported) {
            return;
        }

        switch (state) {
        case SEEN_NOTHING:
            if (seen == ALOAD_0) {
                state = SEEN_ALOAD_0;
            }
            break;

        case SEEN_ALOAD_0:
            if ((seen == INVOKEVIRTUAL) && "java/lang/Object".equals(getClassConstantOperand())) {
                String methodName = getNameConstantOperand();
                if ("wait".equals(methodName) || "notify".equals(methodName) || "notifyAll".equals(methodName)) {
                    bugReporter.reportBug(new BugInstance(this, "PS_PUBLIC_SEMAPHORES", NORMAL_PRIORITY).addClassAndMethod(this)
                            .addSourceLine(this));
                    alreadyReported = true;
                }
            }
            state = SEEN_NOTHING;
            break;
        default:
            break;
        }

    }

}
