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/*
 * SpotBugs - Find bugs in Java programs
 *
 * 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 edu.umd.cs.findbugs.BugAccumulator;
import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.OpcodeStack;
import edu.umd.cs.findbugs.ba.XField;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.bcel.OpcodeStackDetector;
import java.util.Optional;
import java.util.stream.Stream;
import org.apache.bcel.Const;
import org.apache.bcel.classfile.JavaClass;

public class FindInstanceLockOnSharedStaticData extends OpcodeStackDetector {

    private static final String JAVA_LANG_CLASS = "java.lang.Class";

    private final BugAccumulator bugAccumulator;
    private boolean isInsideSynchronizedBlock;
    private Optional maybeLockObject;
    private boolean isLockObjectInstanceOfJavaLangClass;

    public FindInstanceLockOnSharedStaticData(BugReporter bugReporter) {
        this.bugAccumulator = new BugAccumulator(bugReporter);
        isInsideSynchronizedBlock = false;
        maybeLockObject = Optional.empty();
        isLockObjectInstanceOfJavaLangClass = false;
    }

    @Override
    public void sawOpcode(int seen) {

        if (seen == Const.MONITORENTER) {
            isInsideSynchronizedBlock = true;
            OpcodeStack.Item lockObject = stack.getStackItem(0);
            maybeLockObject = Optional.ofNullable(lockObject.getXField());

            // Locking on java.lang.Class objects is appropriate, since there is only a single instance of them
            if (!maybeLockObject.isPresent()) {
                try {
                    Optional javaClassOfLockObject = Optional.ofNullable(lockObject.getJavaClass());
                    isLockObjectInstanceOfJavaLangClass = javaClassOfLockObject
                            .map(javaClass -> javaClass.getClassName().equals(JAVA_LANG_CLASS))
                            .orElse(false);
                } catch (ClassNotFoundException ignored) {
                }
            }

            return;
        } else if (seen == Const.MONITOREXIT) {
            isInsideSynchronizedBlock = false;
            maybeLockObject = Optional.empty();
            return;
        }

        if (seen == Const.PUTSTATIC) {
            XMethod modificationMethod = getXMethod();
            Optional fieldToModify = Optional.ofNullable(getXFieldOperand());
            boolean unsecuredModificationByMethod =
                    fieldToModify.isPresent() && modificationMethod.isSynchronized() && !modificationMethod.isStatic();
            boolean isLockObjectAppropriate =
                    maybeLockObject.map(XField::isStatic).orElse(false) || isLockObjectInstanceOfJavaLangClass;

            if (unsecuredModificationByMethod && !(isInsideSynchronizedBlock && isLockObjectAppropriate)) {
                bugAccumulator.accumulateBug(
                        new BugInstance(this, "SSD_DO_NOT_USE_INSTANCE_LOCK_ON_SHARED_STATIC_DATA", NORMAL_PRIORITY)
                                .addClassAndMethod(this)
                                .addString(fieldToModify.get().getName())
                                .addString("synchronized method"),
                        this);
                return;
            }

            if (fieldToModify.isPresent() && isInsideSynchronizedBlock && !isLockObjectAppropriate) {
                bugAccumulator.accumulateBug(
                        new BugInstance(this, "SSD_DO_NOT_USE_INSTANCE_LOCK_ON_SHARED_STATIC_DATA", NORMAL_PRIORITY)
                                .addClassAndMethod(this)
                                .addString(fieldToModify.get().getName())
                                .addString("synchronization lock"),
                        this);
            }
        }

    }

    @Override
    public void visitAfter(JavaClass obj) {
        bugAccumulator.reportAccumulatedBugs();
    }

    @Override
    public void visit(JavaClass obj) {
        boolean classIsInteresting = Stream.of(obj.getFields()).anyMatch(field -> field.isStatic() && !field.isFinal());
        if (classIsInteresting) {
            isInsideSynchronizedBlock = false;
            maybeLockObject = Optional.empty();
            isLockObjectInstanceOfJavaLangClass = false;
            super.visit(obj);
        }
    }

}