/*
 * FindBugs - Find bugs in Java programs
 * Copyright (C) 2004-2006 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 java.util.HashSet;

import org.apache.bcel.classfile.Code;

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.bcel.OpcodeStackDetector;
import edu.umd.cs.findbugs.visitclass.PreorderVisitor;

/**
 * We found a problem with the new OpenJDK that everyone is now using to compile
 * and run java code. In particular, the java.util.logging.Logger behavior has
 * changed. Instead of using strong references, it now uses weak references
 * internally. That's a reasonable change, but unfortunately some code relies on
 * the old behavior - when changing logger configuration, it simply drops the
 * logger reference. That means that the garbage collector is free to reclaim
 * that memory, which means that the logger configuration is lost.
 */
public class LostLoggerDueToWeakReference extends OpcodeStackDetector {

    final BugReporter bugReporter;

    final BugAccumulator bugAccumulator;

    final HashSet<String> namesOfSetterMethods = new HashSet<String>();

    public LostLoggerDueToWeakReference(BugReporter bugReporter) {
        this.bugReporter = bugReporter;
        this.bugAccumulator = new BugAccumulator(bugReporter);
        namesOfSetterMethods.add("addHandler");
        namesOfSetterMethods.add("setUseParentHandlers");
        namesOfSetterMethods.add("setLevel");
        namesOfSetterMethods.add("setFilter");
    }

    @Override
    public void visit(Code code) {
        if (getMethodSig().indexOf("Logger") == -1) {
            sawGetLogger = -1;
            loggerEscaped = loggerImported = false;
            super.visit(code); // make callbacks to sawOpcode for all opcodes
            if (false) {
                System.out.println(getFullyQualifiedMethodName());
                System.out.printf("%d %s %s\n", sawGetLogger, loggerEscaped, loggerImported);

            }
            if (sawGetLogger >= 0 && !loggerEscaped && !loggerImported)
                bugAccumulator.reportAccumulatedBugs();
            else
                bugAccumulator.clearBugs();
        }
    }

    int sawGetLogger;

    boolean loggerEscaped;

    boolean loggerImported;

    @Override
    public void sawOpcode(int seen) {
        switch (seen) {
        case INVOKESTATIC:
            if (getClassConstantOperand().equals("java/util/logging/Logger") && getNameConstantOperand().equals("getLogger")) {
                OpcodeStack.Item item = stack.getStackItem(0);
                if (!"".equals(item.getConstant()))
                    sawGetLogger = getPC();
                break;
            }
            checkForImport();
            break;
        case INVOKEVIRTUAL:
            if (getClassConstantOperand().equals("java/util/logging/Logger")
                    && namesOfSetterMethods.contains(getNameConstantOperand())) {
                int priority = HIGH_PRIORITY;
                if (getMethod().isStatic() && getMethodName().equals("main") && getMethodSig().equals("([Ljava/lang/String;)V"))
                    priority = NORMAL_PRIORITY;
                ;
                bugAccumulator.accumulateBug(
                        new BugInstance(this, "LG_LOST_LOGGER_DUE_TO_WEAK_REFERENCE", priority).addClassAndMethod(this), this);
                break;
            }
            checkForImport();
            checkForMethodExportImport();
            break;

        case INVOKEINTERFACE:
        case INVOKESPECIAL:
            checkForImport();
            checkForMethodExportImport();
            break;

        case CHECKCAST:
            String sig = getClassConstantOperand();
            if (sig.indexOf("Logger") >= 0)
                loggerImported = true;
            break;

        case GETFIELD:
        case GETSTATIC:
            checkForImport();
            break;
        case PUTFIELD:
        case PUTSTATIC:
            checkForFieldEscape();
        }

    }

    private void checkForImport() {
        if (getSigConstantOperand().endsWith("Logger;"))
            loggerImported = true;
    }

    private void checkForMethodExportImport() {
        int numArguments = PreorderVisitor.getNumberArguments(getSigConstantOperand());
        for (int i = 0; i < numArguments; i++) {
            OpcodeStack.Item item = stack.getStackItem(i);
            if (item.getSignature().endsWith("Logger;"))
                loggerEscaped = true;
        }
        String sig = getSigConstantOperand();
        int pos = sig.indexOf(")");
        int loggerPos = sig.indexOf("Logger");
        if (0 <= loggerPos && loggerPos < pos)
            loggerEscaped = true;
    }

    private void checkForFieldEscape() {
        String sig = getSigConstantOperand();
        if (sig.indexOf("Logger") >= 0)
            loggerEscaped = true;
        OpcodeStack.Item item = stack.getStackItem(0);
        if (item.getSignature().endsWith("Logger;"))
            loggerEscaped = true;

    }

    private void emitWarning() {
        System.out.println("Warn about " + getMethodName()); // TODO
    }

}