/*
 * FindBugs - Find Bugs in Java programs
 * 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 java.util.Iterator;

import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.ARETURN;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.InstructionHandle;
import org.apache.bcel.generic.ReferenceType;

import edu.umd.cs.findbugs.FindBugsAnalysisFeatures;
import edu.umd.cs.findbugs.SystemProperties;
import edu.umd.cs.findbugs.ba.AnalysisContext;
import edu.umd.cs.findbugs.ba.CFG;
import edu.umd.cs.findbugs.ba.CFGBuilderException;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Location;
import edu.umd.cs.findbugs.ba.XFactory;
import edu.umd.cs.findbugs.ba.XMethod;
import edu.umd.cs.findbugs.ba.npe.IsNullValue;
import edu.umd.cs.findbugs.ba.npe.IsNullValueDataflow;
import edu.umd.cs.findbugs.ba.npe.IsNullValueFrame;

/**
 * Build database of methods that return values guaranteed to be nonnull
 *
 */
public class BuildNonnullReturnDatabase {
    public static final boolean VERBOSE_DEBUG = SystemProperties.getBoolean("fnd.debug.nullarg.verbose");

    private static final boolean DEBUG = SystemProperties.getBoolean("fnd.debug.nullarg") || VERBOSE_DEBUG;

    public void visitClassContext(ClassContext classContext) {
        boolean fullAnalysis = AnalysisContext.currentAnalysisContext().getBoolProperty(
                FindBugsAnalysisFeatures.INTERPROCEDURAL_ANALYSIS_OF_REFERENCED_CLASSES);
        if (!fullAnalysis && !AnalysisContext.currentAnalysisContext()./*
         * getSubtypes
         * ().
         */isApplicationClass(classContext.getJavaClass())) {
            return;
        }
        if (VERBOSE_DEBUG) {
            System.out.println("Visiting class " + classContext.getJavaClass().getClassName());
        }

        for (Method m : classContext.getMethodsInCallOrder()) {
            considerMethod(classContext, m);
        }
    }

    private void considerMethod(ClassContext classContext, Method method) {
        if ((method.getReturnType() instanceof ReferenceType) && classContext.getMethodGen(method) != null) {
            if (VERBOSE_DEBUG) {
                System.out.println("Check " + method);
            }
            analyzeMethod(classContext, method);
        }
    }

    protected int returnsReference;

    protected int returnsNonNull;

    private void analyzeMethod(ClassContext classContext, Method method) {
        returnsReference++;
        try {
            CFG cfg = classContext.getCFG(method);

            IsNullValueDataflow inv = classContext.getIsNullValueDataflow(method);
            boolean guaranteedNonNull = true;
            for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
                Location location = i.next();
                InstructionHandle handle = location.getHandle();
                Instruction ins = handle.getInstruction();

                if (!(ins instanceof ARETURN)) {
                    continue;
                }
                IsNullValueFrame frame = inv.getFactAtLocation(location);
                if (!frame.isValid()) {
                    continue;
                }
                IsNullValue value = frame.getTopValue();
                if (!value.isDefinitelyNotNull()) {
                    guaranteedNonNull = false;
                    break;
                }

            }

            XMethod xmethod = XFactory.createXMethod(classContext.getJavaClass(), method);
            if (guaranteedNonNull) {
                returnsNonNull++;
                AnalysisContext.currentAnalysisContext().getReturnValueNullnessPropertyDatabase()
                .setProperty(xmethod.getMethodDescriptor(), guaranteedNonNull);
                if (DEBUG) {
                    System.out.println("Unconditional deref: " + xmethod + "=" + guaranteedNonNull);
                }

            }

        } catch (CFGBuilderException e) {
            XMethod xmethod = XFactory.createXMethod(classContext.getJavaClass(), method);

            AnalysisContext.currentAnalysisContext().getLookupFailureCallback()
            .logError("Error analyzing " + xmethod + " for unconditional deref training", e);
        } catch (DataflowAnalysisException e) {
            XMethod xmethod = XFactory.createXMethod(classContext.getJavaClass(), method);
            AnalysisContext.currentAnalysisContext().getLookupFailureCallback()
            .logError("Error analyzing " + xmethod + " for unconditional deref training", e);
        }
    }

}
