/*
 * 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.props;

import java.util.BitSet;
import java.util.Iterator;

import org.apache.bcel.Constants;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.Instruction;
import org.apache.bcel.generic.ReferenceType;
import org.apache.bcel.generic.Type;

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.ca.Call;
import edu.umd.cs.findbugs.ba.ca.CallList;
import edu.umd.cs.findbugs.ba.ca.CallListDataflow;
import edu.umd.cs.findbugs.ba.type.TypeDataflow;
import edu.umd.cs.findbugs.ba.type.TypeFrame;

/**
 * Utility methods for creating general warning properties.
 * 
 * @author David Hovemeyer
 */
public abstract class WarningPropertyUtil {

	/** Set of instructions which operate on a receiver object. */
	private static final BitSet receiverObjectInstructionSet= new BitSet();
	static {
		receiverObjectInstructionSet.set(Constants.INVOKEINTERFACE);
		receiverObjectInstructionSet.set(Constants.INVOKEVIRTUAL);
		receiverObjectInstructionSet.set(Constants.INVOKESPECIAL);
		receiverObjectInstructionSet.set(Constants.GETFIELD);
		receiverObjectInstructionSet.set(Constants.PUTFIELD);
		receiverObjectInstructionSet.set(Constants.CHECKCAST);
		receiverObjectInstructionSet.set(Constants.INSTANCEOF);
	}

	/**
	 * Get a Location matching the given PC value.
	 * Because of JSR subroutines, there may be multiple
	 * Locations referring to the given instruction.  This method simply
	 * returns one of them arbitrarily.
	 * 
	 * @param classContext the ClassContext containing the method
	 * @param method       the method
	 * @param pc           a PC value of an instruction in the method
	 * @return a Location corresponding to the PC value, or null
	 *         if no such Location can be found
	 * @throws CFGBuilderException
	 */
	private static Location pcToLocation(
			ClassContext classContext,
			Method method,
			int pc) throws CFGBuilderException {
		CFG cfg = classContext.getCFG(method);
		for (Iterator<Location> i = cfg.locationIterator(); i.hasNext();) {
			Location location = i.next();
			if (location.getHandle().getPosition() == pc)
				return location;
		}
		return null;
	}

	/**
	 * Add a RECEIVER_OBJECT_TYPE warning property for a particular
	 * location in a method to given warning property set.
	 * 
	 * @param propertySet  the property set
	 * @param classContext ClassContext of the class containing the method 
	 * @param method       the method
	 * @param location     Location within the method
	 */
	private static void addReceiverObjectType(
			WarningPropertySet<WarningProperty> propertySet,
			ClassContext classContext,
			Method method,
			Location location) {
		try {
			Instruction ins = location.getHandle().getInstruction();

			if (!receiverObjectInstructionSet.get(ins.getOpcode()))
				return;

			TypeDataflow typeDataflow = classContext.getTypeDataflow(method);
			TypeFrame frame = typeDataflow.getFactAtLocation(location);
			if (frame.isValid()) {
				Type type = frame.getInstance(ins, classContext.getConstantPoolGen());
				if (type instanceof ReferenceType) {
					propertySet.setProperty(GeneralWarningProperty.RECEIVER_OBJECT_TYPE, type.toString());
				}
			}
		} catch (DataflowAnalysisException e) {
			// Ignore
		} catch (CFGBuilderException e) {
			// Ignore
		}
	}

	/**
	 * Add CALLED_METHOD_<i>n</i> warning properties based on methods
	 * which have been called and returned normally at given Location.
	 * 
	 * @param propertySet  the WarningPropertySet
	 * @param classContext the ClassContext
	 * @param method       the Method
	 * @param location     the Location
	 */
	private static void addRecentlyCalledMethods(
			WarningPropertySet<WarningProperty> propertySet,
			ClassContext classContext,
			Method method,
			Location location) {
		try {
			CallListDataflow dataflow = classContext.getCallListDataflow(method);
			CallList callList = dataflow.getFactAtLocation(location);
			if (!callList.isValid())
				return;
			int count = 0;
			for (Iterator<Call> i = callList.callIterator(); count < 4 && i.hasNext(); ++count) {
				Call call = i.next();
				WarningProperty prop = null;
				switch (count) {
				case 0:
					prop = GeneralWarningProperty.CALLED_METHOD_1; break;
				case 1:
					prop = GeneralWarningProperty.CALLED_METHOD_2; break;
				case 2:
					prop = GeneralWarningProperty.CALLED_METHOD_3; break;
				case 3:
					prop = GeneralWarningProperty.CALLED_METHOD_4; break;
				}
				// XXX: encode class name? signature? break down as words?
				propertySet.setProperty(prop, call.getMethodName());
			}
		} catch (CFGBuilderException e) {
			// Ignore
		} catch (DataflowAnalysisException e) {
			// Ignore
		}
	}

	/**
	 * Add all relevant general warning properties to the given property set
	 * for the given Location.
	 * 
	 * @param propertySet  the WarningPropertySet
	 * @param classContext the ClassContext
	 * @param method       the Method
	 * @param location     the Location
	 */
	public static void addPropertiesForDataMining(
			WarningPropertySet<WarningProperty> propertySet,
			ClassContext classContext,
			Method method,
			Location location) {
		addReceiverObjectType(propertySet, classContext, method, location);
		addRecentlyCalledMethods(propertySet, classContext, method, location);
	}

	/**
	 * Add all relevant general warning properties to the given property set
	 * for the given Location.
	 * 
	 * @param propertySet  the WarningPropertySet
	 * @param classContext the ClassContext
	 * @param method       the Method
	 * @param pc           the bytecode offset of an instruction to get properties for
	 */
	public static void addPropertiesForLocation(
			WarningPropertySet<WarningProperty> propertySet,
			ClassContext classContext,
			Method method,
			int pc) {
		try {
			Location location = pcToLocation(classContext, method, pc);
			if (location != null) {
				addPropertiesForDataMining(propertySet, classContext, method, location);
			}
		} catch (CFGBuilderException e) {
			// Ignore
		}
	}
}
