/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003-2005 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.ba.type;

import java.util.BitSet;

import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
import edu.umd.cs.findbugs.ba.Frame;

/**
 * A specialization of {@link Frame} for determining the types of values in the
 * Java stack frame (locals and operand stack).
 *
 * @author David Hovemeyer
 * @see Frame
 * @see TypeAnalysis
 */
public class TypeFrame extends Frame<Type> {
    private final BitSet exactTypeSet;

    /**
     * Constructor.
     */
    public TypeFrame(int numLocals) {
        super(numLocals);
        this.exactTypeSet = new BitSet();
    }

    /**
     * Set whether or not a type in a given slot is exact.
     *
     * @param slot
     *            the slot
     * @param isExact
     *            true if the slot contains an exact type, false if just an
     *            upper bound
     */
    public void setExact(int slot, boolean isExact) {
        exactTypeSet.set(slot, isExact);
    }

    /**
     * Get whether or not a type in a given slot is exact.
     *
     * @param slot
     *            the slot
     * @return true if the slot contains an exact type, false if just an upper
     *         bound
     */
    public boolean isExact(int slot) {
        return exactTypeSet.get(slot);
    }

    /**
     * Clear the exact type set. The result is that all slots will be assumed
     * <em>not</em> to contain an exact type.
     */
    public void clearExactSet() {
        exactTypeSet.clear();
    }

    @Override
    public void setTop() {
        super.setTop();
        clearExactSet();
    }

    @Override
    public void copyFrom(Frame<Type> other_) {
        clearExactSet();

        TypeFrame other = (TypeFrame) other_;

        this.exactTypeSet.or(other.exactTypeSet);

        super.copyFrom(other_);
    }

    @Override
    protected String valueToString(Type value) {
        return String.valueOf(value) + ",";
    }

    /**
     * Get the single instance of the "Top" type.
     */
    public static Type getTopType() {
        return TopType.instance();
    }

    /**
     * Get the single instance of the "Bottom" type.
     */
    public static Type getBottomType() {
        return BottomType.instance();
    }

    /**
     * Get the single instance of the "LongExtra" type.
     */
    public static Type getLongExtraType() {
        return LongExtraType.instance();
    }

    /**
     * Get the single instance of the "DoubleExtra" type.
     */
    public static Type getDoubleExtraType() {
        return DoubleExtraType.instance();
    }

    /**
     * Get the single instance of the "Null" type.
     */
    public static Type getNullType() {
        return NullType.instance();
    }

    @Override
    public void pushValue(Type value) {

        super.pushValue(value);

        try {
            exactTypeSet.clear(getStackLocation(0));
        } catch (DataflowAnalysisException e) {
            assert false;
        }

    }

    /**
     * Pop a value off of the Java operand stack.
     *
     * @return the value that was popped
     * @throws DataflowAnalysisException
     *             if the Java operand stack is empty
     */
    @Override
    public Type popValue() throws DataflowAnalysisException {

        exactTypeSet.clear(getStackLocation(0));
        return super.popValue();
    }

    @Override
    public String toString() {
        if (isTop()) {
            return "[TOP]";
        }
        if (isBottom()) {
            return "[BOTTOM]";
        }
        StringBuilder buf = new StringBuilder();
        buf.append('[');
        int numSlots = getNumSlots();
        int start = 0;
        for (int i = start; i < numSlots; ++i) {

            if (i == getNumLocals()) {
                // Use a "|" character to visually separate locals from
                // the operand stack.
                int last = buf.length() - 1;
                if (last >= 0) {
                    if (buf.charAt(last) == ',') {
                        buf.deleteCharAt(last);
                    }
                }
                buf.append(" | ");
            }
            if (isExact(i)) {
                buf.append("!");
            }
            String value = valueToString(getValue(i));
            if (i == numSlots - 1 && value.endsWith(",")) {
                value = value.substring(0, value.length() - 1);
            }
            buf.append(value);
            // buf.append(' ');
        }
        buf.append(']');
        return buf.toString();
    }

}

