/*
 * Bytecode Analysis Framework
 * Copyright (C) 2003,2004 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.bcp;

/**
 * A ByteCodePattern is a pattern matching a sequence of bytecode instructions.
 * 
 * @author David Hovemeyer
 * @see PatternElement
 * @see PatternMatcher
 */
public class ByteCodePattern {
    private PatternElement first, last;

    private int interElementWild;

    private int numElements;

    private int dummyVariableCount;

    /**
     * Add a PatternElement to the end of the pattern.
     * 
     * @param element
     *            the PatternElement
     * @return this object
     */
    public ByteCodePattern add(PatternElement element) {
        if (first != null)
            addInterElementWild();
        addElement(element);
        return this;
    }

    /**
     * Add a wildcard to match between 0 and given number of instructions. If
     * there is already a wildcard at the end of the current pattern, resets its
     * max value to that given.
     * 
     * @param numWild
     *            maximum number of instructions to be matched by the wildcard
     */
    public ByteCodePattern addWild(int numWild) {
        Wild wild = isLastWild();
        if (wild != null)
            wild.setMinAndMax(0, numWild);
        else
            addElement(new Wild(numWild));
        return this;
    }

    /**
     * Set number of inter-element wildcards to create between explicit
     * PatternElements. By default, no implicit wildcards are created.
     * 
     * @param numWild
     *            the number of wildcard instructions which may be matched
     *            between explicit PatternElements
     * @return this object
     */
    public ByteCodePattern setInterElementWild(int numWild) {
        this.interElementWild = numWild;
        return this;
    }

    /**
     * Get the first PatternElement in the pattern.
     */
    public PatternElement getFirst() {
        return first;
    }

    /**
     * Get a dummy variable name. The name returned will begin with the
     * <code>'$'</code> character, and will be different than any previous dummy
     * variable name allocated by this object. Dummy variable names are useful
     * for creating PatternElements where you don't care whether the value it
     * uses is the same as one used by another PatternElement.
     */
    public String dummyVariable() {
        StringBuilder buf = new StringBuilder();
        buf.append("$_");
        buf.append(dummyVariableCount++);
        return buf.toString();
    }

    private void addInterElementWild() {
        if (interElementWild > 0 && isLastWild() == null)
            addElement(new Wild(interElementWild));
    }

    private void addElement(PatternElement element) {
        element.setIndex(numElements++);
        if (first == null) {
            first = last = element;
        } else {
            last.setNext(element);
            last = element;
        }
    }

    private Wild isLastWild() {
        if (last != null && last instanceof Wild)
            return (Wild) last;
        else
            return null;
    }
}

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