/*
 * Copyright (c) 1998, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
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 *
 */

package javax.swing.text.html.parser;

import java.util.BitSet;
import java.util.Vector;
import java.io.*;


/**
 * A stack of tags. Used while parsing an HTML document.
 * It, together with the ContentModelStates, defines the
 * complete state of the parser while reading a document.
 * When a start tag is encountered an element is pushed onto
 * the stack, when an end tag is encountered an element is popped
 * off the stack.
 *
 * @see Parser
 * @see DTD
 * @see ContentModelState
 * @author      Arthur van Hoff
 */
final
class TagStack implements DTDConstants {
    TagElement tag;
    Element elem;
    ContentModelState state;
    TagStack next;
    BitSet inclusions;
    BitSet exclusions;
    boolean net;
    boolean pre;

    /**
     * Construct a stack element.
     */
    TagStack(TagElement tag, TagStack next) {
        this.tag = tag;
        this.elem = tag.getElement();
        this.next = next;

        Element elem = tag.getElement();
        if (elem.getContent() != null) {
            this.state = new ContentModelState(elem.getContent());
        }

        if (next != null) {
            inclusions = next.inclusions;
            exclusions = next.exclusions;
            pre = next.pre;
        }
        if (tag.isPreformatted()) {
            pre = true;
        }

        if (elem.inclusions != null) {
            if (inclusions != null) {
                inclusions = (BitSet)inclusions.clone();
                inclusions.or(elem.inclusions);
            } else {
                inclusions = elem.inclusions;
            }
        }
        if (elem.exclusions != null) {
            if (exclusions != null) {
                exclusions = (BitSet)exclusions.clone();
                exclusions.or(elem.exclusions);
            } else {
                exclusions = elem.exclusions;
            }
        }
    }

    /**
     * Return the element that must come next in the
     * input stream.
     */
    public Element first() {
        return (state != null) ? state.first() : null;
    }

    /**
     * Return the ContentModel that must be satisfied by
     * what comes next in the input stream.
     */
    public ContentModel contentModel() {
        if (state == null) {
            return null;
        } else {
            return state.getModel();
        }
    }

    /**
     * Return true if the element that is contained at
     * the index specified by the parameter is part of
     * the exclusions specified in the DTD for the element
     * currently on the TagStack.
     */
    boolean excluded(int elemIndex) {
        return (exclusions != null) && exclusions.get(elem.getIndex());
    }


    /**
     * Advance the state by reducing the given element.
     * Returns false if the element is not legal and the
     * state is not advanced.
     */
    boolean advance(Element elem) {
        if ((exclusions != null) && exclusions.get(elem.getIndex())) {
            return false;
        }
        if (state != null) {
            ContentModelState newState = state.advance(elem);
            if (newState != null) {
                state = newState;
                return true;
            }
        } else if (this.elem.getType() == ANY) {
            return true;
        }
        return (inclusions != null) && inclusions.get(elem.getIndex());
    }

    /**
     * Return true if the current state can be terminated.
     */
    boolean terminate() {
        return (state == null) || state.terminate();
    }

    /**
     * Convert to a string.
     */
    public String toString() {
        return (next == null) ?
            "<" + tag.getElement().getName() + ">" :
            next + " <" + tag.getElement().getName() + ">";
    }
}
