package org.madore.damlengine;

import java.io.Writer;
import java.io.IOException;
import org.w3c.dom.*;

public final class Unparser {

    private Document doc;
    private Node cursor;
    private enum Dir { PUSHING, POPPING };
    private Dir dir;
    private Writer out;

    public Unparser(Document doc, Writer out) {
	this.doc = doc;
	this.out = out;
    }

    protected void enter() {
	Node chld = cursor.getFirstChild();
	if ( chld == null ) {
	    dir = Dir.POPPING;
	} else {
	    cursor = chld;
	    dir = Dir.PUSHING;
	}
    }

    protected void skip() {
	Node nsib = cursor.getNextSibling();
	if ( nsib == null ) {
	    cursor = cursor.getParentNode();
	    dir = Dir.POPPING;
	} else {
	    cursor = nsib;
	    dir = Dir.PUSHING;
	}
    }

    public static String quote(String s) {
	StringBuilder buf = new StringBuilder(s.length()+64);
	int ptr0 = 0;  int ptr;
	for ( ptr=0 ; ptr<s.length() ; ptr++ ) {
	    char ch = s.charAt(ptr);
	    String qch = null;
	    switch ( ch ) {
	    case '&': qch = "&amp;"; break;
	    case '<': qch = "&lt;"; break;
	    case '>': qch = "&gt;"; break;
	    case '"': qch = "&quot;"; break;
	    }
	    if ( qch != null ) {
		buf.append(s, ptr0, ptr);
		buf.append(qch);
	    }
	}
	buf.append(s, ptr0, ptr);
	return buf.toString();
    }

    protected void unparseOne()
	throws IOException {
	// System.err.println("unparseOne(): cursor.nodeName="+cursor.getNodeName());
	switch ( dir ) {
	case PUSHING:
	    if ( cursor.getNodeType() == Node.ELEMENT_NODE ) {
		Element elt = (Element)cursor;
		String qname = elt.getTagName();
		out.write("<"+qname);
		if ( elt.hasAttributes() ) {
		    NamedNodeMap attrs = elt.getAttributes();
		    Node n2;
		    for ( int i=0 ; (n2=attrs.item(i)) != null ; i++ ) {
			Attr attr = (Attr)n2;
			out.write(" "+attr.getName()+"=\""+quote(attr.getValue())+"\"");

		    }
		}
		if ( ! elt.hasChildNodes() && ( qname.equals("br") || qname.equals("hr")
						|| qname.equals("img")
						|| qname.equals("area")
						|| qname.equals("base")
						|| qname.equals("basefont")
						|| qname.equals("col")
						|| qname.equals("frame")
						|| qname.equals("input")
						|| qname.equals("isindex")
						|| qname.equals("link")
						|| qname.equals("meta")
						|| qname.equals("param") ) ) {
		    out.write(" />");
		    skip();
		} else {
		    out.write(">");
		    enter();
		}
	    } else if ( cursor.getNodeType() == Node.DOCUMENT_NODE ) {
		enter();
	    } else if ( cursor.getNodeType() == Node.TEXT_NODE ) {
		out.write(quote(((Text)cursor).getData()));
		skip();
	    } else if ( cursor.getNodeType() == Node.COMMENT_NODE ) {
		// FIXME: comments could conceivably contain the "--" string
		out.write("<!--"+((Comment)cursor).getData()+"-->");
		skip();
	    } else if ( cursor.getNodeType() == Node.CDATA_SECTION_NODE ) {
		// FIXME: cdata section could conceivably contain the "]]>" string
		out.write("<![CDATA["+((CDATASection)cursor).getData()+"]]>");
		skip();
	    } else {
		skip();
	    }
	    break;
	case POPPING:
	    if ( cursor.getNodeType() == Node.ELEMENT_NODE ) {
		Element elt = (Element)cursor;
		out.write("</"+elt.getTagName()+">");
	    }
	    skip();
	    break;
	}
    }

    public void unparse()
	throws IOException {
	out.write("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
	DocumentType doctype = doc.getDoctype();
	if ( doctype != null ) {
	    String externalId = "";
	    if ( doctype.getPublicId() != null ) {
		externalId = " PUBLIC \""+doctype.getPublicId()+"\" \""
		    +doctype.getSystemId()+"\"";
	    } else if ( doctype.getSystemId() != null ) {
		externalId = " SYSTEM \""+doctype.getSystemId()+"\"";
	    }
	    out.write("<!DOCTYPE "+doctype.getName()+externalId+">\n");
	}
	cursor = doc.getDocumentElement();
	dir = Dir.PUSHING;
	while ( cursor != null ) {
	    unparseOne();
	}
	out.write("\n");
	out.flush();
    }

}