package com.jclark.xsl.sax;

import org.xml.sax.*;
import java.io.OutputStream;
import java.io.IOException;

public class Indenter implements OutputDocumentHandler, CommentHandler, RawCharactersHandler {
  private DocumentHandler documentHandler = null;
  private CommentHandler commentHandler = null;
  private RawCharactersHandler rawCharactersHandler;
  private char[] newline = new char[]{'\n'};

  static private final byte IN_PCDATA_CHUNK = 0;
  static private final byte JUST_HAD_START_TAG = 1;
  static private final byte OTHER = 2;

  private byte state = IN_PCDATA_CHUNK;

  public Indenter(DocumentHandler handler,
		  RawCharactersHandler rawCharactersHandler) {
    this.documentHandler = handler;
    if (handler instanceof CommentHandler)
      this.commentHandler =(CommentHandler)handler;
    else
      this.commentHandler = null;
    this.rawCharactersHandler = rawCharactersHandler;
  }

  public DocumentHandler init(Destination dest, AttributeList atts)
    throws IOException, SAXException {
    if (documentHandler instanceof OutputDocumentHandler)
      documentHandler = ((OutputDocumentHandler)documentHandler).init(dest, atts);
    return this;
  }

  public void setDocumentLocator(Locator locator) {
    documentHandler.setDocumentLocator(locator);
  }

  public void startDocument()
    throws SAXException {
    documentHandler.startDocument();
  }

  public void endDocument()
    throws SAXException {
    maybeNewline();
    documentHandler.endDocument();
  }

  public void startElement(String name, AttributeList atts)
    throws SAXException {
    maybeNewline();
    state = JUST_HAD_START_TAG;
    documentHandler.startElement(name, atts);
  }

  public void endElement(String name)
    throws SAXException {
    if (state == JUST_HAD_START_TAG)
      state = OTHER;
    else
      maybeNewline();
    documentHandler.endElement(name);
  }

  public void characters(char ch[], int start, int length)
    throws SAXException {
    if (length > 0) {
      documentHandler.characters(ch, start, length);
      state = IN_PCDATA_CHUNK;
    }
  }

  public void ignorableWhitespace(char ch[], int start, int length)
    throws SAXException {
    if (length > 0) {
      documentHandler.ignorableWhitespace(ch, start, length);
      state = IN_PCDATA_CHUNK;
    }
    
  }

  public void rawCharacters(String chars) throws SAXException {
    if (chars.length() > 0) {
      rawCharactersHandler.rawCharacters(chars);
      state = IN_PCDATA_CHUNK;
    }
  }

  private final void maybeNewline() throws SAXException {
    if (state != IN_PCDATA_CHUNK) {
      documentHandler.characters(newline, 0, 1);
      newline[0] = '\n';
    }
    state = OTHER;
  }

  public void processingInstruction(String target, String data)
    throws SAXException {
    maybeNewline();
    documentHandler.processingInstruction(target, data);
  }

  public void comment(String contents)
    throws SAXException {
    if (commentHandler != null) {
      maybeNewline();
      commentHandler.comment(contents);
    }
  }
}