package net.sourceforge.phpeclipse.wiki.xml;

import java.util.ArrayList;

import com.thoughtworks.xstream.alias.ClassMapper;
import com.thoughtworks.xstream.converters.ConversionException;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

/**
 *  Converts a Page object from and to xml
 */
public class PageConverter implements Converter {
  protected ClassMapper classMapper;

  protected String classAttributeIdentifier;

  public PageConverter(ClassMapper classMapper, String classAttributeIdentifier) {
    this.classMapper = classMapper;
    this.classAttributeIdentifier = classAttributeIdentifier;
  }

  public boolean canConvert(Class type) {
    return type.equals(Page.class);
  }

  public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
    Page page = (Page) source;
    writer.startNode("title");
    writer.setValue(page.title);
    writer.endNode();

    ArrayList list = page.listOfRevisions;
    for (int i = 0; i < list.size(); i++) {
      Object item = list.get(i);
      writeItem(item, context, writer);
    }
  }

  public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
    Page page = (Page) createPage(context.getRequiredType());
    reader.moveDown();
    page.title = (String) reader.getValue();
    reader.moveUp();
    populatePage(reader, context, page);
    return page;
  }

  protected void populatePage(HierarchicalStreamReader reader, UnmarshallingContext context, Page page) {
    ArrayList list = page.listOfRevisions;
    if (list == null) {
      page.listOfRevisions = new ArrayList();
      list = page.listOfRevisions;
    }
    while (reader.hasMoreChildren()) {
      reader.moveDown();
      Object item = readItem(reader, context, page);
      list.add(item);
      reader.moveUp();
    }
  }

  protected void writeItem(Object item, MarshallingContext context, HierarchicalStreamWriter writer) {
    // PUBLISHED API METHOD! If changing signature, ensure backwards compatability.
    if (item == null) {
      // todo: this is duplicated in TreeMarshaller.start()
      writer.startNode(classMapper.lookupName(ClassMapper.Null.class));
      writer.endNode();
    } else {
      writer.startNode(classMapper.lookupName(item.getClass()));
      context.convertAnother(item);
      writer.endNode();
    }
  }

  protected Object readItem(HierarchicalStreamReader reader, UnmarshallingContext context, Object current) {
    // PUBLISHED API METHOD! If changing signature, ensure backwards compatability.
    String classAttribute = reader.getAttribute(classAttributeIdentifier);
    Class type;
    if (classAttribute == null) {
      type = classMapper.lookupType(reader.getNodeName());
    } else {
      type = classMapper.lookupType(classAttribute);
    }
    return context.convertAnother(current, type);
  }

  protected Object createPage(Class type) {
    Class defaultType = classMapper.lookupDefaultType(type);
    try {
      return defaultType.newInstance();
    } catch (InstantiationException e) {
      throw new ConversionException("Cannot instantiate " + defaultType.getName(), e);
    } catch (IllegalAccessException e) {
      throw new ConversionException("Cannot instantiate " + defaultType.getName(), e);
    }
  }
}