/**
 * Copyright (c) 2006, Gaudenz Alder
 */
package com.mxgraph.io;

import java.util.Map;

import org.w3c.dom.Element;
import org.w3c.dom.Node;

import com.mxgraph.model.mxGraphModel.mxChildChange;
import com.mxgraph.model.mxICell;

/**
 * Codec for mxChildChanges. This class is created and registered dynamically at load time and used
 * implicitely via mxCodec and the mxCodecRegistry.
 */
public class mxChildChangeCodec extends mxObjectCodec {

  /**
   * Constructs a new model codec.
   */
  public mxChildChangeCodec() {
    this(new mxChildChange(), new String[] {"model", "child", "previousIndex"},
        new String[] {"parent", "previous"}, null);
  }

  /**
   * Constructs a new model codec for the given arguments.
   */
  public mxChildChangeCodec(Object template, String[] exclude, String[] idrefs,
      Map<String, String> mapping) {
    super(template, exclude, idrefs, mapping);
  }

  /*
   * (non-Javadoc)
   * 
   * @see com.mxgraph.io.mxObjectCodec#isReference(java.lang.Object, java.lang.String,
   * java.lang.Object, boolean)
   */
  @Override
  public boolean isReference(Object obj, String attr, Object value, boolean isWrite) {
    if (attr.equals("child") && obj instanceof mxChildChange
        && (((mxChildChange) obj).getPrevious() != null || !isWrite)) {
      return true;
    }

    return idrefs.contains(attr);
  }

  /*
   * (non-Javadoc)
   * 
   * @see com.mxgraph.io.mxObjectCodec#afterEncode(com.mxgraph.io.mxCodec, java.lang.Object,
   * org.w3c.dom.Node)
   */
  @Override
  public Node afterEncode(mxCodec enc, Object obj, Node node) {
    if (obj instanceof mxChildChange) {
      mxChildChange change = (mxChildChange) obj;
      Object child = change.getChild();

      if (isReference(obj, "child", child, true)) {
        // Encodes as reference (id)
        mxCodec.setAttribute(node, "child", enc.getId(child));
      } else {
        // At this point, the encoder is no longer able to know which cells
        // are new, so we have to encode the complete cell hierarchy and
        // ignore the ones that are already there at decoding time. Note:
        // This can only be resolved by moving the notify event into the
        // execute of the edit.
        enc.encodeCell((mxICell) child, node, true);
      }
    }

    return node;
  }

  /**
   * Reads the cells into the graph model. All cells are children of the root element in the node.
   */
  public Node beforeDecode(mxCodec dec, Node node, Object into) {
    if (into instanceof mxChildChange) {
      mxChildChange change = (mxChildChange) into;

      if (node.getFirstChild() != null && node.getFirstChild().getNodeType() == Node.ELEMENT_NODE) {
        // Makes sure the original node isn't modified
        node = node.cloneNode(true);

        Node tmp = node.getFirstChild();
        change.setChild(dec.decodeCell(tmp, false));

        Node tmp2 = tmp.getNextSibling();
        tmp.getParentNode().removeChild(tmp);
        tmp = tmp2;

        while (tmp != null) {
          tmp2 = tmp.getNextSibling();

          if (tmp.getNodeType() == Node.ELEMENT_NODE) {
            // Ignores all existing cells because those do not need
            // to be re-inserted into the model. Since the encoded
            // version of these cells contains the new parent, this
            // would leave to an inconsistent state on the model
            // (ie. a parent change without a call to
            // parentForCellChanged).
            String id = ((Element) tmp).getAttribute("id");

            if (dec.lookup(id) == null) {
              dec.decodeCell(tmp, true);
            }
          }

          tmp.getParentNode().removeChild(tmp);
          tmp = tmp2;
        }
      } else {
        String childRef = ((Element) node).getAttribute("child");
        change.setChild((mxICell) dec.getObject(childRef));
      }
    }

    return node;
  }

  /*
   * (non-Javadoc)
   * 
   * @see com.mxgraph.io.mxObjectCodec#afterDecode(com.mxgraph.io.mxCodec, org.w3c.dom.Node,
   * java.lang.Object)
   */
  @Override
  public Object afterDecode(mxCodec dec, Node node, Object obj) {
    if (obj instanceof mxChildChange) {
      mxChildChange change = (mxChildChange) obj;

      // Cells are encoded here after a complete transaction so the previous
      // parent must be restored on the cell for the case where the cell was
      // added. This is needed for the local model to identify the cell as a
      // new cell and register the ID.
      ((mxICell) change.getChild()).setParent((mxICell) change.getPrevious());
      change.setPrevious(change.getParent());
      change.setPreviousIndex(change.getIndex());
    }

    return obj;
  }

}