// Read a Graph from XML File
import java.io.*;
import java.net.*;
import java.util.*;

import mit16_410_13.*;

class Ps2XMLGraph
{
  Hashtable vertices;

  Ps2XMLGraph ()
  {
    vertices = new Hashtable();
  }
	
  public Dictionary readGraph (String path)
  {
    XMLStream strm;
    FileInputStream istrm=null;
		
    try {
      Ps2Vertex currentVertex=null;
      boolean ingraph=false;
      istrm=new FileInputStream(path);
      strm=new XMLStream(istrm, System.out);
      System.out.println("Reading from "+path);
	  
      String txt=strm.readText();  // Read any preceding text
      for (XMLTag atag=strm.readNextTag(); atag!=null; atag=strm.readNextTag()) {
	String tagid=atag.getTagID();
	if (tagid.equals("GRAPH")) {
	  if (ingraph) System.out.println("Nested GRAPH not allowed\n");
	  ingraph=true;
	}
	else if (tagid.equals("/GRAPH")) {
	  if (ingraph) ingraph=false;
	  else System.out.println("/GRAPH not in a GRAPH");
	}
	else if (tagid.equals("VERTEX")) {
	  if (ingraph) currentVertex=findVertexCreate(atag.getAttribute("name"));
	  else {
	    System.out.println("VERTEX not in a GRAPH");
	    ingraph=true; // recover
	    currentVertex=findVertexCreate(atag.getAttribute("name"));
	  }
	}
	else if (tagid.equals("/VERTEX")) {
	  currentVertex=null;
	}
	else if (tagid.equals("EDGE")) {
	  if (currentVertex==null) {
	    System.out.println("Edge not embedded in a vertex\n");
	  }
	  else {
	    Ps2Vertex tovertex=findVertexCreate(atag.getAttribute("vertex"));
	    currentVertex.addEdge(new Ps2Edge(tovertex));
	  }
	}
	else if (tagid.equals("/EDGE")) { } // Nothing to do
	else {
	    System.out.println("Unknown Tag:  ");
	    atag.writeTag(strm);
	}
	txt=strm.readText();
      }
    }
    catch (Exception e) {
      System.out.println("Exception: "+e.toString());
    }
    finally {
      try { if (istrm!=null) istrm.close(); } catch (Exception e) {}
    }
    return vertices;
  }
	
  Ps2Vertex findVertexCreate (String name)
  {
    Ps2Vertex nd=(Ps2Vertex)vertices.get(name);
    if (nd!=null) return nd;
    else {
      Ps2Vertex vertex=new Ps2Vertex(name);
      vertices.put(name, vertex);
      return vertex;
    }
  }
}

// Fin