import  mit16_410_13.*;

import java.util.LinkedList;
import java.io.*;

class PS9base
{
    public PS9base () { ; }
	
    // reads the HMM description as XML invoking addTransition as necessary.
    public void readHMM (String pathname) throws java.io.FileNotFoundException
    {
	XMLStream strm;
	FileInputStream istrm=null;
	boolean inhmm=false, instate=false, intransition=false;
	String state=null;
	try {
	    istrm=new FileInputStream(pathname);
	    strm=new XMLStream(istrm, System.out);
	    System.out.println("Reading from "+pathname);
	    
	    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("HMM")) {
		    if (inhmm) System.out.println("Nested HMM not allowed\n");
		    inhmm=true;
		}
		else if (tagid.equals("/HMM")) {
		    if (instate||intransition||(!inhmm)) System.out.println("/HMM nesting error");
		    inhmm=false;
		}
		else if (tagid.equals("STATE")) {
		    if (instate) System.out.println("Nested states not allowed\n");
		    else if (intransition||(!inhmm)) System.out.println("STATE nesting error");
		    else state=atag.getAttribute("name");
		    instate=true;
		}
		else if (tagid.equals("/STATE")) {
		    if ((!instate)||intransition||(!inhmm)) System.out.println("/STATE nesting error");
		    instate=false;
		}	
		else if (tagid.equals("TRANSITION")) {
		    if (intransition) System.out.println("Nested transitions not allowed\n");
		    else if ((!instate)||(!inhmm)) System.out.println("TRANSITION nesting error");
		    else {
			addTransition(state,
				      atag.getAttribute("to"),
				      atag.getAttribute("symbol"),
				      (new Double(atag.getAttribute("probability"))).doubleValue());
		    }
		    intransition=true;
		}
		else if (tagid.equals("/TRANSITION")) {
		    if ((!instate)||(!intransition)||(!inhmm)) System.out.println("/TRANSITION nesting error");
		    intransition=false;
		}	
		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) {}
	}
    }
    // You are expected to implement this in your subclass.  The default
    // implementation simply prints out the 
    void addTransition (String from,         // originating state
			String to,           // state transitioned to
			String symbol,       // transition action symbol 
			double probability)  // transition probability
    {
	System.out.println("Transition from state "+from+" to state "+to+" with action="+symbol+" and probability="+probability);
    }
}