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

import mit16_410_13.*;

class LPXMLReader
{
  Simplex lprogram;

	LPXMLReader ()
  {
    lprogram=null;
  }
	
  public Simplex readLP (String path)
  {
    XMLStream strm;
    FileInputStream istrm=null;
		
    try {
      LinkedList vars=null;
      String name=null;
      String inequality=null;
			double value=0.0;
			boolean maximizeprocessed=false;
			int constraintsprocessed=0;
			int processing=0; // 0= nothing, 1=Maximize, 2=Constraint
      boolean inlpproblem=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("LPPROBLEM")) {
					if (inlpproblem) System.out.println("Nested LPPROBLEM not allowed\n");
					inlpproblem=true;
					lprogram=new Simplex(); // instantiate the problem
				}
				else if (tagid.equals("/LPPROBLEM")) {
					if (inlpproblem) inlpproblem=false;
					else System.out.println("/LPPROBLEM not in an LPPROBLEM");
				}
				else if (tagid.equals("MAXIMIZE")) {
					if (!inlpproblem) {
						System.out.println("MAXIMIZE not in an LPPROBLEM");
						inlpproblem=true; // recover
					}
					if (processing==1) {
						System.out.println("Nested MAXIMIZE not allowed");
					}
					processing=1; // processing a maximize.
					name=atag.getAttribute("name");
					inequality=atag.getAttribute("inequality");
					//double y=new Double(atag.getAttribute("y")).doubleValue();
					vars=new LinkedList();
				}
				else if (tagid.equals("/MAXIMIZE")) {
					lprogram.addObjectiveFunction(name, vars);
					name=null;
					vars=null;
					processing=0;
				}	
				else if (tagid.equals("CONSTRAINT")) {
					if (!inlpproblem) {
						System.out.println("CONSTRAINT not embedded in a LPPROBLEM\n");
					}
					else {
						inequality=atag.getAttribute("inequality");
						value=new Double(atag.getAttribute("value")).doubleValue();
						vars=new LinkedList();
						processing=2; // Processing a constraint.
					}
				}
				else if (tagid.equals("/CONSTRAINT")) {
					if (processing!=2) System.out.println("/CONSTRAINT not in a CONSTRAINT");
					else if (!inlpproblem) System.out.println("/CONSTRAINT not in an LPPROBLEM");
					else {
						lprogram.addConstraint(inequality, value, vars);
						processing=0;
						vars=null;
						inequality=null;
					}
				}	
				else if (tagid.equals("VARIABLE")) {
					vars.add(new Variable(atag.getAttribute("name"), new Double(atag.getAttribute("coefficient")).doubleValue()));
				}
				else if (tagid.equals("/VARIABLE")) { }
				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 lprogram;
	}
}

// Fin