package IR;

import java.util.*;

public class SymbolTable {

    private Hashtable table;
    private SymbolTable parent;
    private HashSet valueset;
  
    public SymbolTable() {
	table = new Hashtable();
	valueset = new HashSet();
	this.parent = null;
    }

    public SymbolTable(SymbolTable parent) {
	table = new Hashtable();
	this.parent = parent;
    }

    public void add(Descriptor d) {
	add(d.getSymbol(), d);
    }
    
    public void add(String name, Descriptor d) {
	if (!table.containsKey(name))
	    table.put(name, new HashSet());
	HashSet hs=(HashSet)table.get(name);
	hs.add(d);
	valueset.add(d);
    }

    public Set getSet(String name) {
	return getPSet(name);
    }

    private HashSet getPSet(String name) {
	HashSet hs=null;
	if (parent!=null)
	    hs=parent.getPSet(name);
	else
	    hs=new HashSet();
	if (table.containsKey(name)) {
	    hs.addAll((HashSet)table.get(name));
	}
	return hs;
    }

    public Set getSetFromSameScope(String name) {
	return getPSetFromSameScope(name);
    }

    private HashSet getPSetFromSameScope(String name) {
	if (table.containsKey(name)) {
	    HashSet hs=(HashSet)table.get(name);
	    return hs;
	} else
	    return new HashSet();
    }

    public Descriptor get(String name) {
	Descriptor d = getFromSameScope(name);
	if (d == null && parent != null) {
	    return parent.get(name);
	} else {
	    return d;
	}
    }

    public Descriptor getFromSameScope(String name) {
	if (table.containsKey(name)) {
	    HashSet hs=(HashSet) table.get(name);
	    return (Descriptor) hs.iterator().next();
	} else
	    return null;

    }
    
    public Enumeration getNames() {
	return table.keys();
    }

    public Iterator getNamesIterator() {
	return table.keySet().iterator();
    }

    public Set getValueSet() {
	return valueset;
    }

    public Iterator getDescriptorsIterator() {
	return getValueSet().iterator();
    }

    public Set getAllValueSet() {
	HashSet hs=null;
	if (parent!=null)
	    hs=(HashSet) parent.getAllValueSet();
	else
	    hs=new HashSet();
	hs.addAll(valueset);
	return hs;
    }

    public Iterator getAllDescriptorsIterator() {
	return getAllValueSet().iterator();
    }

    public boolean contains(String name) {
        return (get(name) != null);
    }
	    
    public SymbolTable getParent() {
	return parent;
    }
    
    public void setParent(SymbolTable parent) {
	this.parent = parent;
    }

    public String toString() {
        return "ST: " + table.toString();               
    }
}