package Triangle.ContextualAnalyzer;

import java.util.List;
import java.util.Map;
import java.util.Stack;

import Triangle.AbstractSyntaxTrees.Declaration;
import java.util.ArrayList;
import java.util.HashMap;

public final class SymbolTable {

  private Map<String, Stack<Declaration>> symtab;
  private List<List<String>> scopeStack;

  public SymbolTable () {
      symtab = new HashMap<String, Stack<Declaration>>();
      scopeStack = new ArrayList<List<String>>();
  }

  // Opens a new level in the identification table, 1 higher than the
  // current topmost level.
  public void openScope () {
        // new empty list
	scopeStack.add(new ArrayList<String>());
  }

  // Closes the topmost level in the identification table, discarding
  // all entries belonging to that level.
  public void closeScope () {
      //delete from symtab
      for(int i = 0; i < scopeStack.get(scopeStack.size() -1).size(); i++){
         if(symtab.containsKey(scopeStack.get(scopeStack.size() -1).get(i))){
             symtab.get(scopeStack.get(scopeStack.size() -1).get(i)).pop();
             if(symtab.get(scopeStack.get(scopeStack.size() -1).get(i)).empty()){
                 symtab.remove(scopeStack.get(scopeStack.size() -1).get(i));
             }
         }
      }
      // delete top list
      scopeStack.remove(scopeStack.size()-1);
  }

  // Makes a new entry in the identification table for the given identifier
  // and attribute. The new entry belongs to the current level.
  // duplicated is set to to true if there is already an entry for the
  // same identifier at the current level.
  public void enter (String id, Declaration attr) {
      scopeStack.get(scopeStack.size()-1).add(id);
      if(symtab.containsKey(id)){
          symtab.get(id).push(attr);
      }else{
          symtab.put(id, new Stack<Declaration>());
          symtab.get(id).push(attr);
      }
  }

  // Finds an entry for the given identifier in the identification table,
  // if any. If there are several entries for that identifier, finds the
  // entry at the highest level, in accordance with the scope rules.
  // Returns null if no entry is found.
  // otherwise returns the attribute field of the entry found.
  public Declaration retrieve (String id) {
	
      if(symtab.containsKey(id)){
          return symtab.get(id).firstElement();
      }
         
      return null;
  }

}