namespace NTERA.Interpreter
{
	public partial class Interpreter
	{
		private void If() 
        {
            bool result = Expr().BinOp(new Value(0), Token.Equal).Real == 1;

            Match(Token.Then);
            GetNextToken();

            if (result)
            {
                int i = ifcounter;
                while (true)
                {
                    if (lastToken == Token.If)
                    {
                        i++;
                    }
                    else if (lastToken == Token.Else)
                    {
                        if (i == ifcounter)
                        {
                            GetNextToken();
                            return;
                        }
                    }
                    else if (lastToken == Token.EndIf)
                    {
                        if(i == ifcounter)
                        {
                            GetNextToken();
                            return;
                        }
                        i--;
                    }
                    GetNextToken();
                }
            }
        }

		private void Else()
		{
			int i = ifcounter;
			while (true)
            {
                if (lastToken == Token.If)
                {
                    i++;
                }
                else if (lastToken == Token.EndIf)
                {
                    if(i == ifcounter)
                    {
                        GetNextToken();
                        return;
                    }
                    i--;
                }
				GetNextToken ();
			}
		}

		private void End()
        {
            exit = true;
        }

		private void Let()
        {
            if (lastToken != Token.Equal)
            {
                Match(Token.Identifer);
                GetNextToken();
                Match(Token.Equal);
            }

            string id = lex.Identifer;

            GetNextToken();
            
            SetVar(id, Expr());
        }

		private void For()
        {
            Match(Token.Identifer);
            string var = lex.Identifer;

            GetNextToken();
            Match(Token.Equal);

            GetNextToken();
            Value v  = Expr();

            if (loops.ContainsKey(var))
            {
                loops[var] = lineMarker;
            }
            else
            {
                SetVar(var, v);
                loops.Add(var, lineMarker);
            }

            Match(Token.To);

            GetNextToken();
            v = Expr();
            
            if (vars[var].BinOp(v, Token.More).Real == 1)
            {
                while (true)
                {
                    while (!(GetNextToken() == Token.Identifer && prevToken == Token.Next)) ;
                    if (lex.Identifer == var)
                    {
                        loops.Remove(var);
                        GetNextToken();
                        Match(Token.NewLine);
                        break;
                    }
                }
            }
        }

		private void Next()
        {
            Match(Token.Identifer);
            string var = lex.Identifer;
            vars[var] = vars[var].BinOp(new Value(1), Token.Plus);
            lex.GoTo(new Marker(loops[var].Pointer - 1, loops[var].Line, loops[var].Column - 1));
            lastToken = Token.NewLine;
        }
	}
}