Method parse

src/query/expression/Expressions.java:43–69

Parses an expression into a tree @param expression The expression to parse (as a string) @param metric_queries A list to store the parsed metrics in @param data_query The time series query @return The parsed tree ready for evaluation @throws IllegalArgumentException if the expression was null, empty

(final String expression,
                                     final List<String> metric_queries,
                                     final TSQuery data_query)

   * be found.
   */
  public static ExpressionTree parse(final String expression,
                                     final List<String> metric_queries,
                                     final TSQuery data_query) {
    if (expression == null || expression.isEmpty()) {
      throw new IllegalArgumentException("Expression may not be null or empty");
    }
    if (expression.indexOf('(') == -1 || expression.indexOf(')') == -1) {
      throw new IllegalArgumentException("Invalid Expression: " + expression);
    }

    final ExpressionReader reader = new ExpressionReader(expression.toCharArray());
    // consume any whitespace ahead of the expression
    reader.skipWhitespaces();

    final String function_name = reader.readFuncName();
    final Expression root_expression = ExpressionFactory.getByName(function_name);

    final ExpressionTree root = new ExpressionTree(root_expression, data_query);
    reader.skipWhitespaces();
    
    if (reader.peek() == '(') {
      reader.next();
      parse(reader, metric_queries, root, data_query);
    }

    return root;
  }

  /**
   * Parses a list of string expressions into the proper trees, adding the