support for functions in where clause

parser.cpp

@@ -444,8 +444,9 @@ namespace usql {
     std::unique_ptr<Node> Parser::parse_operand_node() {
 	    auto token_type = m_lexer.tokenType();
 
+	    // parenthised expression
 	    if (token_type == TokenType::open_paren) {
-		    m_lexer.skipToken(TokenType::open_paren);
+		    // open paren already consumed
 		    auto left = parse_expression();
 		    do {
 			left = parse_expression(std::move(left));
@@ -455,21 +456,39 @@ namespace usql {
 		    return left;
 	    }
 
-	    std::string tokenString = m_lexer.consumeCurrentToken().token_string;
-	    switch (token_type) {
-		    case TokenType::int_number:
-			    return std::make_unique<IntValueNode>(std::stoi(tokenString));
-		    case TokenType::double_number:
-			    return std::make_unique<DoubleValueNode>(std::stod(tokenString));
-		    case TokenType::string_literal:
-			    return std::make_unique<StringValueNode>(tokenString);
-		    case TokenType::identifier:
-			    return std::make_unique<DatabaseValueNode>(tokenString);
-		    case TokenType::keyword_null:
-		   	    return std::make_unique<NullValueNode>();
-		    default:
-			    throw Exception("Unknown operand node " + tokenString);
+	    // function call
+	    if (token_type == TokenType::identifier && m_lexer.nextTokenType() == TokenType::open_paren) {
+		std::string function_name = m_lexer.consumeCurrentToken().token_string;
+		std::vector<std::unique_ptr<Node>> pars;
+
+		m_lexer.skipToken(TokenType::open_paren);
+		while (m_lexer.tokenType() != TokenType::close_paren) {        // TODO handle errors
+			pars.push_back(parse_operand_node());
+			m_lexer.skipTokenOptional(TokenType::comma);
+		}
+		m_lexer.skipToken(TokenType::close_paren);
+		return std::make_unique<FunctionNode>(function_name, std::move(pars));
 	    }
+
+	    // numbers and strings
+	    std::string tokenString = m_lexer.consumeCurrentToken().token_string;
+
+	    if (token_type == TokenType::int_number)
+		return std::make_unique<IntValueNode>(std::stoi(tokenString));
+	    if (token_type == TokenType::double_number)
+		return std::make_unique<DoubleValueNode>(std::stod(tokenString));
+	    if (token_type == TokenType::string_literal)
+		return std::make_unique<StringValueNode>(tokenString);
+		
+	    // db column
+	    if (token_type == TokenType::identifier)
+		return std::make_unique<DatabaseValueNode>(tokenString);
+
+	    // null
+	    if (token_type == TokenType::keyword_null)
+		return std::make_unique<NullValueNode>();
+
+	    throw Exception("Unknown operand node " + tokenString);
     }
 
     RelationalOperatorType Parser::parse_relational_operator() {