grammar Rdl;

filter
   : logical_expression
   | '[' ']'
   ;


expression
    : conditional_expression
    | logical_expression
    | value
    ;

conditional_expression
    : '{' conditional_operator ':' '{' '"if"' ':' conditional_expression ',' '"then"' ':' expression ',' '"else"' ':' expression '}' '}'
    | logical_expression
    ;

logical_expression
    : compare_expression
    | '[' compare_expression (',' logical_operator ',' compare_expression)* ']'
    | '[' logical_expression ',' logical_operator ',' logical_expression ']'
    ;

compare_expression
    : '{' column_name ':' '{' comparison_operator ':' value '}' '}'
    ;

column_name
    : (ESC | SAFECODEPOINT)+ '.' (ESC | SAFECODEPOINT)+
    | STRING
    ;

comparison_operator
    : '"$eq"'
    | '"$ne"'
    | '"$gte"'
    | '"lte"'
    | '"$gt"'
    | '"$lt"'
    | '"$in"'
    ;

logical_operator
    : '"$and"'
    | '"$or"'
    ;

conditional_operator
    : '"$cond"'
    ;



scalar_function
    : math_function
    | string_function
    | date_function
    ;

math_function
    : '"$abs"'
    | '"$add"'
    | '"$ceil"'
    | '"$divide"'
    | '"$floor"'
    | '"$multiply"'
    | '"$pow"'
    | '"$subtract"'
    ;

string_function
    : '"$concat"'
    | '"$substring"'
    | '"$to_upper"'
    | '"$to_lower"'
    | '"$trim"'
    ;

date_function
    : '"$format_date"'
    | '"$month"'
    | '"$day"'
    | '"$year"'
    ;

aggregate_function
    : '"$avg"'
    | '"$count"'
    | '"$max"'
    | '"$min"'
    | '"$sum"'
    ;

value
   : STRING
   | NUMBER
   | column_name
   | array
   | 'true'
   | 'false'
   | 'null'
   ;

array
   : '[' value (',' value)* ']'
   | '[' ']'
   ;


STRING
   : '"' (ESC | SAFECODEPOINT)* '"'
   ;


fragment ESC
   : '\\' (["\\/bfnrt] | UNICODE)
   ;
fragment UNICODE
   : 'u' HEX HEX HEX HEX
   ;
fragment HEX
   : [0-9a-fA-F]
   ;
fragment SAFECODEPOINT
   : ~ ["\\\u0000-\u001F]
   ;


NUMBER
   : '-'? INT ('.' [0-9] +)? EXP?
   ;


fragment INT
   : '0' | [1-9] [0-9]*
   ;

// no leading zeros

fragment EXP
   : [Ee] [+\-]? INT
   ;

// \- since - means "range" inside [...]

WS
   : [ \t\n\r] + -> skip
   ;