grammar lang;

// PARSER RULES
program : func_body?;

return_stmt : 'return' test ';';
if_stmt
    : 'if' test '{' stmt* '}' ('else if' test '{' stmt* '}')* ('else' '{' stmt* '}')?
    | 'if' paren_test stmt ('else if' paren_test stmt)* ('else' stmt)?
    ;

param : ID (':' ID) ('=' test)?;
let_params : param (',' param)*;
func_body : stmt+;

func_def_stmt
    : 'func' ID '(' let_params? ')' (':' ID) '{' func_body? '}'
    ;

let_def_stmt
    : 'pub'? ('final' | 'static')? 'let' let_params ';'
    ;

func_call_stmt
    : ID ('(' (arglist)? ')' | '[' test ']')
    ;

stmt
    : ';'
    | test '=' test ';'
    | test op_augassign test ';'
    | test ('++' | '--') ';'
    | ('++' | '--') test ';'
    | if_stmt
    | paren_test ';'
    | test ';'
    | let_def_stmt
    | func_def_stmt
    | func_call_stmt ';'
    ;

paren_test: '(' test ')';
test: or_test ('?' test ':' test)?
    ;
or_test: and_test ('||' and_test)*
    ;
and_test: not_test ('&&' not_test)*
    ;
not_test: '!' not_test | comparison
    ;
comparison: expr (op_comp expr)*
    ;

op_augassign : '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '<<=' | '>>=' | '**=';
op_comp : '<' | '>' | '<=' | '>=' | '!=' | '==' | 'is' | 'has';

expr: xor_expr ('|' xor_expr)*
    ;
xor_expr: and_expr ('^' and_expr)*
    ;
and_expr: shift_expr ('&' shift_expr)*
    ;
shift_expr: arith_expr (('<<'|'>>') arith_expr)*
    ;
arith_expr: term (('+'|'-') term)*
    ;
term: factor (('*'|'/'|'%') factor)*
    ;
factor: ('+'|'-'|'~') factor | power
    ;
power: atom trailer* ('**' factor)?
    ;

atom : ID | NUMBER | STRING;

trailer
    : '(' (arglist)? ')' | '[' test ']' | '.' ID
    ;

arglist
    : test (',' test)*
    ;

// LEXER RULES
ID : [a-zA-Z_] [a-zA-Z0-9_]+;

STRING : '"' (ESC_SEQ | ~('\\'|'"'))* '"';
CHAR : '\'' (ESC_SEQ | ~('\\'|'\'')) '\'';

NUMBER
    : SIGN? [0-9]+ EXPONENT?
    | SIGN? [0-9]+ '.' [0-9]+ EXPONENT? 'f'?
    | SIGN? '.' [0-9]+ EXPONENT? 'f'?
    | SIGN? HEX_NUMBER
    ;

HEX_NUMBER
    : '0' [xX] HEX+
    ;

fragment
HEX
    : [a-fA-F0-9]
    ;

EXPONENT
    : [eE] SIGN? [0-9]+
    ;

fragment
ESC_SEQ
    : '\\' ('b'|'t'|'n'|'f'|'r'|'"'|'\''|'\\')
    | UNICODE_ESC
    | OCTAL_ESC
    ;

fragment
OCTAL_ESC
    : '\\' ('0'..'3') ('0'..'7') ('0'..'7')
    | '\\' ('0'..'7') ('0'..'7')
    | '\\' ('0'..'7')
    ;

fragment
UNICODE_ESC
    : '\\' 'u' HEX HEX HEX HEX
    ;

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

UNKNOWN : . -> skip;

fragment
SIGN
    : [+-]
    ;