grammar Demo;

program: programPart+;

programPart: statement #MainStatement
           | functionDefinition #ProgPartFunctionDefinition
           ;

statement : println ';'
          | print ';'
          | varDeclaration ';'
          | assignment ';'
          | branch
          ;

branch : 'if' '(' condition=expression ')' onTrue=block 'else' onFalse=block ;

block : '{' statementList '}' ;

expression: left=expression '/' right=expression #Div
          | left=expression '*' right=expression #Mult
          | left=expression '-' right=expression #Minus
          | left=expression '+' right=expression #Plus
          | left=expression operator=('<' | '<=' | '>' | '>=') right=expression #Relational
          | left=expression operator='&&' right=expression #And
          | left=expression operator='||' right=expression #Or
          | number=NUMBER #Number
          | txt=STRING #String
          | varName=IDENTIFIER #Variable
          | functionCall #FuncCallExpression
          ;

varDeclaration: 'int' varName=IDENTIFIER ;

assignment: varName=IDENTIFIER '=' expr=expression ;

println: 'println(' argument=expression ')' ;

print: 'print(' argument=expression ')' ;

functionDefinition: 'int' funcName=IDENTIFIER '(' params=parameters')' '{' statements=statementList 'return' retValue=expression ';' '}' ;

statementList : (statement)* ;

parameters:
          | declarations+=varDeclaration (',' declarations+=varDeclaration)*
          ;

functionCall: funcName=IDENTIFIER '(' args=expressionList ')';

expressionList:
              | expressions+=expression (',' expressions+=expression)*
              ;

// Terminals
IDENTIFIER: [A-Za-z][A-Za-z0-9]*;
NUMBER: [0-9]+;
WHITESPACE: [ \t\n\r]+ -> skip;
STRING: '"' .*? '"';