grammar Decaf;

program: classdecl+;

//class identifier{...}
classdecl:  AccessModifierPublic? 'class' Identifier OpenCurlyBracket  (constuctorDecl|fieldDecl|methodDecl)*(MainMethodDecl block)? ClosedCurlyBracket;
constuctorDecl: AccessModifierPublic? Identifier OpenRoundBracket parameterList? ClosedRoundBracket block; //Method without

//Method and FieldVar
methodDecl: AccessModifierPublic? (type | Void) Identifier OpenRoundBracket parameterList? ClosedRoundBracket block;
fieldDecl: AccessModifierPublic? type Identifier Semicolon;

//Parameters
parameterList: parameter(Comma parameter)*;
parameter: type Identifier;

//property, object.a, 3+1, a = 3
expression: subExpression | binaryExpr;
//subExpression to dissolve left-recusion
subExpression: This | assignableExpr | stmtExpr | OpenRoundBracket subExpression ClosedRoundBracket;
assignableExpr: Identifier | instVar;
instVar:  subReceiver? receivingMethod* Identifier;

//.trim().toLength().toLowerCase().count ...
methodCall: receiver? receivingMethod* Identifier OpenRoundBracket argumentList ClosedRoundBracket;
argumentList: expression? | expression (Comma expression)+;

subReceiver: ((This | newDecl | Identifier) Dot);
receiver: ((This | instVar | newDecl | Identifier) Dot);
receivingMethod: Identifier OpenRoundBracket argumentList ClosedRoundBracket Dot;


binaryExpr: calcExpr | nonCalcExpr| value | Not binaryExpr;

calcExpr: calcExpr LineOperator dotExpr | dotExpr;
dotExpr: dotExpr DotOperator dotSubExpr | dotSubExpr;
dotSubExpr: IntValue | Identifier | instVar | methodCall | OpenRoundBracket calcExpr ClosedRoundBracket;
nonCalcExpr: subExpression nonCalcOperator expression;
nonCalcOperator: LogicalOpertor | ComparisonOperator;

//Statement but also expression
//a = expr, new Object(), method(param1)
stmtExpr: assign | newDecl | methodCall;

//Statements
//int a, {...}, while(a > 10){...}, if(...){...} else if{...} else{...}
statement: returnStmt Semicolon | localVarDecl Semicolon | block | whileStmt | ifElseStmt | stmtExpr Semicolon;
returnStmt: Return (expression)?;
localVarDecl: type Identifier (Assign expression)?;
block: OpenCurlyBracket statement* ClosedCurlyBracket;
whileStmt: While OpenRoundBracket expression ClosedRoundBracket statement;
ifElseStmt: ifStmt elseStmt?;
ifStmt: If OpenRoundBracket expression ClosedRoundBracket statement;
elseStmt: Else statement;
assign: assignableExpr Assign expression;
newDecl: New Identifier OpenRoundBracket argumentList ClosedRoundBracket;


type: Int | Boolean  | Char | Identifier;
value: IntValue | BooleanValue | CharValue | NullValue;

//Access modifier
AccessModifierPublic    : 'public' ;
MainMethodDecl          : 'public static void main(String[] args)';



//Operators
DotOperator         : Multipilkation | Division | Modulo;
LineOperator        : Plus | Minus;
ComparisonOperator  : Greater | Less | GreaterEqual | LessEqual | Equal | NotEqual;
LogicalOpertor      : And | Or;

Assign          : '=';
Minus           : '-';
Plus            : '+';
Multipilkation  : '*';
Division        : '/';
Modulo          : '%';
Greater         : '>';
Less            : '<';
GreaterEqual    : '>=';
LessEqual       : '<=';
Equal           : '==';
NotEqual        : '!=';
Not             : '!';
And             : '&&';
Or              : '||';

//Symbols
Dot                 : '.';
OpenRoundBracket    : '(';
ClosedRoundBracket  : ')';
OpenCurlyBracket    : '{';
ClosedCurlyBracket  : '}';
Semicolon           : ';';
Comma               : ',';

//Keywords
Class   : 'class';
This    : 'this';
While   : 'while';
If      : 'if';
Else    : 'else';
Return  : 'return';
New     : 'new';

//Identifier
fragment Alpabetic : [a-zA-Z];
fragment Numeric: [0-9];
fragment ValidIdentSymbols : Alpabetic|Numeric|'$'|'_';
Identifier: Alpabetic ValidIdentSymbols*;

//Types
Void    : 'void';
Int     : 'int';
Boolean : 'bool';
Char    : 'char';

//Values
IntValue : ('+'|'-')*[0-9]+;
CharValue: '\''~[\r\n]?'\'';
BooleanValue: 'true'|'false';
NullValue: 'null';

//Whitespace? Right into the trash it gooeesss
WS : [ \t\r\n] -> skip;