grammar Test;

options{
backtrack=true;
}

var	:	PATHTERM;

PATHTERM: (PERCENT VARNAME PATHEXP);
PERCENT: '$';
VARNAME: ((ALPHA) (ALPHA|DIGIT)*);
fragment ALPHA: ('a'..'z' | 'A'..'Z');
fragment DIGIT: ('0'..'9');

xPath:    PATHEXP;
PATHEXP:    ('/' RelativePathExpr?) |    ('//' RelativePathExpr) |    RelativePathExpr;
fragment RelativePathExpr:    primaryStep = StepExpr (( '/' | '//' ) trailingStep = StepExpr )*;    
fragment StepExpr:    ( '.' | AbbrevForwardStep) (Predicate)?;
fragment AbbrevForwardStep:    attributeFlag = '@'? (stQName = QName | stNodeExpansion =  '*')   ;
fragment Predicate:    '[' PredicateExpr ']';     
fragment PredicateExpr:    Expr (('and'|'or') Expr)* |  '(' Expr ')';   
fragment Expr:    PATHEXP (Comparisonexpr | Containmentexpr); 
fragment Comparisonexpr : (COMPARISONOP ) Literal; 
fragment Containmentexpr : ('contains' | 'excludes') '(' STRINGLITERAL ')';
fragment Literal : STRINGLITERAL | NumericLiteral | VarRef;
fragment NumericLiteral: INTEGERLITERAL | DECIMALLITERAL | DOUBLELITERAL;
fragment QName: (NCName ':' NCName) | NCName;
// ---------------- Lexer Rules ---------------- //
fragment LETTER:  '\u0024' | '\u005f'|'\u0041'..'\u005a' | '\u0061'..'\u007a' | '\u00c0'..'\u00d6' | '\u00d8'..'\u00f6' | 
       '\u00f8'..'\u00ff' | '\u0100'..'\u1fff' | '\u3040'..'\u318f' | '\u3300'..'\u337f' | 
       '\u3400'..'\u3d2d' | '\u4e00'..'\u9fff' | '\uf900'..'\ufaff';
fragment INTEGERLITERAL :  ('-')?('0'..'9')+;
fragment DECIMALLITERAL :  ('-')?('.' ('0'..'9')+)  | (('0'..'9')+ '.' '0'..'9'*);
fragment DOUBLELITERAL  :  ('-')?(('.' ('0'..'9')+) | (('0'..'9')+ ('.' '0'..'9'*)?)) ('e' | 'E') ('+' | '-')? ('0'..'9')+;
fragment STRINGLITERAL : ('"' ~('"')* '"') | ('\'' ~('\'')* '\'');
fragment COMPARISONOP : ('=' | '<' | '>' | '<>' | '!=' | '<=' | '>=');
fragment VarRef: '$' NCName;
fragment NCName : (LETTER) (LETTER | ('0'..'9') | '.' | '-')*;
WS  :  ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ {$channel=HIDDEN;};
SL_COMMENT: '--' (~('\n'|'\r'))* ('\n'|'\r'('\n')?) {$channel=HIDDEN;};
ML_COMMENT: '/**' (options {greedy=false;} : .)* '*/' {$channel=HIDDEN;};