WFT Grammar starting point

wft.g

grammar wft;

@header {
}
@lexer::header {
}
@members {
}
wftFile:
    {
        System.out.println("Heyo!");
    }
    (CommentLine | assignment | NewLine)*
    itemTypeDefinition
    EOF
    ;

/**
 * ItemTypeDefinition
 * DEFINE ITEM_TYPE
 * END ITEM_TYPE
 */
itemTypeDefinition:
    'DEFINE ITEM_TYPE' NewLine
    (KeyName|TransStmt|BaseStmt|NewLine)+
        WhiteSpace* 'DEFINE ITEM_ATTRIBUTE' NewLine
        (KeyName|TransStmt|BaseStmt)*
        WhiteSpace* 'END ITEM_ATTRIBUTE' NewLine
    'END ITEM_TYPE'
    ;

/**
 * KeyName
 * KEY NAME VARCHAR2(8)
 */
KeyName: WhiteSpace* KeyNameStart .* {$channel = HIDDEN;} NewLine;
fragment KeyNameStart: 'KEY NAME VARCHAR2(';

/**
 * TransStmt
 * TRANS DISPLAY_NAME VARCHAR2(80)
 */
TransStmt: WhiteSpace* TransStmtStart .* {$channel = HIDDEN;} NewLine;
fragment TransStmtStart: 'TRANS';

/**
 * BaseStmt
 BASE PROTECT_LEVEL NUMBER
 */
BaseStmt: WhiteSpace* BaseStmtStart .* {$channel = HIDDEN;} NewLine;
fragment BaseStmtStart: 'BASE';

/**
 * Assignment
 */
assignment:
    {
        System.out.println("Assignment found!");
    }
    target=AssignmentTarget
    WhiteSpace '=' WhiteSpace
    value=String {
    }
    NewLine;

AssignmentTarget: A (A|D|'_')*;
String: '"' ~'"'* '"'
;

/**
 * Comment
 */
CommentLine: CommentStart .* {$channel = HIDDEN;} NewLine;
fragment CommentStart: '#';

// Lexer rules

fragment D: '0'..'9';
fragment A: 'A'..'Z'
    | 'a'..'z';
StringLength: D+;
NewLine   : '\r' '\n' | '\n' | '\r';
WhiteSpace: ' ';