searchbox3.py

import lark

parser = lark.Lark(r'''
    ?atom   : atom or atom
            | atom and atom
            | "(" atom ")"
            | compare
            | value

    compare : value ":" value
            | value "=" value
            | value ">" value
            | value ">=" value
            | value "<" value
            | value "<=" value
            | "-" value
    
    and     : "&" | " "
    or.1     : "|" | / or /i
    value   : /\w+/i
            | ESCAPED_STRING
    
    %import common.ESCAPED_STRING
''', start='atom')


def parse(q):
    try:
        return parser.parse(q.strip())
    except lark.exceptions.UnexpectedCharacters:
        return None


if __name__ == '__main__':
    """
    value	a

    compare
      value	a
      value	b

    None
    atom
      compare
        value	a
        value	b
      and
      compare
        value	c
        value	d

    compare
      value	"a:b"
      value	c

    compare
      value	"a b"
      value	c

    compare
      value	a
      value	"b:c"

    atom
      compare
        value	a
        value	b
      or	 OR 
      compare
        value	c
        value	d

    atom
      compare
        value	a
        value	b
      or	 OR 
      compare
        value	c
        value	d
    """
    for q in [
        'a',
        'a:b',
        'a:b:c',
        'a:b c:d',
        '"a:b":c',
        '"a b":c',
        'a:"b:c"',
        '(a:b) OR c:d',
        'a:b OR (c:d)'
    ]:
        print(getattr(parse(q), 'pretty', lambda: None)())