import logging; log = logging.getLogger('pvl.syslog.filter')

class SyslogFilter (object) :
    """
        Filter syslog messages.
    """

    def __init__ (self, prog=None) :
        """
            prog        - match tag (process name)
        """

        self.prog = prog

    def match_prog (self, prog) :
        """
            Match given prog?
        """

        # normalize
        prog = prog.lower()

        if prog.startswith('/') :
            # base
            prog = prog.split('/')[-1]

        # match
        if not prog :
            # never matches non-tagged lines
            return False

        elif self.prog.endswith('*') :
            # prefix match
            return prog.startswith(self.prog[:-1])

        else :
            return prog == self.prog

    def filter (self, item) :
        """
            Match given item?
        """

        if self.prog and not self.match_prog(item['prog']) :
            log.debug("prog: %s: %r", self.prog, item['prog'])

        else :
            # ok
            return True

    def __call__ (self, items) :
        for item in items:
            if self.filter(item) :
                yield item