import optparse, sys

from pvl.syslog.parser import SyslogParser
from pvl.syslog.filter import SyslogFilter
from pvl.syslog.syslog import SyslogSource
from pvl.syslog import fifo, tail

# XXX: use optparse parser.error()?
import logging; log = logging.getLogger('pvl.syslog.args')

def parser (parser, prog=None) :
    """
        Optparse option group

            prog        - filter to only process lines from given process
    """
    
    syslog = optparse.OptionGroup(parser, 'Syslog collector')

    syslog.add_option('--syslog-fifo',          metavar='PATH',
            help="Read syslog messages from given fifo")

    syslog.add_option('--syslog-file',          metavar='FILE',
            help="Read syslog messages from given file")

    syslog.add_option('--syslog-tail',          type='float', metavar='TIMEOUT',
            help="Continuously poll file")

    syslog.add_option('--syslog-raw',           action='store_true',
            help="Parse raw syslog lines without timestamp/etc")

    syslog.add_option('--syslog-prog',          metavar='PROG',     default=prog,
            help="Filter by given prog: %default")

    return syslog

def apply (options, optional=False) :
    """
        Handle options, returning a SyslogSource, if any.

        May log.error/sys.exit
    """

    if options.syslog_fifo :
        # fifo pipe
        source = fifo.Fifo(options.syslog_fifo)
        poll = True # select(source)

    elif options.syslog_tail :
        # tail file
        source = tail.TailFile(options.syslog_file)
        poll = options.syslog_tail # select(float)

    elif options.syslog_file :
        # read file
        source = tail.Tail(open(options.syslog_file))
        poll = False # do not loop, just read up to EOF

    elif optional :
        return None

    else :
        # from stdin
        if sys.stdin.isatty() :
            log.warning("Reading syslog messages from TTY?")
        
        source = tail.Tail(sys.stdin)
        poll = False # XXX: tty vs pipe vs file?
    
    # options
    parser = SyslogParser(
        raw     = options.syslog_raw,
    )

    filter = SyslogFilter(
        # glob pattern
        prog    = options.syslog_prog,
    )

    # chain iterables
    syslog = filter(parser(source))

    # polling
    return SyslogSource(syslog, source, poll)