# This file is part of Buildbot.  Buildbot is free software: you can
# redistribute it and/or modify it under the terms of the GNU General Public
# License as published by the Free Software Foundation, version 2.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 51
# Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
# Copyright Buildbot Team Members


# This is a class which watches a maildir for new messages. It uses the
# linux dirwatcher API (if available) to look for new files. The
# .messageReceived method is invoked with the filename of the new message,
# relative to the top of the maildir (so it will look like "new/blahblah").

import os
from twisted.python import log, runtime
from twisted.application import service, internet
from twisted.internet import reactor, defer
dnotify = None
try:
    import dnotify
except:
    log.msg("unable to import dnotify, so Maildir will use polling instead")

class NoSuchMaildir(Exception):
    pass

class MaildirService(service.MultiService):
    pollinterval = 10  # only used if we don't have DNotify

    def __init__(self, basedir=None):
        service.MultiService.__init__(self)
        if basedir:
            self.setBasedir(basedir)
        self.files = []
        self.dnotify = None
        self.timerService = None

    def setBasedir(self, basedir):
        # some users of MaildirService (scheduler.Try_Jobdir, in particular)
        # don't know their basedir until setServiceParent, since it is
        # relative to the buildmaster's basedir. So let them set it late. We
        # don't actually need it until our own startService.
        self.basedir = basedir
        self.newdir = os.path.join(self.basedir, "new")
        self.curdir = os.path.join(self.basedir, "cur")

    def startService(self):
        service.MultiService.startService(self)
        if not os.path.isdir(self.newdir) or not os.path.isdir(self.curdir):
            raise NoSuchMaildir("invalid maildir '%s'" % self.basedir)
        try:
            if dnotify:
                # we must hold an fd open on the directory, so we can get
                # notified when it changes.
                self.dnotify = dnotify.DNotify(self.newdir,
                                               self.dnotify_callback,
                                               [dnotify.DNotify.DN_CREATE])
        except (IOError, OverflowError):
            # IOError is probably linux<2.4.19, which doesn't support
            # dnotify. OverflowError will occur on some 64-bit machines
            # because of a python bug
            log.msg("DNotify failed, falling back to polling")
        if not self.dnotify:
            self.timerService = internet.TimerService(self.pollinterval, self.poll)
            self.timerService.setServiceParent(self)
        self.poll()


    def dnotify_callback(self):
        log.msg("dnotify noticed something, now polling")

        # give it a moment. I found that qmail had problems when the message
        # was removed from the maildir instantly. It shouldn't, that's what
        # maildirs are made for. I wasn't able to eyeball any reason for the
        # problem, and safecat didn't behave the same way, but qmail reports
        # "Temporary_error_on_maildir_delivery" (qmail-local.c:165,
        # maildir_child() process exited with rc not in 0,2,3,4). Not sure
        # why, and I'd have to hack qmail to investigate further, so it's
        # easier to just wait a second before yanking the message out of new/

        reactor.callLater(0.1, self.poll)


    def stopService(self):
        if self.dnotify:
            self.dnotify.remove()
            self.dnotify = None
        if self.timerService is not None:
            self.timerService.disownServiceParent()
            self.timerService = None
        return service.MultiService.stopService(self)

    @defer.inlineCallbacks
    def poll(self):
        try:
            assert self.basedir
            # see what's new
            for f in self.files:
                if not os.path.isfile(os.path.join(self.newdir, f)):
                    self.files.remove(f)
            newfiles = []
            for f in os.listdir(self.newdir):
                if not f in self.files:
                    newfiles.append(f)
            self.files.extend(newfiles)
            for n in newfiles:
                try:
                    yield self.messageReceived(n)
                except:
                    log.err(None, "while reading '%s' from maildir '%s':" % (n, self.basedir))
        except Exception:
            log.err(None, "while polling maildir '%s':" % (self.basedir,))

    def moveToCurDir(self, filename):
        if runtime.platformType == "posix":
            # open the file before moving it, because I'm afraid that once
            # it's in cur/, someone might delete it at any moment
            path = os.path.join(self.newdir, filename)
            f = open(path, "r")
            os.rename(os.path.join(self.newdir, filename),
                      os.path.join(self.curdir, filename))
        elif runtime.platformType == "win32":
            # do this backwards under windows, because you can't move a file
            # that somebody is holding open. This was causing a Permission
            # Denied error on bear's win32-twisted1.3 buildslave.
            os.rename(os.path.join(self.newdir, filename),
                      os.path.join(self.curdir, filename))
            path = os.path.join(self.curdir, filename)
            f = open(path, "r")

        return f

    def messageReceived(self, filename):
        raise NotImplementedError
