import py, os, stat, md5
from Queue import Queue


class RSync(object):
    """ This class allows to synchronise files and directories 
        with one or multiple remote filesystems.

        An RSync instance allows to dynamically add remote targets 
        and then synchronizes the remote filesystems with
        any provided source directory. 

        There is limited support for symlinks, which means that symlinks
        pointing to the sourcetree will be send "as is" while external
        symlinks will be just copied (regardless of existance of such
        a path on remote side). 
    """
    def __init__(self, callback=None, **options):
        for name in options:
            assert name in ('delete')
        self._options = options
        self._callback = callback
        self._channels = {}
        self._receivequeue = Queue()
        self._links = []

    def filter(self, path):
        return True

    def add_target(self, gateway, destdir, finishedcallback=None):
        """ Adds a remote target specified via a 'gateway'
            and a remote destination directory. 
        """
        def itemcallback(req):
            self._receivequeue.put((channel, req))
        channel = gateway.remote_exec(REMOTE_SOURCE)
        channel.setcallback(itemcallback, endmarker = None)
        channel.send((str(destdir), self._options))
        self._channels[channel] = finishedcallback

    def _end_of_channel(self, channel):
        if channel in self._channels:
            # too early!  we must have got an error
            channel.waitclose()
            # or else we raise one
            raise IOError('connection unexpectedly closed: %s ' % (
                channel.gateway,))

    def _process_link(self, channel):
        for link in self._links:
            channel.send(link)
            # completion marker, this host is done
        channel.send(42)

    def _done(self, channel):
        """ Call all callbacks
        """
        finishedcallback = self._channels.pop(channel)
        if finishedcallback:
            finishedcallback()

    def _list_done(self, channel):
        # sum up all to send
        if self._callback:
            s = sum([self._paths[i] for i in self._to_send[channel]])
            self._callback("list", s, channel)

    def _send_item(self, channel, data):
        """ Send one item
        """
        modified_rel_path, checksum = data
        modifiedpath = os.path.join(self._sourcedir, *modified_rel_path)
        try:
            f = open(modifiedpath, 'rb')
            data = f.read()
        except IOError:
            data = None

        # provide info to progress callback function
        modified_rel_path = "/".join(modified_rel_path)
        if data is not None:
            self._paths[modified_rel_path] = len(data)
        else:
            self._paths[modified_rel_path] = 0
        if channel not in self._to_send:
            self._to_send[channel] = []
        self._to_send[channel].append(modified_rel_path)

        if data is not None:
            f.close()
            if checksum is not None and checksum == md5.md5(data).digest():
                data = None     # not really modified
            else:
                # ! there is a reason for the interning:
                # sharing multiple copies of the file's data
                data = intern(data)
                print '%s <= %s' % (
                    channel.gateway.remoteaddress, 
                    modified_rel_path)
        channel.send(data)

    def send(self, sourcedir):
        """ Sends a sourcedir to all added targets. 
        """
        self._sourcedir = str(sourcedir)
        # normalize a trailing '/' away
        self._sourcedir = os.path.dirname(os.path.join(self._sourcedir, 'x'))
        # send directory structure and file timestamps/sizes
        self._send_directory_structure(self._sourcedir)

        # paths and to_send are only used for doing
        # progress-related callbacks
        self._paths = {}
        self._to_send = {}

        # send modified file to clients
        while self._channels:
            channel, req = self._receivequeue.get()
            if req is None:
                self._end_of_channel(channel)
            else:
                command, data = req
                if command == "links":
                    self._process_link(channel)
                elif command == "done":
                    self._done(channel)
                elif command == "ack":
                    if self._callback:
                        self._callback("ack", self._paths[data], channel)
                elif command == "list_done":
                    self._list_done(channel)
                elif command == "send":
                    self._send_item(channel, data)
                    del data
                else:
                    assert "Unknown command %s" % command

    def _broadcast(self, msg):
        for channel in self._channels:
            channel.send(msg)
    
    def _send_link(self, basename, linkpoint):
        self._links.append(("link", basename, linkpoint))

    def _send_directory(self, path):
        # dir: send a list of entries
        names = []
        subpaths = []
        for name in os.listdir(path):
            p = os.path.join(path, name)
            if self.filter(p):
                names.append(name)
                subpaths.append(p)
        self._broadcast(names)
        for p in subpaths:
            self._send_directory_structure(p)

    def _send_link_structure(self, path):
        linkpoint = os.readlink(path)
        basename = path[len(self._sourcedir) + 1:]
        if not linkpoint.startswith(os.sep):
            # relative link, just send it
            # XXX: do sth with ../ links
            self._send_link(basename, linkpoint)
        elif linkpoint.startswith(self._sourcedir):
            self._send_link(basename, linkpoint[len(self._sourcedir) + 1:])
        else:
            self._send_link(basename, linkpoint)
        self._broadcast(None)

    def _send_directory_structure(self, path):
        try:
            st = os.lstat(path)
        except OSError:
            self._broadcast((0, 0))
            return
        if stat.S_ISREG(st.st_mode):
            # regular file: send a timestamp/size pair
            self._broadcast((st.st_mtime, st.st_size))
        elif stat.S_ISDIR(st.st_mode):
            self._send_directory(path)
        elif stat.S_ISLNK(st.st_mode):
            self._send_link_structure(path)
        else:
            raise ValueError, "cannot sync %r" % (path,)

REMOTE_SOURCE = py.path.local(__file__).dirpath().\
                join('rsync_remote.py').open().read() + "\nf()"