import gtk

from rdflib import URIRef

class Local(object):

    """placeholder for the local uri that EditChoice does not

    manage. Set resourceObservable to Local to indicate that you're

    unlinked"""

class EditChoice(gtk.HBox):

    """

    this is a gtk port of editchoice.EditChoice

    """

    def __init__(self, graph, resourceObservable, label="Editing:"):

        """

        getResource is called to get the URI of the currently

        """

        self.graph = graph

        # the outer box should have a distinctive border so it's more

        # obviously a special drop target

        gtk.HBox.__init__(self)

        self.pack_start(gtk.Label(label), expand=False)

        # this is just a label, but it should look like a physical

        # 'thing' (and gtk labels don't work as drag sources)

        self.currentLink = gtk.Button("http://bar")

        self.pack_start(self.currentLink)

        self.unlinkButton = gtk.Button(label="Unlink")

        self.pack_start(self.unlinkButton, expand=False)

        self.unlinkButton.connect("clicked", self.onUnlink)

        self.show_all()

        self.resourceObservable = resourceObservable

        resourceObservable.subscribe(self.uriChanged)

        self.makeDragSource()

        self.makeDropTarget()

    def makeDropTarget(self):

        def ddr(widget, drag_context, x, y, selection_data, info, timestamp):

            if selection_data.type != 'text/uri-list':

                raise ValueError("unknown DnD selection type %r" %

                                 selection_data.type)

            self.resourceObservable(URIRef(selection_data.data.strip()))

        self.currentLink.drag_dest_set(flags=gtk.DEST_DEFAULT_ALL,

                            targets=[('text/uri-list', 0, 0)],

                            actions=gtk.gdk.ACTION_LINK  | gtk.gdk.ACTION_COPY)

        self.currentLink.connect("drag_data_received", ddr)

    def makeDragSource(self):

        self.currentLink.drag_source_set(

            start_button_mask=gtk.gdk.BUTTON1_MASK,

            targets=[('text/uri-list', 0, 0)],

            actions=gtk.gdk.ACTION_LINK | gtk.gdk.ACTION_COPY)

        def source_drag_data_get(btn, context, selection_data, info, time):

            selection_data.set(selection_data.target, 8,

                               self.resourceObservable())

        self.currentLink.connect("drag_data_get", source_drag_data_get)

    def uriChanged(self, newUri):

        # if this resource had a type icon or a thumbnail, those would be

        # cool to show in here too

        if newUri is Local:

            self.currentLink.set_label("(local)")

            self.currentLink.drag_source_unset()

        else:

            self.graph.addHandler(self.updateLabel)

            self.makeDragSource()

        self.unlinkButton.set_sensitive(newUri is not Local)

    def updateLabel(self):

        uri = self.resourceObservable()

        label = self.graph.label(uri)

        self.currentLink.set_label(label or uri or "")

    def onUnlink(self, *args):

        self.resourceObservable(Local)