observe-hook: add new thread to leave graphs upon removing a group

pkg/arvo/app/observe-hook.hoon

@@ -10,10 +10,13 @@
 +$  card  card:agent:gall
 +$  versioned-state
   $%  state-0
+      state-0
   ==
 ::
 +$  serial   @uv
 +$  state-0  [%0 observers=(map serial observer:sur)]
++$  state-1  [%1 observers=(map serial observer:sur)]
+::
 ++  got-by-val
   |=  [a=(map serial observer:sur) b=observer:sur]
   ^-  serial
@@ -24,7 +27,7 @@
 --
 ::
 %-  agent:dbug
-=|  state-0
+=|  state-1
 =*  state  -
 ::
 ^-  agent:gall
@@ -35,8 +38,14 @@
 ++  on-init
   |^  ^-  (quip card _this)
   :_  this
-  :_  ~
-  (act /inv-gra [%watch %invite-store /invitatory/graph %invite-accepted-graph])
+  :~  %+  act
+        /inv-gra
+      [%watch %invite-store /invitatory/graph %invite-accepted-graph]
+    ::
+      %+  act
+        /grp-gra
+      [%watch %group-store /groups %group-leave-graph]
+  ==
   ::
   ++  act
     |=  [=wire =action:sur]
@@ -56,7 +65,17 @@
 ++  on-load
   |=  old-vase=vase
   ^-  (quip card _this)
-  `this(state !<(state-0 old-vase))
+  =/  old-state  !<(versioned-state old-vase)
+  ?-  -.old-state
+    %1  `this(state old-state)
+  ::
+      %0
+    =.  this(state [%1 observers.old-state])
+    %+  on-poke
+      %observe-action
+    !>  ^-  action:sur
+    [%watch %group-store /groups %group-leave-graph]
+  ==
 ::
 ++  on-poke
   |=  [=mark =vase]

pkg/arvo/ted/group/leave-graph.hoon

@@ -0,0 +1,35 @@
+/-  spider, grp=group-store, gra=graph-store, met=metadata-store
+/+  strandio, res=resource
+::
+=*  strand    strand:spider
+=*  poke-our  poke-our:strandio
+=*  scry      scry:strandio
+::
+^-  thread:spider
+|=  arg=vase
+=/  m  (strand ,vase)
+^-  form:m
+=+  !<([=update:grp ~] arg)
+?.  ?=(%remove-group -.update)
+  (pure:m !>(~))
+::
+::  get graphs associated with group and archive them
+=/  graphs=(list path)
+  %+  turn
+    %~  tap  in
+    %~  key  by
+    ^-  associations:met
+    %+  scry
+      %noun
+    (weld /group (en-path:res resource.update))
+  |=  [g=group-path:met m=md-resource:met]
+  ^-  path
+  app-path.m
+|-
+?~  groups
+  (pure:m !>(~))
+;<  ~  bind:m
+  %+  poke-our  %graph-store
+  !>  ^-  update:graph-store
+  [%archive-graph (de-path:res i.groups)]
+$(groups t.groups)