::                                                      ::  ::
::::  /app/hall/hoon                                    ::  ::
  ::                                                    ::  ::
::
::TODO  document gate samples fully.
::
::TODO  for using moons as tmp identities for friends: stories may want to keep
::      lists of moons (or just ships in general?) that we define as "standalone"
::      so that the "convert to true identity" doesn't happen for them.
::
::TODO  uncouple presence from subscription state. have hall send an initial
::      presence when we sub to someplace, and remove that when we unsub, but
::      don't make the target source do that.
::
/-    hall                                              ::<  structures
/+    hall, hall-legacy                                 ::<  libraries
/=    seed  /~  !>(.)
::
::::
  ::
=,  hall
=>  ::>  ||
    ::>  ||  %arch
    ::>  ||
    ::>    data structures
    ::
    |%
    ::>  ||  %state                                     ::
    ::>    state data structures                        ::
    ++  state                                           ::>  application state
      $:  stories/(map naem story)                      ::<  conversations
          outbox/(map serial tracking)                  ::<  sent messages
          log/(map naem @ud)                            ::<  logged to clay
          nicks/(map ship nick)                         ::<  local nicknames
          binds/(jug char audience)                     ::<  circle glyph lookup
          public/(set circle)                           ::<  publicly member of
          rir/wire                                      ::<  current rumor wire
      ==                                                ::
    ++  story                                           ::>  wire content
      $:  count/@ud                                     ::<  (lent grams)
          grams/(list telegram)                         ::<  all messages
          known/(map serial @ud)                        ::<  messages heard
          sourced/(map circle (list @ud))               ::<  messages by circle
          sequence/(map circle @ud)                     ::<  last-heard p circle
          locals/group                                  ::<  local status
          remotes/(map circle group)                    ::<  remote status
          shape/config                                  ::<  configuration
          mirrors/(map circle config)                   ::<  remote config
          peers/(jar ship query)                        ::<  subscribers
          inherited/_|                                  ::<  from parent?
      ==                                                ::
    ::>  ||  %deltas                                    ::
    ::>    changes to state                             ::
    ++  delta                                           ::
      $%  ::  public state                              ::
          {$public add/? cir/circle}                    ::<  show/hide membership
          ::  messaging state                           ::
          {$out cir/circle out/(list thought)}          ::<  send msgs to circle
          $:  $done                                     ::>  set delivery state
              cir/circle                                ::
              ses/(list serial)                         ::
              res/delivery                              ::
          ==                                            ::
          ::  shared ui state                           ::
          {$glyph diff-glyph}                           ::<  un/bound glyph
          {$nick diff-nick}                             ::<  changed nickname
          ::  story state                               ::
          {$story nom/naem det/delta-story}             ::<  change to story
          ::  side-effects                              ::
          {$init $~}                                    ::<  initialize
          {$observe who/ship}                           ::<  watch burden bearer
          $:  $present                                  ::>  send %present cmd
              hos/ship                                  ::
              nos/(set naem)                            ::
              dif/diff-status                           ::
          ==                                            ::
      ==                                                ::
    ++  delta-story                                     ::>  story delta
      $?  diff-story                                    ::<  both in & outward
      $%  {$inherited ihr/?}                            ::<  inherited flag
          {$follow sub/? srs/(set source)}              ::<  un/subscribe
          {$sequent cir/circle num/@ud}                 ::<  update last-heard
          {$gram src/circle gam/telegram}               ::<  new/changed msgs
      ==  ==                                            ::
    ::>  ||  %out                                       ::
    ::>    outgoing data                                ::
    ++  move  (pair bone card)                          ::<  all actions
    ++  lime                                            ::>  diff fruit
      $%  {$hall-prize prize}                           ::
          {$hall-rumor rumor}                           ::
      ==                                                ::
    ++  pear                                            ::>  poke fruit
      $%  {$hall-command command}                       ::
          {$hall-action action}                         ::TODO  see ++gentle-quit
      ==                                                ::
    ++  card                                            ::>  general card
      $%  {$diff lime}                                  ::
          {$info wire ship term nori:clay}              ::
          {$peer wire dock path}                        ::
          {$poke wire dock pear}                        ::
          {$pull wire dock $~}                          ::
          {$quit $~}                                    ::
      ==                                                ::
    ++  weir                                            ::>  parsed wire
      $%  {$repeat cir/circle ses/(list serial)}        ::<  messaging wire
          {$circle nom/naem src/source}                 ::<  subscription wire
      ==                                                ::
    --
::
::>  ||
::>  ||  %work
::>  ||
::>    functional cores and arms.
::
|_  {bol/bowl:gall state}
::
++  prep                                                ::<  prepare state
  ::>  adapts state.
  ::
  |=  old/(unit state)
  ^-  (quip move _..prep)
  ?~  old
    %-  pre-bake
    ta-done:ta-init:ta
  [~ ..prep(+<+ u.old)]
::
::>  ||
::>  ||  %engines
::>  ||
::>    main cores.
::+|
::
++  ta                                                  ::<  per transaction
  ::>  thinker core, used for processing pokes into
  ::>  deltas.
  ::
  |_  ::>  deltas: deltas created by core operations.
      ::
      deltas/(list delta)
  ::
  ++  ta-done                                           ::<  resolve core
    ::>  produces the moves stored in ++ta's moves.
    ::>  they are produced in reverse order because
    ::>  ++ta-emil and ++ta-emit add them to the head of
    ::>  the {moves}.
    ::>  we don't produce any new state, because ++ta
    ::>  doesn't make any changes to it itself.
    ::
    ^-  (list delta)
    (flop deltas)
  ::
  ::>  ||
  ::>  ||  %emitters
  ::>  ||
  ::>    arms that create outward changes.
  ::+|
  ::
  ++  ta-delta                                          ::<  emit a delta
    ::>  adds a delta to the head of {deltas}.
    ::
    |=  det/delta
    %_(+> deltas [det deltas])
  ::
  ++  ta-deltas                                         ::<  emit delta list
    ::>  adds multiple deltas to the head of {deltas}.
    ::>  flops to stay consistent with ++ta-delta.
    ::
    |=  des/(list delta)
    %_(+> deltas (welp (flop des) deltas))
  ::
  ++  ta-note                                           ::<  tell user
    ::>  sends {msg} as an %app message to the user's
    ::>  inbox.
    ::
    |=  msg/tape
    %+  ta-action  %phrase
    :-  [[our.bol %inbox] ~ ~]
    [%app dap.bol %lin | (crip msg)]~
  ::
  ++  ta-evil                                           ::<  emit error
    ::>  tracing printf and crash.
    ::
    |=  msg/cord
    ~|  [%hall-ta-evil msg]
    !!
  ::
  ::>  ||
  ::>  ||  %data
  ::>  ||
  ::>    utility functions for data retrieval.
  ::+|
  ::
  ++  ta-know                                           ::<  story monad
    ::>  produces a gill that takes a gate.
    ::>  if the story {nom} exists, calls the gate with
    ::>  a story core. if it doesn't, does nothing.
    ::
    |=  nom/naem
    |=  fun/$-(_so _ta)
    ^+  +>+>
    =+  pur=(~(get by stories) nom)
    ?~  pur
      %-  ta-evil
      (crip "no story '{(trip nom)}'")
    (fun ~(. so nom ~ u.pur))
  ::
  ::>  ||
  ::>  ||  %interaction-events
  ::>  ||
  ::>    arms that apply events we received.
  ::+|
  ::
  ++  ta-init                                           ::<  initialize app
    ::>  populate state on first boot.
    ::>  creates our default mailbox and journal.
    ::
    ::  create default circles.
    =>  %+  roll
          ^-  (list {security naem cord})
          :~  [%mailbox %inbox 'default home']
              [%journal %public 'visible activity']
          ==
        |=  {{typ/security nom/naem des/cord} _ta}
        (ta-action [%create nom des typ])
    %-  ta-deltas
    ::  if needed, subscribe to our parent's /burden.
    =+  sen=(above our.bol)
    ?:  ?|  !=(%czar (clan:title sen))
            =(sen our.bol)
            =(%pawn (clan:title our.bol))
        ==
      ~
    [%init ~]~
  ::
  ++  ta-apply                                          ::<  apply command
    ::>  applies the command sent by {src}.
    ::
    |=  {src/ship cod/command}
    ^+  +>
    ?-  -.cod
      ::>  %publish commands prompt us (as a circle host)
      ::>  to verify and distribute messages.
      $publish  (ta-think | src +.cod)
      ::>  %present commands are used to ask us to set
      ::>  someone's status in the indicated stories.
      $present  (ta-present src +.cod)
      ::>  %bearing commands are used by our children to
      ::>  let us know they're bearing our /burden. we
      ::>  need to watch them to allow changes to go up.
      $bearing  (ta-observe src)  ::TODO  isn't this redundant with ta-subscribe?
    ==
  ::
  ++  ta-present                                        ::<  update a status
    ::>  sets status for the indicated stories,
    ::>  but only if they have write permission there.
    ::
    |=  {who/ship nos/(set naem) dif/diff-status}
    ^+  +>
    %-  ta-deltas
    %+  murn  ~(tap in nos)
    |=  n/naem
    ^-  (unit delta)
    ?.  (~(has by stories) n)  ~
    ::  only have presence if you have write permission.
    ?.  (~(so-admire so n ~ (~(got by stories) n)) who)
      ~
    `[%story n %status [our.bol n] who dif]
  ::
  ++  ta-action                                         ::<  apply client action
    ::>  performs action sent by a client.
    ::
    |=  act/action
    ^+  +>
    =<  work
    ::>  ||
    ::>  ||  %actions
    ::>  ||
    ::>    action processing core
    ::>
    ::>  ++work calls the appropriate action processing
    ::>  arm. most use ++affect to retrieve the affected
    ::>  story, crashing if it doesn't exist.
    |%
    ::  ||  %utility
    ::+|
    ++  work                                            ::<  perform action
      ^+  ..ta-action
      ?-  -.act
        ::  circle configuration
        $create  (action-create +.act)
        $source  (action-source +.act)
        $depict  (action-depict +.act)
        $filter  (action-filter +.act)
        $permit  (action-permit +.act)
        $delete  (action-delete +.act)
        ::  messaging
        $convey  (action-convey +.act)
        $phrase  (action-phrase +.act)
        ::  personal metadata
        $notify  (action-notify +.act)
        $naming  (action-naming +.act)
        ::  changing shared ui
        $glyph   (action-glyph +.act)
        $nick    (action-nick +.act)
        ::  misc changes
        $public  (action-public +.act)
      ==
    ::
    ++  affect                                          ::<  delta to story
      ::>  store a delta about a story. if the story
      ::>  does not exist, crash.
      ::
      |=  {nom/naem det/delta-story}
      ?:  (~(has by stories) nom)
        (impact nom det)
      (ta-evil (crip "no story {(trip nom)}"))
    ::
    ++  impact                                          ::<  delta for story
      ::>  Store a delta about a story.
      ::
      |=  {nom/naem det/delta-story}
      (ta-delta %story nom det)
    ::
    ++  present                                         ::<  send status update
      ::>
      ::
      |=  {aud/audience dif/diff-status}
      ^+  ..ta-action
      =/  cic
        ^-  (jug ship naem)
        %-  ~(rep in aud)
        |=  {c/circle m/(jug ship naem)}
        (~(put ju m) hos.c nom.c)
      =?  ..ta-action  (~(has by cic) our.bol)
        %-  ~(rep in (~(get ju cic) our.bol))
        |=  {n/naem _ta}  ::  beware, urbit/arvo#447
        (affect n %status [our.bol n] our.bol dif)
      =.  cic  (~(del by cic) our.bol)
      %-  ta-deltas
      %-  ~(rep by cic)
      |=  {{h/ship s/(set naem)} l/(list delta)}
      :_  l
      [%present h s dif]
    ::
    ::>  ||  %circle-configuration
    ::+|
    ++  action-create                                   ::<  create story
      ::>  creates a story with the specified parameters.
      ::
      |=  {nom/naem des/cord typ/security}
      ^+  ..ta-action
      ?.  (~(has in stories) nom)
        %^  impact  nom  %new
        :*  [[[our.bol nom] ~] ~ ~]
            des
            *filter
            :-  typ
            ?.  ?=(?($village $journal) typ)  ~
            [our.bol ~ ~]
        ==
      (ta-evil (crip "{(trip nom)}: already exists"))
    ::
    ++  action-delete                                   ::<  delete + announce
      ::>  delete story {nom}, optionally announcing the
      ::>  event with message {mes}.
      ::
      |=  {nom/naem mes/(unit cord)}
      ^+  ..ta-action
      =?  ..ta-action  ?=(^ mes)
        %+  action-phrase
          [[our.bol nom] ~ ~]
        [%lin | u.mes]~
      (affect nom %remove ~)
    ::
    ++  action-depict                                   ::<  change description
      ::>  change description of story {nom} to {des}.
      ::
      |=  {nom/naem cap/cord}
      (affect nom %config [our.bol nom] %caption cap)
    ::
    ++  action-filter                                   ::<  change message rules
      ::>  replaces the story's current filter with the
      ::>  specified one.
      ::
      |=  {nom/naem fit/filter}
      (affect nom %config [our.bol nom] %filter fit)
    ::
    ++  action-permit                                   ::<  invite/banish
      ::>  invite to/banish from story {nom} all {sis}.
      ::
      |=  {nom/naem inv/? sis/(set ship)}
      =+  soy=(~(get by stories) nom)
      ?~  soy
        (ta-evil (crip "no story {(trip nom)}"))
      so-done:(~(so-permit so nom ~ u.soy) inv sis)
    ::
    ++  action-source                                   ::<  un/sub p to/from r
      ::>  add/remove {pos} as sources for story {nom}.
      ::
      |=  {nom/naem sub/? srs/(set source)}
      =+  soy=(~(get by stories) nom)
      ?~  soy
        (ta-evil (crip "no story {(trip nom)}"))
      so-done:(~(so-sources so nom ~ u.soy) sub srs)
    ::
    ::>  ||  %messaging
    ::+|
    ++  action-convey                                   ::<  post exact
      ::>  sends the messages provided in the action.
      ::
      |=  tos/(list thought)
      (ta-think & our.bol tos)
    ::
    ++  action-phrase                                   ::<  post easy
      ::>  sends the message contents provided in the
      ::>  action generating a serial and setting a
      ::>  timestamp.
      ::
      |=  {aud/audience ses/(list speech)}
      ^+  ..ta-action
      =-  (ta-think & our.bol tos)
      |-  ^-  tos/(list thought)
      ?~  ses  ~
      =^  sir  eny.bol  ~(uniq hall bol)
      :_  $(ses t.ses)
      [sir aud [now.bol i.ses]]
    ::
    ::>  ||  %personal-metadata
    ::+|
    ::
    ++  action-notify                                   ::<  our presence update
      ::>  notify the audience of our new presence state,
      ::>  or tell them to remove us if {pes} is ~.
      ::
      |=  {aud/audience pes/(unit presence)}
      ^+  ..ta-action
      ?~  pes  (present aud %remove ~)
      (present aud %presence u.pes)
    ::
    ++  action-naming                                   ::<  our name update
      ::>
      ::
      |=  {aud/audience man/human}
      ^+  ..ta-action
      (present aud %human %full man)
    ::
    ::>  ||  %changing-shared-ui
    ::+|
    ++  action-nick                                     ::<  new identity
      ::>  assigns a new local identity ("nickname") to the
      ::>  target ship.
      ::
      |=  {who/ship nic/nick}
      ^+  ..ta-action
      ?.  =((~(get by nicks) who) `nic)  ..ta-action    ::<  no change
      (ta-delta %nick who nic)
    ::
    ++  action-glyph                                    ::<  bind a glyph
      ::>  un/bind glyph {lif} to audience {aud}.
      ::
      |=  {lif/char aud/audience bin/?}
      (ta-delta %glyph bin lif aud)
    ::
    ++  action-public                                   ::<  show/hide membership
      ::>  add or remove a circle from the public
      ::>  membership list.
      ::
      |=  {add/? cir/circle}
      (ta-delta %public add cir)
    --
  ::
  ::>  ||
  ::>  ||  %subscription-events
  ::>  ||
  ::>    arms that react to subscription events.
  ::+|
  ::
  ++  ta-observe                                        ::<  watch burden bearer
    ::>  subscribe to a child who is bearing our burden.
    ::TODO  everyone should be able to bear if they so desire.
    ::
    |=  who/ship
    ^+  +>
    ?.  =(our.bol (above who))
      ~&([%not-our-bearer who] +>)
    (ta-delta %observe who)
  ::
  ++  ta-subscribe                                      ::<  listen to
    ::>  reaction to incoming subscriptions.
    ::
    |=  {her/ship qer/query}
    ^+  +>
    ?+  -.qer  +>
      $burden   (ta-observe her)
      $circle   %+  ta-delta  %story
                [nom.qer %peer & her qer]
    ==
  ::
  ++  ta-greet                                          ::<  subscription success
    ::>  store a started subscription as source.
    ::
    |=  {nom/naem src/source}
    %-  (ta-know nom)  |=  sor/_so  =<  so-done
    (so-greet:sor src)
  ::
  ++  ta-leave                                          ::<  subscription failed
    ::>  removes {src} from story {nom}'s sources.
    ::
    |=  {nom/naem src/source}
    %-  (ta-know nom)  |=  sor/_so  =<  so-done
    (so-leave:sor src)
  ::
  ++  ta-take                                           ::<  apply prize
    ::>  for a %burden prize, bear the burden in a new
    ::>  or existing story.
    ::>  for a %circle prize, use ++so to accept it.
    ::>  for a %report prize, silently ignore.
    ::
    |=  {wir/wire piz/prize}
    ^+  +>
    ?+  -.piz  ~&([%ignoring-prize -.piz] +>)
        $report
      +>
    ::
        $burden
      =+  sos=~(tap by sos.piz)
      |-  ^+  ..ta-take
      ?~  sos  ..ta-take
      =.  ..ta-take
        =+  (fall (~(get by stories) p.i.sos) *story)
        =>  (~(so-bear so p.i.sos ~ -) q.i.sos)
        =.  acs  (flop acs)
        |-  ^+  ..ta-take
        ?~  acs  ..ta-take
        =.  ..ta-take  (ta-action i.acs)
        $(acs t.acs)
      $(sos t.sos)
      ::TODO  runtime error
      ::%+  roll  ~(tap by sos.piz)
      ::|=  {{n/naem b/burden} _..ta-take}
      ::=+  (fall (~(get by stories) n) *story)
      ::so-done:(~(so-bear so n ~ -) b)
    ::
        $circle
      =+  wer=(etch wir)
      ?>  ?=($circle -.wer)
      %-  (ta-know nom.wer)  |=  sor/_so  =<  so-done
      (so-take:sor cir.src.wer +.piz)
    ==
  ::
  ++  ta-hear                                           ::<  apply rumor
    ::>  apply changes from a rumor to our state.
    ::>  for %burden, authoratively apply the story
    ::>  diff. if it's a new one, bear it.
    ::>  for %circle, apply the story diff normally.
    ::
    |=  {wir/wire rum/rumor}
    ^+  +>
    ?+  -.rum
      ~&([%ignoring-rumor -.rum] +>)
    ::
        $burden
      ?+  -.rum.rum
        %-  (ta-know nom.rum)  |=  sor/_so  =<  so-done
        (so-hear:sor & [our.bol nom.rum] rum.rum)
      ::
          $new
        =?  +>  !(~(has by stories) nom.rum)
          (ta-delta %story +.rum)
        =>  =+  (fall (~(get by stories) nom.rum) *story)
            %-  ~(so-bear so nom.rum ~ -)
            [~ [cof.rum.rum ~] [~ ~]]
        =.  acs  (flop acs)
        |-  ^+  +>+
        ?~  acs  +>+
        =.  +>+  (ta-action i.acs)
        $(acs t.acs)
        ::TODO  runtime error
        ::=<  so-done
        ::%-  ~(so-bear so nom.rum ~ (fall (~(get by stories) nom.rum) *story))
        ::[~ [cof.rum.rum ~] [~ ~]]
      ==
    ::
        $circle
      =+  wer=(etch wir)
      ?>  ?=($circle -.wer)
      %-  (ta-know nom.wer)  |=  sor/_so  =<  so-done
      (so-hear:sor | cir.src.wer rum.rum)
    ==
  ::
  ++  ta-repeat                                         ::<  message delivered
    ::>  message got delivered. if an error was returned
    ::>  mark the message as rejected. if not, received.
    ::
    |=  {who/circle ses/(list serial) fal/(unit tang)}
    ^+  +>
    ~?  ?=(^ fal)  u.fal
    =-  (ta-delta %done who ses -)
    ?~  fal  %accepted
    ~>(%slog.[0 u.fal] %rejected)
  ::
  ++  ta-resub                                          ::<  subscription dropped
    ::>  when a subscription gets dropped by gall, we
    ::>  resubscribe.
    ::
    |=  {nom/naem src/source}
    ^+  +>
    %-  (ta-know nom)  |=  sor/_so  =<  so-done
    (so-resub:sor src)
  ::
  ::>  ||
  ::>  ||  %messaging
  ::>  ||
  ::>    arms for sending and processing messages.
  ::+|
  ::
  ++  ta-think                                          ::<  publish or review
    ::>  consumes each thought.
    ::
    |=  {pub/? aut/ship tos/(list thought)}
    ^+  +>
    ?~  tos  +>
    $(tos t.tos, +> (ta-consume pub aut i.tos))
  ::
  ++  ta-consume                                        ::<  to each audience
    ::>  conducts thought {tot} to each circle in its audience.
    ::
    |=  {pub/? aut/ship tot/thought}
    =+  aud=~(tap in aud.tot)
    |-  ^+  +>.^$
    ?~  aud  +>.^$
    $(aud t.aud, +>.^$ (ta-conduct pub aut i.aud tot))
  ::
  ++  ta-conduct                                        ::<  thought to circle
    ::>  either publishes or records a thought.
    ::
    |=  {pub/? aut/ship cir/circle tot/thought}
    ^+  +>
    ?:  pub
      ?.  (team:title our.bol aut)
        (ta-note "strange author {(scow %p aut)}")
      =.  aut  our.bol
      ?:  =(aut hos.cir)
        ?:  (~(has by stories) nom.cir)
          (ta-record nom.cir hos.cir tot)
        ::TODO  avenue for abuse?
        (ta-note "have no story {(scow %tas nom.cir)}")
      (ta-transmit cir tot)
    ?.  =(our.bol hos.cir)  +>
    (ta-record nom.cir aut tot)
  ::
  ++  ta-record                                         ::<  add to story
    ::>  add or update telegram {gam} in story {nom}.
    ::
    |=  {nom/naem gam/telegram}
    %-  (ta-know nom)  |=  sor/_so  =<  so-done
    (so-learn:sor [our.bol nom] gam)
  ::
  ++  ta-transmit                                       ::<  send message
    ::>  sends thought {tot} to {cir}.
    ::
    |=  {cir/circle tot/thought}
    ^+  +>
    (ta-delta %out cir tot ~)
  ::
  ::>  ||
  ::>  ||  %stories
  ::>  ||
  ::>    arms for modifying stories.
  ::+|
  ::
  ++  so                                                ::<  story core
    ::>  story core, used for doing work on a story.
    ::
    |_  ::>  nom: story name in {stories}.
        ::>  acs: hall actions issued due to changes.
        ::>  story is faceless to ease data access.
        ::
        $:  nom/naem
            acs/(list action)
            story
        ==
    ::
    ++  so-done                                         ::<  apply changes
      ::>  apply actions generated by story operations.
      ::TODO  maybe produce list of actions, apply in ++ta
      ::
      ^+  +>
      =.  acs  (flop acs)
      |-  ^+  +>+
      ?~  acs  +>+
      =.  +>+  (ta-action i.acs)
      $(acs t.acs)
    ::
    ::>  ||
    ::>  ||  %emitters
    ::>  ||
    ::>    arms that create outward changes.
    ::+|
    ::
    ++  so-act                                          ::<  send action
      ::>  stores a hall action.
      ::
      |=  act/action
      ^+  +>
      +>(acs [act acs])
    ::
    ++  so-note                                         ::<  tell user
      ::>  sends {msg} as an %app message to the user's
      ::>  inbox.
      ::
      |=  msg/cord
      ^+  +>
      %+  so-act  %phrase
      :-  [[our.bol %inbox] ~ ~]
      [%app dap.bol %lin | msg]~
    ::
    ++  so-delta                                        ::<  send delta
      ::>  store delta in ++ta core.
      ::
      |=  det/delta
      ^+  +>
      +>(deltas [det deltas])
    ::
    ++  so-deltas                                       ::<  send delta list
      ::>  store multiple deltas in ++ta core.
      ::
      |=  des/(list delta)
      %_(+> deltas (welp (flop des) deltas))
    ::
    ++  so-delta-our                                    ::<  send delta of us
      ::>  adds a delta about this story.
      ::
      |=  det/delta-story
      ^+  +>
      (so-delta %story nom det)
    ::
    ++  so-deltas-our                                   ::<  send deltas of us
      ::>  adds multiple deltas about this story.
      ::
      |=  des/(list delta-story)
      ^+  +>
      %-  so-deltas
      %+  turn  des
      |=  d/delta-story
      [%story nom d]
    ::
    ::>  ||
    ::>  ||  %data
    ::>  ||
    ::>    utility functions for data retrieval.
    ::+|
    ::
    ++  so-cir  [our.bol nom]                           ::<  us as circle
    ::
    ::>  ||
    ::>  ||  %interaction-events
    ::>  ||
    ::>    arms that apply events we received.
    ::+|
    ::
    ++  so-take                                         ::<  accept circle prize
      ::>  apply the prize as if it were rumors.
      ::
      |=  {src/circle nes/(list envelope) cos/lobby pes/crowd}
      ^+  +>
      =.  +>.$
        (so-hear | src %config src %full loc.cos)
      =.  +>.$
        =+  los=~(tap by loc.pes)
        |-
        ?~  los  +>.^$
        =.  +>.^$
          (so-hear | src %status src p.i.los %full q.i.los)
        $(los t.los)
        ::TODO  ideally you'd just do this, but that runtime errors...
        ::%-  ~(rep in loc.pes)
        ::|=  {{w/ship s/status} _+>.$}
        ::(so-hear | src %status src w %full s)
      (so-unpack src nes)
    ::
    ++  so-hear                                         ::<  accept circle rumor
      ::>  apply changes from a rumor to this story.
      ::
      |=  {bur/? src/circle rum/rumor-story}
      ::TODO  tall-form gate comments like this for everything?
      ::|=  $:  ::>  bur: whether the story is inherited
      ::        ::>  src: story to change
      ::        ::>  rum: change to this story
      ::        ::
      ::        bur/?
      ::        src/circle
      ::        rum/rumor-story
      ::    ==
      ^+  +>
      ?-  -.rum
        $new      ?:  =(src so-cir)
                    (so-config-full ~ cof.rum)
                  $(rum [%config src %full cof.rum])
        $bear     (so-bear bur.rum)
        $peer     (so-delta-our rum)
        $gram     (so-open src nev.rum)
        $config   ::  full changes to us need to get split up.
                  ?:  &(=(cir.rum so-cir) ?=($full -.dif.rum))
                    (so-config-full `shape cof.dif.rum)
                  ::  we only subscribe to remotes' configs.
                  ?:  =(src cir.rum)
                    (so-delta-our rum)
                  ~!  %unexpected-remote-config-from-remote
                  !!
        $status   ::  we only subscribe to remotes' locals.
                  ?:  |(=(src cir.rum) =(src so-cir))
                    (so-delta-our rum)
                  ~!  %unexpected-remote-status-from-remote
                  !!
        $remove   (so-delta-our %config src %remove ~)
      ==
    ::
    ++  so-bear                                         ::<  accept burden
      ::>  add what was pushed down from above to our
      ::>  state. in case of conflict, existing data is
      ::>  overwritten.
      ::
      |=  {gaz/(list telegram) cos/lobby pes/crowd}
      ^+  +>
      =*  self  +>
      ::  local config
      =.  self
        (so-config-full `shape loc.cos)
      ::  remote config
      =.  self
        =+  rem=~(tap by rem.cos)
        |-  ^+  self
        ?~  rem  self
        =.  self
          (so-delta-our %config p.i.rem %full q.i.rem)
        $(rem t.rem)
        ::TODO  eats previous change?
        ::%+  roll  ~(tap by rem.cos)
        ::|=  {{r/circle c/config} _self}
        ::(so-delta-our %config r %full c)
      ::  local status
      =.  self
        =+  sas=~(tap by loc.pes)
        |-  ^+  self
        ?~  sas  self
        =.  deltas
          :_  deltas
          :^  %story  nom  %status
          [[our.bol nom] p.i.sas %full q.i.sas]
        $(sas t.sas)
        ::TODO  ideally do below, but runtime error at so-delta-our
        ::%+  roll  ~(tap by loc.pes)
        ::|=  {{w/ship s/status} _self}
        ::(so-delta-our %status so-cir w %full s)
      ::  remote status
      =.  self
        =+  rem=~(tap by rem.pes)
        |-  ^+  self
        ?~  rem  self
        =.  deltas
          %+  welp  deltas
          =+  gop=~(tap by q.i.rem)
          =|  l/(list delta)
          |-  ^+  l
          ?~  gop  l
          =.  l  [[%story nom %status p.i.rem p.i.gop %full q.i.gop] l]
          $(gop t.gop)
        $(rem t.rem)
        ::TODO  below eats state?
        ::%+  roll  ~(tap by rem.pes)
        ::|=  {{c/circle g/group} _self}
        ::%+  roll  ~(tap by g)
        ::|=  {{w/ship s/status} _self}
        ::(so-delta-our %status c w %full s)
      ::  telegrams
      =.  self
        %_  self
            deltas
          %+  welp  deltas
          %-  flop
          %+  turn  gaz
          |=  t/telegram
          ^-  delta
          :+  %story  nom
          ::TODO  this really should have sent us the message
          ::      src as well but that's not an easy fix.
          :+  %gram  [(above our.bol) nom]
          ::  in audience, replace above with us.
          =-  t(aud -)
          =+  (~(del in aud.t) [(above our.bol) nom])
          (~(put in -) so-cir)
        ==
        ::TODO  ideally do below, but runtime error
        ::%-  so-deltas-our
        ::%+  turn  gaz
        ::|=  t/telegram
        ::^-  delta-story
        :::-  %gram
        ::::  in audience, replace above with us.
        ::=-  t(aud -)
        ::=+  (~(del in aud.t) [(above our.bol) nom])
        ::(~(put in -) so-cir)
      ::  inherited flag
      %_(self deltas [[%story nom %inherited &] deltas])
      ::TODO  runtime error
      ::(so-delta-our %inherited &)
    ::
    ::>  ||
    ::>  ||  %changes
    ::>  ||
    ::>    arms that make miscellaneous changes to this story.
    ::+|
    ::
    ++  so-config-full                                  ::<  split full config
      ::>  split a %full config delta up into multiple
      ::>  smaller ones, for easier application.
      ::
      |=  {old/(unit config) cof/config}
      ^+  +>
      ~?  &(?=(^ old) !=(src.u.old src.cof))
        %maybe-missing-src-changes
      %-  so-deltas
      %+  turn
        %+  weld
          ^-  (list delta-story)
          ?~  old  ~
          ::TODO?  what to do about src?
          :~  ::[%follow | src.u.old]
              [%config so-cir %permit | sis.con.u.old]
          ==
        ^-  (list delta-story)
        :~  ::[%follow & src.cof]
            [%config so-cir %caption cap.cof]
            [%config so-cir %filter fit.cof]
            [%config so-cir %secure sec.con.cof]
            [%config so-cir %permit & sis.con.cof]
        ==
      |=  d/delta-story
      [%story nom d]
    ::
    ++  so-sources                                      ::<  change source
      ::>  adds or removes {srs} from our sources,
      ::>  skipping over ones we already (don't) have.
      ::
      |=  {add/? srs/(set source)}
      ^+  +>
      =/  sus/(set source)
        %.  src.shape
        ?:(add ~(dif in srs) ~(int in srs))
      ::  we only make a delta for removals here,
      ::  because we don't need to wait for ++reap when
      ::  pulling subscriptions.
      =?  +>.$  !add
        =+  sos=~(tap in sus)
        |-  ^+  +>.^$
        ?~  sos  +>.^$
        =.  +>.^$  (so-delta-our %config so-cir %source | i.sos)
        $(sos t.sos)
        ::TODO  ideally below, but unexplained runtime error at `so-delta-our`
        ::%+  roll  ~(tap in sus)
        ::|=  {src/source _+>.$}
        ::^+  +>.^$
        ::(so-delta-our %config so-cir %source | src)
      ?~  sus  +>.$
      (so-delta-our %follow add sus)
    ::
    ++  so-depict                                       ::<  change description
      ::>  modifies our caption.
      ::
      |=  cap/cord
      ^+  +>
      ?:  =(cap cap.shape)  +>
      (so-delta-our %config so-cir %caption cap)
    ::
    ++  so-filter                                       ::<  change message rules
      ::>  modifies our filter.
      ::
      |=  fit/filter
      ^+  +>
      ?:  =(fit fit.shape)  +>
      (so-delta-our %config so-cir %filter fit)
    ::
    ++  so-delete                                       ::<  delete story
      ::>  deletes this story. removes it from {stories}
      ::>  and unsubscribes from all src.
      ::
      (so-delta-our %remove ~)
    ::
    ::>  ||
    ::>  ||  %subscriptions
    ::>  ||
    ::>    arms for starting and ending subscriptions
    ::+|
    ::
    ++  so-greet                                        ::<  subscription started
      ::>  store a started subscription as source.
      ::
      |=  src/source
      ^+  +>
      ?:  (~(has in src.shape) src)  +>
      (so-delta-our %config so-cir %source & src)
    ::
    ++  so-leave                                        ::<  subscription ended
      ::>  delete {src} from our sources.
      ::
      |=  src/source
      ^+  +>
      ?.  (~(has in src.shape) src)  +>
      (so-delta-our %config so-cir %source | src)
    ::
    ++  so-resub                                        ::<  subscription revived
      ::>  re-subscribe to a dropped subscription.
      ::>  if it was already active, we continue where
      ::>  we left off.
      ::
      |=  src/source
      ^+  +>
      =+  seq=(~(get by sequence) cir.src)
      ::  if we're past the range, don't resubscribe.
      ?:  ?&  ?=(^ ran.src)
              ?=(^ tal.u.ran.src)
            ::
              ?-  -.u.tal.u.ran.src
                $da   (gte now.bol +.u.tal.u.ran.src)
                $ud   ?&  ?=(^ seq)
                          (gte u.seq +.u.tal.u.ran.src)
                      ==
              ==
          ==
        (so-delta-our %follow | [src ~ ~])
      =-  (so-delta-our %follow & [[cir.src -] ~ ~])
      ^-  range
      ?~  seq  ran.src
      =-  `[[%ud u.seq] -]
      ?~  ran.src  ~
      tal.u.ran.src
    ::
    ++  so-first-grams                                  ::<  beginning of stream
      ::>  find all grams that fall within the range.
      ::
      |=  ran/range
      ^-  (list telegram)
      =+  [num=0 gaz=grams zeg=*(list telegram)]
      ::  fill in empty ranges to select all grams.
      =.  ran
        ?~  ran  `[[%ud 0] `[%ud count]]
        ?~  tal.u.ran  `[hed.u.ran `[%ud count]]
        ran
      ::  never fails, but compiler needs it.
      ?>  &(?=(^ ran) ?=(^ tal.u.ran))
      %-  flop
      |-  ^-  (list telegram)
      ?~  gaz  zeg
      ?:  ?-  -.u.tal.u.ran                             ::  after the end
            $ud  (lth +.u.tal.u.ran num)
            $da  (lth +.u.tal.u.ran wen.i.gaz)
          ==
        ::  if past the river, we're done searching.
        zeg
      ?:  ?-  -.hed.u.ran                               ::  before the start
            $ud  (lth num +.hed.u.ran)
            $da  (lth wen.i.gaz +.hed.u.ran)
          ==
        ::  if before the river, continue onward.
        $(num +(num), gaz t.gaz)
      ::  if in the river, add this gram and continue.
      $(num +(num), gaz t.gaz, zeg [i.gaz zeg])
    ::
    ++  so-in-range                                     ::<  place in range?
      ::>  produces two booleans: whether we're
      ::>  currently in the range, and whether the range
      ::>  has passed.
      ::TODO  to deal with changed messages, we'll want
      ::      to be able to pass in a num.
      ::
      |=  ran/range
      ^-  {in/? done/?}
      ?~  ran  [& |]
      =/  min
        ?-  -.hed.u.ran
          $ud  (gth count +.hed.u.ran)
          $da  (gth now.bol +.hed.u.ran)
        ==
      ?~  tal.u.ran
        [min |]
      =-  [&(min -) !-]
      ?-  -.u.tal.u.ran
        $ud  (gte +(+.u.tal.u.ran) count)
        $da  (gte +.u.tal.u.ran now.bol)
      ==
    ::
    ::>  ||
    ::>  ||  %messaging
    ::>  ||
    ::>    arms for adding to this story's messages.
    ::+|
    ::
    ++  so-sane                                         ::<  sanitize
      ::>  sanitize %lin speech according to our settings.
      ::
      |=  sep/speech
      ^-  speech
      ?.  ?=($lin -.sep)  sep
      %_  sep
          msg
        %-  crip
        %-  tufa
        %+  turn  (tuba (trip msg.sep))
        |=  a/@c
        ::  always replace control characters.
        ?:  |((lth a 32) =(a `@c`127))
          `@`'?'
        ::  if desired, remove uppercasing.
        ?:  ?&  !cas.fit.shape
                (gte a 'A')
                (lte a 'Z')
            ==
          (add a 32)
        ::  if desired, replace non-ascii characters.
        ?:  ?&  !utf.fit.shape
                (gth a 127)
            ==
          `@`'?'
        a
      ==
    ::
    ++  so-unpack                                       ::<  process envelopes
      ::>  learn telegrams from list of envelopes and
      ::>  update the sequence of the source if needed.
      ::
      |=  {src/circle nes/(list envelope)}
      ^+  +>
      =.  +>  (so-lesson src (turn nes tail))
      =/  num
        %+  roll  nes
        |=  {nev/envelope max/@ud}
        ?:((gth num.nev max) num.nev max)
      ?.  (gth num (fall (~(get by sequence) src) 0))
        +>.$
      (so-delta-our %sequent src num)
    ::
    ++  so-open                                         ::<  process envelope
      ::>  learn telegram from envelope and update the
      ::>  sequence of the source if needed.
      ::
      |=  {src/circle nev/envelope}
      ^+  +>
      =.  +>  (so-learn src gam.nev)
      ?.  (gth num.nev (fall (~(get by sequence) src) 0))
        +>
      (so-delta-our %sequent src num.nev)
    ::
    ++  so-lesson                                       ::<  learn messages
      ::>  learn all telegrams in a list.
      ::
      |=  {src/circle gaz/(list telegram)}
      ^+  +>
      ?~  gaz  +>
      $(gaz t.gaz, +> (so-learn src i.gaz))
    ::
    ++  so-learn                                        ::<  save/update message
      ::>  store an incoming telegram, updating if it
      ::>  already exists.
      ::
      |=  {src/circle gam/telegram}
      ^+  +>
      ::  check for write permissions.
      ?.  (so-admire aut.gam)  +>
      ::  clean up the message to conform to our rules.
      =.  sep.gam  (so-sane sep.gam)
      (so-delta-our %gram src gam)
    ::
    ::>  ||
    ::>  ||  %permissions
    ::>  ||
    ::>    arms relating to story permissions.
    ::+|
    ::
    ++  so-permit                                       ::<  invite/banish
      ::>  update config to dis/allow ships permission.
      ::
      |=  {inv/? sis/(set ship)}
      ^+  +>
      ::>  wyt:  whitelist?
      ::>  add:  add to list?
      =/  wyt/?  ?=(?($village $journal) sec.con.shape)
      =/  add/?  =(inv wyt)
      =/  sus/(set ship)
        %.  sis.con.shape
        ?:(add ~(dif in sis) ~(int in sis))
      =.  +>.$
        ::  if banishing: notify only those affected.
        ::  if inviting: notify all targets.
        =?  sis  !inv  sus
        =-  (so-act [%phrase - [%inv inv so-cir]~])
        %-  ~(rep in `(set ship)`sis)
        |=  {s/ship a/audience}
        (~(put in a) [s %inbox])
      ?~  sus  +>.$
      ::  if banished, remove their presences.
      =?  +>.$  !inv
        %-  so-deltas-our
        %+  turn  ~(tap in `(set ship)`sus)
        |=  s/ship
        :+  %status  so-cir
        [s %remove ~]
      (so-delta-our %config so-cir %permit [add sus])
    ::
    ++  so-admire                                       ::<  accept from
      ::>  checks {her} write permissions.
      ::
      |=  her/ship
      ^-  ?
      ?-  sec.con.shape
        $channel  !(~(has in sis.con.shape) her)        ::<  blacklist
        $village  (~(has in sis.con.shape) her)         ::<  whitelist
        $journal  (~(has in sis.con.shape) her)         ::<  author whitelist
        $mailbox  !(~(has in sis.con.shape) her)        ::<  author blacklist
      ==
    ::
    ++  so-visible                                      ::<  display to
      ::>  checks {her} read permissions.
      ::
      |=  her/ship
      ^-  ?
      ?-  sec.con.shape
        $channel  !(~(has in sis.con.shape) her)        ::<  blacklist
        $village  (~(has in sis.con.shape) her)         ::<  whitelist
        $journal  &                                     ::<  all
        $mailbox  (team:title our.bol her)              ::<  our team
      ==
    --
  --
::
++  da                                                  ::<  delta application
  ::>  core for doing things, mostly applying deltas to
  ::>  application state, but also dealing with events
  ::>  that aren't pokes.
  ::>  where appropriate, creates moves. those get
  ::>  produced when finalizing with ++da-done.
  ::
  |_  ::>  moves: moves created by core operations.
      ::
      moves/(list move)
  ::
  ++  da-done                                           ::<  resolve core
    ::>  produces the moves stored in ++da's moves.
    ::>  they are produced in reverse order because
    ::>  ++da-emil and ++da-emit add them to the head of
    ::>  the {moves}.
    ::
    ^-  (quip move _+>)
    [(flop moves) +>]
  ::
  ::>  ||
  ::>  ||  %emitters
  ::>  ||
  ::>    arms that create outward changes.
  ::+|
  ::
  ++  da-emil                                           ::<  emit move list
    ::>  adds multiple moves to the head of {moves}.
    ::>  flops to stay consistent with ++ta-emit.
    ::
    |=  mol/(list move)
    %_(+> moves (welp (flop mol) moves))
  ::
  ++  da-emit                                           ::<  emit a move
    ::>  adds a move to the head of {moves}.
    ::
    |=  mov/move
    %_(+> moves [mov moves])
  ::
  ++  da-present                                        ::<  send %present cmd
    ::>
    ::
    |=  {hos/ship nos/(set naem) dif/diff-status}
    ^+  +>
    %-  da-emit
    :*  ost.bol
        %poke
        /present
        [hos dap.bol]
        [%hall-command %present nos dif]
    ==
  ::
  ::>  ||
  ::>  ||  %change-application
  ::>  ||
  ::>    arms that change the application state.
  ::+|
  ::
  ++  da-change                                         ::<  apply delta
    ::>  modifies application state according to the
    ::>  change specified in {dif}.
    ::
    |=  det/delta
    ^+  +>
    ?-  -.det
      $public   (da-change-public +.det)
      $out      (da-change-out +.det)
      $done     (da-change-done +.det)
      $glyph    (da-change-glyph +.det)
      $nick     (da-change-nick +.det)
      $story    (da-change-story +.det)
      $init     da-init
      $observe  (da-observe +.det)
      $present  (da-present +.det)
    ==
  ::
  ++  da-init                                           ::<  startup side-effects
    ::>  apply %init delta, querying the /burden of the
    ::>  ship above us.
    ::
    (da-emit (wire-to-peer /burden))
  ::
  ++  da-observe                                        ::<  watch burden bearer
    ::>  apply %observe delta, querying the /report of
    ::>  {who} below us.
    ::
    |=  who/ship
    (da-emit (wire-to-peer /report/(scot %p who)))
  ::
  ++  da-change-public                                  ::<  show/hide membership
    ::>  add/remove a circle to/from the public
    ::>  membership list.
    ::
    |=  {add/? cir/circle}
    ^+  +>
    =-  +>.$(public -)
    ?:  add  (~(put in public) cir)
    (~(del in public) cir)
  ::
  ++  da-change-out                                     ::<  outgoing messages
    ::>  apply an %out delta, sending a message.
    ::
    |=  {cir/circle out/(list thought)}
    ^+  +>
    =+  ses=(turn out head)
    =.  outbox
      ::  for every serial, add %pending state.
      %+  roll  ses
      |=  {s/serial o/_outbox}
      =?  o  ?=($~ o)  outbox
      =+  t=(fall (~(get by o) s) *tracking)
      %+  ~(put by o)  s
      (~(put by t) cir %pending)
    %+  da-emit  ost.bol
    :*  %poke
        /repeat/(scot %p hos.cir)/[nom.cir]/(scot %ud (jam ses))
        [hos.cir dap.bol]
        [%hall-command %publish out]
    ==
  ::
  ++  da-change-done                                    ::<  delivered messages
    ::>  apply a %done delta, setting new delivery state
    ::>  for messages.
    ::
    |=  {cir/circle ses/(list serial) res/delivery}
    ^+  +>
    %_  +>
        outbox
      ::  for every serial, set new delivery state.
      %-  ~(gas by outbox)
      %+  turn  ses
      |=  s/serial
      :-  s
      %+  ~(put by (~(got by outbox) s))
      cir  res
    ==
  ::
  ++  da-change-glyph                                   ::<  un/bound glyph
    ::>  apply a %glyph delta, un/binding a glyph to/from
    ::>  an audience.
    ::
    |=  {bin/? gyf/char aud/audience}
    ^+  +>
    ?:  bin
      %_  +>
        binds  (~(put ju binds) gyf aud)
      ==
    =/  ole/(list audience)
      ?.  =(aud ~)  [aud ~]
      ~(tap in (~(get ju binds) gyf))
    |-  ^+  +>.^$
    ?~  ole  +>.^$
    %_  $
      binds  (~(del ju binds) gyf i.ole)
      ole  t.ole
    ==
  ::
  ++  da-change-nick                                    ::<  changed nickname
    ::>  apply a %nick delta, setting a nickname for a
    ::>  ship.
    ::
    |=  {who/ship nic/nick}
    ^+  +>
    +>(nicks (change-nicks nicks who nic))
  ::
  ::>  ||
  ::>  ||  %stories
  ::>  ||
  ::>    arms for modifying stories.
  ::+|
  ::
  ++  da-change-story                                   ::<  apply circle delta
    ::>  apply a %story delta, redirecting the delta
    ::>  itself to ++sa-change.
    ::>  in case of a new or deleted story, specialized
    ::>  arms are called.
    ::
    |=  {nom/naem det/delta-story}
    ^+  +>
    ?+  -.det
      =<  sa-done
      %.  det
      =+  (fall (~(get by stories) nom) *story)
      ~(sa-change sa nom -)
    ::
      $new      (da-create nom +.det)
      $bear     ~&(%unexpected-unsplit-bear +>)
      $remove   (da-delete nom)
    ==
  ::
  ++  da-create                                         ::<  configure story
    ::>  creates story {nom} with config {con}.
    ::
    |=  {nom/naem cof/config}
    ^+  +>
    =<  sa-done
    %-  ~(sa-change sa nom *story)
    [%config [our.bol nom] %full cof]
  ::
  ++  da-delete                                         ::<  delete story
    ::>  calls the story core to delete story {nom}.
    ::
    |=  nom/naem
    ^+  +>
    =.  +>
      %-  da-emil
      ~(sa-delete sa nom (~(got by stories) nom))
    +>(stories (~(del by stories) nom))
  ::
  ++  sa                                                ::<  story delta core
    ::>  story core, used for doing work on a story.
    ::
    |_  ::>  nom: story name in {stories}.
        ::>  story is faceless to ease data access.
        ::
        $:  nom/naem
            story
        ==
    ::
    ++  sa-done                                         ::<  apply changes
      ::>  put changed story back into the map.
      ::
      +>(stories (~(put by stories) nom +<+))
    ::
    ::>  ||
    ::>  ||  %emitters
    ::>  ||
    ::>    arms that create outward changes.
    ::+|
    ::
    ++  sa-emil                                         ::<  emit move list
      ::>  adds multiple moves to the head of {moves}.
      ::>  flops to stay consistent with ++ta-emit.
      ::
      |=  mol/(list move)
      %_(+> moves (welp (flop mol) moves))
    ::
    ++  sa-emit                                         ::<  emit a move
      ::>  adds a move to the head of {moves}.
      ::
      |=  mov/move
      %_(+> moves [mov moves])
    ::
    ++  sa-sauce                                        ::<  play cards
      ::>  cards to moves.
      ::
      |=  {ost/bone cub/(list card)}
      ^-  (list move)
      (flop (turn cub |=(a/card [ost a])))
    ::
    ::>  ||
    ::>  ||  %data
    ::>  ||
    ::>    utility functions for data retrieval.
    ::+|
    ::
    ++  sa-cir  [our.bol nom]
    ::
    ::>  ||
    ::>  ||  %delta-application
    ::>  ||
    ::>    arms for applying deltas.
    ::+|
    ::
    ++  sa-delete                                       ::<  deletion of story
      ::>  apply a %remove story delta, unsubscribing
      ::>  this story from all its active sources.
      ::
      %+  weld
        (sa-abjure src.shape)
      (sa-eject ~(key by peers))
    ::
    ++  sa-change                                       ::<  apply circle delta
      ::>  figure out whether to apply a %story delta to
      ::>  local or remote data.
      ::
      |=  det/delta-story
      ^+  +>
      %.  det
      ?:  ?&  ?=(?($config $status) -.det)
              !=(cir.det sa-cir)
          ==
        sa-change-remote
      sa-change-local
    ::
    ++  sa-change-local                                 ::<  apply our delta
      ::>  apply a %story delta to local data.
      ::
      |=  det/delta-story
      ^+  +>
      ?+  -.det
        ~&([%unexpected-delta-local -.det] !!)
      ::
          $inherited
        +>(inherited ihr.det)
      ::
          $peer
        ?:  add.det
          +>(peers (~(add ja peers) who.det qer.det))
        =+  qes=(~(get ja peers) who.det)
        =.  qes
          =+  res=(find ~[qer.det] qes)
          ?~  res  qes
          (oust [u.res 1] qes)
        ?~  qes  +>.$(peers (~(del by peers) who.det))
        +>.$(peers (~(put in peers) who.det qes))
      ::
          $follow
        (sa-emil (sa-follow-effects sub.det srs.det))
      ::
          $sequent
        +>(sequence (~(put by sequence) cir.det num.det))
      ::
          $gram
        (sa-change-gram +.det)
      ::
          $config
        =.  +>
          %-  sa-emil
          (sa-config-effects shape dif.det)
        +>(shape (change-config shape dif.det))
      ::
          $status
        %_  +>
            locals
          %+  ~(put by locals)  who.det
          %+  change-status
            (fall (~(get by locals) who.det) *status)
          dif.det
        ==
      ==
    ::
    ++  sa-change-gram                                  ::<  save/update message
      ::>  apply a %gram delta, either appending or
      ::>  updating a message.
      ::
      |=  {src/circle gam/telegram}
      ^+  +>
      ::TODO  move "known" logic up into ++so? that way,
      ::      we can attach message numbers to changes.
      =+  old=(~(get by known) uid.gam)
      =.  sourced
        =+  sed=(fall (~(get by sourced) src) ~)
        ?~  old  (~(put by sourced) src [count sed])
        ?^  (find ~[u.old] sed)  sourced
        %+  ~(put by sourced)  src
        :-  count
        (fall (~(get by sourced) src) ~)
      ?~  old
        ::  new message
        %_  +>.$
          grams    (welp grams [gam ~])
          count    +(count)
          known    (~(put by known) uid.gam count)
        ==
      ::  changed message
      %_  +>.$
        grams    %+  welp
                 (scag (dec (max u.old 1)) grams)
                 [gam (slag u.old grams)]
      ==
    ::
    ++  sa-change-remote                                ::<  apply remote's delta
      ::>  apply a story diff to remote data.
      ::
      |=  det/delta-story
      ^+  +>
      ?+  -.det
        ~&([%unexpected-delta-remote -.det] !!)
      ::
          $config
        ?:  ?=($remove -.dif.det)
          +>(mirrors (~(del by mirrors) cir.det))
        =/  new/config
          %+  change-config
          (fall (~(get by mirrors) cir.det) *config)
          dif.det
        +>.$(mirrors (~(put by mirrors) cir.det new))
      ::
          $status
        %_  +>.$
            remotes
          %+  ~(put by remotes)  cir.det
          =+  ole=(fall (~(get by remotes) cir.det) *group)
          ?:  ?=($remove -.dif.det)  (~(del by ole) who.det)
          =+  old=(fall (~(get by ole) who.det) *status)
          (~(put by ole) who.det (change-status old dif.det))
        ==
      ==
    ::
    ++  sa-config-effects                               ::<  config side-effects
      ::>  apply side-effects for a %config delta.
      ::
      |=  {old/config dif/diff-config}
      ^-  (list move)
      ?+  -.dif  ~
        $permit   (sa-permit-effects sec.con.old sis.con.old +.dif)
        ::NOTE  when doing a lone %secure, calculate the
        ::      necessary %permit deltas alongside it.
      ==
    ::
    ++  sa-follow-effects                               ::<  un/subscribe
      ::>  apply side-effects for a %follow delta,
      ::>  un/subscribing this story to/from {cos}.
      ::
      |=  {sub/? srs/(set source)}
      ^-  (list move)
      %.  srs
      ?:(sub sa-acquire sa-abjure)
    ::
    ++  sa-permit-effects                               ::<  notify permitted
      ::>  apply side-effects for a %permit delta,
      ::>  kicking the subscriptions of {sis} if they
      ::>  are being banished.
      ::
      |=  {sec/security old/(set ship) add/? sis/(set ship)}
      ^-  (list move)
      =/  wyt  ?=(?($village $journal) sec)
      =/  inv  =(wyt add)
      ?:  inv  ~
      =/  sus/(set ship)
        %.  sis.con.shape
        ?:(add ~(dif in sis) ~(int in sis))
      (sa-eject sus)
    ::
    ::>  ||
    ::>  ||  %subscriptions
    ::>  ||
    ::>    arms for starting and ending subscriptions
    ::+|
    ::
    ++  sa-acquire                                      ::<  subscribe us
      ::>  subscribes this story to each circle.
      ::
      |=  srs/(set source)
      =-  (murn - same)
      %+  turn  ~(tap in srs)
      |=  {cir/circle ran/range}
      ^-  (unit move)
      ?:  =(cir sa-cir)  ~  ::  ignore self-subs
      =+  wat=~[%grams %config-l %group-l]
      `(wire-to-peer (circle-wire nom wat cir ran))
    ::
    ++  sa-abjure                                       ::<  unsubscribe us
      ::>  unsubscribes this story from each circle.
      ::
      |=  srs/(set source)
      ^-  (list move)
      %+  turn  ~(tap in srs)
      |=  {cir/circle ran/range}
      ^-  move
      =/  wir
        %^  circle-wire  nom
          ~[%grams %config-l %group-l]
        [cir ran]
      [0 %pull wir [hos.cir dap.bol] ~]
    ::
    ++  sa-eject                                        ::<  unsubscribe ships
      ::>  removes ships {sis} from {followers}.
      ::
      |=  sis/(set ship)
      ^-  (list move)
      %-  zing
      %+  turn  ~(tap in sup.bol)
      |=  {b/bone s/ship p/path}
      ^-  (list move)
      ?.  ?&  (~(has in sis) s)
              ?=({$circle @tas *} p)
              =(i.t.p nom)
          ==
        ~
      (gentle-quit b s (path-to-query p))
    ::
    ++  sa-unearth                                      ::<  ships' bones
      ::>  find the bones in {sup.bol} that belong to
      ::>  a ship in {sis}.
      ::
      |=  sis/(set ship)
      ^-  (set bone)
      %-  ~(rep in sup.bol)
      |=  {{b/bone s/ship p/path} c/(set bone)}
      ?.  ?&  (~(has in sis) s)
              ?=({$circle @tas *} p)
              =(i.t.p nom)
          ==
        c
      (~(put in c) b)
    --
--
::
::
::>  ||
::>  ||  %wire-utility
::>  ||
::+|
::
++  circle-wire                                         ::<  /circle peer wire
  ::>  constructs a /circle %peer path for subscribing
  ::>  {nom} to a source.
  ::
  |=  {nom/naem wat/(list circle-data) source}
  ^-  wire
  ;:  weld
    /circle/[nom]/(scot %p hos.cir)/[nom.cir]
    (sort wat gth)  ::  consistence
    (range-to-path ran)
  ==
::
++  wire-to-peer                                        ::<  peer move from wire
  ::>  builds the peer move associated with the wire.
  ::
  |=  wir/wire
  ^-  move
  =+  tar=(wire-to-target wir)
  [0 %peer wir [p.tar dap.bol] q.tar]
::
++  wire-to-target                                      ::<  ship+path from wire
  ::>  parses {wir} to obtain the target ship and the
  ::>  query path.
  ::
  |=  wir/wire
  ^-  (pair ship path)
  ?+  wir  ~&(wir !!)
      {$circle @ @ *}
    :-  (slav %p i.t.t.wir)
    (welp /circle t.t.t.wir)
  ::
      {$burden *}
    :-  (above our.bol)
    /burden/(scot %p our.bol)
  ::
      {$report @ *}
    :-  (slav %p i.t.wir)
    /report
  ==
::
++  etch                                                ::<  parse wire
  ::>  parses {wir} to obtain either %circle with story
  ::>  and circle or %repeat with message number, source
  ::>  ship, story and serials.
  ::
  |=  wir/wire
  ^-  weir
  ?+    wir  !!
      {$circle @ @ @ *}
      :: $circle, us, host, target
    :^    %circle
        i.t.wir
      [(slav %p i.t.t.wir) i.t.t.t.wir]
    (path-to-range t.t.t.t.wir)
  ::
      {$repeat @ @ @ $~}
    :+  %repeat
      [(slav %p i.t.wir) i.t.t.wir]
    ((list serial) (cue (slav %ud i.t.t.t.wir)))
  ==
::
++  etch-circle                                         ::<  parse /circle wire
  ::>  parses a /circle wire, call a gate with the
  ::>  result.
  ::
  |=  $:  wir/wire
          $=  fun
          $-  {nom/naem src/source}
              {(list move) _.}
      ==
  =+  wer=(etch wir)
  ?>(?=($circle -.wer) (fun nom.wer src.wer))
::
++  etch-repeat                                         ::<  parse /repeat wire
  ::>  parses a /repeat wire, call gate with the result.
  ::
  |=  $:  wir/wire
          $=  fun
          $-  {cir/circle ses/(list serial)}
              {(list move) _.}
      ==
  =+  wer=(etch wir)
  ?>(?=($repeat -.wer) (fun cir.wer ses.wer))
::
++  gentle-quit                                         ::<  quit other, pull us
  ::>  we want to gently pull our own subscriptions,
  ::>  rather than quitting them, so that we may
  ::>  differentiate between a gall/ames quit and a
  ::>  foreign quit. but since wex.bol isn't filled,
  ::>  we'll have to just guess at what the correct wire
  ::>  wire is. this is truly terrible, but will have to
  ::>  do for now.
  ::TODO  get rid of this once gall improves.
  ::      it needs to tell us the difference between
  ::      an app-caused quit and a queue-caused one.
  ::      (aka connected/disconnected/rejected state)
  ::
  |=  {bon/bone who/ship qer/query}
  ^-  (list move)
  ?.  ?=($circle -.qer)  ~
  ?.  =(who our.bol)  [bon %quit ~]~
  %-  zing
  %+  turn  ~(tap in ~(key by stories))
  |=  n/naem
  ^-  (list move)
  :~  :^  0  %poke  /
      :+  [our.bol dap.bol]  %hall-action
      :^  %source  n  |
      [[[our.bol nom.qer] ran.qer] ~ ~]
    ::
      :^  0  %pull
        %^  circle-wire  n  ~(tap in wat.qer)
        [[our.bol nom.qer] ran.qer]
      [[our.bol dap.bol] ~]
  ==
::
::>  ||
::>  ||  %new-events
::>  ||
::+|
++  bake                                                ::<  apply state delta
  ::>  applies a change to the application state,
  ::>  producing side-effects.
  ::
  |=  det/delta
  ^-  (quip move _+>)
  da-done:(da-change:da det)
::
++  pre-bake                                            ::<  apply more deltas
  ::>  bake a list of deltas.
  ::
  |=  des/(list delta)
  ^-  (quip move _+>)
  =|  moz/(list move)
  |-  ^-  (quip move _+>.^$)
  ?~  des  [moz +>.^$]
  =^  mos  +>.^$  (bake i.des)
  $(moz :(welp moz mos (affection i.des)), des t.des)
  ::TODO  ideally you'd just do this, but that runtime errors on "bake"...
  ::%+  roll  des
  ::|=  {d/delta m/(list move) _+>.$}
  ::=^  mos  +>.^$  (bake d)
  ::[:(welp m mos (affection d)) +>.^$]
::
++  peek                                                ::<  query on state
  ::>  find the result (if any) for a given query.
  ::
  |=  qer/query
  ^-  (unit (unit prize))
  ?-  -.qer
      $client
    ``[%client binds nicks]
  ::
      $circles
    =-  ``[%circles -]
    %-  ~(gas in *(set naem))
    %+  murn  ~(tap by stories)
    |=  {n/naem s/story}
    ^-  (unit naem)
    ?:((~(so-visible so:ta n ~ s) who.qer) `n ~)
  ::
      $public
    ``[%public public]
  ::
      $burden
    :+  ~  ~
    :-  %burden
    %-  ~(gas in *(map naem burden))
    %+  murn  ~(tap by stories)
    |=  {n/naem s/story}
    ^-  (unit (pair naem burden))
    ::  only auto-federate channels for now.
    ?.  ?=($channel sec.con.shape.s)  ~
    :+  ~  n
    :+  grams.s
      [shape.s mirrors.s]
    [locals.s remotes.s]
  ::
      $report
    ::TODO  gall note: need to be able to subscirbe to just changes... or just
    ::      data etc.
    ``[%report ~]
  ::
      $peers
    =+  soy=(~(get by stories) nom.qer)
    ?~  soy  ~
    ``[%peers peers.u.soy]
  ::
      $circle  ::REVIEW  should we send precs & config to out of range subs?
    =+  soy=(~(get by stories) nom.qer)
    ?~  soy  ~
    :+  ~  ~
    :-  %circle
    :+  %+  turn
          =-  (~(so-first-grams so:ta nom.qer ~ -) ran.qer)
          ::TODO  this can be done more efficiently.
          ?~  wer.qer  u.soy
          %_  u.soy
              grams
            ?.  (~(has by sourced.u.soy) u.wer.qer)  ~
            %+  turn  (~(got by sourced.u.soy) u.wer.qer)
            |=  n/@ud
            (snag (sub count.u.soy +(n)) grams.u.soy)
          ==
        (cury gram-to-envelope nom.qer)
      :-  shape.u.soy
      ?.  (~(has in wat.qer) %config-r)  ~
      mirrors.u.soy
    :-  locals.u.soy
    ?.  (~(has in wat.qer) %group-r)  ~
    remotes.u.soy
  ==
::
++  dedicate                                            ::<  rumor-story to theirs
  ::>  modify a %story diff to make it about their ship
  ::>  instead of ours.
  ::
  |=  {who/ship nom/naem det/delta-story}
  ^-  rumor-story
  ?+  -.det  det
    ::
    ::>  internal-only changes.
    $follow     !!
    $inherited  !!
    $sequent    !!
  ::
      $gram
    :+  %gram
      ?.  =(src.det [our.bol nom])
        src.det
      [who nom]
    %+  gram-to-envelope  nom
    %_  gam.det
        aud
      %-  ~(run in aud.gam.det)
      |=  c/circle
      ?.  =(c [our.bol nom])  c
      [who nom]
    ==
  ::
      $config
    ?.  =(cir.det [our.bol nom])
      det
    det(cir [who nom])
  ::
      $status
    ?.  =(cir.det [our.bol nom])
      det
    det(cir [who nom])
  ==
::
++  gram-to-envelope                                   ::<  wrap gram with nr
  ::>  deduce the initial msg number from a telegram
  ::>  for a given story. assumes both story and
  ::>  telegram are known.
  ::
  |=  {nom/naem gam/telegram}
  ^-  envelope
  :_  gam
  %.  uid.gam
  ~(got by known:(~(got by stories) nom))
::
++  circle-feel-story                                   ::<
  ::>
  ::
  |=  $:  wer/(unit circle)
          wat/(set circle-data)
          nom/naem
          det/delta-story
      ==
  ^-  ?
  ?&
    ?~  wer  &
    ?+  -.det  &
      $gram     =(src.det u.wer)
      $config   =(cir.det u.wer)
      $status   =(cir.det u.wer)
    ==
  ::
    ?:  =(wat ~)  &
    %-  ~(has in wat)
    ?+  -.det  %hasnot
      $gram     %grams
      $new      %config-l
      $config   ?:  =(cir.det [our.bol nom])
                %config-l  %config-r
      $status   ?:  =(cir.det [our.bol nom])
                %group-l  %group-r
    ==
  ==
::
++  feel                                                ::<  delta to rumor
  ::>  if the given delta changes the result of the given
  ::>  query, produce the relevant rumor.
  ::
  |=  {qer/query det/delta}
  ^-  (unit rumor)
  ?-  -.qer
      $client
    ::  changes to shared ui state apply.
    ?+  -.det  ~
      $glyph  `[%client det]
      $nick   `[%client det]
    ==
  ::
      $circles
    ::NOTE  this is another case where having access to
    ::      the pre-delta state would be nice to have.
    ?.  ?=($story -.det)  ~
    =;  add/(unit ?)
      ?~  add  ~
      `[%circles u.add nom.det]
    ::REVIEW  this could be considered leaky, since it
    ::        doesn't check if {who} ever knew of {nom},
    ::        but does that matter? can't really check..
    ?:  ?=($remove -.det.det)  `|
    =+  soy=(~(got by stories) who.qer)
    ?.  ?|  ?=($new -.det.det)
            ?&  ?=($config -.det.det)
                ?=($permit -.dif.det.det)
                ?=(?($channel $village) sec.con.shape.soy)
                (~(has in sis.dif.det.det) who.qer)
            ==
        ==
      ~
    `(~(so-visible so:ta nom.det ~ soy) who.qer)
  ::
      $public
    ?.  ?=($public -.det)  ~
    `det
  ::
      $burden
    ?:  &(=(who.qer src.bol) =(rir /(scot %p src.bol)/report))  ~
    ?.  ?=($story -.det)  ~
    ?:  ?=(?($follow $inherited $sequent) -.det.det)  ~
    ::  only burden channels for now.
    ?.  (~(has by stories) nom.det)  ~
    ?.  =(%channel sec.con.shape:(~(got by stories) nom.det))  ~
    `[%burden nom.det (dedicate who.qer nom.det det.det)]
  ::
      $report
    ::  only send changes we didn't get from above.
    ?:  =(src.bol (above our.bol))  ~
    ::  only send story reports about grams, status and peers.
    ?.  ?=($story -.det)  ~
    ?.  ?=(?($gram $status $peer) -.det.det)  ~
    =+  soy=(~(got by stories) nom.det)
    ::  and only if the story is inherited.
    ?.  inherited.soy  ~
    ::  only burden channels for now.
    ?.  =(%channel sec.con.shape.soy)  ~
    `[%burden nom.det (dedicate (above our.bol) nom.det det.det)]
  ::
      $peers
    ?.  ?=($story -.det)      ~
    ?.  =(nom.qer nom.det)    ~
    ?.  ?=($peer -.det.det)   ~
    `[%peers +.det.det]
  ::
      $circle
    ?.  ?=($story -.det)                              ~
    ?.  =(nom.qer nom.det)                            ~
    ?.  %-  circle-feel-story
        [wer.qer wat.qer nom.det det.det]             ~
    =/  sor  (~(got by stories) nom.qer)
    ?.  =<  in  %.  ran.qer
        ~(so-in-range so:ta nom.qer ~ sor)            ~
    ?.  ?=(?($gram $new $config $status) -.det.det)   ~
    :+  ~  %circle
    ?+  det.det  det.det
        {$gram *}
      :+  %gram  src.det.det
      (gram-to-envelope nom.det gam.det.det)
    ==
  ==
::
++  affection                                           ::<  rumors to interested
  ::>  for a given delta, send rumors to all queries it
  ::>  affects.
  ::
  |=  det/delta
  ^-  (list move)
  ::  cache results for paths.
  =|  res/(map path (list move))
  %-  zing
  %+  turn  ~(tap by sup.bol)
  |=  {b/bone s/ship p/path}
  ^-  (list move)
  =+  mur=(~(get by res) p)
  ?^  mur  u.mur
  =-  =.  res  (~(put by res) p -)
      -
  =+  qer=(path-to-query p)
  %+  welp
    =+  rum=(feel qer det)
    ?~  rum  ~
    [b %diff %hall-rumor u.rum]~
  ?.  ?=($circle -.qer)  ~
  ::  kill the subscription if we forgot the story.
  ?.  (~(has by stories) nom.qer)  (gentle-quit b s qer)
  ::  kill the subscription if it's past its range.
  =-  ?:(done:- (gentle-quit b s qer) ~)
  %.  ran.qer
  =-  ~(so-in-range so:ta nom.qer ~ -)
  (~(got by stories) nom.qer)
::
++  path-to-query                                       ::<  path, coins, query
  ::>  parse a path into a (list coin), then parse that
  ::>  into a query structure.
  ::
  |=  pax/path
  ?.  ?=({$circle @tas *} pax)
    (coins-to-query (path-to-coins pax))
  =/  qer/query  [%circle i.t.pax ~ ~ ~]
  ?>  ?=($circle -.qer)  ::  for type system.
  =+  pax=t.t.pax
  =+  ^-  {qer/query pax/path}
    ?.  ?=({@ @ *} pax)  [qer pax]
    =+  hos=(slaw %p i.pax)
    ?~  hos  [qer pax]
    :_  t.t.pax
    qer(wer `[u.hos i.t.pax])
  ?>  ?=($circle -.qer)
  |-  ^+  qer
  ?~  pax  qer
  ::TODO  can probably do this a bit better...
  ?+  i.pax
    qer(ran (path-to-range pax))
  ::
    circle-data   %_  $  pax  t.pax
                    wat.qer   (~(put in wat.qer) i.pax)
                  ==
    $group        %_  $  pax  t.pax
                    wat.qer   %-  ~(uni in wat.qer)
                              ^+  wat.qer
                              (sy %group-l %group-r ~)
                  ==
    $config       %_  $  pax  t.pax
                    wat.qer   %-  ~(uni in wat.qer)
                              ^+  wat.qer
                              (sy %config-l %config-r ~)
                  ==
  ==
::
++  path-to-coins                                       ::<  path to coin list
  ::>  parse a path into a list of coins.
  ::
  |=  pax/path
  ^-  (list coin)
  %+  turn  `path`pax
  |=  a/@ta
  (need (slay a))
::
++  coins-to-query                                      ::<  coin list to query
  ::>  parse a list of coins into a query structure.
  ::
  ^-  $-((list coin) query)
  =>  depa
  |^  %-  af  :~
          [%client ul]
          [%circles (at /[%p])]
          [%public ul]
          [%burden (at /[%p])]
          [%report ul]
      ==
  ++  term  (do %tas)
  ++  rang  (mu (al plac (mu (un plac))))
  ++  plac  (or %da %ud)
  --
::
++  leak                                                ::<  visible to
  ::>  determine if the given query is visible to the
  ::>  ship.
  ::
  |=  {who/ship qer/query}
  ^-  ?
  ?-  -.qer
    $client   (team:title our.bol who)
    $circles  =(who who.qer)
    $public   &
    $burden   ?&  =(who who.qer)
                  =(our.bol (above who))
              ==
    $peers    =(who our.bol)  ::TODO  or so-visible?
    $report   =(who (above our.bol))
  ::
      $circle
    ?.  (~(has by stories) nom.qer)  |
    %.  who
    ~(so-visible so:ta nom.qer ~ (~(got by stories) nom.qer))
  ==
::
::>  ||
::>  ||  %poke-events
::>  ||
::+|
::
++  poke-hall-command                                   ::<  accept command
  ::>  incoming hall command. process it and update logs.
  ::
  |=  cod/command
  ^-  (quip move _+>)
  =^  mos  +>.$
    %-  pre-bake
    ta-done:(ta-apply:ta src.bol cod)
  =^  mow  +>.$
    log-all-to-file
  [(welp mos mow) +>.$]
::
++  poke-hall-action                                    ::<  accept action
  ::>  incoming hall action. process it.
  ::
  |=  act/action
  ^-  (quip move _+>)
  ?.  (team:title src.bol our.bol)
    %-  pre-bake
    =<  ta-done
    %-  ta-note:ta
    "hall-action stranger {(scow %p src.bol)}"
  =^  mos  +>.$
    %-  pre-bake
    ta-done:(ta-action:ta act)
  =^  mow  +>.$
    log-all-to-file
  [(welp mos mow) +>.$]
::
::>  ||
::>  ||  %subscription-events
::>  ||
::+|
::
++  diff-hall-prize                                     ::<  accept prize
  ::>  accept a query result.
  ::
  |=  {wir/wire piz/prize}
  ^-  (quip move _+>)
  =^  mos  +>.$
    %-  pre-bake
    =>  (ta-take:ta wir piz)
    (flop deltas)
    ::TODO  ideally this, but runtime error for %burden prize
    ::%-  pre-bake
    ::ta-done:(ta-take:ta wir piz)
  =^  mow  +>.$
    log-all-to-file
  [(welp mos mow) +>.$]
::
++  diff-hall-rumor                                     ::<  accept rumor
  ::>  accept a query result change.
  ::
  |=  {wir/wire rum/rumor}
  ^-  (quip move _+>)
  ::NOTE  to keep us from echoing changes back to their
  ::      sender, we want to know (in ++feel) if a delta
  ::      was caused by a rumor from a /report.
  ::      if gall worked as advertised, we'd use ost.bol
  ::      and wex.bol to find out, but wex is never set,
  ::      so we just keep track of the "current rumor
  ::      wire" instead.
  =.  rir  wir
  =^  mos  +>.$
    %-  pre-bake
    =>  (ta-hear:ta wir rum)
    (flop deltas)
    ::TODO  runtime error for %burden rumors.
    ::ta-done:(ta-hear:ta wir rum)
  =^  mow  +>.$
    log-all-to-file
  [(welp mos mow) +>.$]
::
++  peer                                                ::<  accept subscription
  ::>  incoming subscription on {pax}.
  ::
  |=  pax/path
  ^-  (quip move _+>)
  ?:  ?=({$sole *} pax)  ~&(%hall-no-sole !!)
  =+  qer=(path-to-query pax)
  ?.  (leak src.bol qer)  ~&(%peer-invisible !!)
  =^  mos  +>.$
    %-  pre-bake
    ta-done:(ta-subscribe:ta src.bol qer)
  :_  +>.$
  =+  piz=(peek qer)
  ?~  piz  ~&([%query-unavailable pax] mos)
  ?~  u.piz  ~&([%query-invalid pax] mos)
  :_  mos
  [ost.bol %diff %hall-prize u.u.piz]
::
++  pull                                                ::<  unsubscribe
  ::>  unsubscribes.
  ::
  |=  pax/path
  ^-  (quip move _+>)
  [~ +>]
::
++  pull-circle                                         ::<  circle unsubscribe
  ::>  someone ends a /circle subscription.
  ::
  |=  pax/path
  ^-  (quip move _+>)
  %-  pre-bake
  :_  ~
  =+  qer=(path-to-query %circle pax)
  ?>  ?=($circle -.qer)
  :+  %story  nom.qer
  [%peer | src.bol qer]
::
++  reap                                                ::<  subscription n/ack
  ::>  update state to reflect subscription success
  ::
  |=  {wir/wire fal/(unit tang)}
  ^-  (quip move _+>)
  ?.  ?=($circle -.wir)
    ?~  fal  [~ +>]
    ~|  reap-fail+wir
    (mean u.fal)
  %+  etch-circle  wir
  |=  {nom/naem src/source}
  ?~  fal
    %-  pre-bake
    ta-done:(ta-greet:ta nom src)
  =.  u.fal  [>%failed-subscribe nom src< u.fal]
  %-  (slog (flop u.fal))
  %-  pre-bake
  ta-done:(ta-leave:ta nom src)
::
++  quit                                                ::<  dropped subscription
  ::>  gall dropped out subscription. resubscribe.
  ::
  |=  wir/wire
  ^-  (quip move _+>)
  :_  +>
  ?.  =(src.bol our.bol)  ~
  [(wire-to-peer wir) ~]
::
++  quit-circle                                         ::<  dropped circle sub
  ::>  gall dropped our subscription. resubscribe.
  ::
  |=  wir/wire
  ^-  (quip move _+>)
  %+  etch-circle  [%circle wir]
  |=  {nom/naem src/source}
  %-  pre-bake
  ::  when we got kicked, don't resub, remove source.
  ?.  =(src.bol our.bol)
    ta-done:(ta-action:ta %source nom | [src ~ ~])
  ta-done:(ta-resub:ta nom src)
::
++  coup-repeat                                         ::<  message n/ack
  ::>  ack from ++ta-transmit. mark the message as
  ::>  received or rejected.
  ::
  |=  {wir/wire fal/(unit tang)}
  ^-  (quip move _+>)
  %+  etch-repeat  [%repeat wir]
  |=  {cir/circle ses/(list serial)}
  %-  pre-bake
  ta-done:(ta-repeat:ta cir ses fal)
::
::>  ||
::>  ||  %logging
::>  ||
::+|
::
++  poke-hall-save                                      ::<  save as log
  ::>  stores the telegrams of story {nom} in a log file,
  ::>  to be re-loaded by ++poke-hall-load.
  ::TODO  maybe update to also store sourced list.
  ::
  |=  nom/naem
  ^-  (quip move _+>)
  =/  paf/path
    /(scot %p our.bol)/home/(scot %da now.bol)/hall/[nom]/hall-telegrams
  =+  grams:(~(got by stories) nom)
  :_  +>.$
  :_  ~
  :*  ost.bol
      %info
      /jamfile
      our.bol
      (foal:space:userlib paf [%hall-telegrams !>(-)])
  ==
::
++  poke-load-legacy                                    ::<  load legacy grams
  ::>  loads legacy messages into the story {nom}.
  ::
  |=  nom/naem
  ^-  (quip move _+>)
  =/  jams/json
    .^  json
        %cx
        /(scot %p our.bol)/home/(scot %da now.bol)/hall/legacy-telegrams/json
    ==
  =+  grams=(from-json:hall-legacy jams)
  ~&  [%loaded (lent grams)]
  %-  pre-bake
  %+  turn  (flop grams)
  |=  t/telegram
  [%story nom %gram [our.bol nom] t]
::
++  poke-hall-load                                      ::<  load from log
  ::>  loads the telegrams of story {nom} into our state,
  ::>  as saved in ++poke-hall-save.
  ::
  |=  nom/naem
  ^-  (quip move _+>)
  =/  grams
    .^  (list telegram)
        %cx
        /(scot %p our.bol)/home/(scot %da now.bol)/hall/[nom]/hall-telegrams
    ==
  %-  pre-bake
  %+  turn  grams
  |=  t/telegram
  [%story nom %gram [our.bol nom] t]
::
++  poke-hall-log                                       ::<  start logging
  ::>  starts logging story {nom}'s messages.
  ::
  |=  nom/naem
  ^-  (quip move _+>)
  :-  [(log-to-file nom) ~]
  %=  +>.$
      log
    %+  ~(put by log)  nom
    count:(~(got by stories) nom)
  ==
::
++  poke-hall-unlog                                     ::<  stop logging
  ::>  stops logging story {nom}'s messages.
  ::
  |=  nom/naem
  ^-  (quip move _+>)
  :-  ~
  +>.$(log (~(del by log) nom))
::
++  log-all-to-file                                     ::<  update stories logs
  ::>  for every story we're logging, (over)writes all
  ::>  their grams to log files if new ones have arrived.
  ::
  ^-  (quip move _.)
  :_  %_  .
          log
        %-  ~(urn by log)
        |=  {nom/naem len/@ud}
        count:(~(got by stories) nom)
      ==
  %+  murn  ~(tap by log)
  |=  {nom/naem len/@ud}
  ^-  (unit move)
  ?:  (gte len count:(~(got by stories) nom))
    ~
  `(log-to-file nom)
::
++  log-to-file                                         ::<  update story log
  ::>  logs all grams of story {nom} to a file.
  ::
  |=  nom/naem
  ^-  move
  =+  ^-  paf/path
      =+  day=(year %*(. (yore now.bol) +.t +:*tarp))
      %+  en-beam:format  [our.bol %home da+now.bol]
      /hall-telegrams/(scot %da day)/[nom]/hall
  =+  grams:(~(got by stories) nom)
  :*  ost.bol
      %info
      /jamfile
      our.bol
      (foal:space:userlib paf [%hall-telegrams !>(-)])
  ==
--