::                                                      ::  ::
::::  /hook/core/drum/lib                               ::  ::
  ::                                                    ::  ::
/?    310                                               ::  version
!:                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
|%                                                      ::  ::
++  drum-part  ,[%drum %0 drum-pith]                    ::
++  drum-pith                                           ::
  $:  eel=(set gill)                                    ::  connect to 
      ray=(set well)                                    ::  
      fur=(map dude (unit server))                      ::  servers
      bin=(map bone source)                             ::  terminals
  ==                                                    ::
++  drum-start  well                                    ::  start (local) server
::                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
++  server                                              ::  running server
  $:  syd=desk                                          ::  app identity
      cas=case                                          ::  boot case
  ==                                                    ::
++  source                                              ::  input device
  $:  edg=_80                                           ::  terminal columns
      off=@ud                                           ::  window offset
      kil=(unit (list ,@c))                             ::  kill buffer
      maz=master                                        ::  master window
      inx=@ud                                           ::  ring index
      fug=(map gill (unit target))                      ::  connections
      mir=(pair ,@ud (list ,@c))                        ::  mirrored terminal
  ==                                                    ::
++  master                                              ::  master buffer
  $:  liv=?                                             ::  master is live
      tar=target                                        ::  master target
  ==                                                    ::
++  history                                             ::  past input
  $:  pos=@ud                                           ::  input position
      num=@ud                                           ::  number of entries
      lay=(map ,@ud (list ,@c))                         ::  editing overlay
      old=(list (list ,@c))                             ::  entries proper
  ==                                                    ::
++  search                                              ::  reverse-i-search
  $:  pos=@ud                                           ::  search position
      str=(list ,@c)                                    ::  search string
  ==                                                    ::
++  target                                              ::  application target
  $:  ris=(unit search)                                 ::  reverse-i-search
      hit=history                                       ::  all past input
      pom=sole-prompt                                   ::  static prompt
      inp=sole-command                                  ::  input state
  ==                                                    ::
++  ukase                                               ::  master command
  $%  [%add p=(list gill)]                              ::  attach to
      [%del p=(list gill)]                              ::  detach from
      [%new p=(list well)]                              ::  create
  ==                                                    ::
::                                                      ::  ::
::::                                                    ::  ::
  ::                                                    ::  ::
++  deft-apes                                           ::  default servers
  |=  our=ship
  %-  ~(gas in *(set well))
  =+  myr=(clan our)
  ?:  =(%pawn myr)
    [[%base %dojo] ~]
  ?:  =(%earl myr)  ~
  [[%home %dojo] [%home %talk] ~]
::
++  deft-fish                                           ::  default connects
  |=  our=ship
  %-  ~(gas in *(set gill))
  ^-  (list gill)
  =+  myr=(clan our)
  ?:  =(%pawn myr)
    [[our %dojo] ~]
  ?:  =(%earl myr)
    =+  dad=(sein our)
    [[dad %dojo] [dad %talk] ~]
  [[our %dojo] [our %talk] ~]
::
++  deft-mast                                           ::  default master
  |=  our=ship
  ^-  master
  :*  %&
      *(unit search)
      *history
      [%& %sole "{(scow %p our)}# "]
      *sole-command
  ==
::
++  deft-pipe                                           ::  default source
  |=  our=ship                                          ::
  ^-  source                                            ::  
  :*  80                                                ::  edg
      0                                                 ::  off
      ~                                                 ::  kil
      (deft-mast our)                                   ::  maz
      0                                                 ::  inx
      ~                                                 ::  fug
      [0 ~]                                             ::  mir
  ==
::
++  deft-tart  *target                                  ::  default target
++  drum-port                                           ::  initial part
  |=  our=ship
  ^-  drum-part 
  :*  %drum
      %0
      (deft-fish our)                                   ::  eel
      (deft-apes our)                                   ::  ray
      ~                                                 ::  fur
      ~                                                 ::  bin
  ==                                                    ::
::
++  drum-path                                           ::  encode path
  |=  gyl=gill
  [%drum (scot %p p.gyl) q.gyl ~]
::
++  drum-phat                                           ::  decode path
  |=  way=wire  ^-  gill
  ?>(?=([@ @ ~] way) [(slav %p i.way) i.t.way])
::
++  drum-work                                           ::  work in drum
  |=  [[hide from] drum-part]
  =+  (fall (~(get by bin) ost) (deft-pipe our))
  =>  |%                                                ::  arvo structures
      ++  pear                                          ::  request
        $%  [%sole-action p=sole-action]                ::
        ==                                              ::
      ++  lime                                          ::  update
        $%  [%dill-blit dill-blit]                      ::
        ==                                              ::
      ++  card                                          ::  general card
        $%  [%conf wire dock %load ship term]           ::
            [%diff lime]                                ::
            [%peer wire dock path]                      ::
            [%poke wire dock pear]                      ::
            [%pull wire dock ~]                         ::
            [%pass wire note]                           ::
        ==                                              ::
      ++  move  (pair bone card)                        ::  user-level move
      ++  sp                                            ::  command parser
        |%  ++  sp-ukase
              %+  knee  *ukase  |.  ~+
              ;~  pose
                (stag %add ;~(pfix lus sp-gills))
                (stag %del ;~(pfix hep sp-gills))
                (stag %new ;~(pfix tar sp-wells))
              ==
            ::
            ++  sp-gills
              ;~  pose
                (most ;~(plug com ace) sp-gill)
                %+  cook
                  |=  a=ship
                  [[a %dojo] [a %talk] ~]
                ;~(pfix sig fed:ag)
              ==
            ::
            ++  sp-gill
              ;~  pose
                (stag our sym)
                ;~  plug
                  ;~(pfix sig fed:ag)
                  ;~(pfix fas sym)
                ==
              ==
            ++  sp-well
              ;~  pose
                (stag %home sym)
                ;~(plug sym ;~(pfix fas sym))
              ==
            ++  sp-wells  (most ;~(plug com ace) sp-well)
        --
      --
  |_  [moz=(list move) biz=(list dill-blit)]
  ++  diff-sole-effect                                  ::
    |=  [way=wire fec=sole-effect]  =<  se-abet
    =+  gyl=(drum-phat way)
    ?:  (se-aint gyl)  +>.$
    (se-diff gyl fec)
  ::
  ++  peer                                              ::
    |=   pax=path  =<  se-abet
    ^+  +>
    ?.  ?|  =(our src)                                  ::  ourself
            &(=(%duke (clan our)) =(our (sein src)))    ::  or our own yacht
        ==                                              ::
      ~|  [%drum-unauthorized our/our src/src]          ::  very simplistic
      !!
    se-view:(se-text "[{<src>}, driving {<our>}]")
  ::
  ++  poke-dill-belt                                    ::
    |=  bet=dill-belt   
    =<  se-abet  =<  se-view
    (se-belt bet)
  ::
  ++  poke-start                                        ::
    |=  wel=well  
    =<  se-abet  =<  se-view
    (se-born wel)
  ::
  ++  reap                                              ::
    |=  [way=wire saw=(unit tang)]  
    =<  se-abet  =<  se-view
    =+  gyl=(drum-phat way)
    ?~  saw
      (se-join gyl)
    (se-dump:(se-drop & gyl) u.saw)
  ::
  ++  take-coup                                         ::
    |=  [way=wire saw=(unit tang)]  
    =<  se-abet  =<  se-view
    ?~  saw  +>
    =+  gyl=(drum-phat way)
    ?:  (se-aint gyl)  +>.$
    ~&  [%drum-coup-fail src ost gyl u.saw]
    (se-dump:(se-drop & gyl) u.saw)
  ::
  ++  take-onto                                         ::
    |=  [way=wire saw=(each suss tang)]  
    =<  se-abet  =<  se-view
    ?>  ?=([@ @ ~] way)
    ?>  (~(has by fur) i.t.way)
    =+  wel=`well`[i.way i.t.way]
    ?-  -.saw
      %|  (se-dump p.saw)
      %&  ?>  =(q.wel p.p.saw)
          =.  +>.$  (se-text "[{<p.saw>}]")
          +>.$(fur (~(put by fur) q.wel `[p.wel %da r.p.saw]))  
    == 
  ::
  ++  quit
    |=  way=wire  
    =<  se-abet  =<  se-view
    =+  gyl=(drum-phat way)
    ~&  [%drum-quit src ost gyl]
    (se-drop %| gyl)
  ::                                                    ::  ::
  ::::                                                  ::  ::
    ::                                                  ::  ::
  ++  se-abet                                           ::  resolve
    ^-  (quip move *drum-part)
    =.  .  se-adze:se-adit
    :_  %_(+>+>+<+ bin (~(put by bin) ost `source`+>+<))
    ^-  (list move)
    %+  welp  (flop moz) 
    ^-  (list move)
    ?~  biz  ~
    [ost %diff %dill-blit ?~(t.biz i.biz [%mor (flop biz)])]~
  ::
  ++  se-adit                                           ::  update servers
    =+  yar=(~(tap by ray))
    |-  ^+  +>
    ?~  yar  +>
    =+  hig=(~(get by fur) q.i.yar) 
    ?:  &(?=(^ hig) |(?=(~ u.hig) =(p.i.yar syd.u.u.hig)))  $(yar t.yar)
    %=    $
        yar  t.yar
        +>
      %-  se-emit(fur (~(put by fur) q.i.yar ~))
      [ost %conf [%drum p.i.yar q.i.yar ~] [our q.i.yar] %load our p.i.yar]
    ==
  ::
  ++  se-adze                                           ::  update connections
    =+  lee=(~(tap by eel))
    |-  ^+  +>
    ?~  lee  +>
    ?:  (~(has by fug) i.lee)  $(lee t.lee)
    $(lee t.lee, +> (se-peer i.lee))
  ::
  ++  se-aint                                           ::  ignore result
    |=  gyl=gill
    ^-  ?
    ?.  (~(has by bin) ost)  &
    =+  gyr=(~(get by fug) gyl)
    |(?=(~ gyr) ?=([~ ~] gyr))
  ::
  ++  se-alas                                           ::  recalculate index
    |=  gyl=gill
    ^+  +>
    =+  [xin=0 wag=se-amor]
    ?:  =(~ wag)  +>.$(inx 0)
    |-  ^+  +>.^$
    ?~  wag  +>.^$(inx 0)
    ?:  =(i.wag gyl)  +>.^$(inx xin)
    $(wag t.wag, xin +(xin))
  ::
  ++  se-amor                                           ::  live targets
    ^-  (list gill)
    (skim (~(tap in eel)) |=(gill ?=([~ ~ *] (~(get by fug) +<))))
  ::
  ++  se-anon                                           ::  rotate index
    =+  wag=se-amor
    ?~  wag  +
    ::  ~&  [%se-anon inx/inx wag/wag nex/(mod +(inx) (lent se-amor))]
    +(inx (mod +(inx) (lent se-amor)))
  ::
  ++  se-agon                                           ::  current gill
    ^-  (unit gill)
    =+  wag=se-amor
    ?~  wag  ~
    `(snag inx se-amor)
  ::
  ++  se-belt                                           ::  handle input
    |=  bet=dill-belt
    ^+  +>
    ?:  ?=(%rez -.bet)
      +>(edg (dec p.bet))
    ?:  ?=(%yow -.bet)
      ~&  [%no-yow -.bet]
      +>
    =+  gul=se-agon
    =+  tur=`(unit (unit target))`?~(gul ~ (~(get by fug) u.gul))
    ?:  &(!liv.maz |(=(~ gul) =(~ tur) =([~ ~] tur)))  (se-blit %bel ~)
    =+  ^=  taz
        ?:  liv.maz 
          ~(. ta [& %& `gill`(fall gul [our %none])] `target`tar.maz)
        ~(. ta [& %| (need gul)] `target`(need (need tur)))
    =<  ta-abet
    ?-  -.bet
      %aro  (ta-aro:taz p.bet)
      %bac  ta-bac:taz
      %cru  (ta-cru:taz p.bet q.bet)
      %ctl  (ta-ctl:taz p.bet)
      %del  ta-del:taz
      %met  (ta-met:taz p.bet)
      %ret  ta-ret:taz
      %txt  (ta-txt:taz p.bet)
    ==
  ::
  ++  se-born                                           ::  new server
    |=  wel=well
    ^+  +>
    ?:  (~(has in ray) wel)
      (se-text "[already running {<p.wel>}/{<q.wel>}]")
    +>(ray (~(put in ray) wel), eel (~(put in eel) [our q.wel]))
  ::
  ++  se-dump                                           ::  print tanks
    |=  tac=(list tank)
    ^+  +>
    =+  wol=`wall`(zing (turn tac |=(a=tank (~(win re a) [0 edg]))))
    |-  ^+  +>.^$
    ?~  wol  +>.^$
    $(wol t.wol, +>.^$ (se-blit %out (tuba i.wol)))
  ::
  ++  se-drop                                           ::  disconnect
    |=  [pej=? gyl=gill]
    ^+  +>
    =+  lag=se-agon
    ?.  (~(has by fug) gyl)  +>.$
    =.  fug  (~(del by fug) gyl)
    =.  eel  ?.(pej eel (~(del in eel) gyl))
    =.  +>.$  ?.  &(?=(^ lag) !=(gyl u.lag))  
                +>.$(inx 0)
              (se-alas u.lag)
    =.  +>.$  (se-text "[detached from {<gyl>}]")
    se-prom(liv.maz ?~(fug & liv.maz))
  ::
  ++  se-joke                                           ::  prepare connection
    |=  gyl=gill
    ^+  +>
    =+  lag=se-agon
    ?~  lag  +>.$
    ?:  =(~ fug)  +>.$
    (se-alas(fug (~(put by fug) gyl ~)) u.lag)
  ::
  ++  se-join                                           ::  confirm connection
    |=  gyl=gill
    ^+  +>
    =.  +>  (se-text "[connected to {<gyl>}]")
    ?>  =(~ (~(got by fug) gyl))
    (se-alas:se-prom(liv.maz |, fug (~(put by fug) gyl `*target)) gyl)
  ::
  ++  se-nuke                                           ::  teardown
    |=  gyl=gill
    ^+  +>
    (se-drop:(se-pull(liv.maz |) gyl) & gyl)
  ::
  ++  se-like                                           ::  act in master
    |=  kus=ukase
    ?-    -.kus
        %add  
      |-  ^+  +>.^$
      ?~  p.kus  +>.^$
      $(p.kus t.p.kus, +>.^$ (se-link i.p.kus))
    ::
        %del
      |-  ^+  +>.^$
      ?~  p.kus  +>.^$
      $(p.kus t.p.kus, +>.^$ (se-nuke i.p.kus))
    ::
        %new
      |-  ^+  +>.^$
      ?~  p.kus  +>.^$
      $(p.kus t.p.kus, +>.^$ (se-born i.p.kus))
    ==
  ::
  ++  se-plot                                           ::  status line
    ^-  tape
    =+  lag=se-agon
    =+  ^=  pry
        |=  gill  ^-  tape
        =+((trip q.+<) ?:(=(our p.+>-) - :(welp (scow %p p.+>-) "/" -)))
    =+  ^=  yey
        |=  gill  ^-  tape
        =+((pry +<) ?:(=(lag `+>-) ['*' -] -))
    =+  ^=  yal  ^-  (list tape)
        %+  weld
          ^-  (list tape)
          %+  turn  (~(tap by fug))
          |=  [a=gill b=(unit target)]
          =+  c=(yey a)
          ?~(b ['?' c] c)
        ^-  (list tape)
        %+  turn  (skip (~(tap by fur)) |=([term *] (~(has by fug) [our +<-])))
        |=([term *] ['-' (pry our +<-)])
    |-  ^-  tape
    ?~  yal  ~
    ?~  t.yal  i.yal
    :(welp i.yal ", " $(yal t.yal))
  ::
  ++  se-prom                                           ::  update drum prompt
    ^+  .
    =+  mux=se-plot
    %_    +
        cad.pom.tar.maz
      (welp (scow %p our) ?~(mux "# " :(welp ":" mux "# ")))
    ==
  ::
  ++  se-link                                           ::  connect to app
    |=  gyl=gill
    +>(eel (~(put in eel) gyl))
  ::
  ++  se-blit                                           ::  give output
    |=  bil=dill-blit
    +>(biz [bil biz])
  ::
  ++  se-show                                           ::  show buffer, raw
    |=  lin=(pair ,@ud (list ,@c))
    ^+  +>
    ?:  =(mir lin)  +>
    =.  +>  ?:(=(q.mir q.lin) +> (se-blit %pro q.lin))
    =.  +>  ?:(=(p.mir p.lin) +> (se-blit %hop p.lin))
    +>(mir lin)
  ::
  ++  se-just                                           ::  adjusted buffer 
    |=  lin=(pair ,@ud (list ,@c))
    ^+  +>
    =.  off  ?:((lth p.lin edg) 0 (sub p.lin edg))
    (se-show (sub p.lin off) (scag edg (slag off q.lin)))
  ::
  ++  se-view                                           ::  flush buffer
    ?:  liv.maz
      (se-just ~(ta-vew ta [& & ~zod %$] tar.maz))
    =+  gul=se-agon
    ?~  gul  se-view(liv.maz &)
    =+  gyr=(~(get by fug) u.gul)
    ?~  gyr  se-view(liv.maz &)
    ?~  u.gyr  se-view(liv.maz &)
    %-  se-just
    ~(ta-vew ta [& | u.gul] u.u.gyr)
  ::
  ++  se-emit                                           ::  emit move
    |=  mov=move
    %_(+> moz [mov moz])
  ::
  ++  se-text                                           ::  return text
    |=  txt=tape
    (se-blit %out (tuba txt))
  ::
  ++  se-poke                                           ::  send a poke
    |=  [gyl=gill par=pear]
    (se-emit ost %poke (drum-path gyl) gyl par)
  ::
  ++  se-peer                                           ::  send a peer
    |=  gyl=gill
    (se-emit(fug (~(put by fug) gyl ~)) ost %peer (drum-path gyl) gyl /sole)
  ::
  ++  se-pull                                           ::  cancel subscription
    |=  gyl=gill
    (se-emit ost %pull (drum-path gyl) gyl ~)
  ::
  ++  se-tame                                           ::  switch connection
    |=  gyl=gill
    ^+  ta
    ~(. ta [& %| gyl] (need (~(got by fug) gyl)))
  ::
  ++  se-diff                                           ::  receive results
    |=  [gyl=gill fec=sole-effect]
    ^+  +>
    ta-abet:(ta-fec:(se-tame gyl) fec)
  ::
  ++  ta                                                ::  per target
    |_  $:  $:  liv=?                                   ::  don't delete
                mav=?                                   ::  showing master
                gyl=gill                                ::  target app
            ==                                          ::
            target                                      ::  target state
        ==                                              ::
    ++  ta-abet                                         ::  resolve
      ^+  ..ta
      =.  liv.maz  mav
      ?:  mav
        ?.  liv
          (se-blit `dill-blit`[%qit ~])
        se-prom:+>(tar.maz +<+)
      ?.  liv  
        =.  ..ta  (se-nuke gyl) 
        ..ta(liv.maz =(~ fug))
      ..ta(fug (~(put by fug) gyl ``target`+<+))
    ::
    ++  ta-ant                                          ::  toggle master
      ^+  .
      ?:  mav
        ?:  =(~ fug)  ta-bel
        %_  .
          mav      |
          +<+      (need (~(got by fug) gyl))
          tar.maz  +<+
        ==
      %_  .
        mav  &
        +<+  tar.maz
        fug  (~(put by fug) gyl `+<+) 
      ==
    ::
    ++  ta-act                                          ::  send action
      |=  act=sole-action
      ^+  +>
      ?:  mav  
        +>.$
      +>.$(+> (se-poke gyl %sole-action act))
    ::
    ++  ta-aro                                          ::  hear arrow
      |=  key=?(%d %l %r %u)
      ^+  +>
      ?-  key
        %d  =.  ris  ~
            ?.  =(num.hit pos.hit) 
              (ta-mov +(pos.hit))
            ?:  =(0 (lent buf.say.inp))
              ta-bel
            (ta-hom:ta-nex %set ~)
        %l  ?^  ris  ta-bel
            ?:  =(0 pos.inp)  ta-bel 
            +>(pos.inp (dec pos.inp))
        %r  ?^  ris  ta-bel
            ?:  =((lent buf.say.inp) pos.inp) 
              ta-bel
            +>(pos.inp +(pos.inp))
        %u  =.  ris  ~
            ?:(=(0 pos.hit) ta-bel (ta-mov (dec pos.hit)))
      ==
    ::
    ++  ta-bel  .(+> (se-blit %bel ~))                  ::  beep
    ++  ta-cat                                          ::  mass insert
      |=  [pos=@ud txt=(list ,@c)]
      ^-  sole-edit
      :-  %mor
      |-  ^-  (list sole-edit)
      ?~  txt  ~
      [[%ins pos i.txt] $(pos +(pos), txt t.txt)]
    ::
    ++  ta-cut                                          ::  mass delete
      |=  [pos=@ud num=@ud]
      ^-  sole-edit
      :-  %mor
      |-(?:(=(0 num) ~ [[%del pos] $(num (dec num))]))
    ::
    ++  ta-det                                          ::  send edit
      |=  ted=sole-edit
      ^+  +>
      (ta-act %det [[his.ven.say.inp own.ven.say.inp] (sham buf.say.inp) ted])
    ::
    ++  ta-bac                                          ::  hear backspace
      ^+  .
      ?^  ris
        ?:  =(~ str.u.ris)
          ta-bel
        .(str.u.ris (scag (dec (lent str.u.ris)) str.u.ris))
      ?:  =(0 pos.inp)
        .(+> (se-blit %bel ~))
      =+  pre=(dec pos.inp)
      (ta-hom(pos.inp pre) %del pre)
    ::
    ++  ta-ctl                                          ::  hear control
      |=  key=@ud
      ^+  +>
      ?+    key  ta-bel
          %a  +>(pos.inp 0)
          %b  (ta-aro %l)
          %c  ta-bel(ris ~)
          %d  ?:  &(=(0 pos.inp) =(0 (lent buf.say.inp)))
                +>(liv |)
              ta-del
          %e  +>(pos.inp (lent buf.say.inp))
          %f  (ta-aro %r)
          %g  ta-bel(ris ~)
          %k  =+  len=(lent buf.say.inp)
              ?:  =(pos.inp len)
                ta-bel 
              %-  ta-hom(kil `(slag pos.inp buf.say.inp))
              (ta-cut pos.inp (sub len pos.inp))
          %l  +>(+> (se-blit %clr ~))
          %n  (ta-aro %d)
          %p  (ta-aro %u)
          %r  ?~  ris 
                +>(ris `[pos.hit ~]) 
              ?:  =(0 pos.u.ris)
                ta-bel
              (ta-ser ~)
          %t  =+  len=(lent buf.say.inp)
              ?:  |(=(0 pos.inp) (lth len 2))
                ta-bel
              =+  sop=?:(=(len pos.inp) (dec pos.inp) pos.inp) 
              =.  pos.inp  +(sop)
              %-  ta-hom
              :~  %mor
                  [%del sop]
                  [%ins (dec sop) (snag sop buf.say.inp)]
              ==
          %u  ?:  =(0 pos.inp)
                ta-bel
              %-  ta-hom(pos.inp 0, kil `(scag pos.inp buf.say.inp))
              (ta-cut 0 pos.inp)
          %v  ta-ant
          %x  +>(+> se-anon)
          %y  ?~  kil  ta-bel 
              %-  ta-hom(pos.inp (add pos.inp (lent u.kil)))
              (ta-cat pos.inp u.kil)
      ==
    ::
    ++  ta-cru                                          ::  hear crud
      |=  [lab=@tas tac=(list tank)]
      =.  +>+>  (se-text (trip lab))
      (ta-tan tac)
    ::
    ++  ta-del                                          ::  hear delete
      ^+  .
      ?:  =((lent buf.say.inp) pos.inp)
        .(+> (se-blit %bel ~))
      (ta-hom %del pos.inp)
    ::
    ++  ta-erl                                          ::  hear local error
      |=  pos=@ud 
      ta-bel(pos.inp (min pos (lent buf.say.inp)))
    ::
    ++  ta-err                                          ::  hear remote error
      |=  pos=@ud 
      (ta-erl (~(transpose cs say.inp) pos))
    ::
    ++  ta-fec                                          ::  apply effect
      |=  fec=sole-effect
      ^+  +>
      ?-    -.fec
        %bel  ta-bel
        %blk  +>
        %clr  +>(+> (se-blit fec))
        %det  (ta-got +.fec)
        %err  (ta-err +.fec)
        %mor  |-  ^+  +>.^$
              ?~  p.fec  +>.^$
              $(p.fec t.p.fec, +>.^$ ^$(fec i.p.fec))
        %nex  ta-nex
        %pro  (ta-pro +.fec)
        %tan  (ta-tan p.fec)
        %sag  +>(+> (se-blit fec))
        %sav  +>(+> (se-blit fec))
        %txt  $(fec [%tan [%leaf p.fec]~])
      ==
    ::
    ++  ta-dog                                          ::  change cursor
      |=  ted=sole-edit
      %_    +>
          pos.inp
        =+  len=(lent buf.say.inp)
        %+  min  len
        |-  ^-  @ud
        ?-  -.ted
          %del  ?:((gth pos.inp p.ted) (dec pos.inp) pos.inp)
          %ins  ?:((lte pos.inp p.ted) +(pos.inp) pos.inp)
          %mor  |-  ^-  @ud
                ?~  p.ted  pos.inp
                $(p.ted t.p.ted, pos.inp ^$(ted i.p.ted))
          %nop  pos.inp
          %set  len
        ==
      ==
    ::
    ++  ta-got                                          ::  apply change
      |=  cal=sole-change
      =^  ted  say.inp  (~(receive cs say.inp) cal)
      (ta-dog ted)
    ::
    ++  ta-hom                                          ::  local edit
      |=  ted=sole-edit
      ^+  +>
      =.  +>  (ta-det ted)
      =.  +>  (ta-dog(say.inp (~(commit cs say.inp) ted)) ted)
      +>
    ::
    ++  ta-met                                          ::  meta key
      |=  key=@ud
      ~&  [%ta-met key]
      +>
    ::
    ++  ta-mov                                          ::  move in history
      |=  sop=@ud
      ^+  +>
      ?:  =(sop pos.hit)  +>
      %+  %=  ta-hom
            pos.hit  sop
            lay.hit  %+  ~(put by lay.hit)  
                       pos.hit 
                     buf.say.inp
          ==
        %set
      %-  (bond |.((snag (sub num.hit +(sop)) old.hit)))
      (~(get by lay.hit) sop)
    ::
    ++  ta-nex                                          ::  advance history
      %_  .
        num.hit  +(num.hit)
        pos.hit  +(num.hit)
        ris  ~
        lay.hit  ~
        old.hit  [buf.say.inp old.hit]
      ==
    ::
    ++  ta-pro                                          ::  set prompt
      |=  pom=sole-prompt
      +>(pom pom(cad :(welp (scow %p p.gyl) ":" (trip q.gyl) cad.pom)))
    ::
    ++  ta-ret                                          ::  hear return
      ?.  mav
        (ta-act %ret ~)
      =+  txt=(tufa buf.say.inp)
      =+  fey=(rose txt sp-ukase:sp)
      ?-  -.fey
        %|  (ta-erl (lent (tuba (scag p.fey txt))))
        %&  ?~  p.fey 
              (ta-erl (lent buf.say.inp))
            =.  +>+>  (se-like u.p.fey)
            =.  pom  pom.tar.maz
            (ta-hom:ta-nex %set ~)
      ==
    ::
    ++  ta-ser                                          ::  reverse search
      |=  ext=(list ,@c)
      ^+  +>
      ?:  |(?=(~ ris) =(0 pos.u.ris))  ta-bel
      =+  tot=(weld str.u.ris ext)
      =+  dol=(slag (sub num.hit pos.u.ris) old.hit)
      =+  sop=pos.u.ris
      =+  ^=  ser
          =+  ^=  beg
              |=  [a=(list ,@c) b=(list ,@c)]  ^-  ?
              ?~(a & ?~(b | &(=(i.a i.b) $(a t.a, b t.b))))
          |=  [a=(list ,@c) b=(list ,@c)]  ^-  ?
          ?~(a & ?~(b | |((beg a b) $(b t.b))))
      =+  ^=  sup  
          |-  ^-  (unit ,@ud)
          ?~  dol  ~
          ?:  (ser tot i.dol)
            `sop
          $(sop (dec sop), dol t.dol)
      ?~  sup  ta-bel
      (ta-mov(str.u.ris tot, pos.u.ris (dec u.sup)) (dec u.sup))
    ::
    ++  ta-tan                                          ::  print tanks
      |=  tac=(list tank)
      =+  wol=`wall`(zing (turn tac |=(a=tank (~(win re a) [0 edg]))))
      |-  ^+  +>.^$
      ?~  wol  +>.^$
      $(wol t.wol, +>+>.^$ (se-text i.wol))
    ::
    ++  ta-txt                                          ::  hear text
      |=  txt=(list ,@c)
      ^+  +>
      ?^  ris
        (ta-ser txt)
      %-  ta-hom(pos.inp (add (lent txt) pos.inp))
      :-  %mor
      |-  ^-  (list sole-edit)
      ?~  txt  ~
      [[%ins pos.inp i.txt] $(pos.inp +(pos.inp), txt t.txt)]
    ::
    ++  ta-vew                                          ::  computed prompt
      |-  ^-  (pair ,@ud (list ,@c))
      ?^  ris
        %=    $
            ris  ~
            cad.pom 
          :(welp "(reverse-i-search)'" (tufa str.u.ris) "': ")
        ==
      =-  [(add pos.inp (lent p.vew)) (weld (tuba p.vew) q.vew)]
      ^=  vew  ^-  (pair tape (list ,@c))
      ?:  vis.pom  [cad.pom buf.say.inp]
      :-  ;:  welp
            cad.pom
            ?~  buf.say.inp  ~
            ;:  welp
              "<"
              (scow %p (end 4 1 (sham buf.say.inp)))
              "> "
            ==
          ==
      =+  len=(lent buf.say.inp) 
      |-  ^-  (list ,@c) 
      ?:(=(0 len) ~ [`@c`'*' $(len (dec len))])
    --
  --
--