honeylisp/game/entity.fnl

(local util (require :lib.util))
(local tiles (util.require :game.tiles))
(local {: vm : org} (require :game.defs))
(local {: lo : hi} util)
(local itile
  (let [tilelist (tiles.loadgfx tiles.fn-tiles)]
    (fn [label] (tiles.find-itile tilelist label))))

; Entity memory layout:
; +0 - yx
; +2 - event handler
; +4 - link word
; +6 - link pointer

; All entities exist in a single page in RAM - with this structure we can have up to 32
; (players are handled specially and never require a link)
; if we really need more we could have one page for entities and one page for link data
; hellmaze level 2 from MS-DOS Neut Tower has 36 entities - good excuse to simplify IMO
; The entity count for a level is stored after the map.

(local ev {
  :touch 0
  :act   1
  :deact 2
  :tog   3
})

(vm:word :entity-count :lit :map-entity-count :bget)
(vm:def :lookup-entity ; i -- entity
  [:lda vm.TOP :x]
  [:asl :a] [:asl :a] [:asl :a] ; x8
  [:sta vm.TOP :x]
  [:lda #(hi org.entity.org)]
  [:sta vm.TOPH :x])
(vm:word :entity-at ; yx -- entity|0
  :>r 0 :entity-count
  (vm:while [:dup] :dec ; entity|0 i
    :dup :lookup-entity :get :rtop :=
    (vm:when :lookup-entity :swap)
  ) :drop :rdrop)
(vm.code:append :responder [:dw 0])
(vm:word :get-responder :lit :responder :get)
(vm:word :responder-itile :get-responder :get :itile-at)
(vm:word :entity>do ; entity ev --
  :over :lit :responder :dup :get :>r :set
  :swap 2 :+ :get :execute
  :r> :lit :responder :set)

(vm:word :linked-entity :get-responder :dup 4 :+ :get :dup (vm:if [:dup :. :execute] [:drop 6 :+ :dup :. :get]) :dup :.)
(vm:word :touch-entity ; yx -- f
  :entity-at :dup (vm:when ev.touch :entity>do vm.true))

(vm:word :set-entitytile ; e itile --
  :swap :get :swap :update-itile)

(vm:word :set-respondertile ; itile --
  :get-responder :get :swap :update-itile)

(vm:word :handle-onoff ; ev off on --
  :<rot (vm:case
    [ev.act :swap :drop :set-respondertile]
    [ev.deact :drop :set-respondertile]
    [ev.tog :dup :responder-itile := (vm:if [:drop :set-respondertile] [:set-respondertile :drop])]
    [:else :drop :drop]))
(vm:word :activation-ev? ; ev -- f
  :dup ev.act := :over ev.deact := :| :swap ev.tog := :|)
(vm:word :activate-link ; ev itile-on --
  :swap :activation-ev? (vm:if [
    :responder-itile :dup :. := (vm:if [ev.act] [ev.deact])
    :linked-entity :swap :entity>do
  ] [:drop]))

(vm:word :door ; ev --
  :dup :. :dup (vm:case
    [ev.touch :drop :responder-itile (itile :dooropen) := (vm:when :move-player)]
    [:else (itile :doorclosed) (itile :dooropen) :handle-onoff]))

(vm:word :switch ; ev --
  :dup ev.touch := (vm:when :drop ev.tog)
  :dup (itile :switchoff) (itile :switchon) :handle-onoff
  (itile :switchon) :activate-link)

(vm:word :term ; ev --
  :dup ev.touch := (vm:when :drop ev.act)
  :dup (itile :termoff) (itile :termon) :handle-onoff)

(fn append-from-map [map entity-org]
  (each [_ entity (ipairs map.objects)]
    (when entity.name
      (entity-org:append entity.name))
    (entity-org:append
      [:db (- entity.x 1)] [:db (- entity.y 1)]
      [:ref entity.func]
      (if (and entity.linkword (> (length entity.linkword) 0)) [:ref entity.linkword] [:dw 0])
      (if entity.link [:dw (+ entity-org.org (* (- entity.link 1) 8))] [:dw 0]))))

{: ev : append-from-map}