honeylisp/game/init.fnl

(local lume (require :lib.lume))
(local asm (require :asm.asm))
(local VM (require :asm.vm))
(local tile (require :game.tiles))
(local link (require :link))
(local {: lo : hi} (require :lib.util))

(local prg (asm.new))
; (prg:debug-to "test.dbg")

(local tiles (prg:org 0x6100))
(local vm (VM.new prg))
(local code1 vm.code)
(link.machine:stub code1 :next)

(local mon {
  :hexout :0xfdda
  :putchar :0xfded
  :bell :0xff3a
})

(fn achar [c] (bit.bor (string.byte c) 0x80))
(fn astr [s]
  (-> [(string.byte s 1 -1)]
    (lume.map #(bit.bor $1 0x80))
    (-> (table.unpack) (string.char))))

; a handful of debugging words
(vm:def :.
  [:lda vm.TOPH :x]
  [:jsr mon.hexout]
  [:lda vm.TOP :x]
  [:jsr mon.hexout]
  [:lda (achar " ")]
  [:jsr mon.putchar]
  (vm:drop))

(vm:def :stacklen
  (vm:reserve)
  [:txa] [:lsr :a] [:sta vm.TOP :x]
  [:lda 0] [:sta vm.TOPH :x])

(vm:word :.s
  :stacklen (prg:parse-addr vm.TOP) :swap
  (vm:for :dup :get :. :inc :inc) :drop)

; Graphics routines
(vm:def :hires
  [:sta :0xc050]
  [:sta :0xc057]
  [:sta :0xc052])

(vm:def :mixed [:sta :0xc051])

; starting address:
; 0x2000 + (x*2) + (y%4 * 0x100) + ((y/4) * 0x28)
; x between 0-19
; y between 0-12
; yx - 16-bit value, low byte x, high byte y
(code1:append :screeny-lookup [:bytes "\0\040\080"])
(vm:def :tile>screen ; yx -- p
  [:lda vm.TOPH :x]         ; a=y
  [:lsr :a] [:lsr :a]       ; a=y/4
  [:tay]                    ; y=y/4
  [:lda 0x03]
  [:and vm.TOPH :x]         ; a=y%4
  [:ora 0x20]               ; a=0x20 + y%4
  [:sta vm.TOPH :x]         ; high byte is set (and y is wiped)
  [:lda vm.TOP :x]          ; a=x
  [:asl :a]                 ; a = x*2
  [:clc]
  [:adc :screeny-lookup :y] ; a=x*2 + (y/4)*0x28
  [:sta vm.TOP :x]          ; low byte is set
)

; note: the graphical tile data must not cross a page boundary
; (this happens automatically because each tile is 32 bytes and we
; start them on a page; this lets lookup-tile be fast)
(fn draw-block []
  [:block
    [:clc]
    [:ldy 8]
  :loop
    [:lda [vm.TOP :x]]
    [:sta [vm.ST1 :x]]
    [:inc vm.TOP :x]
    [:lda vm.ST1H :x]
    [:adc 4]
    [:sta vm.ST1H :x]
    [:dey]
    [:bne :loop]])

(fn draw-vertical-block []
  [:block
    (draw-block)
    [:lda vm.ST1H :x]
    [:sbc 31] ; with carry clear this is 32
    [:sta vm.ST1H :x]
    [:lda vm.ST1 :x]
    [:ora 0x80]
    [:sta vm.ST1 :x]
    (draw-block)])

(vm:def :drawtile ; p gfx --
  (draw-vertical-block)
  [:lda vm.ST1H :x]
  [:sbc 31]
  [:sta vm.ST1H :x]
  [:lda vm.ST1 :x]
  [:sbc 0x7f]
  [:sta vm.ST1 :x]
  (draw-vertical-block)
  (vm:drop) (vm:drop))

(vm:def :cleargfx
  (vm:push 0x4000)
  [:block :page
    [:dec vm.TOPH :x]
    [:lda 0]
    [:block :start
      [:sta [vm.TOP :x]]
      [:inc vm.TOP :x]
      [:bne :start]]
    [:lda vm.TOPH :x]
    [:cmp 0x20]
    [:bne :page]]
  (vm:drop))

(vm:word :drawmaprow ; pscreen pmap -- pmap
  20 (vm:for
    :2dup :bget :lookup-tile :drawtile
    :inc :swap :inc :inc :swap) :swap :drop)

(vm:word :drawmap
  :lit :map 0x0c00 (vm:until 0x100 :-
    :dup :tile>screen ; pmap yx pscreen
    :<rot :drawmaprow :swap ; pmap yx
  :dup :not) :drop :drop)

(vm:def :lookup-tile ; itile -- ptile
  ; each tile is 32 bytes; 2^5
  ; we save some cycles by storing the indices as lllhhhhh, so we don't need to shift them'
  [:lda vm.TOP :x] [:tay]
  [:and 0x1f]
  [:clc] [:adc #(hi tiles.org)]
  [:sta vm.TOPH :x]
  [:tya] [:and 0xe0]
  [:sta vm.TOP :x])

(tile.appendtiles (tile.loadtiles) tiles)

; thought:
; hotswap-safe debug stub at root of call stack
; but REPL debug stub should be very available as a task

; 19x11 means full map is 209 bytes
(: (prg:org 0x6800) :append :map [:bytes (string.rep "\0\032\064\096\128\160\192\224\001\033\065\097\129\161\193" 17)])
(code1:append :main
  [:jsr :reset]
  [:jsr :interpret]
  [:vm :hires ; :mixed
    :cleargfx
    (vm:forever
     :debug-stub :drawmap
    )
;    0x0000 :tile>screen 0 :lookup-tile :drawtile
    :quit])

(prg:assemble)