; ── SWARM FORAGER ────────────────────────────
; Random walk to find food, dead reckoning to
; navigate home. Pheromone marks food for others.
; Hit play, then try improving it!

; ── Registers ──
.alias dx   r1           ; x displacement from nest
.alias dy   r2           ; y displacement from nest
.alias ret  r3           ; return address for CALL

; ── Pheromone ──
.const TRAIL CH_RED      ; marks food locations

; ── Roles (visible in simulation viewer) ──
.tag 0 foraging
.tag 1 homing

; ──────────────────────────────────────────────
main:
    CARRYING
    JNE r0 0 go_home
    TAG foraging

; ── SEARCH: find food ─────────────────────────
search:
    SENSE FOOD
    JNE r0 0 grab
    SMELL TRAIL
    JNE r0 0 step
    RANDOM r0 4
    ADD r0 1
step:
    CALL ret move_track
    JMP main

grab:
    CALL ret move_track
    PICKUP
    MARK TRAIL 100
    JMP main

; ── GO HOME: dead reckon toward nest ──────────
go_home:
    TAG homing
    SENSE NEST
    JNE r0 0 deliver
    RANDOM r0 4
    JEQ r0 0 wander       ; 25% random to unstick walls
    CALL ret home_dir
    CALL ret move_track
    JMP main
wander:
    RANDOM r0 4
    ADD r0 1
    CALL ret move_track
    JMP main

deliver:
    CALL ret move_track
    DROP
    JMP main

; ══════════════════════════════════════════════
; SUBROUTINES — CALL ret <label>, return JMP ret
; ══════════════════════════════════════════════

; home_dir: set r0 = direction toward nest
home_dir:
    SET r4 dx
    JGT dx 0 hd_dxp
    SET r4 0
    SUB r4 dx
hd_dxp:
    SET r5 dy
    JGT dy 0 hd_dyp
    SET r5 0
    SUB r5 dy
hd_dyp:
    JGT r5 r4 hd_y
    JGT dx 0 hd_w
    SET r0 2
    JMP ret
hd_w:
    SET r0 4
    JMP ret
hd_y:
    JGT dy 0 hd_n
    SET r0 3
    JMP ret
hd_n:
    SET r0 1
    JMP ret

; move_track: MOVE r0, then update dx/dy
move_track:
    MOVE r0
    JEQ r0 1 mt_n
    JEQ r0 2 mt_e
    JEQ r0 3 mt_s
    SUB dx 1
    JMP ret
mt_n:
    SUB dy 1
    JMP ret
mt_e:
    ADD dx 1
    JMP ret
mt_s:
    ADD dy 1
    JMP ret