; Bulls and Cows game in N8A for n808 VM
; Enter your guesses digit by digit, you have 7 attempts
; After each guess, the game replies with bulls.cows
; (if you have 4.0, you win)
; On victory or after running out of attempts, the game
; displays the target digits and halts
; Created by Luxferre in 2025, released into public domain

; constants/variables section
#1 va
#2 vb
#3 vc
#4 vd
#10 c10
#11 counter
#12 octr
#13 ictr
#14 frac
#20 bcctr
#60 dig_0
#61 dig_1
#62 dig_2
#63 dig_3
#64 dig_4
#65 dig_5
#66 dig_6
#67 dig_7
#68 dig_8
#69 dig_9
#70 src_base ; source base address
#71 trg_base ; target base address

; constant/variable assignments
dca 10 @c10      ; constant 10
dca 0 @dig_0     ; assign digits from 0 to 9
dca 1 @dig_1
dca 2 @dig_2
dca 3 @dig_3
dca 4 @dig_4
dca 5 @dig_5
dca 6 @dig_6
dca 7 @dig_7
dca 8 @dig_8
dca 9 @dig_9
dca 60 @src_base ; set the source base address (60)
dca 80 @trg_base ; set the target base address (80)
dca 10 @frac     ; prepare the @frac variable
set 0 0 @frac    ; set 0.1 to @frac

; main logic

; random unique 4-digit generator (into the addresses 81..84)

dca 4 @counter    ; set the counter to 4
:dsl dca 9 @va    ; digit selection loop start, set the upper boundary to @va
rnd 0 @va @va     ; select a random digit from 0 to 9 inclusively into @va
add @src_base @va ; add the source base address to @va
dca @vb @vb       ; init @vb with its own address
ivc @va @vb       ; copy the value at address in @va into @vb
dca 10 @vc        ; init @vc with the constant 10
sub @vb @vc       ; @vb - 10 => @vc
jeq @vc :dsl      ; jump back to the digit selection if the value at @vc is 0
ica 10 @va        ; set the value at the address in @va to 10
dva @counter @va  ; copy the counter to @va
add @trg_base @va ; add the target base address to the counter in @va
dca @vb @vc       ; copy the address of @vb into @vc 
ivc @vc @va       ; copy the value from @vb (address stored at @vc) to the cell address at @va
dec @counter      ; decrement the counter
jgt @counter :dsl ; jump back to digit selection if it still is above zero

; player guess loop 

dca 7 @counter        ; set the attempt count to 7
:prm inp 91 94        ; input the guess digit by digit into loc 91..94
dca 90 @src_base      ; set 90 as the new source base address
dca 0 @bcctr          ; init bull/cow counter
dca 4 @octr           ; init outer loop counter
:olp dca 4 @ictr      ; start of the outer loop, init inner loop counter
:ilp dva @octr @va    ; start of the inner loop, copy the outer counter
dva @trg_base @vb     ; fetch the target base address
add @va @vb           ; get the address of the target digit in @vb
dva @ictr @va         ; copy the inner counter
dva @src_base @vc     ; fetch the source base address
add @va @vc           ; get the address of the entered digit in @vc
dca @va @va           ; init @va with its own address
ivc @vb @va           ; copy the target digit into @va
dca @vd @vd           ; init @vd with its own address
ivc @vc @vd           ; copy the entered digit into @vd
sub @vd @va           ; save the digits difference into @va
jne @va :ei           ; jump to the next comparator if the digits don't match
dva @ictr @vb         ; load the inner counter into @vb
sub @octr @vb         ; save the _counters_ difference into @vb
jne @vb :cc           ; jump to the cow counter if the indices don't match
inc @bcctr            ; increment the bull counter if they do
juc :ei               ; skip the next instruction
:cc add @frac @bcctr  ; increase the cow counter if they don't
:ei dec @ictr         ; decrement the inner loop counter
jgt @ictr :ilp        ; jump to the start of the inner loop if still > 0
dec @octr             ; decrement the outer loop counter
jgt @octr :olp        ; jump to the start of the outer loop if still > 0
out @bcctr @bcctr     ; output the match result
dca 4 @va             ; store the constant 4 into @va
sub @bcctr @va        ; get the difference between bull/cow counter and 4
jeq @va :end          ; jump to the last instruction if they match
dec @counter          ; decrement the attempt counter
jgt @counter :prm     ; jump to guess prompt if the counter is above 0
:end out 81 84        ; output the target number before halting