; E04-S02: software-frame ABI test in x128.
;
; The fixture runs with CR=$0E and IRQs masked so the frame stack at
; $B800-$BFFF is RAM. It restores the entry CR before returning to BASIC.
; Checks:
;   +0/+1  recursive two-byte result (sum 1..50 = 1275 = $04FB)
;   +2     one-byte return (5+7 = 12)
;   +3     overflow error (FRAME_ERR_STACK)
;   +4/+5  SP after the overflow unwinds ($C000)
;   +6     frame_error after overflow (FRAME_ERR_STACK)
;   +7     FP low after unwinding (0)
; Failure bits: 1 recursion, 2 one-byte return, 4 overflow, 8 stack state.

.setcpu "6502"
.include "../../src/common/c128.inc"
.include "../../src/common/mailbox.inc"
.include "../../src/common/frames.inc"

.import frame_init, frame_enter, frame_leave, frame_discard
.import frame_push_byte, frame_push_word, frame_error

.segment "LOADADDR"
        .word $1C01

.segment "EXEHDR"
        .word basic_end
        .word 10
        .byte $9E
        .byte "7181"
        .byte $00
basic_end:
        .word $0000

.segment "MAILBOX"
        .res MB_SIZE

.segment "STARTUP"
.export test_entry
test_entry:
        php
        sei
        ldx #MB_SIZE - 1
        lda #$00
@clr:   sta MB_BASE,x
        dex
        bpl @clr
        lda #MB_MAGIC0_VALUE
        sta MB_MAGIC0
        lda #MB_MAGIC1_VALUE
        sta MB_MAGIC1
        lda #MB_PROD_PROGRAM
        sta MB_PRODUCER
        lda #MB_ST_RUNNING
        sta MB_STATUS
        lda #$00
        sta fail_mask
        sta sum_lo
        sta sum_hi
        sta byte_sum
        sta ov_error
        sta MB_CODE
        sta MB_CODE+1

        jsr frame_init
        lda MMU_CR
        sta saved_cr
        lda #CR_RAM0_KERNAL
        sta MMU_CR

        ; ------------------------------------------------ successful recursion
        jsr frame_init
        lda #<50
        ldx #>50
        jsr frame_push_word
        bcs @rec_push_fail
        jsr recurse
        bcs @rec_call_fail
        sta sum_lo
        stx sum_hi
        lda #2
        ldx #0
        jsr frame_discard
        lda sum_lo
        cmp #$FB
        bne @rec_bad
        lda sum_hi
        cmp #$04
        bne @rec_bad
        lda FRAME_SP
        cmp #<FRAME_STACK_TOP
        bne @rec_bad
        lda FRAME_SP+1
        cmp #>FRAME_STACK_TOP
        bne @rec_bad
        jmp @byte_return
@rec_push_fail:
        lda #$01
        jsr fail
        jmp @byte_return
@rec_call_fail:
        lda #2
        ldx #0
        jsr frame_discard
        lda #$01
        jsr fail
        jmp @byte_return
@rec_bad:
        lda #$01
        jsr fail

        ; --------------------------------------------------- one-byte return
@byte_return:
        jsr frame_init
        lda #7
        jsr frame_push_byte
        bcs @byte_fail
        lda #5
        jsr frame_push_byte
        bcs @byte_fail
        jsr sum_bytes
        bcs @byte_fail
        sta byte_sum
        lda #2
        ldx #0
        jsr frame_discard
        lda byte_sum
        cmp #12
        beq @overflow
@byte_fail:
        lda #$02
        jsr fail

        ; ------------------------------------------------------ stack overflow
@overflow:
        jsr frame_init
        lda #<1000
        ldx #>1000
        jsr frame_push_word
        bcs @ov_push_fail
        jsr recurse
        bcc @ov_no_fault
        lda #2
        ldx #0
        jsr frame_discard
        lda frame_error
        sta ov_error
        cmp #FRAME_ERR_STACK
        beq @ov_check_sp
        lda #$04
        jsr fail
        jmp @ov_check_sp
@ov_push_fail:
        lda #$04
        jsr fail
        jmp @finish
@ov_no_fault:
        lda #2
        ldx #0
        jsr frame_discard
        lda #$04
        jsr fail
@ov_check_sp:
        lda FRAME_SP
        cmp #<FRAME_STACK_TOP
        bne @ov_bad
        lda FRAME_SP+1
        cmp #>FRAME_STACK_TOP
        bne @ov_bad
        lda FRAME_FP
        ora FRAME_FP+1
        beq @finish
@ov_bad:
        lda #$08
        jsr fail

        ; ---------------------------------------------- hardware-stack guard
        tsx
        stx saved_hw_sp
        ldx #$20
        txs
        lda #0
        ldx #0
        jsr frame_enter
        ldx saved_hw_sp
        txs
        bcc @hw_bad
        lda frame_error
        cmp #FRAME_ERR_STACK
        beq @finish
@hw_bad:
        lda #$10
        jsr fail

        ; ---------------------------------------------------------- report
@finish:
        lda sum_lo
        sta MB_DATA+0
        lda sum_hi
        sta MB_DATA+1
        lda byte_sum
        sta MB_DATA+2
        lda ov_error
        sta MB_DATA+3
        lda FRAME_SP
        sta MB_DATA+4
        lda FRAME_SP+1
        sta MB_DATA+5
        lda frame_error
        sta MB_DATA+6
        lda FRAME_FP
        sta MB_DATA+7

        lda saved_cr
        sta MMU_CR
        lda fail_mask
        sta MB_CODE
        lda #$00
        sta MB_CODE+1
        lda #MB_ST_FAIL
        ldx fail_mask
        bne @status
        lda #MB_ST_PASS
@status:
        sta MB_STATUS

        ldy #$00
@print: lda message,y
        beq @end
        sty print_y
        jsr CHROUT
        ldy print_y
        iny
        bne @print
@end:   plp
        rts

.segment "CODE"
fail:
        ora fail_mask
        sta fail_mask
        rts

; recurse(depth) -> depth + recurse(depth-1), zero at depth 0.
; Arguments: depth word at FP+2. Locals: depth word, result word.
recurse:
        lda #24
        ldx #0
        jsr frame_enter
        bcc @entered
        jmp @entry_err
@entered:

        ; local +0/+1 = depth, local +2/+3 = sentinel/result
        ldy #2
        lda (FRAME_FP),y
        ldy #0
        sta (FRAME_SP),y
        ldy #3
        lda (FRAME_FP),y
        ldy #1
        sta (FRAME_SP),y
        ldy #2
        lda #$A5
        sta (FRAME_SP),y
        iny
        lda #$5A
        sta (FRAME_SP),y

        ldy #0
        lda (FRAME_SP),y
        sta depth
        iny
        lda (FRAME_SP),y
        sta depth+1
        lda depth
        ora depth+1
        beq @zero

        lda depth
        sec
        sbc #1
        sta calc
        lda depth+1
        sbc #0
        sta calc+1
        lda calc
        ldx calc+1
        jsr frame_push_word
        bcs @push_err

        jsr recurse
        bcs @nested_err
        sta result
        stx result+1
        lda #2
        ldx #0
        jsr frame_discard

        ldy #2
        lda (FRAME_SP),y
        cmp #$A5
        bne @corrupt
        iny
        lda (FRAME_SP),y
        cmp #$5A
        bne @corrupt

        ldy #0
        lda (FRAME_SP),y
        clc
        adc result
        sta result
        ldy #1
        lda (FRAME_SP),y
        adc result+1
        sta result+1
        ldy #2
        lda result
        sta (FRAME_SP),y
        ldy #3
        lda result+1
        sta (FRAME_SP),y
        lda result
        ldx result+1
        jmp @leave

@zero:  lda #0
        ldx #0
@leave:
        sta ret_lo
        stx ret_hi
        jsr frame_leave
        lda ret_lo
        ldx ret_hi
        clc
        rts
@entry_err:
        lda #FRAME_ERR_STACK
        sec
        rts
@push_err:
        jsr frame_leave
        lda #FRAME_ERR_STACK
        sec
        rts
@nested_err:
        lda #2
        ldx #0
        jsr frame_discard
        jsr frame_leave
        lda #FRAME_ERR_STACK
        sec
        rts
@corrupt:
        lda #2
        ldx #0
        jsr frame_discard
        jsr frame_leave
        lda #FRAME_ERR_STATE
        sec
        rts

; sum_bytes(a,b) -> A = a+b. Two byte arguments at FP+2 and FP+3.
sum_bytes:
        lda #0
        ldx #0
        jsr frame_enter
        bcs @out
        ldy #2
        lda (FRAME_FP),y
        iny
        clc
        adc (FRAME_FP),y
        sta sum_result
        jsr frame_leave
        lda sum_result
        clc
        rts
@out:   sec
        rts

.segment "RODATA"
message:        .byte "NOVA128 FRAME TEST DONE", $0D, $00

.segment "BSS"
fail_mask:      .res 1
print_y:        .res 1
saved_cr:       .res 1
saved_hw_sp:    .res 1
sum_lo:         .res 1
sum_hi:         .res 1
byte_sum:       .res 1
ov_error:       .res 1
depth:          .res 2
calc:           .res 2
result:         .res 2
ret_lo:         .res 1
ret_hi:         .res 1
sum_result:     .res 1