;   brainfuck_interpreter_v0.asm - Naive and unoptimised implementation of a brainfuck interpreter
;
;   This file is part of the 9086 project.
;
;   Copyright (c) 2024 Efthymios Kritikos
;
;   This program is free software: you can redistribute it and/or modify
;   it under the terms of the GNU General Public License as published by
;   the Free Software Foundation, either version 3 of the License, or
;   (at your option) any later version.
;
;   This program is distributed in the hope that it will be useful,
;   but WITHOUT ANY WARRANTY; without even the implied warranty of
;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;   GNU General Public License for more details.
;
;   You should have received a copy of the GNU General Public License
;   along with this program.  If not, see <http://www.gnu.org/licenses/>.

mov bx,#bootup_msg
mov ah,#0x02
bootup_print:
mov dl,[bx]
int #0x21
inc bx
cmp dl,#0x0A
jne bootup_print

mov si,#prog
mov BX,#data
mov CX,#bracket
dec si
INTERPRET:
inc si
mov al,[si]
cmp al,#'+
jz WAS_PLUS
cmp al,#'-
jz WAS_MINUS
cmp al,#'>
jz WAS_MR
cmp al,#'<
jz WAS_ML
cmp al,#'[
jz WAS_PL
cmp al,#']
jz WAS_PR
cmp al,#'.
jz WAS_PRINT
jmp PROG_END

WAS_PLUS:
inc BYTE [BX]
JMP INTERPRET

WAS_MINUS:
dec BYTE [BX]
JMP INTERPRET

WAS_MR:
inc bx
JMP INTERPRET

WAS_ML:
dec bx
JMP INTERPRET

WAS_PL:
MOV AL,[BX]
cmp AL,#0
jz SKIP_CODE_BLOCK
;have to enter loop
MOV AX,SI
inc CX
inc CX
MOV SI,CX
mov [SI],AX
mov SI,AX
JMP INTERPRET

SKIP_CODE_BLOCK:
;have to skip loop
MOV DX,#0
SKIP_LOOP:
INC SI
mov AL,[SI]
CMP AL,#']
JZ WAS_CLOSE1
CMP AL,#'[
JZ WAS_OPEN1
JMP SKIP_LOOP

WAS_CLOSE1:
CMP DX,#0
JZ INTERPRET
DEC DX
JMP SKIP_LOOP
WAS_OPEN1:
INC DX
JMP SKIP_LOOP

WAS_PR:
mov AL,[BX]
cmp AL,#0
JZ EXIT_PR
MOV SI,CX
mov ax,[SI]
mov si,ax
JMP INTERPRET


EXIT_PR:
DEC CX
DEC CX
jmp INTERPRET


WAS_PRINT:
mov ah, #0x02
MOV DL,[BX]
int #0x21
JMP INTERPRET

PROG_END:
hlt

bootup_msg: .ASCII 'Brainfuck interpreter v0\n'
bracket: .BLKB 280
data: .BLKB 560