%include "io.inc"

global main

section .text

;
; arg1 = n
;
sum:
    push ebp                ; save caller EBP
    mov ebp, esp

    cmp dword [ebp + 8], 0  ; if (arg1 > 0)
    jng .false              ; jump if not greater

.true____unused_label:      ; arg1 > 0
    mov edx, [ebp + 8]      ; copy arg1 to newarg1
    dec edx                 ; newarg1--
    push edx                ; push newarg1
    call sum                ; recursion call. Result will be in EAX
    add esp, 4              ; drop pushed newarg1 after call
    add eax, [ebp + 8]      ; result += arg1
    jmp .end                ;

.false:                     ; arg1 <= 0
    mov eax, 0              ; result = 0

.end:
    ; mov esp, ebp          ; useless sh*t
    pop ebp                 ; restore caller EBP
    ret                     ; return back to caller, EAX already contains result

main:
    push 5
    call sum ; 5 + 4 + 3 + 2 + 1 + 0 = 15

    PRINT_DEC 4, eax

    ; system call exit()

    xor eax, eax
    mov al, 1
    xor ebx, ebx
    int 0x80