%include "IO_DEFS.asm"

section .data 
    message1          db  "Enter a positive integer: "
    message1_length   equ $ - message1

section .bss
    phrase resb 100

section .text
   global _start

_start:

    ; prompt the user
    mov     rax, SYS_WRITE
    mov     rdi, STDOUT
    mov     rsi, message1
    mov     rdx, message1_length
    syscall

    ;read a number 
    mov rax, SYS_READ
    mov rdi, STDIN
    lea rsi, [phrase]
    mov rdx, 100
    syscall

    ;eax will be the constructed number
    ;r9d will be the lcv
    ;r10 will be the address of the next character

    ;r10d will be the end address of the string
    ;r11 will be the character

    ;   r8 = 0
    ;   r9 = start pos of string
    ;   
    ;   while r9 != 0 
    ;     r8 = r8 * 10
    ;     load the character at the pos r9 into r11
    ;     add that to r8
    ;     subtract '0' from r8
    ;     increment r9
    ;   jump if r9 is not equal to r10

    mov r9d, eax
    add r9d, -1
    mov r11, 0
    mov ecx, 10
    mov eax, 0
    lea r10, [phrase]
top:
    mul ecx
    mov byte r11b, [r10]
    inc r10
    sub r11, '0'
    add eax, r11d

    dec r9
    test r9,r9
    jnz top



    ; Exit
    mov eax, SYS_EXIT
    mov edx, SUCCESS
    syscall