%include "CONSTANTS.h"

MAX_LEN equ 100

section .data
    prompt: db `Enter some text, up to %d characters `,0
    endl: db `\n`,0
    debugFmt1: db `\n%d characters were input\n`,0
    debugFmt2: db `\n The string is "%s"\n`,0
    debugFmt3: db `\n phrase[%d] = '%c'\n`,0

section .bss
    phrase: resb MAX_LEN+1 

section .text

global main
main:
 
    ; prompt for input
    mov rdi, prompt
    mov rsi, MAX_LEN
    call CallPrintf

    ; flush the buffer
    mov rdi, 0
    call Flush

    ; call read to read up to MAX_LEN into the buffer
    ; this will read until the end of line, or MAX_LEN is read
    ; and will store it into buffer, inclding the newline
    mov rax, SYS_READ
    mov rdi, STDIN
    mov rsi, phrase
    mov rdx, MAX_LEN
    syscall

    ; r12 will hold the length of the string
    mov r12, rax
    dec r12
   
    ; print the number of bytes input 
    mov rdi, debugFmt1
    mov rsi, rax
    call CallPrintf

    mov byte [phrase + r12], 0
    ; print the string input
    mov rdi, debugFmt2
    mov rsi, phrase
    call CallPrintf

    ; let r13 be i
    ; i = 0
    mov r13, 0

TopOfLoop:  
    ; while i < size
    cmp r13, r12
    je OutOfLoop

    ;   if islower(phrase[i] )
    ; rdx = phrase[i]
    mov rdx, 0
    mov dl, byte [phrase + r13]

    ; is it less than 'a', if so, escape the if
    cmp rdx, 61h
    jl  PastIf

    ; is it more than 'z', if so escape
    cmp rdx, 7ah
    jg  PastIf

    ; it must be between a and z, so subtract 20h
    ;  the difference between a and A

    ;      phrase[i] = toupper(phrase[i])
    sub rdx, 20h
    mov byte[phrase+r13], dl

PastIf:
    ;   ++i;
    inc r13

    jmp TopOfLoop

OutOfLoop:

    mov byte [phrase + r12], 0
    ; print the string input
    mov rdi, debugFmt2
    mov rsi, phrase
    call CallPrintf
   
    jmp Exit