; Number Addition Challenge - DNRY
; ------------------------------------------------------
; Ask the user to input two values between 0-9999
; Accept two user inputs
; Add the two user inputs together into a memory address
; The program can end with the sum in the memory address
; Hint: remember that each digit is stored in ascii
; Updated for DNRY - use functions to limit repeating code
; ------------------------------------------------------
; Data section
value1: db 0x04 db [0x00,0x05]
value2: db 0x04 db [0x00,0x05]
string1: db "Please Enter Value 1"
string2: db "Please Enter Value 2"
null: db 0x0
sum: dw 0x0000
; Functions section
; Function to print a string
def print_message{
    mov AH, 0x13
    sub CX, BP
    int 0x10
    ret
}

def convert_ascii_raw {
    mov CL, byte [BX,1]                                     ; Put length of value 1 array into CX for looping
    mov SI, BX
    add SI, 0x02
    convert_to_decimal_1:
    lods byte                                               ; Load byte of ascii into AL
    sub AL, 0x30                                            ; Convert from ascii to raw number
    push CX                                                 ; Preserve CX for outerloop
    dec CX                                                  ; Counter needs to decrement to account for first number being in 0 position
    mov AH, 0x00                                            ; Zero out AH so it's empty for math
    mov DX, AX                                              ; Put AX into BX so we can use AL to hold the smaller mul number of 10
    cmp CX, 0x00                                            ; Check if CX is 0, if it we don't need to do exponent bc it's last digit
    je after_exp_1                                          ; If it is 0 jump over exponent
    exp_loop_1:
    mov AX, 10                                              ; Mov 10 into AL so we can multiply
    mul DX                                                  ; Multiply the contents of BX by 10
    mov DX, AX                                              ; The results of mul will be in AX, mov back to BX to mul again if needed
    loop exp_loop_1                                         ; Loop back and do exponent again if needed
    after_exp_1:
    pop CX                                                  ; Pop the initial CX back for the outer loop to count through remaining digits
    pop BX
    add word [BX], DX                                       ; Add the result to the total sum
    push BX
    loop convert_to_decimal_1                               ; Loop back for next digit if required
    pop AX
    ret
}
start:
; Print Message 1
mov CX, offset string2
mov BP, offset string1
call print_message
; Accept Value 1
mov AH, 0xa
mov DX, offset value1
int 0x21
; Print Message 2
mov CX, offset null
mov BP, offset string2
call print_message
; Accept Value 2
mov AH, 0xa
mov DX, offset value2
int 0x21
; Convert Value 1 contents from ascii to decimal
mov BL, offset value1
lea AX, word sum
push AX
call convert_ascii_raw
; Convert Value 2 contents from ascii to decimal, and add them to sum
mov BL, offset value2
lea AX, word sum
push AX
call convert_ascii_raw