main:
    mov si, welcome 
    call printf 
     
    mloop: 
        mov si, prompt          ; The prompt is beginning 
        call printf

        mov di, input
        call getinput

        mov si, input
        mov di, cmd_hello       ; Command: hello
        call strcmp 
        jz .hello

        mov si, input
        mov di, cmd_help        ; Command: help
        call strcmp 
        jz .help

        mov si, input
        mov di, cmd_stats       ; Command: stats
        call strcmp 
        jz .stats

        mov si, input
        mov di, err_cmd         ; Command entered is invalid
        call printf 
        jmp mloop               ; Infinity loop 
         
        .hello: 
            mov si, msg_hello 
            call printf 
            jmp mloop 
         
        .help: 
            mov si, msg_help 
            call printf 
            jmp mloop 
             
        .stats: 
            mov si, ax 
            call printf 
            jmp mloop 

; === Functions === 
printf:
    mov ah, 0eh 
    mov bh, 99h 

    .nextchar: 
        lodsb 
        or al, al 
        jz .return 
        int 10h 
        jmp .nextchar 

    .return: 
        ret 

getinput: 
    xor cl, cl 
     
    .loop: 
        mov ah, 00h
        int 16h         ; Key press wait

        cmp al, 08h     ; Backspace key 
        je .backspace   ; Handle 
         
        cmp al, 0dh     ; Enter key 
        je .enter       ; Handle 
         
        cmp cl, 3fh     ; Inputted 63 characters 
        je .loop        ; Only backspace and enter are accepted 

        mov ah, 0eh    
        int 10h 
         
        stosb 
        inc cl 
        jmp .loop 
         
    .backspace: 
        cmp cl, 0       ; Begin of the input 
        je .loop        ; Ignore 
         
        dec di 
        mov byte[di], 0 ; Delete character 
        dec cl          ; Decrementing the string counter 
         
        mov ah, 0eh 
        mov al, 08h 
        int 10h         ; Print the backspace 
         
        mov al, ' ' 
        int 10h         ; Blank character 
         
        mov al, 08h 
        int 10h         ; Backspace one more time 
         
        jmp .loop       ; Goes back to the loop 
         
    .enter: 
        mov al, 0       ; Null terminator 
        stosb 
         
        mov ah, 0eh 
         
        mov al, 0dh     ; Enter character 
        int 10h 
         
        mov al, 0ah     ; Newline character 
        int 10h 
         
        ret 
         
strcmp:
        push cx ; I'm taking advantage of CL counter used in getinput.
        rep cmpsb
        pop cx
        ;ZF == 1 == equal
        ret 

welcome db "Welcome To The Second DOS Shell For Your DOS ", 0dh, 0ah, 0ah, 0 
prompt db ">", 0

input rb 255


; ==== Commands ========================== 
cmd_help db "help", 0
msg_help db "Valid Commands: help - hello", 0dh, 0ah, 0

cmd_hello db "hello", 0
msg_hello db "Hi all!", 0dh, 0ah, 0

cmd_stats db "stats", 0

err_cmd db "The command you entered doesn't exist!", 0dh, 0ah, 0