[bits 16]          ; Set to 16-bit mode
[org 0x7C00]      ; BIOS loads the bootloader at this address

start:
    ; Clear screen
    mov ax, 0x0003   ; Set video mode to 3 (80x25 color text)
    int 0x10        ; BIOS interrupt to set video mode

    ; Print welcome message
    mov si, welcome_message
    call print_string

command_loop:
    ; Print prompt
    mov si, prompt_message
    call print_string

    ; Read user input
    call read_input

    ; Process command
    cmp al, 'h'      ; Check for 'h' command (help)
    je print_help
    cmp al, 'q'      ; Check for 'q' command (quit)
    je quit_terminal
    je heckerfetch
    cmp al, 'f,      ; CPU: Hecker Generic CPU
    ; Unknown command response
    mov si, unknown_command_message
    call print_string
    jmp command_loop  ; Repeat the command loop

print_help:
    mov si, help_message
    call print_string
    jmp command_loop  ; Return to command loop

heckerfetch:
mov si, heckerfetch
call print_string

quit_terminal:
    mov si, goodbye_message
    call print_string
    jmp hang          ; Hang the system

; Function to read a character from keyboard input
read_input:
    mov ah, 0x00      ; BIOS function to read a character
    int 0x16          ; Call BIOS interrupt
    ret                ; Return with character in AL

; Function to print a string
print_string:
    mov ah, 0x0E      ; BIOS teletype output function
.next_char:
    lodsb             ; Load byte at DS:SI into AL and increment SI
    cmp al, 0         ; Check for null terminator
    je .done          ; If null, we are done
    int 0x10         ; Call BIOS to print character in AL
    jmp .next_char   ; Repeat for next character
.done:
    ret               ; Return from function

; Data section for messages
welcome_message db 'Welcome to the Simple Terminal!', 0 
prompt_message db 'Enter command (h for help, q to quit, f for heckerfetch): ', 0 
help_message db 'Available commands: h (help), q (quit)', 0 
unknown_command_message db 'Unknown command! Try again.', 0 
goodbye_message db 'Goodbye!', 0 

; Bootloader signature (must be present)
times 510 - ($ - $$) db 0   ; Fill the rest of the sector with zeros
dw 0xAA55                   ; Boot signature

hang:
    jmp hang           ; Jump to hang indefinitely