; The OS/K Team licenses this file to you under the MIT license.
; See the LICENSE file in the project root for more information.

argbuf.size := 256
argbuf = [argbuf.size]
argv0 = [argbuf.size]
argv1pos = 0

stdin_echoing = 1

ps1 = "C:\\> "

main:

.print_prompt:
    mov rcx, STRLEN_MAX
    mov rdx, ps1
    prns.rep.nz rdx

    ; empty argbuf
    mov rcx, argbuf.size
    mov rdx, argbuf
    stosb.rep rdx, 0

    ; iterator through argbuf
    xor rcx, rcx

.input_loop:
    pause
    pause

    ; Fill .buf with user input
    scan rax
    b.z rax, 0, .input_loop

    ; backspace character?
    b.nz rax, 8, .handle_input

    ; anything to delete?
    b.z rcx, 0, .input_loop

    ; delete it
    dec rcx
    add rdx, rcx, argbuf
    mov b[rdx], 0

    ; update screen
    cmp b[stdin_echoing], 1
    prn.z 8

    jmp .input_loop

.handle_input:
    cmp b[stdin_echoing], 1
    prn.z rax
    b.z rax, 10, .extract_argv0

    ; when max line length is reached,
    ; force a newline
    b.z rcx, argbuf.size, .extract_argv0

    ; add character to buffer and increase iterator (rcx)
    add rdx, rcx, argbuf
    mov b[rdx], rax
    inc rcx

    ; another one
    jmp .input_loop

.extract_argv0:

    ; did we read anything at all?
    ; if not, just go back to waiting input
    b.z rcx, 0, .print_prompt

    ; find first whitespace or null-terminator
    mov rcx, argbuf.size
    mov rdx, argbuf
    scasb.rep.nz rdx, ' '

    ; argv1 exists? if so, save its position
    ; (to do)

    ; empty argv0
    mov rcx, argbuf.size
    mov rax, argv0
    stosb.rep rax, 0

    ; extract argv0
    sub rcx, rdx, argbuf
    mov rdx, argbuf
    mov rax, argv0
    movsb.rep rax, rdx

.detect_builtin:

.builtin_dir = "dir"

    mov ax0, argv0
    mov ax1, .builtin_dir
    call strcmp
    b.z rax, 0, .handle_DIR

    ; fallthrough

.exec_prog:

    ; fallthrough

.not_found:
    mov rcx, STRLEN_MAX
    mov rdx, argv0
    prns.rep.nz rdx

    mov rdx, .errmsg
    prns.rep.nz rdx

    jmp .print_prompt

.errmsg = " : command not found\n"

;
; call builtins
;
.handle_DIR:
    call builtins.dir
    jmp .print_prompt