; 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
    mov r11, rdx
    b.z b[r11], 0, .no_argv1
    inc r11

.next_space:
    mov r10, b[r11]
    b.z r10, 0, .no_argv1

    ; skip spaces
    cmp r10, ' '
    inc.z r11
    jmp.z .next_space

    mov q[argv1pos], r11

    ; fallthrough

.no_argv1:
    ; 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_cls = "cls"
    mov ax0, argv0
    mov ax1, .builtin_cls
    call strcmp
    b.z rax, 0, .handle_CLS

.builtin_date = "date"
    mov ax0, argv0
    mov ax1, .builtin_date
    call strcmp
    b.z rax, 0, .handle_DATE

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

.builtin_echo = "echo"
    mov ax0, argv0
    mov ax1, .builtin_echo
    call strcmp
    b.z rax, 0, .handle_ECHO

.builtin_exit = "exit"
    mov ax0, argv0
    mov ax1, .builtin_exit
    call strcmp
    b.z rax, 0, .handle_EXIT

.builtin_help = "help"
    mov ax0, argv0
    mov ax1, .builtin_help
    call strcmp
    b.z rax, 0, .handle_HELP

.builtin_print = "print"
    mov ax0, argv0
    mov ax1, .builtin_print
    call strcmp
    b.z rax, 0, .handle_PRINT

.builtin_time = "time"
    mov ax0, argv0
    mov ax1, .builtin_time
    call strcmp
    b.z rax, 0, .handle_TIME

.builtin_ver = "ver"
    mov ax0, argv0
    mov ax1, .builtin_ver
    call strcmp
    b.z rax, 0, .handle_VER

    ; 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_CLS:
    prn 0xC15000AF
    jmp .print_prompt

.handle_DATE:
    time ax0
    call GetTimeUTC

    push b[rax+3]
    mov rcx, b[rax+4]
    inc rcx
    push rcx
    push w[rax+6]

    mov ax0, .datefmt
    call printf

    add rsp, 8*5

    jmp .print_prompt

.datefmt = "%d/%d/%d\n"

.handle_DIR:
    call builtins.dir
    jmp .print_prompt

.handle_ECHO:
    mov rdx, q[argv1pos]
    b.z rdx, 0, .echo.end

    mov rcx, argbuf.size
    prns.rep.nz rdx

.echo.end:
    prn 10
    jmp .print_prompt

.handle_EXIT:
    mov rax, Sys.Shutdown
    trap 0

.handle_PRINT:
    jmp .print_prompt

.handle_TIME:
    time ax0
    call GetTimeUTC

    push b[rax]
    push b[rax+1]
    push b[rax+2]
    mov ax0, .timefmt
    call printf
    add rsp, 3*8

    jmp .print_prompt

.timefmt = "%d:%d:%d\n"

.handle_VER:
    mov rcx, STRLEN_MAX
    mov rdx, cmd.versionstr
    prns.rep.nz rdx
    prn 10

    jmp .print_prompt

.handle_HELP:
    mov rcx, STRLEN_MAX

    mov rdx, .helpmsg
    prns.rep.nz rdx
    mov rdx, .helpmsg.cls
    prns.rep.nz rdx
    mov rdx, .helpmsg.date
    prns.rep.nz rdx
    mov rdx, .helpmsg.dir
    prns.rep.nz rdx
    mov rdx, .helpmsg.echo
    prns.rep.nz rdx
    mov rdx, .helpmsg.exit
    prns.rep.nz rdx
    mov rdx, .helpmsg.help
    prns.rep.nz rdx
    mov rdx, .helpmsg.print
    prns.rep.nz rdx
    mov rdx, .helpmsg.time
    prns.rep.nz rdx
    mov rdx, .helpmsg.ver
    prns.rep.nz rdx

    jmp .print_prompt

.helpmsg       = "The following commands are built-in:\n"
.helpmsg.cls   = "    CLS        Clear screen\n"
.helpmsg.date  = "    DATE       Display current date\n"
.helpmsg.dir   = "    DIR        Print contents of current directory\n"
.helpmsg.echo  = "    ECHO       Write arguments to standard output\n"
.helpmsg.exit  = "    EXIT       Initiate machine shutdown\n"
.helpmsg.help  = "    HELP       Display these messages\n"
.helpmsg.print = "    PRINT      Display contents of text file\n"
.helpmsg.time  = "    TIME       Display current time of day\n"
.helpmsg.ver   = "    VER        Display current COMMAND.COM and DOS kernel versions\n"