import sys
import os

CHECKED = "[x]"
UNCHECKED = "[ ]"

if os.name == "nt":
    import msvcrt

    def getch():
        ch = msvcrt.getwch()
        if ch in ("\x00", "\xe0"):  # special key prefix
            return "\x1b" + msvcrt.getwch()
        return ch
else:
    import tty, termios

    def getch():
        fd = sys.stdin.fileno()
        old = termios.tcgetattr(fd)
        try:
            tty.setraw(fd)
            ch = sys.stdin.read(1)
            if ch == "\x1b":
                sys.stdin.read(1)  # [
                return "\x1b" + sys.stdin.read(1)
            return ch
        finally:
            termios.tcsetattr(fd, termios.TCSADRAIN, old)


def clear():
    os.system("cls" if os.name == "nt" else "clear")


def render(items, checked, cursor):
    clear()
    print("  Checklist  (↑↓ move, Space toggle, + add, A all, N none, q quit)\n")
    for i, item in enumerate(items):
        mark = CHECKED if checked[i] else UNCHECKED
        pointer = ">" if i == cursor else " "
        print(f"  {pointer} {mark} {item}")
    done = sum(checked)
    print(f"\n  {done}/{len(items)} done")


def prompt_new_task():
    print("\n  New task (Enter to confirm, Esc to cancel): ", end="", flush=True)
    buf = []
    while True:
        if os.name == "nt":
            ch = msvcrt.getwch()
        else:
            import tty, termios
            fd = sys.stdin.fileno()
            old = termios.tcgetattr(fd)
            try:
                tty.setraw(fd)
                ch = sys.stdin.read(1)
            finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old)

        if ch in ("\r", "\n"):
            print()
            return "".join(buf).strip() or None
        elif ch == "\x1b":
            print()
            return None
        elif ch in ("\x08", "\x7f"):  # backspace
            if buf:
                buf.pop()
                sys.stdout.write("\b \b")
                sys.stdout.flush()
        elif ch == "\x03":
            raise KeyboardInterrupt
        elif ch >= " ":
            buf.append(ch)
            sys.stdout.write(ch)
            sys.stdout.flush()


def run(items):
    items = list(items)
    checked = [False] * len(items)
    cursor = 0

    # Windows arrow key codes via msvcrt: up=H, down=P
    UP = "\x1bH" if os.name == "nt" else "\x1bA"
    DOWN = "\x1bP" if os.name == "nt" else "\x1bB"

    while True:
        render(items, checked, cursor)
        ch = getch()

        if ch == UP:
            cursor = (cursor - 1) % len(items)
        elif ch == DOWN:
            cursor = (cursor + 1) % len(items)
        elif ch == " ":
            checked[cursor] = not checked[cursor]
        elif ch in ("+", "i"):
            task = prompt_new_task()
            if task:
                items.append(task)
                checked.append(False)
                cursor = len(items) - 1
        elif ch == "A":
            checked = [True] * len(items)
        elif ch == "N":
            checked = [False] * len(items)
        elif ch in ("q", "\x03", "\x1b"):
            break

    clear()
    print("Final checklist:")
    for i, item in enumerate(items):
        mark = CHECKED if checked[i] else UNCHECKED
        print(f"  {mark} {item}")


DEFAULT_ITEMS = [
    "Buy groceries",
    "Write unit tests",
    "Review pull request",
    "Update documentation",
    "Deploy to staging",
]

if __name__ == "__main__":
    items = sys.argv[1:] if len(sys.argv) > 1 else DEFAULT_ITEMS
    run(items)