import sys
import tty
import termios


def syntax_highlight(text, sel_start=None, sel_end=None):
    if sel_start is not None and sel_end is not None and sel_start != sel_end:
        s = min(sel_start, sel_end)
        e = max(sel_start, sel_end)
        result = text[:s] + u"\u001b[7m" + text[s:e] + u"\u001b[0m" + text[e:]
        stripped = result
        return stripped
    stripped = text.rstrip()
    trailing = len(text) - len(stripped)
    if trailing > 0:
        return stripped + u"\u001b[41m" + " " * trailing + u"\u001b[0m"
    return text


def word_boundary_left(text, index):
    i = index
    while i > 0 and text[i - 1] == " ":
        i -= 1
    while i > 0 and text[i - 1] != " ":
        i -= 1
    return i


def word_boundary_right(text, index):
    i = index
    while i < len(text) and text[i] == " ":
        i += 1
    while i < len(text) and text[i] != " ":
        i += 1
    return i


def render(prompt, prompt_len, text, index, sel_anchor):
    sys.stdout.write(u"\u001b[1000D")
    sys.stdout.write(u"\u001b[0K")
    sys.stdout.write(prompt)
    sys.stdout.write(syntax_highlight(text, sel_anchor, index))
    sys.stdout.write(u"\u001b[1000D")
    target = prompt_len + index
    if target > 0:
        sys.stdout.write(u"\u001b[" + str(target) + "C")
    sys.stdout.flush()


def read_char():
    return ord(sys.stdin.read(1))


def command_line():
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    prompt = u"\u001b[32;1m>>> \u001b[0m"
    prompt_len = 4

    try:
        tty.setraw(fd)

        while True:
            text = ""
            index = 0
            sel_anchor = None

            sys.stdout.write(prompt)
            sys.stdout.flush()

            while True:
                char = read_char()

                if char == 3:
                    sys.stdout.write(u"\r\n")
                    sys.stdout.flush()
                    return

                elif char == 4:
                    if not text:
                        sys.stdout.write(u"\r\n")
                        sys.stdout.flush()
                        return

                elif char == 1:
                    index = 0
                    sel_anchor = None

                elif char == 5:
                    index = len(text)
                    sel_anchor = None

                elif char == 11:
                    text = text[:index]
                    sel_anchor = None

                elif char == 21:
                    text = text[index:]
                    index = 0
                    sel_anchor = None

                elif char == 23:
                    new_index = word_boundary_left(text, index)
                    text = text[:new_index] + text[index:]
                    index = new_index
                    sel_anchor = None

                elif 32 <= char <= 126:
                    if sel_anchor is not None:
                        s = min(sel_anchor, index)
                        e = max(sel_anchor, index)
                        text = text[:s] + chr(char) + text[e:]
                        index = s + 1
                        sel_anchor = None
                    else:
                        text = text[:index] + chr(char) + text[index:]
                        index += 1

                elif char in {10, 13}:
                    sys.stdout.write(u"\u001b[1000D")
                    sys.stdout.write(u"\u001b[0K")
                    sys.stdout.write(prompt + text + u"\r\n")
                    sys.stdout.write(u"\u001b[36m=>\u001b[0m " + text + u"\r\n")
                    sys.stdout.flush()
                    sel_anchor = None
                    break

                elif char == 127:
                    if sel_anchor is not None:
                        s = min(sel_anchor, index)
                        e = max(sel_anchor, index)
                        text = text[:s] + text[e:]
                        index = s
                        sel_anchor = None
                    elif index > 0:
                        text = text[:index - 1] + text[index:]
                        index -= 1

                elif char == 27:
                    next1 = read_char()

                    if next1 == 91:
                        next2 = read_char()

                        if next2 == 68:
                            index = max(0, index - 1)
                            sel_anchor = None

                        elif next2 == 67:
                            index = min(len(text), index + 1)
                            sel_anchor = None

                        elif next2 == 65:
                            pass

                        elif next2 == 66:
                            pass

                        elif next2 == 72:
                            index = 0
                            sel_anchor = None

                        elif next2 == 70:
                            index = len(text)
                            sel_anchor = None

                        elif next2 == 51:
                            next3 = read_char()
                            if next3 == 126:
                                if sel_anchor is not None:
                                    s = min(sel_anchor, index)
                                    e = max(sel_anchor, index)
                                    text = text[:s] + text[e:]
                                    index = s
                                    sel_anchor = None
                                elif index < len(text):
                                    text = text[:index] + text[index + 1:]

                        elif next2 == 52:
                            next3 = read_char()
                            if next3 == 126:
                                index = len(text)
                                sel_anchor = None

                        elif next2 == 49:
                            next3 = read_char()
                            if next3 == 126:
                                index = 0
                                sel_anchor = None
                            elif next3 == 59:
                                next4 = read_char()
                                next5 = read_char()
                                if next4 == 50:
                                    if next5 == 68:
                                        if sel_anchor is None:
                                            sel_anchor = index
                                        index = max(0, index - 1)
                                    elif next5 == 67:
                                        if sel_anchor is None:
                                            sel_anchor = index
                                        index = min(len(text), index + 1)
                                    elif next5 == 72:
                                        if sel_anchor is None:
                                            sel_anchor = index
                                        index = 0
                                    elif next5 == 70:
                                        if sel_anchor is None:
                                            sel_anchor = index
                                        index = len(text)
                                elif next4 == 53:
                                    if next5 == 68:
                                        index = word_boundary_left(text, index)
                                        sel_anchor = None
                                    elif next5 == 67:
                                        index = word_boundary_right(text, index)
                                        sel_anchor = None

                    elif next1 == 98:
                        index = word_boundary_left(text, index)
                        sel_anchor = None

                    elif next1 == 102:
                        index = word_boundary_right(text, index)
                        sel_anchor = None

                    elif next1 == 100:
                        new_index = word_boundary_right(text, index)
                        text = text[:index] + text[new_index:]
                        sel_anchor = None

                    elif next1 == 127:
                        new_index = word_boundary_left(text, index)
                        text = text[:new_index] + text[index:]
                        index = new_index
                        sel_anchor = None

                    elif next1 == 98:
                        index = word_boundary_left(text, index)

                render(prompt, prompt_len, text, index, sel_anchor)

    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        sys.stdout.write(u"\u001b[0m\r\n")
        sys.stdout.flush()


command_line()