import struct
import re


# Unicode surrogate handling from
# https://github.com/LonamiWebs/Telethon/blob/master/telethon/extensions/markdown.py
def add_surrogates(text):
    if text is None:
        return None
    return "".join("".join(chr(y) for y in struct.unpack("<HH", x.encode("utf-16-le")))
                   if (0x10000 <= ord(x) <= 0x10FFFF) else x for x in text)


def remove_surrogates(text):
    if text is None:
        return None
    return text.encode("utf-16", "surrogatepass").decode("utf-16")


def trim_reply_fallback_text(text):
    if not text.startswith("> ") or "\n" not in text:
        return text
    lines = text.split("\n")
    while len(lines) > 0 and lines[0].startswith("> "):
        lines.pop(0)
    return "\n".join(lines)


HTML_REPLY_FALLBACK_REGEX = re.compile(r"^<blockquote data-mx-reply>[\s\S]+?</blockquote>")


def trim_reply_fallback_html(html):
    return HTML_REPLY_FALLBACK_REGEX.sub("", html)