from __future__ import annotations

import re


def markdown_to_viber(md_text: str) -> str:
    text = md_text

    text = re.sub(r"\*\*(.+?)\*\*", r"<b>\1</b>", text)
    text = re.sub(r"__([^_]+)__", r"<b>\1</b>", text)
    text = re.sub(r"\*([^*\n]+)\*", r"<i>\1</i>", text)
    text = re.sub(r"(?<!\w)_([^_\n]+)_(?!\w)", r"<i>\1</i>", text)
    text = re.sub(r"`([^`\n]+)`", r"<font color='#888888'>\1</font>", text)
    text = re.sub(r"~~(.+?)~~", r"", text)
    text = re.sub(r"!\[[^\]]*\]\([^)]*\)", "", text)
    text = re.sub(r"\[([^\]]+)\]\(([^)]+)\)", r"<a href='\2'>\1</a>", text)
    text = re.sub(r"^#{1,6}\s+(.+)$", r"<b>\1</b>", text, flags=re.MULTILINE)
    text = re.sub(r"^>\s+(.+)$", r"<i>\1</i>", text, flags=re.MULTILINE)
    text = re.sub(r"^-{3,}$", "────────────", text, flags=re.MULTILINE)
    text = re.sub(r"^[*-]\s+(.+)$", r"• \1", text, flags=re.MULTILINE)

    return text.strip()


def escape_viber_html(text: str) -> str:
    text = text.replace("&", "&amp;")
    text = text.replace("<", "&lt;")
    text = text.replace(">", "&gt;")
    return text


def chunk_text(text: str, limit: int = 7000) -> list[str]:
    if len(text) <= limit:
        return [text]

    chunks: list[str] = []
    while len(text) > limit:
        split_point = text.rfind("\n", 0, limit)
        if split_point == -1 or split_point < limit // 2:
            split_point = text.rfind(". ", 0, limit)
        if split_point == -1 or split_point < limit // 2:
            split_point = text.rfind(" ", 0, limit)
        if split_point == -1 or split_point < limit // 2:
            split_point = limit

        chunks.append(text[:split_point].strip())
        text = text[split_point:].strip()

    if text:
        chunks.append(text)
    return chunks