from __future__ import annotations

import re

TEXT_CHUNK_LIMIT = 10000

_MD_IMAGE_RE = re.compile(r"!\[.*?\]\([^)]+\)")
_MD_LINK_RE = re.compile(r"\[([^\]]+)\]\(([^)]+)\)")
_MD_BOLD_RE = re.compile(r"\*\*(.+?)\*\*")
_MD_ITALIC_RE = re.compile(r"(?<!\w)[*_](.+?)[*_](?!\w)")
_MD_CODE_RE = re.compile(r"`([^`]+)`")
_MD_CODE_BLOCK_RE = re.compile(r"```[\s\S]*?```")


def markdown_to_plain_text(md_text: str) -> str:
    text = md_text
    text = _MD_IMAGE_RE.sub("[图片]", text)
    text = _MD_LINK_RE.sub(r"\1 (\2)", text)
    text = _MD_BOLD_RE.sub(r"\1", text)
    text = _MD_ITALIC_RE.sub(r"\1", text)
    text = _MD_CODE_BLOCK_RE.sub("", text)
    text = _MD_CODE_RE.sub(r"\1", text)

    text = text.replace("\r\n", "\n").replace("\r", "\n")
    text = re.sub(r"\n{3,}", "\n\n", text)

    return text.strip()


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

    chunks: list[str] = []
    paragraphs = text.split("\n\n")
    current = ""

    for para in paragraphs:
        if len(current) + len(para) + 2 <= limit:
            current = (current + "\n\n" + para) if current else para
        else:
            if current:
                chunks.append(current)
            if len(para) > limit:
                for i in range(0, len(para), limit):
                    chunks.append(para[i : i + limit])
                current = ""
            else:
                current = para

    if current:
        chunks.append(current)

    return chunks if chunks else [text]


def markdown_to_native(md_text: str) -> str:
    return markdown_to_plain_text(md_text)


def native_to_markdown(native_content: str) -> str:
    return native_content