"""
asset:// 与旧占位符清理。

迁移与渲染共用：从正文移除 {{IMAGE:...}} / {{{{IMAGE:...}}}}。
"""

import re
from typing import Callable

_PLACEHOLDER_RE = re.compile(
    r"\{\{\{\{IMAGE:(.*?)\}\}\}\}|\{\{IMAGE:(.*?)\}\}",
    re.DOTALL,
)

_ASSET_REF_RE = re.compile(r"!\[([^\]]*)\]\(asset://([a-zA-Z0-9_-]+)\)")


def strip_legacy_image_placeholders(text: str | None) -> str:
    """移除正文中的旧 IMAGE 占位符，保留其余 markdown。"""
    if not text:
        return ""
    return _PLACEHOLDER_RE.sub("", text).strip()


def parse_asset_refs(markdown: str) -> list[tuple[int, int, str, str]]:
    refs = []
    for m in _ASSET_REF_RE.finditer(markdown or ""):
        refs.append((m.start(), m.end(), m.group(1) or "", m.group(2) or ""))
    return refs


def collect_asset_ids_from_markdown(markdown: str) -> list[str]:
    return [m.group(2) for m in _ASSET_REF_RE.finditer(markdown or "") if m.group(2)]


def collect_asset_ids_for_chapter(chapter) -> set[str]:
    """章节正文（canonical + 各 section）与 cover_asset_id 中出现的 asset id。"""
    ids: set[str] = set()
    md = getattr(chapter, "canonical_markdown", None) or ""
    ids.update(collect_asset_ids_from_markdown(md))
    for sec in getattr(chapter, "sections", None) or []:
        ids.update(collect_asset_ids_from_markdown(getattr(sec, "content", None) or ""))
    cid = getattr(chapter, "cover_asset_id", None)
    if cid:
        ids.add(str(cid))
    return ids


def collect_asset_ids_for_chapters(chapters: list) -> set[str]:
    combined: set[str] = set()
    for ch in chapters or []:
        combined |= collect_asset_ids_for_chapter(ch)
    return combined


def split_markdown_by_asset_refs(
    markdown: str,
    resolve_asset: Callable[[str], str | None],
) -> list[dict]:
    blocks: list[dict] = []
    refs = parse_asset_refs(markdown or "")
    if not refs:
        text = (markdown or "").strip()
        if text:
            blocks.append({"type": "text", "value": text})
        return blocks

    pos = 0
    for start, end, caption, asset_id in refs:
        if start > pos:
            text = markdown[pos:start].strip()
            if text:
                blocks.append({"type": "text", "value": text})
        url = resolve_asset(asset_id) if asset_id else None
        if url:
            blocks.append({"type": "image", "url": url, "caption": caption})
        pos = end

    if pos < len(markdown or ""):
        text = markdown[pos:].strip()
        if text:
            blocks.append({"type": "text", "value": text})

    return blocks


def resolve_asset_refs_in_markdown(
    markdown: str,
    resolve_asset: Callable[[str], str | None],
) -> str:
    if not markdown or not resolve_asset:
        return markdown or ""

    def repl(m):
        caption, asset_id = m.group(1) or "", m.group(2) or ""
        url = resolve_asset(asset_id) if asset_id else None
        if url:
            return f"![{caption}]({url})"
        return m.group(0)

    return _ASSET_REF_RE.sub(repl, markdown)