"""Splitter 注册表 — 按文件扩展名自动选择分块器."""
from pathlib import Path
from src.core.splitters.base import Splitter

# 扩展名 → Splitter 类名映射
_DEFAULT_MAP: dict[str, str] = {
    ".md": "markdown",
    ".markdown": "markdown",
    ".txt": "text",
    ".pdf": "pdf",
    ".html": "html",
    ".htm": "html",
    ".epub": "epub",
}

# 所有支持的扩展名集合（供外部遍历文件使用）
SUPPORTED_SUFFIXES = frozenset(_DEFAULT_MAP.keys())

# 用户可注册自定义 Splitter
_custom_registry: dict[str, type[Splitter]] = {}


def register_splitter(ext: str, splitter_cls: type[Splitter]) -> None:
    """注册自定义 Splitter 类.

    注意: 此函数非线程安全，请在程序启动时调用（单线程阶段）。
    运行时动态注册需自行加锁。
    """
    ext = ext.lower() if ext.startswith(".") else f".{ext}"
    _custom_registry[ext] = splitter_cls


def get_splitter(
    file_path: str,
    max_size: int = 1000,
    overlap: int = 100,
) -> Splitter:
    """根据文件扩展名自动选择 Splitter，未匹配回退到 TextSplitter.

    Args:
        file_path: 文件路径（用于提取扩展名）
        max_size: 分块最大字符数
        overlap: 相邻块重叠字符数

    Returns:
        对应格式的 Splitter 实例
    """
    ext = Path(file_path).suffix.lower()

    # 优先查用户自定义注册
    if ext in _custom_registry:
        return _custom_registry[ext](max_size=max_size, overlap=overlap)

    kind = _DEFAULT_MAP.get(ext, "text")

    if kind == "markdown":
        from src.core.splitters.markdown import MarkdownSplitter
        return MarkdownSplitter(max_size=max_size, overlap=overlap)

    if kind == "text":
        from src.core.splitters.text import TextSplitter
        return TextSplitter(max_size=max_size, overlap=overlap)

    if kind == "pdf":
        from src.core.splitters.pdf import PDFSplitter
        return PDFSplitter(max_size=max_size, overlap=overlap)

    if kind == "html":
        from src.core.splitters.html import HTMLSplitter
        return HTMLSplitter(max_size=max_size, overlap=overlap)

    if kind == "epub":
        from src.core.splitters.epub import EPUBSplitter
        return EPUBSplitter(max_size=max_size, overlap=overlap)

    # 回退
    from src.core.splitters.text import TextSplitter
    return TextSplitter(max_size=max_size, overlap=overlap)