import re

from app.config import CHUNK_OVERLAP, CHUNK_SIZE


def chunk_text(text: str, size: int = CHUNK_SIZE, overlap: int = CHUNK_OVERLAP) -> list[str]:
    """按中文标点和段落边界切分，相邻切片保留一小段重叠。"""
    text = re.sub(r"\r\n?", "\n", text).replace("\x00", "").strip()
    if not text:
        return []
    if len(text) <= size:
        return [text]

    units = [unit for unit in re.split(r"(?<=[。！？；\n])", text) if unit]
    pieces: list[str] = []
    step = max(1, size - overlap)
    for unit in units:
        if len(unit) <= size:
            pieces.append(unit)
            continue
        for start in range(0, len(unit), step):
            pieces.append(unit[start : start + size])

    chunks: list[str] = []
    buffer = ""
    for piece in pieces:
        if not buffer:
            buffer = piece
            continue
        if len(buffer) + len(piece) <= size:
            buffer += piece
            continue
        chunks.append(buffer.strip())
        tail = buffer[-overlap:] if overlap else ""
        candidate = f"{tail}{piece}"
        buffer = candidate if len(candidate) <= size else piece
    if buffer.strip():
        chunks.append(buffer.strip())

    result: list[str] = []
    for chunk in chunks:
        chunk = re.sub(r"\n{3,}", "\n\n", chunk).strip()
        if len(chunk) < 8 or (result and chunk == result[-1]):
            continue
        result.append(chunk)
    return result or [text]