"""白板服务（文本记事本）：CRUD + 文本更新 + 清空。

不持有 WebSocket 连接状态（那是 hub 的职责）；删除白板时通过可选的 hub 回调
通知 hub 踢出该 board 的所有在线连接，由 controller 在装配时注入，避免 service -> hub
的硬依赖（保持低耦合）。
"""

from __future__ import annotations

import re
from typing import TYPE_CHECKING

from fastapi import HTTPException

from ..config import get_settings
from ..dao.whiteboard_dao import WhiteboardDAO
from ..schemas.whiteboard import WhiteboardListItem, WhiteboardOut

if TYPE_CHECKING:  # 避免运行时循环导入
    from .whiteboard_hub import WhiteboardHub

# board_id 合法字符集：字母数字下划线短横线
_BOARD_ID_RE = re.compile(r"^[a-zA-Z0-9_-]+$")


class WhiteboardService:
    def __init__(self, dao: WhiteboardDAO, hub: "WhiteboardHub | None" = None) -> None:
        self.dao = dao
        self.hub = hub
        cfg = get_settings().whiteboard
        self.max_board_id_length = cfg.max_board_id_length
        self.list_limit = cfg.list_limit
        # 文本内容长度上限（防滥用）
        self.max_content_length = 256 * 1024

    # ---------------- 校验 ----------------

    def validate_board_id(self, board_id: str) -> None:
        """非法 board_id 直接 400（防路径穿越/注入）。"""
        if (
            not board_id
            or len(board_id) > self.max_board_id_length
            or not _BOARD_ID_RE.match(board_id)
        ):
            raise HTTPException(400, "board_id 非法（仅允许字母数字下划线短横线，1-64 字符）")

    def validate_content(self, content: str) -> None:
        if not isinstance(content, str):
            raise HTTPException(400, "content 必须是字符串")
        if len(content) > self.max_content_length:
            raise HTTPException(
                413,
                f"文本过长（{len(content)} > {self.max_content_length}），请缩减内容",
            )

    # ---------------- 读 ----------------

    def get_or_create(self, board_id: str) -> WhiteboardOut:
        self.validate_board_id(board_id)
        board = self.dao.get_or_create(board_id)
        return WhiteboardOut.model_validate(board)

    def list_all(self, limit: int = 100, offset: int = 0) -> tuple[int, list[WhiteboardListItem]]:
        limit = min(max(limit, 0), self.list_limit) or self.list_limit
        offset = max(offset, 0)
        total = self.dao.count()
        rows = self.dao.list_all(limit=limit, offset=offset)
        items = [WhiteboardListItem.model_validate(r) for r in rows]
        return total, items

    # ---------------- 写 ----------------

    def update_content(self, board_id: str, content: str) -> WhiteboardOut:
        """整体替换文本内容（客户端 debounce 后发完整文本）。"""
        self.validate_board_id(board_id)
        self.validate_content(content)
        board = self.dao.update_content(board_id, content)
        if board is None:
            raise HTTPException(404, "白板不存在")
        return WhiteboardOut.model_validate(board)

    def clear(self, board_id: str) -> WhiteboardOut:
        """清空白板（内容置空），edit_count 仍自增以记录这次修改。"""
        return self.update_content(board_id, "")

    def delete(self, board_id: str) -> bool:
        """删除白板；同时通知 hub 踢出该 board 的所有在线连接。"""
        self.validate_board_id(board_id)
        ok = self.dao.delete(board_id)
        if ok and self.hub is not None:
            # hub.close_board 是 async，但删除走 REST 同步路径；安排到事件循环里执行
            import asyncio

            try:
                loop = asyncio.get_running_loop()
                loop.create_task(self.hub.close_board(board_id))
            except RuntimeError:
                # 无运行中事件循环（如脚本调用）：同步调用会报错，忽略即可
                pass
        return ok