import math
import uuid
from dataclasses import dataclass, field
from datetime import datetime, timedelta
from threading import Lock
from typing import (
    Any,
    Dict,
    Generic,
    List,
    Optional,
    Protocol,
    Sequence,
    Tuple,
    TypeVar,
    Union,
)

from app.schemas.message import Message
from app.schemas.notification import ChannelCapabilityManager
from app.schemas.types import NotificationChannel


class _UserInteractionEntry(Protocol):
    """声明按用户维护的交互状态所需的最小字段。"""

    request_id: str
    user_id: str
    created_at: datetime


InteractionEntryT = TypeVar("InteractionEntryT", bound=_UserInteractionEntry)


class _ExpiringUserInteractionStore(Generic[InteractionEntryT]):
    """提供单用户单会话的过期状态存储和双向索引。"""

    _ttl = timedelta(hours=24)

    def __init__(self) -> None:
        """初始化按请求 ID、用户 ID 查询的线程安全状态表。"""
        self._by_id: Dict[str, InteractionEntryT] = {}
        self._by_user: Dict[str, str] = {}
        self._lock = Lock()

    def _cleanup_locked(self) -> None:
        """在持锁状态下移除超过统一保留时间的交互状态。"""
        expire_before = datetime.now() - self._ttl
        expired = [
            request_id
            for request_id, request in self._by_id.items()
            if request.created_at < expire_before
        ]
        for request_id in expired:
            request = self._by_id.pop(request_id, None)
            if request:
                self._by_user.pop(str(request.user_id), None)

    def _replace_locked(self, request: InteractionEntryT) -> None:
        """在持锁状态下替换用户旧状态并写入新的双向索引。"""
        user_key = str(request.user_id)
        old_request_id = self._by_user.get(user_key)
        if old_request_id:
            self._by_id.pop(old_request_id, None)
        self._by_id[request.request_id] = request
        self._by_user[user_key] = request.request_id

    def get_by_user(self, user_id: Union[str, int]) -> Optional[InteractionEntryT]:
        """按用户返回当前仍有效的交互状态。"""
        with self._lock:
            self._cleanup_locked()
            request_id = self._by_user.get(str(user_id))
            if not request_id:
                return None
            return self._by_id.get(request_id)

    def get_by_id(
            self, request_id: str, user_id: Union[str, int]
    ) -> Optional[InteractionEntryT]:
        """按请求 ID 查询状态，并校验请求属于当前用户。"""
        with self._lock:
            self._cleanup_locked()
            request = self._by_id.get(request_id)
            if not request or str(request.user_id) != str(user_id):
                return None
            return request

    def remove(self, request_id: str) -> None:
        """删除指定交互状态及其用户索引。"""
        with self._lock:
            request = self._by_id.pop(request_id, None)
            if request:
                self._by_user.pop(str(request.user_id), None)

    def clear(self) -> None:
        """清空全部交互状态，供生命周期结束和测试场景使用。"""
        with self._lock:
            self._by_id.clear()
            self._by_user.clear()


@dataclass
class PendingSlashInteraction:
    """
    通用 slash 命令交互上下文。
    """

    request_id: str
    user_id: str
    channel: Optional[NotificationChannel]
    source: Optional[str]
    username: Optional[str]
    command: str
    page: int = 0
    awaiting_input: Optional[str] = None
    created_at: datetime = field(default_factory=datetime.now)


class SlashInteractionManager(
        _ExpiringUserInteractionStore[PendingSlashInteraction]
):
    """
    管理单个 slash 命令的交互会话。
    """

    def create_or_replace(
            self,
            user_id: Union[str, int],
            command: str,
            channel: Optional[NotificationChannel],
            source: Optional[str],
            username: Optional[str],
    ) -> PendingSlashInteraction:
        """为用户创建 slash 会话并替换其上一条会话。"""
        with self._lock:
            self._cleanup_locked()
            user_key = str(user_id)
            request = PendingSlashInteraction(
                request_id=uuid.uuid4().hex[:12],
                user_id=user_key,
                command=command,
                channel=channel,
                source=source,
                username=username,
            )
            self._replace_locked(request)
            return request


@dataclass(frozen=True, slots=True)
class InteractionContext:
    """描述一次与渠道无关的用户交互上下文。"""

    channel: NotificationChannel
    source: Optional[str]
    user_id: Union[str, int]
    username: Optional[str]
    original_message_id: Optional[Union[str, int]] = None
    original_chat_id: Optional[str] = None
    is_channel_admin: Optional[bool] = None


@dataclass(frozen=True, slots=True)
class InteractionDispatch:
    """描述交互路由是否命中以及是否延迟结束处理状态。"""

    handled: bool
    defer_processing_finish: bool = False


class MessageGateway(Protocol):
    """声明交互控制器使用的消息发送和编辑能力。"""

    def post_message(self, message: Message) -> None:
        """发送一条交互消息。"""
        ...

    def edit_message(
            self,
            channel: NotificationChannel,
            source: str,
            message_id: Union[str, int],
            chat_id: Union[str, int],
            text: str,
            title: Optional[str] = None,
            buttons: Optional[List[List[Dict[str, Any]]]] = None,
            metadata: Optional[Dict[str, Any]] = None,
    ) -> bool:
        """编辑一条已发送的交互消息。"""
        ...


def supports_interaction_buttons(channel: Optional[NotificationChannel]) -> bool:
    """
    渠道同时支持按钮和回调时，优先使用按钮交互。
    """
    return bool(
        channel
        and ChannelCapabilityManager.supports_buttons(channel)
        and ChannelCapabilityManager.supports_callbacks(channel)
    )


def supports_markdown(channel: Optional[NotificationChannel]) -> bool:
    """
    仅在支持 Markdown 的渠道上输出 Markdown 内容。
    """
    return bool(channel and ChannelCapabilityManager.supports_markdown(channel))


def page_items(
        items: Sequence[Any],
        page: int,
        page_size: int,
) -> Tuple[List[Any], int, int]:
    """
    对列表做分页并规范化页码。
    """
    total = len(items)
    if total == 0:
        return [], 0, 1
    total_pages = max(1, math.ceil(total / max(1, page_size)))
    page = min(max(0, page), total_pages - 1)
    start = page * page_size
    end = start + page_size
    return list(items[start:end]), page, total_pages


def build_navigation_buttons(
        prefix: str,
        request: Any,
        page: int,
        total_pages: int,
) -> List[List[dict]]:
    """
    构造标准上一页/下一页按钮。
    """
    buttons = []
    nav_row = []
    if page > 0:
        nav_row.append(
            {
                "text": "⬅️ 上一页",
                "callback_data": f"{prefix}:{request.request_id}:page-prev",
            }
        )
    if page < total_pages - 1:
        nav_row.append(
            {
                "text": "下一页 ➡️",
                "callback_data": f"{prefix}:{request.request_id}:page-next",
            }
        )
    if nav_row:
        buttons.append(nav_row)
    return buttons


def update_or_post_message(
        chain,
        channel: NotificationChannel,
        source: Optional[str],
        userid: Union[str, int],
        username: Optional[str],
        title: str,
        text: str,
        buttons: Optional[List[List[dict]]] = None,
        original_message_id: Optional[Union[str, int]] = None,
        original_chat_id: Optional[str] = None,
) -> None:
    """
    优先编辑原消息，失败时回退为发送新消息。
    """
    if (
            original_message_id
            and original_chat_id
            and ChannelCapabilityManager.supports_editing(channel)
    ):
        edit_kwargs = {}
        if channel == NotificationChannel.WebAgent:
            edit_kwargs["metadata"] = {"userid": userid}
        edited = chain.edit_message(
            channel=channel,
            source=source,
            message_id=original_message_id,
            chat_id=original_chat_id,
            title=title,
            text=text,
            buttons=buttons,
            **edit_kwargs,
        )
        if edited:
            return

    chain.post_message(
        Message(
            channel=channel,
            source=source,
            userid=userid,
            username=username,
            title=title,
            text=text,
            buttons=buttons,
            # 编辑失败回退发新消息时保留原消息上下文，
            # 保证飞书等渠道能回复到原会话（如群聊），而不是发给私聊。
            original_message_id=original_message_id,
            original_chat_id=original_chat_id,
            save_history=False,
        )
    )


def escape_markdown_table_cell(value: object) -> str:
    """
    最小化转义 Markdown 表格中的特殊字符。
    """
    text = str(value or "").replace("\n", "<br>")
    return text.replace("|", "\\|")


def format_markdown_table(
        headers: Sequence[str],
        rows: Sequence[Sequence[object]],
) -> str:
    """
    生成 Markdown 表格文本。
    """
    header_line = (
        "| "
        + " | ".join(escape_markdown_table_cell(item) for item in headers)
        + " |"
    )
    separator_line = "| " + " | ".join("---" for _ in headers) + " |"
    data_lines = [
        "| "
        + " | ".join(escape_markdown_table_cell(item) for item in row)
        + " |"
        for row in rows
    ]
    return "\n".join([header_line, separator_line, *data_lines])