# -*- coding: utf-8 -*-
"""
事件处理器基类与装饰器系统
─────────────────────────────────────────────────────────────────
提供两种注册处理器的方式：
  1. 继承 BaseEventHandler 类（面向对象风格）
  2. 使用 @on_event 装饰器（函数式风格）
─────────────────────────────────────────────────────────────────
"""

from __future__ import annotations

import functools
import inspect
import logging
from abc import ABC, abstractmethod
from typing import Callable, List, Optional, Union

from uas.event.event_model import Event
from uas.event.event_type import EventType

logger = logging.getLogger(__name__)


# ─────────────────────────────────────────────────────────────────
# 处理器描述符
# ─────────────────────────────────────────────────────────────────

class HandlerDescriptor:
    """
    处理器注册描述符
    记录处理器函数与其绑定的事件类型、优先级、过滤条件
    """
    def __init__(
        self,
        fn:          Callable,
        event_types: List[Union[EventType, str]],
        priority:    int   = 0,       # 同类型处理器执行顺序（越小越先）
        condition:   Optional[Callable[[Event], bool]] = None,
        once:        bool  = False,   # 是否只执行一次
        name:        str   = "",
    ):
        self.fn          = fn
        self.event_types = [
            t.value if isinstance(t, EventType) else t
            for t in event_types
        ]
        self.priority    = priority
        self.condition   = condition
        self.once        = once
        self.name        = name or fn.__name__
        self.call_count  = 0
        self.is_async    = inspect.iscoroutinefunction(fn)

    def matches(self, event: Event) -> bool:
        """检查事件是否匹配此处理器"""
        type_match = (
            event.type_key in self.event_types or
            "*" in self.event_types             # 通配符
        )
        if not type_match:
            return False
        if self.condition and not self.condition(event):
            return False
        return True

    def __repr__(self):
        return (f"Handler({self.name!r}, types={self.event_types}, "
                f"priority={self.priority}, async={self.is_async})")


# ─────────────────────────────────────────────────────────────────
# 抽象基类（面向对象风格）
# ─────────────────────────────────────────────────────────────────

class BaseEventHandler(ABC):
    """
    事件处理器抽象基类
    子类实现 handle() 方法，并声明 event_types 属性

    示例：
        class DeviceErrorHandler(BaseEventHandler):
            event_types = [EventType.DEVICE_ERROR]
            priority    = 10

            def handle(self, event: Event) -> Optional[dict]:
                print(f"处理设备错误: {event.params}")
                return {"action": "restart"}
    """

    event_types: List[Union[EventType, str]] = []
    priority:    int                         = 0
    condition:   Optional[Callable]          = None

    def __init__(self):
        self.logger = logging.getLogger(self.__class__.__name__)
        self._descriptor = HandlerDescriptor(
            fn          = self.handle,
            event_types = self.event_types,
            priority    = self.priority,
            condition   = self.condition,
            name        = self.__class__.__name__,
        )

    @abstractmethod
    def handle(self, event: Event):
        """
        处理事件
        :return: 可选的处理结果数据（写入 EventResult.data）
        """
        ...

    @property
    def descriptor(self) -> HandlerDescriptor:
        return self._descriptor


# ─────────────────────────────────────────────────────────────────
# 装饰器（函数式风格）
# ─────────────────────────────────────────────────────────────────

# 全局装饰器注册表（供 EventBus 扫描）
_decorator_handlers: List[HandlerDescriptor] = []


def on_event(
    *event_types: Union[EventType, str],
    priority:  int                          = 0,
    condition: Optional[Callable[[Event], bool]] = None,
    once:      bool                         = False,
):
    """
    事件处理器装饰器（函数式风格）

    示例：
        @on_event(EventType.DEVICE_ERROR, EventType.DEVICE_WARNING)
        def handle_device_issue(event: Event):
            print(f"设备问题: {event.message}")

        @on_event(EventType.SYSTEM_HEARTBEAT, priority=-10)
        async def async_heartbeat(event: Event):
            await asyncio.sleep(0)
            print("心跳处理（异步）")

        # 带条件过滤
        @on_event(EventType.DEVICE_ERROR,
                  condition=lambda e: e.params.get("code") == "E001")
        def handle_e001(event: Event):
            print("仅处理 E001 错误")
    """
    def decorator(fn: Callable) -> Callable:
        desc = HandlerDescriptor(
            fn          = fn,
            event_types = list(event_types),
            priority    = priority,
            condition   = condition,
            once        = once,
            name        = fn.__name__,
        )
        _decorator_handlers.append(desc)
        logger.debug(f"@on_event 注册: {desc}")

        @functools.wraps(fn)
        def wrapper(*args, **kwargs):
            return fn(*args, **kwargs)
        wrapper._handler_descriptor = desc
        return wrapper
    return decorator


def get_decorator_handlers() -> List[HandlerDescriptor]:
    """获取所有通过 @on_event 注册的处理器描述符"""
    return list(_decorator_handlers)