//! 事件总线 — 基于 tokio::sync::broadcast 的发布/订阅

use tokio::sync::broadcast;
use df_types::events::WorkflowEvent;

/// 事件总线
#[derive(Debug)]
pub struct EventBus {
    sender: broadcast::Sender<WorkflowEvent>,
}

/// 事件订阅者
pub type EventSubscriber = broadcast::Receiver<WorkflowEvent>;

/// 默认事件通道容量
const DEFAULT_CAPACITY: usize = 256;

impl EventBus {
    /// 创建事件总线
    pub fn new() -> Self {
        let (sender, _) = broadcast::channel(DEFAULT_CAPACITY);
        Self { sender }
    }

    /// 创建指定容量的事件总线
    pub fn with_capacity(capacity: usize) -> Self {
        let (sender, _) = broadcast::channel(capacity);
        Self { sender }
    }

    /// 发送事件
    pub async fn send(&self, event: WorkflowEvent) {
        // broadcast::send 是同步的，忽略接收者已关闭的错误
        let _ = self.sender.send(event);
    }

    /// 订阅事件
    pub fn subscribe(&self) -> EventSubscriber {
        self.sender.subscribe()
    }
}

impl Default for EventBus {
    fn default() -> Self {
        Self::new()
    }
}

impl Clone for EventBus {
    fn clone(&self) -> Self {
        Self {
            sender: self.sender.clone(),
        }
    }
}