import Foundation
import Combine

/// 事件总线 — Bricks事件发布/订阅系统
/// 对应Bricks的dispatch/subscribe机制
@MainActor
public final class BricksEventBus: ObservableObject {
    
    /// 事件定义: eventName → [callback]
    private var handlers: [String: [(EventData) async -> Void]] = [:]
    
    /// 已发布的事件历史（调试用）
    @Published public var eventLog: [(name: String, data: EventData, timestamp: Date)] = []
    
    private let maxLogSize = 100
    
    public init() {}
    
    // MARK: - 订阅
    
    /// 订阅事件
    public func on(_ eventName: String, handler: @escaping (EventData) async -> Void) {
        if handlers[eventName] == nil {
            handlers[eventName] = []
        }
        handlers[eventName]?.append(handler)
    }
    
    /// 取消订阅
    public func off(_ eventName: String) {
        handlers.removeValue(forKey: eventName)
    }
    
    // MARK: - 发布
    
    /// 派发事件
    public func dispatch(_ eventName: String, data: EventData = [:]) async {
        // 记录日志
        eventLog.append((name: eventName, data: data, timestamp: Date()))
        if eventLog.count > maxLogSize {
            eventLog.removeFirst()
        }
        
        // 调用所有handler
        if let callbacks = handlers[eventName] {
            for callback in callbacks {
                await callback(data)
            }
        }
    }
    
    /// 同步派发（用于UI事件）
    public func dispatchSync(_ eventName: String, data: EventData = [:]) {
        Task { @MainActor in
            await dispatch(eventName, data: data)
        }
    }
    
    // MARK: - 工具
    
    public func hasSubscribers(_ eventName: String) -> Bool {
        !(handlers[eventName]?.isEmpty ?? true)
    }
    
    public func subscriberCount(_ eventName: String) -> Int {
        handlers[eventName]?.count ?? 0
    }
}

/// 事件数据 — 类型安全的事件载荷
public struct EventData: Sendable {
    private var storage: [String: Any]
    
    public init(_ dict: [String: Any] = [:]) {
        self.storage = dict
    }
    
    public subscript(key: String) -> Any? {
        get { storage[key] }
        set { storage[key] = newValue }
    }
    
    public var asDictionary: [String: Any] { storage }
    
    /// 合并两个EventData
    public func merged(with other: EventData) -> EventData {
        var result = EventData()
        for (k, v) in storage { result[k] = v }
        for (k, v) in other.storage { result[k] = v }
        return result
    }
    
    /// 从字典创建
    public static func from(_ dict: [String: Any]) -> EventData {
        EventData(dict)
    }
}

// MARK: - 常用事件名

public enum BricksEvent {
    public static let click = "click"
    public static let submit = "submit"
    public static let change = "change"
    public static let select = "select"
    public static let load = "load"
    public static let render = "render"
    public static let close = "close"
    public static let open = "open"
    public static let toggle = "toggle"
    public static let refresh = "refresh"
    public static let navigate = "navigate"
}