import Foundation

// ─────────────────────────────────────────────────────────────
// Load Balancer for Cross-Device Communication
// ─────────────────────────────────────────────────────────────

/// Load balancing strategies
public enum LoadBalancingStrategy: Sendable {
    case roundRobin
    case leastLoaded
    case random
    case geographic
}

/// Load balancer
public final class LoadBalancer: @unchecked Sendable {
    private var nodes: [DeviceNode] = []
    private var currentIndex: Int = 0
    private let strategy: LoadBalancingStrategy
    private let lock = NSLock()
    
    public init(strategy: LoadBalancingStrategy = .roundRobin) {
        self.strategy = strategy
    }
    
    /// Add a node
    public func addNode(_ node: DeviceNode) {
        lock.lock()
        defer { lock.unlock() }
        nodes.append(node)
    }
    
    /// Remove a node
    public func removeNode(id: String) {
        lock.lock()
        defer { lock.unlock() }
        nodes.removeAll { $0.id == id }
    }
    
    /// Get next node based on strategy
    public func getNextNode() -> DeviceNode? {
        lock.lock()
        defer { lock.unlock() }
        
        let healthyNodes = nodes.filter { $0.status == .healthy }
        guard !healthyNodes.isEmpty else { return nil }
        
        switch strategy {
        case .roundRobin:
            let node = healthyNodes[currentIndex % healthyNodes.count]
            currentIndex += 1
            return node
            
        case .leastLoaded:
            return healthyNodes.min { $0.load < $1.load }
            
        case .random:
            return healthyNodes.randomElement()
            
        case .geographic:
            // Simplified: return node with lowest latency
            return healthyNodes.first
        }
    }
    
    /// Update node status
    public func updateNodeStatus(id: String, status: DeviceStatus, load: Double? = nil) {
        lock.lock()
        defer { lock.unlock() }
        
        if let index = nodes.firstIndex(where: { $0.id == id }) {
            var node = nodes[index]
            node.status = status
            if let load = load {
                node.load = load
            }
            nodes[index] = node
        }
    }
    
    /// Get all nodes
    public func getNodes() -> [DeviceNode] {
        lock.lock()
        defer { lock.unlock() }
        return nodes
    }
    
    /// Get healthy nodes count
    public var healthyNodesCount: Int {
        nodes.filter { $0.status == .healthy }.count
    }
}