import Foundation

// ─────────────────────────────────────────────────────────────
// Cross-Device Client
// ─────────────────────────────────────────────────────────────

/// Cross-device client for making requests to other nodes
public final class CrossDeviceClient: @unchecked Sendable {
    private let session: URLSession
    private let loadBalancer: LoadBalancer
    private let timeout: TimeInterval
    
    public init(
        loadBalancer: LoadBalancer,
        timeout: TimeInterval = 30
    ) {
        self.loadBalancer = loadBalancer
        self.timeout = timeout
        
        let config = URLSessionConfiguration.default
        config.timeoutIntervalForRequest = timeout
        self.session = URLSession(configuration: config)
    }
    
    /// Send request to cluster
    public func sendToCluster(
        endpoint: String,
        method: String = "POST",
        body: Data? = nil
    ) async throws -> CrossDeviceResponse {
        guard let node = loadBalancer.getNextNode() else {
            throw CrossDeviceError.noHealthyNodes
        }
        
        return try await sendToNode(
            node: node,
            endpoint: endpoint,
            method: method,
            body: body
        )
    }
    
    /// Send request to specific node
    public func sendToNode(
        node: DeviceNode,
        endpoint: String,
        method: String = "POST",
        body: Data? = nil
    ) async throws -> CrossDeviceResponse {
        let url = URL(string: "\(node.baseURL)\(endpoint)")!
        var request = URLRequest(url: url)
        request.httpMethod = method
        request.httpBody = body
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.timeoutInterval = timeout
        
        let startTime = Date()
        
        do {
            let (data, response) = try await session.data(for: request)
            let latency = Date().timeIntervalSince(startTime)
            
            guard let httpResponse = response as? HTTPURLResponse else {
                throw CrossDeviceError.invalidResponse
            }
            
            // Update node status
            loadBalancer.updateNodeStatus(
                id: node.id,
                status: httpResponse.statusCode < 500 ? .healthy : .degraded,
                load: nil
            )
            
            return CrossDeviceResponse(
                requestId: UUID().uuidString,
                statusCode: httpResponse.statusCode,
                body: data,
                latency: latency,
                nodeId: node.id
            )
        } catch {
            let latency = Date().timeIntervalSince(startTime)
            
            // Update node status
            loadBalancer.updateNodeStatus(id: node.id, status: .unhealthy)
            
            throw CrossDeviceError.requestFailed(error)
        }
    }
    
    /// Broadcast request to all healthy nodes
    public func broadcastToAll(
        endpoint: String,
        method: String = "POST",
        body: Data? = nil
    ) async throws -> [CrossDeviceResponse] {
        let nodes = loadBalancer.getNodes().filter { $0.status == .healthy }
        
        return try await withThrowingTaskGroup(of: CrossDeviceResponse.self) { group in
            for node in nodes {
                group.addTask {
                    try await self.sendToNode(
                        node: node,
                        endpoint: endpoint,
                        method: method,
                        body: body
                    )
                }
            }
            
            var responses: [CrossDeviceResponse] = []
            for try await response in group {
                responses.append(response)
            }
            return responses
        }
    }
}

/// Cross-device errors
public enum CrossDeviceError: Error, LocalizedError {
    case noHealthyNodes
    case invalidResponse
    case requestFailed(Error)
    case timeout
    
    public var errorDescription: String? {
        switch self {
        case .noHealthyNodes:
            return "No healthy nodes available"
        case .invalidResponse:
            return "Invalid response from node"
        case .requestFailed(let error):
            return "Request failed: \(error.localizedDescription)"
        case .timeout:
            return "Request timed out"
        }
    }
}