#if os(macOS)
import Foundation
import Network

final class ResizeFixtureServer: @unchecked Sendable {
  private let listener: NWListener
  private let queue = DispatchQueue(label: "sheets.resize.fixture")
  private let lock = NSLock()
  private var received: [[String: Int]] = []
  var requests: [[String: Int]] { lock.withLock { received } }
  init() throws { listener = try NWListener(using: .tcp, on: .any) }
  func start() async throws -> URL {
    listener.newConnectionHandler = { [weak self] connection in
      guard let self else { return }
      connection.start(queue: self.queue)
      self.read(connection, buffer: Data())
    }
    return try await withCheckedThrowingContinuation { continuation in
      listener.stateUpdateHandler = { [weak self] state in
        guard let self else { return }
        switch state {
        case .ready:
          self.listener.stateUpdateHandler = nil
          continuation.resume(returning: URL(string: "http://127.0.0.1:\(self.listener.port!.rawValue)")!)
        case .failed(let error):
          self.listener.stateUpdateHandler = nil
          continuation.resume(throwing: error)
        default: break
        }
      }
      listener.start(queue: queue)
    }
  }
  func stop() { listener.cancel() }
  private func read(_ connection: NWConnection, buffer: Data) {
    connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) { [weak self] data, _, complete, error in
      guard let self, let data, error == nil else { connection.cancel(); return }
      var bytes = buffer; bytes.append(data)
      guard let separator = bytes.range(of: Data("\r\n\r\n".utf8)),
            let headers = String(data: bytes[..<separator.lowerBound], encoding: .utf8),
            let lengthLine = headers.components(separatedBy: "\r\n").first(where: { $0.lowercased().hasPrefix("content-length:") }),
            let length = Int(lengthLine.split(separator: ":", maxSplits: 1)[1].trimmingCharacters(in: .whitespaces)),
            bytes.count - separator.upperBound >= length else {
        if !complete { self.read(connection, buffer: bytes) } else { connection.cancel() }
        return
      }
      let body = bytes.subdata(in: separator.upperBound..<(separator.upperBound + length))
      guard let request = try? JSONDecoder().decode([String: Int].self, from: body), let size = request["size"] else { connection.cancel(); return }
      self.lock.withLock { self.received.append(request) }
      let axis = request["col"] == nil ? "rows" : "cols"
      let index = request["col"] ?? request["row"] ?? 0
      let response = "{\"version\":0,\"cells\":[],\"sizes\":{\"\(axis)\":{\"\(index)\":\(size)}}}"
      let message = "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: \(response.utf8.count)\r\nConnection: close\r\n\r\n\(response)"
      connection.send(content: Data(message.utf8), completion: .contentProcessed { _ in connection.cancel() })
    }
  }
}
#endif