import { HubConnection, HubConnectionBuilder, HubConnectionState, LogLevel } from '@microsoft/signalr'
import { TOKEN_KEY } from '@/lib/api'

// Hub URL resolution:
// - Dev: Vite proxy forwards /api → :5443 but SignalR bypasses axios, so we
//   hit the API origin directly from the browser.
// - Prod: VITE_API_BASE_URL (https://api.solutions.com.vn)
const HUB_URL = (import.meta.env.VITE_API_BASE_URL ?? window.location.origin) + '/hubs/notifications'

let connection: HubConnection | null = null
let startPromise: Promise<void> | null = null

/** Lazily starts (or reuses) a single hub connection. Token read on connect. */
export async function ensureConnection(): Promise<HubConnection> {
  if (connection && connection.state === HubConnectionState.Connected) return connection

  if (!connection) {
    connection = new HubConnectionBuilder()
      .withUrl(HUB_URL, {
        accessTokenFactory: () => localStorage.getItem(TOKEN_KEY) ?? '',
      })
      .withAutomaticReconnect([0, 2_000, 5_000, 10_000, 15_000]) // exponential-ish backoff
      .configureLogging(LogLevel.Warning)
      .build()
  }

  if (connection.state === HubConnectionState.Disconnected) {
    startPromise ??= connection.start().catch(err => {
      startPromise = null
      throw err
    })
    await startPromise
    startPromise = null
  }
  return connection
}

/** Stops + forgets the connection. Call on logout. */
export async function stopConnection(): Promise<void> {
  if (!connection) return
  try {
    await connection.stop()
  } catch {
    /* ignore */
  }
  connection = null
  startPromise = null
}