import { ref, onUnmounted } from 'vue'
import { getStatus } from '@/api/backtest'
import { useAuthStore } from '@/stores/auth'

export type TaskState = 'pending' | 'running' | 'done' | 'failed' | 'unknown'

/**
 * Track a task's status + stage via polling (2s) and WebSocket (real-time).
 * Auto-stops on unmount.
 */
export function useTask(taskId: string) {
  const status = ref<TaskState>('unknown')
  const stage = ref('')
  let timer: ReturnType<typeof setInterval> | null = null
  let ws: WebSocket | null = null

  async function poll(): Promise<void> {
    try {
      const s = await getStatus(taskId)
      status.value = s.status as TaskState
      stage.value = s.stage
    } catch {
      /* transient — keep last known state */
    }
  }

  function start(): void {
    poll()
    timer = setInterval(poll, 2000)
    const proto = window.location.protocol === 'https:' ? 'wss' : 'ws'
    const auth = useAuthStore()
    const url = `${proto}://${window.location.host}/api/v1/ws/task/${taskId}?token=${auth.token}`
    try {
      ws = new WebSocket(url)
      ws.onmessage = (ev) => {
        try {
          const msg = JSON.parse(ev.data)
          if (msg.stage) stage.value = msg.stage
          if (msg.status) status.value = msg.status
        } catch {
          /* ignore non-JSON keepalive frames */
        }
      }
    } catch {
      /* WS optional — polling covers it */
    }
  }

  onUnmounted(() => {
    if (timer) clearInterval(timer)
    if (ws) ws.close()
  })

  return { status, stage, start }
}