feat: use incremental polling for queue refresh

src/App.css

@@ -59,6 +59,11 @@ h2 {
   color: #cbd5e1;
 }
 
+.refreshing-indicator {
+  color: #93c5fd;
+  font-size: 0.9rem;
+}
+
 .banner {
   padding: 0.9rem 1rem;
   margin-bottom: 1rem;

src/App.jsx

@@ -1,10 +1,8 @@
-import { useCallback, useEffect, useMemo, useState } from 'react'
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import './App.css'
 
 const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || 'http://app-01:8080'
-const WS_URL = import.meta.env.VITE_WS_URL || ''
 const POLL_INTERVAL_MS = 10000
-const RECONNECT_DELAY_MS = 5000
 
 const statusColors = {
   queued: 'status-queued',
@@ -68,95 +66,68 @@ function DetailRow({ label, value, mono = false, preserve = false }) {
 function App() {
   const [items, setItems] = useState([])
   const [loading, setLoading] = useState(true)
+  const [refreshing, setRefreshing] = useState(false)
   const [error, setError] = useState('')
   const [sort, setSort] = useState({ key: 'created_at', direction: 'desc' })
   const [filters, setFilters] = useState(defaultFilters)
   const [selectedId, setSelectedId] = useState('')
-  const [transport, setTransport] = useState(WS_URL ? 'connecting websocket…' : 'polling')
+  const [transport] = useState('incremental polling')
+  const lastSuccessRef = useRef('')
+
+  const mergeItems = useCallback((incomingItems) => {
+    setItems((current) => {
+      if (!incomingItems.length) return current
+      const next = new Map(current.map((item) => [item.id, item]))
+      incomingItems.forEach((item) => next.set(item.id, item))
+      return Array.from(next.values())
+    })
+  }, [])
+
+  const refreshTimestamp = useCallback((sourceItems) => {
+    const timestamps = sourceItems.map((item) => item.updated_at).filter(Boolean).sort()
+    if (timestamps.length) {
+      lastSuccessRef.current = timestamps[timestamps.length - 1]
+    }
+  }, [])
+
+  const load = useCallback(async (incremental = false) => {
+    if (incremental) setRefreshing(true)
 
-  const load = useCallback(async () => {
     try {
-      const response = await fetch(`${API_BASE_URL}/work`)
+      const url = new URL(`${API_BASE_URL}/work`)
+      if (incremental && lastSuccessRef.current) {
+        url.searchParams.set('since', lastSuccessRef.current)
+      }
+
+      const response = await fetch(url)
       if (!response.ok) throw new Error(`Request failed with ${response.status}`)
       const data = await response.json()
+
+      if (incremental && lastSuccessRef.current) {
+        mergeItems(data)
+      } else {
         setItems(data)
+      }
+
+      refreshTimestamp(data.length ? data : items)
       setError('')
       setSelectedId((current) => {
-        if (current && data.some((item) => item.id === current)) return current
-        return data[0]?.id ?? ''
+        const pool = data.length && incremental ? [...items, ...data] : data.length ? data : items
+        if (current && pool.some((item) => item.id === current)) return current
+        return pool[0]?.id ?? ''
       })
     } catch (err) {
       setError(err.message || 'Failed to load queue')
     } finally {
       setLoading(false)
+      setRefreshing(false)
     }
-  }, [])
+  }, [items, mergeItems, refreshTimestamp])
 
   useEffect(() => {
-    let active = true
-    let socket
-    let pollTimer
-    let reconnectTimer
-
-    const startPolling = () => {
-      setTransport('polling')
-      load()
-      pollTimer = window.setInterval(load, POLL_INTERVAL_MS)
-    }
-
-    const stopPolling = () => {
-      if (pollTimer) window.clearInterval(pollTimer)
-    }
-
-    const connectWebSocket = () => {
-      if (!WS_URL || !active) {
-        startPolling()
-        return
-      }
-
-      try {
-        socket = new WebSocket(WS_URL)
-      } catch {
-        startPolling()
-        return
-      }
-
-      socket.onopen = () => {
-        if (!active) return
-        stopPolling()
-        setTransport('websocket')
-        load()
-      }
-
-      socket.onmessage = () => {
-        if (!active) return
-        load()
-      }
-
-      socket.onerror = () => {
-        if (!active) return
-        setTransport('polling')
-      }
-
-      socket.onclose = () => {
-        if (!active) return
-        startPolling()
-        reconnectTimer = window.setTimeout(() => {
-          stopPolling()
-          connectWebSocket()
-        }, RECONNECT_DELAY_MS)
-      }
-    }
-
-    load()
-    connectWebSocket()
-
-    return () => {
-      active = false
-      stopPolling()
-      if (reconnectTimer) window.clearTimeout(reconnectTimer)
-      if (socket && socket.readyState < 2) socket.close()
-    }
+    load(false)
+    const timer = window.setInterval(() => load(true), POLL_INTERVAL_MS)
+    return () => window.clearInterval(timer)
   }, [load])
 
   const filterOptions = useMemo(
@@ -214,6 +185,7 @@ function App() {
           <span>{filteredItems.length} visible items</span>
           <span>{items.length} total items</span>
           <span>Updates via {transport}</span>
+          {refreshing && <span className="refreshing-indicator">Refreshing…</span>}
         </div>
       </header>