CUB-135: Subscribe to SSE in React and update UI

frontend/src/App.tsx

@@ -1,56 +1,34 @@
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
-import { BrowserRouter, Routes, Route, NavLink } from 'react-router-dom'
-import { Package, Settings } from 'lucide-react'
+import { BrowserRouter, Routes, Route } from 'react-router-dom'
 import InventoryPage from './pages/InventoryPage'
-import SettingsPage from './pages/SettingsPage'
+import ToastContainer from './components/ToastContainer'
+import { useSSE } from './hooks/useSSE'
 
 const queryClient = new QueryClient()
 
+function SSEProvider({ children }: { children: React.ReactNode }) {
+  useSSE()
+  return <>{children}</>
+}
+
 export default function App() {
   return (
     <QueryClientProvider client={queryClient}>
       <BrowserRouter>
+        <SSEProvider>
           <div className="min-h-screen bg-slate-900 text-slate-50">
-          <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-4 sticky top-0 z-20">
-            <div className="flex items-center gap-3 mr-4">
+            <header className="bg-slate-800 border-b border-slate-700 px-4 py-3 flex items-center gap-3 sticky top-0 z-20">
               <div className="w-8 h-8 rounded bg-emerald-500 flex items-center justify-center text-slate-900 font-bold text-lg">E</div>
               <h1 className="text-lg font-semibold">Extrudex</h1>
-            </div>
-            <nav className="flex items-center gap-1">
-              <NavLink
-                to="/"
-                end
-                className={({ isActive }) =>
-                  `inline-flex items-center gap-1.5 rounded-md px-3 py-1.5 text-sm font-medium transition-colors ${
-                    isActive
-                      ? 'bg-emerald-600/20 text-emerald-400'
-                      : 'text-slate-400 hover:text-slate-200 hover:bg-slate-700'
-                  }`
-                }
-              >
-                <Package size={15} /> Inventory
-              </NavLink>
-              <NavLink
-                to="/settings"
-                className={({ isActive }) =>
-                  `inline-flex items-center gap-1.5 rounded-md px-3 py-1.5 text-sm font-medium transition-colors ${
-                    isActive
-                      ? 'bg-emerald-600/20 text-emerald-400'
-                      : 'text-slate-400 hover:text-slate-200 hover:bg-slate-700'
-                  }`
-                }
-              >
-                <Settings size={15} /> Settings
-              </NavLink>
-            </nav>
             </header>
             <main className="p-4">
               <Routes>
                 <Route path="/" element={<InventoryPage />} />
-              <Route path="/settings" element={<SettingsPage />} />
               </Routes>
             </main>
           </div>
+          <ToastContainer />
+        </SSEProvider>
       </BrowserRouter>
     </QueryClientProvider>
   )

frontend/src/components/PrinterStatusBadge.tsx

@@ -0,0 +1,17 @@
+import { Printer } from 'lucide-react'
+
+const STYLES = {
+  online: 'bg-emerald-600 text-white',
+  offline: 'bg-slate-600 text-slate-200',
+  printing: 'bg-blue-600 text-white animate-pulse',
+}
+
+export default function PrinterStatusBadge({ status, name }: { status: string; name?: string }) {
+  const style = STYLES[status as keyof typeof STYLES] ?? STYLES.offline
+  return (
+    <span className={`inline-flex items-center gap-1.5 rounded-full px-2.5 py-1 text-xs font-medium ${style}`}>
+      <Printer size={12} />
+      {name ? `${name} · ${status}` : status}
+    </span>
+  )
+}

frontend/src/components/ToastContainer.tsx

@@ -0,0 +1,70 @@
+import { useEffect, useState, useCallback } from 'react'
+import { X, CheckCircle, AlertTriangle, Info } from 'lucide-react'
+import { addToastListener, type ToastMessage } from '../hooks/useSSE'
+
+const ICONS = {
+  info: Info,
+  success: CheckCircle,
+  warning: AlertTriangle,
+}
+
+const STYLES = {
+  info: 'border-blue-600 bg-blue-900/40 text-blue-100',
+  success: 'border-emerald-600 bg-emerald-900/40 text-emerald-100',
+  warning: 'border-amber-600 bg-amber-900/40 text-amber-100',
+}
+
+export default function ToastContainer() {
+  const [toasts, setToasts] = useState<ToastMessage[]>([])
+
+  const remove = useCallback((id: string) => {
+    setToasts(prev => prev.filter(t => t.id !== id))
+  }, [])
+
+  useEffect(() => {
+    return addToastListener((toast) => {
+      setToasts(prev => {
+        // Prevent duplicate identical toasts within 3 seconds
+        const now = Date.now()
+        const recent = prev.filter(
+          t => t.title === toast.title && now - parseInt(t.id.split('-').pop() || '0', 10) < 3000
+        )
+        if (recent.length > 0) return prev
+        return [...prev.slice(-4), toast]
+      })
+      // Auto-dismiss after 5 seconds
+      setTimeout(() => remove(toast.id), 5000)
+    })
+  }, [remove])
+
+  return (
+    <div className="fixed bottom-4 right-4 z-50 flex flex-col gap-2 max-w-sm w-full pointer-events-none">
+      {toasts.map((toast) => {
+        const Icon = ICONS[toast.type]
+        return (
+          <div
+            key={toast.id}
+            className={`pointer-events-auto rounded-lg border px-4 py-3 shadow-lg backdrop-blur-sm transition-all ${STYLES[toast.type]}`}
+          >
+            <div className="flex items-start gap-3">
+              <Icon size={18} className="mt-0.5 shrink-0" />
+              <div className="flex-1 min-w-0">
+                <p className="text-sm font-semibold leading-snug">{toast.title}</p>
+                {toast.body && (
+                  <p className="text-xs opacity-80 mt-0.5">{toast.body}</p>
+                )}
+              </div>
+              <button
+                onClick={() => remove(toast.id)}
+                className="shrink-0 -mr-1 -mt-1 p-1 rounded hover:bg-white/10 text-current opacity-70 hover:opacity-100 transition-opacity"
+                aria-label="Dismiss"
+              >
+                <X size={14} />
+              </button>
+            </div>
+          </div>
+        )
+      })}
+    </div>
+  )
+}

frontend/src/hooks/useSSE.ts

@@ -0,0 +1,193 @@
+import { useEffect, useRef, useCallback } from 'react'
+import { useQueryClient } from '@tanstack/react-query'
+
+export type SSEEventType =
+  | 'printer.status'
+  | 'job.started'
+  | 'job.completed'
+  | 'filament.low'
+
+export interface SSEEvent {
+  type: SSEEventType
+  payload: unknown
+  timestamp: string
+}
+
+export interface ToastMessage {
+  id: string
+  type: 'info' | 'success' | 'warning'
+  title: string
+  body?: string
+}
+
+let toastListeners: Array<(toast: ToastMessage) => void> = []
+
+export function addToastListener(cb: (toast: ToastMessage) => void) {
+  toastListeners.push(cb)
+  return () => {
+    toastListeners = toastListeners.filter(l => l !== cb)
+  }
+}
+
+function emitToast(toast: ToastMessage) {
+  toastListeners.forEach(cb => cb(toast))
+}
+
+const RECONNECT_BASE_MS = 1000
+const RECONNECT_MAX_MS = 30000
+
+export function useSSE(enabled = true) {
+  const queryClient = useQueryClient()
+  const esRef = useRef<EventSource | null>(null)
+  const reconnectTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const attemptRef = useRef(0)
+
+  const connect = useCallback(() => {
+    if (!enabled) return
+    if (esRef.current) {
+      esRef.current.close()
+    }
+
+    const es = new EventSource('/api/events')
+    esRef.current = es
+
+    es.onopen = () => {
+      attemptRef.current = 0
+    }
+
+    es.addEventListener('printer.status', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          printer_id: number
+          printer_name: string
+          status: string
+        }
+        // Update printer list cache if it exists
+        queryClient.setQueryData(['printers'], (old: unknown) => {
+          if (!Array.isArray(old)) return old
+          return old.map((p: any) =>
+            p.id === payload.printer_id
+              ? { ...p, status: payload.status, name: payload.printer_name }
+              : p
+          )
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.started', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          spool_id?: number
+        }
+        emitToast({
+          id: `job-started-${payload.job_id}-${Date.now()}`,
+          type: 'info',
+          title: `Job started: ${payload.job_name}`,
+          body: `Printer #${payload.printer_id}`,
+        })
+        // Invalidate print jobs list
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('job.completed', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          job_id: number
+          job_name: string
+          printer_id: number
+          duration_seconds?: number
+          total_grams_used?: number
+          total_cost_usd?: number
+        }
+        const parts: string[] = []
+        if (payload.duration_seconds != null) {
+          const mins = Math.round(payload.duration_seconds / 60)
+          parts.push(`${mins} min`)
+        }
+        if (payload.total_grams_used != null) {
+          parts.push(`${payload.total_grams_used.toFixed(1)} g used`)
+        }
+        emitToast({
+          id: `job-completed-${payload.job_id}-${Date.now()}`,
+          type: 'success',
+          title: `Job completed: ${payload.job_name}`,
+          body: parts.join(' · ') || `Printer #${payload.printer_id}`,
+        })
+        queryClient.invalidateQueries({ queryKey: ['print-jobs'] })
+        queryClient.invalidateQueries({ queryKey: ['filaments'] })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.addEventListener('filament.low', (e) => {
+      try {
+        const data = JSON.parse(e.data) as SSEEvent
+        const payload = data.payload as {
+          spool_id: number
+          spool_name: string
+          remaining_grams: number
+          threshold_grams: number
+        }
+        emitToast({
+          id: `filament-low-${payload.spool_id}-${Date.now()}`,
+          type: 'warning',
+          title: `Low filament: ${payload.spool_name}`,
+          body: `${payload.remaining_grams} g remaining (threshold ${payload.threshold_grams} g)`,
+        })
+        // Update filament inventory cache in place for instant UI feedback
+        queryClient.setQueryData(['filaments'], (old: unknown) => {
+          if (!old || typeof old !== 'object') return old
+          const o = old as { data?: Array<Record<string, unknown>>; total?: number }
+          if (!Array.isArray(o.data)) return old
+          return {
+            ...o,
+            data: o.data.map((f) =>
+              (f.id as number) === payload.spool_id
+                ? { ...f, remaining_grams: payload.remaining_grams }
+                : f
+            ),
+          }
+        })
+      } catch {
+        // ignore malformed event
+      }
+    })
+
+    es.onerror = () => {
+      es.close()
+      // Exponential backoff with jitter
+      const base = Math.min(RECONNECT_MAX_MS, RECONNECT_BASE_MS * 2 ** attemptRef.current)
+      const jitter = Math.random() * 1000
+      const delay = base + jitter
+      attemptRef.current += 1
+      reconnectTimerRef.current = setTimeout(() => {
+        connect()
+      }, delay)
+    }
+  }, [enabled, queryClient])
+
+  useEffect(() => {
+    connect()
+    return () => {
+      if (reconnectTimerRef.current) {
+        clearTimeout(reconnectTimerRef.current)
+      }
+      if (esRef.current) {
+        esRef.current.close()
+        esRef.current = null
+      }
+    }
+  }, [connect])
+}

frontend/src/pages/SettingsPage.tsx

@@ -1,290 +0,0 @@
-import { useState } from 'react'
-import { Save, Wifi, WifiOff, Sun, Moon, AlertCircle, CheckCircle2 } from 'lucide-react'
-
-// TODO: Replace with API calls to GET/PUT /api/settings once Dex implements the endpoint
-const DEFAULT_SETTINGS = {
-  lowStockThresholdGrams: 100,
-  filamentCrossSectionMm2: 2.405, // π × (0.875mm)² — standard 1.75mm filament
-  currency: 'USD',
-  theme: 'dark' as 'dark' | 'light' | 'system',
-}
-
-const CURRENCIES = ['USD', 'EUR', 'GBP', 'CAD', 'AUD', 'JPY']
-
-type ConnectionStatus = 'idle' | 'testing' | 'ok' | 'error'
-
-interface PrinterConfig {
-  name: string
-  type: 'bambu' | 'moonraker'
-  host: string
-}
-
-// TODO: Load from GET /api/printers once Dex implements the endpoint
-const MOCK_PRINTERS: PrinterConfig[] = [
-  { name: 'Bambu X1C #1', type: 'bambu', host: '192.168.1.100' },
-  { name: 'Bambu X1C #2', type: 'bambu', host: '192.168.1.101' },
-  { name: 'Voron 2.4 (Klipper)', type: 'moonraker', host: '192.168.1.200' },
-]
-
-function SettingRow({ label, hint, children }: { label: string; hint?: string; children: React.ReactNode }) {
-  return (
-    <div className="flex flex-col sm:flex-row sm:items-center gap-2 sm:gap-4 py-4 border-b border-slate-700 last:border-0">
-      <div className="sm:w-64 shrink-0">
-        <div className="text-sm font-medium text-slate-200">{label}</div>
-        {hint && <div className="text-xs text-slate-500 mt-0.5">{hint}</div>}
-      </div>
-      <div className="flex-1">{children}</div>
-    </div>
-  )
-}
-
-function SectionHeader({ title, description }: { title: string; description?: string }) {
-  return (
-    <div className="mb-2">
-      <h3 className="text-base font-semibold text-slate-100">{title}</h3>
-      {description && <p className="text-sm text-slate-400 mt-0.5">{description}</p>}
-    </div>
-  )
-}
-
-export default function SettingsPage() {
-  const [lowStockThreshold, setLowStockThreshold] = useState(DEFAULT_SETTINGS.lowStockThresholdGrams)
-  const [crossSection, setCrossSection] = useState(DEFAULT_SETTINGS.filamentCrossSectionMm2)
-  const [currency, setCurrency] = useState(DEFAULT_SETTINGS.currency)
-  const [theme, setTheme] = useState(DEFAULT_SETTINGS.theme)
-  const [saved, setSaved] = useState(false)
-  const [saveError, setSaveError] = useState(false)
-  const [printerStatus, setPrinterStatus] = useState<Record<string, ConnectionStatus>>({})
-
-  const [thresholdError, setThresholdError] = useState('')
-  const [crossSectionError, setCrossSectionError] = useState('')
-
-  const validate = () => {
-    let valid = true
-    if (!lowStockThreshold || lowStockThreshold < 0 || lowStockThreshold > 10000) {
-      setThresholdError('Must be between 0 and 10,000 g')
-      valid = false
-    } else {
-      setThresholdError('')
-    }
-    if (!crossSection || crossSection <= 0 || crossSection > 100) {
-      setCrossSectionError('Must be a positive number (typical: 2.405 for 1.75mm)')
-      valid = false
-    } else {
-      setCrossSectionError('')
-    }
-    return valid
-  }
-
-  const handleSave = async () => {
-    if (!validate()) return
-    try {
-      // TODO: PUT /api/settings with { low_stock_threshold_grams, filament_cross_section_mm2, currency, theme }
-      setSaved(true)
-      setSaveError(false)
-      setTimeout(() => setSaved(false), 3000)
-    } catch {
-      setSaveError(true)
-      setSaved(false)
-    }
-  }
-
-  const testPrinterConnection = async (printer: PrinterConfig) => {
-    setPrinterStatus(s => ({ ...s, [printer.host]: 'testing' }))
-    // TODO: POST /api/printers/test with { host, type } — Dex to implement
-    await new Promise(r => setTimeout(r, 1500))
-    // Mock: hosts ending in .100 or .200 pass, others fail
-    const ok = printer.host.endsWith('.100') || printer.host.endsWith('.200')
-    setPrinterStatus(s => ({ ...s, [printer.host]: ok ? 'ok' : 'error' }))
-  }
-
-  return (
-    <div className="space-y-6 max-w-2xl">
-      {/* Header */}
-      <div className="flex flex-col sm:flex-row sm:items-center sm:justify-between gap-3">
-        <div>
-          <h2 className="text-xl font-bold text-slate-100">Settings</h2>
-          <p className="text-sm text-slate-400">App configuration for Extrudex</p>
-        </div>
-        <div className="flex items-center gap-3">
-          {saved && (
-            <span className="inline-flex items-center gap-1.5 text-sm text-emerald-400">
-              <CheckCircle2 size={16} /> Saved
-            </span>
-          )}
-          {saveError && (
-            <span className="inline-flex items-center gap-1.5 text-sm text-red-400">
-              <AlertCircle size={16} /> Save failed
-            </span>
-          )}
-          <button
-            onClick={handleSave}
-            className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-4 py-2 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors"
-          >
-            <Save size={16} /> Save Settings
-          </button>
-        </div>
-      </div>
-
-      {/* Inventory Settings */}
-      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
-        <SectionHeader
-          title="Inventory"
-          description="Controls how spools are tracked and displayed"
-        />
-        <SettingRow
-          label="Low stock threshold"
-          hint="Spools below this weight are flagged as low stock"
-        >
-          <div>
-            <div className="flex items-center gap-2">
-              <input
-                type="number"
-                min={0}
-                max={10000}
-                step={10}
-                value={lowStockThreshold}
-                onChange={e => setLowStockThreshold(Number(e.target.value))}
-                className={`w-32 rounded-lg bg-slate-800 border ${thresholdError ? 'border-red-500' : 'border-slate-700'} px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500`}
-              />
-              <span className="text-sm text-slate-400">grams</span>
-            </div>
-            {thresholdError && <p className="mt-1 text-xs text-red-400">{thresholdError}</p>}
-          </div>
-        </SettingRow>
-
-        <SettingRow
-          label="Filament cross-section area"
-          hint="Used to convert mm extruded → grams (π × r²)"
-        >
-          <div>
-            <div className="flex items-center gap-2">
-              <input
-                type="number"
-                min={0.01}
-                max={100}
-                step={0.001}
-                value={crossSection}
-                onChange={e => setCrossSection(Number(e.target.value))}
-                className={`w-36 rounded-lg bg-slate-800 border ${crossSectionError ? 'border-red-500' : 'border-slate-700'} px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500`}
-              />
-              <span className="text-sm text-slate-400">mm²</span>
-            </div>
-            {crossSectionError && <p className="mt-1 text-xs text-red-400">{crossSectionError}</p>}
-            <p className="mt-1 text-xs text-slate-500">1.75mm filament = 2.405 mm² · 2.85mm filament = 6.379 mm²</p>
-          </div>
-        </SettingRow>
-
-        <SettingRow label="Currency" hint="Used for cost display throughout the app">
-          <select
-            value={currency}
-            onChange={e => setCurrency(e.target.value)}
-            className="rounded-lg bg-slate-800 border border-slate-700 px-3 py-2 text-sm text-slate-100 focus:outline-none focus:ring-2 focus:ring-emerald-500"
-          >
-            {CURRENCIES.map(c => (
-              <option key={c} value={c}>{c}</option>
-            ))}
-          </select>
-        </SettingRow>
-      </div>
-
-      {/* Appearance */}
-      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
-        <SectionHeader title="Appearance" />
-        <SettingRow label="Theme" hint="Override system default color scheme">
-          <div className="flex items-center gap-2">
-            {(['system', 'dark', 'light'] as const).map(t => (
-              <button
-                key={t}
-                onClick={() => setTheme(t)}
-                className={`inline-flex items-center gap-1.5 rounded-lg px-3 py-2 text-sm font-medium border transition-colors ${
-                  theme === t
-                    ? 'bg-emerald-600 border-emerald-500 text-white'
-                    : 'bg-slate-800 border-slate-700 text-slate-300 hover:bg-slate-700'
-                }`}
-              >
-                {t === 'dark' && <Moon size={14} />}
-                {t === 'light' && <Sun size={14} />}
-                {t === 'system' && <span className="text-xs">Auto</span>}
-                {t !== 'system' && <span className="capitalize">{t}</span>}
-                {t === 'system' && <span>System</span>}
-              </button>
-            ))}
-          </div>
-        </SettingRow>
-      </div>
-
-      {/* Printer Connections */}
-      <div className="rounded-lg border border-slate-700 bg-slate-800/50 px-4 pt-4 pb-2">
-        <SectionHeader
-          title="Printer Connections"
-          description="Test connectivity to configured printers"
-        />
-        {/* TODO: Load printer list from GET /api/printers */}
-        {MOCK_PRINTERS.map(printer => {
-          const status = printerStatus[printer.host] ?? 'idle'
-          return (
-            <SettingRow
-              key={printer.host}
-              label={printer.name}
-              hint={`${printer.type === 'bambu' ? 'Bambu MQTT' : 'Moonraker'} · ${printer.host}`}
-            >
-              <div className="flex items-center gap-3">
-                <StatusBadge status={status} />
-                <button
-                  onClick={() => testPrinterConnection(printer)}
-                  disabled={status === 'testing'}
-                  className="inline-flex items-center gap-1.5 rounded-lg bg-slate-700 border border-slate-600 px-3 py-1.5 text-xs font-medium text-slate-200 hover:bg-slate-600 disabled:opacity-50 disabled:cursor-not-allowed transition-colors"
-                >
-                  {status === 'testing' ? (
-                    <>
-                      <span className="animate-spin inline-block w-3 h-3 border border-slate-400 border-t-transparent rounded-full" />
-                      Testing…
-                    </>
-                  ) : (
-                    <>
-                      <Wifi size={12} /> Test Connection
-                    </>
-                  )}
-                </button>
-              </div>
-            </SettingRow>
-          )
-        })}
-      </div>
-
-      {/* Save footer (mobile convenience) */}
-      <div className="flex justify-end pb-4">
-        <button
-          onClick={handleSave}
-          className="inline-flex items-center gap-2 rounded-lg bg-emerald-600 px-5 py-2.5 text-sm font-semibold text-white hover:bg-emerald-500 active:bg-emerald-700 transition-colors"
-        >
-          <Save size={16} /> Save Settings
-        </button>
-      </div>
-    </div>
-  )
-}
-
-function StatusBadge({ status }: { status: ConnectionStatus }) {
-  if (status === 'idle') return null
-  if (status === 'testing') {
-    return (
-      <span className="inline-flex items-center gap-1 rounded-full bg-slate-700 border border-slate-600 px-2 py-0.5 text-xs text-slate-300">
-        Testing…
-      </span>
-    )
-  }
-  if (status === 'ok') {
-    return (
-      <span className="inline-flex items-center gap-1 rounded-full bg-emerald-900/30 border border-emerald-700 px-2 py-0.5 text-xs text-emerald-300">
-        <CheckCircle2 size={11} /> Connected
-      </span>
-    )
-  }
-  return (
-    <span className="inline-flex items-center gap-1 rounded-full bg-red-900/30 border border-red-700 px-2 py-0.5 text-xs text-red-300">
-      <WifiOff size={11} /> Unreachable
-    </span>
-  )
-}