feat: Implement network status banner

src/App.tsx

@@ -18,6 +18,7 @@ import { EntityErrorBoundary } from "@/components/error/EntityErrorBoundary";
 import { breadcrumb } from "@/lib/errorBreadcrumbs";
 import { handleError } from "@/lib/errorHandler";
 import { RetryStatusIndicator } from "@/components/ui/retry-status-indicator";
+import { NetworkStatusBanner } from "@/components/ui/network-status-banner";
 
 // Core routes (eager-loaded for best UX)
 import Index from "./pages/Index";
@@ -134,6 +135,7 @@ function AppContent(): React.JSX.Element {
     <TooltipProvider>
       <NavigationTracker />
         <LocationAutoDetectProvider />
+        <NetworkStatusBanner />
         <RetryStatusIndicator />
         <Toaster />
         <Sonner />

src/components/ui/network-status-banner.tsx

@@ -0,0 +1,83 @@
+import { useEffect, useState } from 'react';
+import { XCircle, Loader2 } from 'lucide-react';
+import { Alert, AlertDescription, AlertTitle } from '@/components/ui/alert';
+import { useCircuitBreakerStatus } from '@/hooks/useCircuitBreakerStatus';
+import { CircuitState } from '@/lib/circuitBreaker';
+import { cn } from '@/lib/utils';
+
+export function NetworkStatusBanner() {
+  const { state, failureCount, isOpen, isHalfOpen } = useCircuitBreakerStatus();
+  const [countdown, setCountdown] = useState(60);
+
+  // Countdown for next retry attempt (when OPEN)
+  useEffect(() => {
+    if (!isOpen) return;
+
+    setCountdown(60); // Reset timeout from circuit breaker config
+    const interval = setInterval(() => {
+      setCountdown(prev => Math.max(0, prev - 1));
+    }, 1000);
+
+    return () => clearInterval(interval);
+  }, [isOpen]);
+
+  // Don't show if circuit is closed
+  if (state === CircuitState.CLOSED) return null;
+
+  // OPEN state - critical error
+  if (isOpen) {
+    return (
+      <Alert 
+        role="alert"
+        aria-live="assertive"
+        aria-atomic="true"
+        variant="destructive" 
+        className={cn(
+          "rounded-none border-x-0 border-t-0",
+          "animate-in slide-in-from-top-4 duration-300",
+          "bg-destructive/90 backdrop-blur-sm"
+        )}
+      >
+        <XCircle className="h-5 w-5 animate-pulse" />
+        <AlertTitle className="font-semibold text-lg">
+          Database Unavailable
+        </AlertTitle>
+        <AlertDescription className="text-sm mt-1">
+          Our systems detected a service outage. <strong>Data and authentication are temporarily unavailable.</strong>
+          {' '}Retrying automatically... (next attempt in {countdown}s)
+          {failureCount > 0 && (
+            <span className="block mt-1 text-xs opacity-80">
+              {failureCount} failed connection attempts detected
+            </span>
+          )}
+        </AlertDescription>
+      </Alert>
+    );
+  }
+
+  // HALF_OPEN state - testing recovery
+  if (isHalfOpen) {
+    return (
+      <Alert 
+        role="alert"
+        aria-live="polite"
+        aria-atomic="true"
+        className={cn(
+          "rounded-none border-x-0 border-t-0",
+          "animate-in slide-in-from-top-4 duration-300",
+          "bg-amber-500/20 dark:bg-amber-500/30 border-amber-500"
+        )}
+      >
+        <Loader2 className="h-5 w-5 animate-spin text-amber-600 dark:text-amber-400" />
+        <AlertTitle className="font-semibold text-amber-900 dark:text-amber-100">
+          Connection Unstable
+        </AlertTitle>
+        <AlertDescription className="text-sm text-amber-800 dark:text-amber-200 mt-1">
+          Testing database connection... Some features may be slow or temporarily unavailable.
+        </AlertDescription>
+      </Alert>
+    );
+  }
+
+  return null;
+}

src/hooks/useCircuitBreakerStatus.ts

@@ -0,0 +1,54 @@
+import { useState, useEffect } from 'react';
+import { supabaseCircuitBreaker, CircuitState } from '@/lib/circuitBreaker';
+import { logger } from '@/lib/logger';
+
+export function useCircuitBreakerStatus() {
+  const [state, setState] = useState<CircuitState>(CircuitState.CLOSED);
+  const [failureCount, setFailureCount] = useState(0);
+  const [lastStateChange, setLastStateChange] = useState<Date>(new Date());
+
+  useEffect(() => {
+    // Check immediately on mount
+    const checkState = () => {
+      const currentState = supabaseCircuitBreaker.getState();
+      const currentFailures = supabaseCircuitBreaker.getFailureCount();
+      
+      setState(prevState => {
+        if (prevState !== currentState) {
+          setLastStateChange(new Date());
+          
+          // Log state changes for monitoring
+          logger.info('Circuit breaker state changed', {
+            from: prevState,
+            to: currentState,
+            failureCount: currentFailures
+          });
+          
+          // Emit custom event for other components
+          window.dispatchEvent(new CustomEvent('circuit-breaker-state-change', {
+            detail: { state: currentState, failureCount: currentFailures }
+          }));
+        }
+        return currentState;
+      });
+      
+      setFailureCount(currentFailures);
+    };
+
+    checkState();
+    
+    // Poll every 5 seconds
+    const interval = setInterval(checkState, 5000);
+    
+    return () => clearInterval(interval);
+  }, []);
+
+  return {
+    state,
+    failureCount,
+    lastStateChange,
+    isOpen: state === CircuitState.OPEN,
+    isHalfOpen: state === CircuitState.HALF_OPEN,
+    isClosed: state === CircuitState.CLOSED
+  };
+}

src/lib/circuitBreaker.ts

@@ -98,6 +98,13 @@ export class CircuitBreaker {
         logger.info('Circuit breaker CLOSED - service recovered', {
           successCount: this.successCount
         });
+        
+        // Emit event for UI components
+        if (typeof window !== 'undefined') {
+          window.dispatchEvent(new CustomEvent('circuit-breaker-closed', {
+            detail: { successCount: this.successCount }
+          }));
+        }
       }
     }
   }
@@ -122,6 +129,16 @@ export class CircuitBreaker {
         monitoringWindow: this.config.monitoringWindow,
         resetTimeout: this.config.resetTimeout
       });
+      
+      // Emit event for UI components
+      if (typeof window !== 'undefined') {
+        window.dispatchEvent(new CustomEvent('circuit-breaker-opened', {
+          detail: {
+            failures: this.failures.length,
+            threshold: this.config.failureThreshold
+          }
+        }));
+      }
     }
   }