1 files changed, 284 insertions, 0 deletions
diff --git a/transport/failover.go b/transport/failover.go
new file mode 100644
index 0000000..77129a3
--- /dev/null
+++ b/transport/failover.go
@@ -0,0 +1,284 @@
+// Package transport - Multi-transport failover for war zones
+package transport
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"time"
+)
+
+// FailoverTransport implements automatic failover between multiple transports
+// Critical for war zones: Tor → Mesh → Bluetooth → Direct
+type FailoverTransport struct {
+	transports     []Transport          // Ordered list of transports to try
+	currentIndex   int                  // Currently active transport
+	mu             sync.RWMutex
+	healthCheck    map[TransportType]time.Time // Last successful connection
+	retryInterval  time.Duration
+	maxRetries     int
+	onFailover     func(from, to TransportType) // Callback when failing over
+}
+
+// FailoverConfig holds failover configuration
+type FailoverConfig struct {
+	RetryInterval time.Duration // Time between retry attempts
+	MaxRetries    int           // Max retries per transport before failing over
+	HealthCheckInterval time.Duration // How often to health check transports
+}
+
+// NewFailoverTransport creates a new failover transport
+func NewFailoverTransport(transports []Transport, config *FailoverConfig) *FailoverTransport {
+	if config == nil {
+		config = &FailoverConfig{
+			RetryInterval:       5 * time.Second,
+			MaxRetries:          3,
+			HealthCheckInterval: 30 * time.Second,
+		}
+	}
+
+	ft := &FailoverTransport{
+		transports:    transports,
+		currentIndex:  0,
+		healthCheck:   make(map[TransportType]time.Time),
+		retryInterval: config.RetryInterval,
+		maxRetries:    config.MaxRetries,
+	}
+
+	// Start health checking
+	go ft.healthCheckLoop(config.HealthCheckInterval)
+
+	return ft
+}
+
+// Connect attempts to connect using transports in priority order
+func (ft *FailoverTransport) Connect(address string) (net.Conn, error) {
+	ft.mu.Lock()
+	startIndex := ft.currentIndex
+	ft.mu.Unlock()
+
+	// Try each transport in order
+	for attempt := 0; attempt < len(ft.transports)*ft.maxRetries; attempt++ {
+		ft.mu.Lock()
+		index := ft.currentIndex
+		transport := ft.transports[index]
+		ft.mu.Unlock()
+
+		transportType := transport.Type()
+
+		// Attempt connection
+		conn, err := transport.Connect(address)
+		if err == nil {
+			// Success!
+			ft.mu.Lock()
+			ft.healthCheck[transportType] = time.Now()
+			ft.mu.Unlock()
+
+			fmt.Printf("✓ Connected via %s\n", transportType)
+			return conn, nil
+		}
+
+		fmt.Printf("✗ %s connection failed: %v\n", transportType, err)
+
+		// Move to next transport
+		ft.mu.Lock()
+		oldIndex := ft.currentIndex
+		ft.currentIndex = (ft.currentIndex + 1) % len(ft.transports)
+		newTransport := ft.transports[ft.currentIndex]
+		ft.mu.Unlock()
+
+		// Notify failover
+		if ft.onFailover != nil && oldIndex != ft.currentIndex {
+			go ft.onFailover(transport.Type(), newTransport.Type())
+		}
+
+		// Wait before retry
+		time.Sleep(ft.retryInterval)
+	}
+
+	return nil, fmt.Errorf("all transports failed after %d attempts", len(ft.transports)*ft.maxRetries)
+}
+
+// Listen starts listening on the highest priority available transport
+func (ft *FailoverTransport) Listen(address string) (net.Listener, error) {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	// Try each transport
+	for _, transport := range ft.transports {
+		listener, err := transport.Listen(address)
+		if err == nil {
+			fmt.Printf("✓ Listening on %s\n", transport.Type())
+			return listener, nil
+		}
+		fmt.Printf("✗ Listen failed on %s: %v\n", transport.Type(), err)
+	}
+
+	return nil, fmt.Errorf("all transports failed to listen")
+}
+
+// Type returns the currently active transport type
+func (ft *FailoverTransport) Type() TransportType {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	if ft.currentIndex < len(ft.transports) {
+		return ft.transports[ft.currentIndex].Type()
+	}
+	return TransportType(-1)
+}
+
+// Close closes all transports
+func (ft *FailoverTransport) Close() error {
+	ft.mu.Lock()
+	defer ft.mu.Unlock()
+
+	var lastErr error
+	for _, transport := range ft.transports {
+		if err := transport.Close(); err != nil {
+			lastErr = err
+		}
+	}
+	return lastErr
+}
+
+// GetCurrentTransport returns the currently active transport
+func (ft *FailoverTransport) GetCurrentTransport() Transport {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	if ft.currentIndex < len(ft.transports) {
+		return ft.transports[ft.currentIndex]
+	}
+	return nil
+}
+
+// GetTransports returns all available transports
+func (ft *FailoverTransport) GetTransports() []Transport {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	return ft.transports
+}
+
+// SetTransportPriority reorders transports by priority
+func (ft *FailoverTransport) SetTransportPriority(types []TransportType) error {
+	ft.mu.Lock()
+	defer ft.mu.Unlock()
+
+	if len(types) != len(ft.transports) {
+		return fmt.Errorf("priority list length mismatch")
+	}
+
+	// Create new ordered list
+	newTransports := make([]Transport, 0, len(ft.transports))
+	for _, targetType := range types {
+		found := false
+		for _, transport := range ft.transports {
+			if transport.Type() == targetType {
+				newTransports = append(newTransports, transport)
+				found = true
+				break
+			}
+		}
+		if !found {
+			return fmt.Errorf("transport type %s not found", targetType)
+		}
+	}
+
+	ft.transports = newTransports
+	ft.currentIndex = 0
+
+	return nil
+}
+
+// healthCheckLoop periodically checks transport health
+func (ft *FailoverTransport) healthCheckLoop(interval time.Duration) {
+	ticker := time.NewTicker(interval)
+	defer ticker.Stop()
+
+	for range ticker.C {
+		ft.performHealthCheck()
+	}
+}
+
+// performHealthCheck checks if current transport is still healthy
+func (ft *FailoverTransport) performHealthCheck() {
+	ft.mu.RLock()
+	current := ft.transports[ft.currentIndex]
+	lastSuccess, exists := ft.healthCheck[current.Type()]
+	ft.mu.RUnlock()
+
+	// If no successful connection in last 5 minutes, try next transport
+	if !exists || time.Since(lastSuccess) > 5*time.Minute {
+		ft.mu.Lock()
+		oldIndex := ft.currentIndex
+		ft.currentIndex = (ft.currentIndex + 1) % len(ft.transports)
+		ft.mu.Unlock()
+
+		if ft.onFailover != nil && oldIndex != ft.currentIndex {
+			ft.mu.RLock()
+			go ft.onFailover(ft.transports[oldIndex].Type(), ft.transports[ft.currentIndex].Type())
+			ft.mu.RUnlock()
+		}
+	}
+}
+
+// SetOnFailover sets callback for failover events
+func (ft *FailoverTransport) SetOnFailover(callback func(from, to TransportType)) {
+	ft.mu.Lock()
+	defer ft.mu.Unlock()
+	ft.onFailover = callback
+}
+
+// GetHealthStatus returns health status of all transports
+func (ft *FailoverTransport) GetHealthStatus() map[TransportType]time.Time {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	status := make(map[TransportType]time.Time)
+	for k, v := range ft.healthCheck {
+		status[k] = v
+	}
+	return status
+}
+
+// String returns a string representation
+func (ft *FailoverTransport) String() string {
+	ft.mu.RLock()
+	defer ft.mu.RUnlock()
+
+	currentType := "none"
+	if ft.currentIndex < len(ft.transports) {
+		currentType = ft.transports[ft.currentIndex].Type().String()
+	}
+
+	return fmt.Sprintf("FailoverTransport(current=%s, transports=%d)",
+		currentType, len(ft.transports))
+}
+
+// ConnectWithRetry attempts connection with exponential backoff
+func (ft *FailoverTransport) ConnectWithRetry(address string, maxAttempts int) (net.Conn, error) {
+	var conn net.Conn
+	var err error
+
+	backoff := 1 * time.Second
+
+	for attempt := 1; attempt <= maxAttempts; attempt++ {
+		conn, err = ft.Connect(address)
+		if err == nil {
+			return conn, nil
+		}
+
+		fmt.Printf("Attempt %d/%d failed, retrying in %v...\n", attempt, maxAttempts, backoff)
+		time.Sleep(backoff)
+
+		// Exponential backoff with jitter
+		backoff *= 2
+		if backoff > 60*time.Second {
+			backoff = 60 * time.Second
+		}
+	}
+
+	return nil, fmt.Errorf("failed after %d attempts: %w", maxAttempts, err)
+}