Add comprehensive godoc documentation to handler.go

Expand documentation comments for SimpleHandler type and its methods
to better explain their purpose, parameters, and behavior.

internal/routewatch/ashandler.go

@@ -171,7 +171,11 @@ func (h *ASHandler) flushBatchLocked() {
 	h.lastFlush = time.Now()
 }
 
-// Stop gracefully stops the handler and flushes remaining batches
+// Stop gracefully shuts down the ASHandler by signaling the background flush
+// goroutine to terminate and waiting for it to complete. Any pending ASN
+// operations in the current batch are flushed to the database before Stop
+// returns. This method should be called during application shutdown to ensure
+// no data is lost.
 func (h *ASHandler) Stop() {
 	close(h.stopCh)
 	h.wg.Wait()

internal/routewatch/peerhandler.go

@@ -47,7 +47,10 @@ type peerUpdate struct {
 	timestamp   time.Time
 }
 
-// NewPeerHandler creates a new batched peer tracking handler
+// NewPeerHandler creates a new PeerHandler with the given database store and logger.
+// It initializes the peer batch buffer and starts a background goroutine that
+// periodically flushes accumulated peer updates to the database. The handler
+// should be stopped by calling Stop when it is no longer needed.
 func NewPeerHandler(db database.Store, logger *logger.Logger) *PeerHandler {
 	h := &PeerHandler{
 		db:        db,
@@ -64,7 +67,9 @@ func NewPeerHandler(db database.Store, logger *logger.Logger) *PeerHandler {
 	return h
 }
 
-// WantsMessage returns true for all message types since we track peers from all messages
+// WantsMessage returns true for all message types since peer information
+// is extracted from every RIS message regardless of type. This satisfies
+// the MessageHandler interface.
 func (h *PeerHandler) WantsMessage(_ string) bool {
 	return true
 }

internal/routewatch/peeringhandler.go

@@ -72,18 +72,25 @@ func NewPeeringHandler(db database.Store, logger *logger.Logger) *PeeringHandler
 	return h
 }
 
-// WantsMessage returns true if this handler wants to process messages of the given type
+// WantsMessage reports whether the handler should receive messages of the
+// given type. PeeringHandler only processes UPDATE messages, as these contain
+// the AS path information needed to extract peering relationships.
 func (h *PeeringHandler) WantsMessage(messageType string) bool {
 	// We only care about UPDATE messages that have AS paths
 	return messageType == "UPDATE"
 }
 
-// QueueCapacity returns the desired queue capacity for this handler
+// QueueCapacity returns the buffer size for the handler's message queue.
+// This value is used by the message dispatcher to allocate the channel
+// buffer when registering the handler.
 func (h *PeeringHandler) QueueCapacity() int {
 	return peeringHandlerQueueSize
 }
 
-// HandleMessage processes a message to extract AS paths
+// HandleMessage processes a BGP UPDATE message by storing its AS path
+// in memory for later batch processing. Messages with AS paths shorter
+// than minPathLengthForPeering are ignored as they cannot contain valid
+// peering information.
 func (h *PeeringHandler) HandleMessage(msg *ristypes.RISMessage) {
 	// Skip if no AS path or only one AS
 	if len(msg.Path) < minPathLengthForPeering {