add interface stats and poe power monitoring via snmp

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nodes.go

@@ -11,9 +11,22 @@ import (
 )
 
 type Interface struct {
-	Name string
-	MAC  net.HardwareAddr
-	IPs  map[string]net.IP
+	Name  string
+	MAC   net.HardwareAddr
+	IPs   map[string]net.IP
+	Stats *InterfaceStats
+}
+
+type InterfaceStats struct {
+	Speed     uint64 // bits per second
+	InErrors  uint64
+	OutErrors uint64
+	PoE       *PoEStats
+}
+
+type PoEStats struct {
+	Power    float64 // watts in use
+	MaxPower float64 // watts allocated/negotiated
 }
 
 func (i *Interface) String() string {
@@ -31,6 +44,9 @@ func (i *Interface) String() string {
 	if len(ips) > 0 {
 		parts = append(parts, fmt.Sprintf("%v", ips))
 	}
+	if i.Stats != nil {
+		parts = append(parts, i.Stats.String())
+	}
 
 	result := parts[0]
 	for _, p := range parts[1:] {
@@ -39,6 +55,45 @@ func (i *Interface) String() string {
 	return result
 }
 
+func (s *InterfaceStats) String() string {
+	var parts []string
+
+	if s.Speed > 0 {
+		if s.Speed >= 1000000000 {
+			parts = append(parts, fmt.Sprintf("%dG", s.Speed/1000000000))
+		} else if s.Speed >= 1000000 {
+			parts = append(parts, fmt.Sprintf("%dM", s.Speed/1000000))
+		} else {
+			parts = append(parts, fmt.Sprintf("%d", s.Speed))
+		}
+	}
+
+	if s.InErrors > 0 || s.OutErrors > 0 {
+		parts = append(parts, fmt.Sprintf("err:%d/%d", s.InErrors, s.OutErrors))
+	}
+
+	if s.PoE != nil {
+		if s.PoE.MaxPower > 0 {
+			parts = append(parts, fmt.Sprintf("poe:%.1f/%.1fW", s.PoE.Power, s.PoE.MaxPower))
+		} else {
+			parts = append(parts, fmt.Sprintf("poe:%.1fW", s.PoE.Power))
+		}
+	}
+
+	return "[" + fmt.Sprintf("%s", joinParts(parts)) + "]"
+}
+
+func joinParts(parts []string) string {
+	result := ""
+	for i, p := range parts {
+		if i > 0 {
+			result += " "
+		}
+		result += p
+	}
+	return result
+}
+
 type Node struct {
 	Name       string
 	Interfaces map[string]*Interface