Fix issue #21 and add aircraft position tracking indicators

- Fix Debian package upgrade issue by separating upgrade vs remove behavior in prerm script
- Add aircraft position tracking statistics in merger GetStatistics() method
- Update frontend to display position tracking indicators in both header and stats view
- Format Go code to maintain consistency

🤖 Generated with [Claude Code](https://claude.ai/code)

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

assets/static/index.html

@@ -53,6 +53,7 @@
             <!-- Summary stats -->
             <div class="stats-summary">
                 <span id="aircraft-count">0 aircraft</span>
+                <span id="position-summary">0 positioned</span>
                 <span id="sources-count">0 sources</span>
                 <span id="active-clients">1 viewer</span>
                 <span id="connection-status" class="connection-status disconnected">Connecting...</span>
@@ -208,6 +209,14 @@
                         <h3>Max Range</h3>
                         <div class="stat-value" id="max-range">0 km</div>
                     </div>
+                    <div class="stat-card">
+                        <h3>Aircraft with Position</h3>
+                        <div class="stat-value" id="aircraft-with-position">0</div>
+                    </div>
+                    <div class="stat-card">
+                        <h3>Aircraft without Position</h3>
+                        <div class="stat-value" id="aircraft-without-position">0</div>
+                    </div>
                 </div>
                 
                 <!-- Charts -->

assets/static/js/modules/ui-manager.js

@@ -244,6 +244,8 @@ export class UIManager {
         const activeViewersEl = document.getElementById('active-viewers');
         const maxRangeEl = document.getElementById('max-range');
         const messagesSecEl = document.getElementById('messages-sec');
+        const aircraftWithPositionEl = document.getElementById('aircraft-with-position');
+        const aircraftWithoutPositionEl = document.getElementById('aircraft-without-position');
         
         if (totalAircraftEl) totalAircraftEl.textContent = this.aircraftData.size;
         if (activeSourcesEl) {
@@ -253,6 +255,14 @@ export class UIManager {
             activeViewersEl.textContent = this.stats.active_clients || 1;
         }
         
+        // Update position tracking statistics from backend
+        if (aircraftWithPositionEl) {
+            aircraftWithPositionEl.textContent = this.stats.aircraft_with_position || 0;
+        }
+        if (aircraftWithoutPositionEl) {
+            aircraftWithoutPositionEl.textContent = this.stats.aircraft_without_position || 0;
+        }
+        
         // Calculate max range
         let maxDistance = 0;
         for (const aircraft of this.aircraftData.values()) {
@@ -270,10 +280,18 @@ export class UIManager {
 
     updateHeaderInfo() {
         const aircraftCountEl = document.getElementById('aircraft-count');
+        const positionSummaryEl = document.getElementById('position-summary');
         const sourcesCountEl = document.getElementById('sources-count');
         const activeClientsEl = document.getElementById('active-clients');
         
         if (aircraftCountEl) aircraftCountEl.textContent = `${this.aircraftData.size} aircraft`;
+        
+        // Update position summary in header
+        if (positionSummaryEl) {
+            const positioned = this.stats.aircraft_with_position || 0;
+            positionSummaryEl.textContent = `${positioned} positioned`;
+        }
+        
         if (sourcesCountEl) sourcesCountEl.textContent = `${this.sourcesData.size} sources`;
         
         // Update active clients count

cmd/vrs-test/main.go

@@ -130,4 +130,4 @@ func main() {
 			fmt.Println("----------------------------------------")
 		}
 	}
-}
+}

debian/DEBIAN/prerm

@@ -2,8 +2,8 @@
 set -e
 
 case "$1" in
-    remove|upgrade|deconfigure)
+    remove|deconfigure)
-        # Stop and disable the service
+        # Stop and disable the service on removal
         if systemctl is-active --quiet skyview-adsb.service; then
             systemctl stop skyview-adsb.service
         fi
@@ -12,6 +12,13 @@ case "$1" in
             systemctl disable skyview-adsb.service
         fi
         ;;
+    upgrade)
+        # Only stop service during upgrade, preserve enabled state
+        if systemctl is-active --quiet skyview-adsb.service; then
+            systemctl stop skyview-adsb.service
+        fi
+        # Don't disable - postinst will restart if service was enabled
+        ;;
 esac
 
 exit 0

internal/client/vrs.go

@@ -36,7 +36,7 @@ type VRSClient struct {
 	errChan  chan error           // Error reporting channel
 	stopChan chan struct{}        // Shutdown signal channel
 	wg       sync.WaitGroup       // Wait group for goroutine coordination
-	
+
 	// Reconnection parameters
 	reconnectDelay time.Duration // Initial reconnect delay
 	maxReconnect   time.Duration // Maximum reconnect delay (for backoff cap)
@@ -116,9 +116,9 @@ func (c *VRSClient) Stop() {
 // Source status is updated to reflect connection state for monitoring
 func (c *VRSClient) run(ctx context.Context) {
 	defer c.wg.Done()
-	
+
 	reconnectDelay := c.reconnectDelay
-	
+
 	for {
 		select {
 		case <-ctx.Done():
@@ -127,16 +127,16 @@ func (c *VRSClient) run(ctx context.Context) {
 			return
 		default:
 		}
-		
+
 		// Connect to VRS JSON stream
 		addr := fmt.Sprintf("%s:%d", c.source.Host, c.source.Port)
 		fmt.Printf("Connecting to VRS JSON stream at %s (%s)...\n", addr, c.source.Name)
-		
+
 		conn, err := net.DialTimeout("tcp", addr, 30*time.Second)
 		if err != nil {
 			fmt.Printf("Failed to connect to VRS source %s: %v\n", c.source.Name, err)
 			c.source.Active = false
-			
+
 			// Exponential backoff
 			time.Sleep(reconnectDelay)
 			if reconnectDelay < c.maxReconnect {
@@ -144,21 +144,21 @@ func (c *VRSClient) run(ctx context.Context) {
 			}
 			continue
 		}
-		
+
 		c.conn = conn
 		c.source.Active = true
 		reconnectDelay = c.reconnectDelay // Reset backoff
-		
+
 		fmt.Printf("Connected to VRS source %s at %s\n", c.source.Name, addr)
-		
+
 		// Create parser for this connection
 		c.parser = vrs.NewParser(conn, c.source.ID)
-		
+
 		// Start processing messages
 		c.wg.Add(2)
 		go c.readMessages()
 		go c.processMessages()
-		
+
 		// Wait for disconnect
 		select {
 		case <-ctx.Done():
@@ -172,7 +172,7 @@ func (c *VRSClient) run(ctx context.Context) {
 			c.conn.Close()
 			c.source.Active = false
 		}
-		
+
 		// Wait for goroutines to finish
 		time.Sleep(1 * time.Second)
 	}
@@ -206,7 +206,7 @@ func (c *VRSClient) readMessages() {
 // and conflict resolution based on signal strength
 func (c *VRSClient) processMessages() {
 	defer c.wg.Done()
-	
+
 	for {
 		select {
 		case <-c.stopChan:
@@ -215,7 +215,7 @@ func (c *VRSClient) processMessages() {
 			if msg == nil {
 				return
 			}
-			
+
 			// Process each aircraft in the message
 			for _, vrsAircraft := range msg.AcList {
 				// Convert VRS aircraft to internal format
@@ -223,7 +223,7 @@ func (c *VRSClient) processMessages() {
 				if aircraft == nil {
 					continue // Skip invalid aircraft
 				}
-				
+
 				// Update merger with new data
 				// Note: VRS doesn't provide signal strength, so we use a default value
 				c.merger.UpdateAircraft(
@@ -232,7 +232,7 @@ func (c *VRSClient) processMessages() {
 					-30.0, // Default signal strength for VRS sources
 					vrsAircraft.GetTimestamp(),
 				)
-				
+
 				// Update source statistics
 				c.source.Messages++
 			}
@@ -258,75 +258,75 @@ func (c *VRSClient) convertVRSToAircraft(vrs *vrs.VRSAircraft) *modes.Aircraft {
 	if err != nil {
 		return nil // Invalid ICAO, skip this aircraft
 	}
-	
+
 	// Create aircraft structure
 	aircraft := &modes.Aircraft{
 		ICAO24: icao,
 	}
-	
+
 	// Set position if available
 	if vrs.HasPosition() {
 		aircraft.Latitude = vrs.Lat
 		aircraft.Longitude = vrs.Long
 		aircraft.PositionValid = true
 	}
-	
+
 	// Set altitude if available
 	if vrs.HasAltitude() {
 		aircraft.Altitude = vrs.GetAltitude()
 		aircraft.AltitudeValid = true
-		
+
 		// Set barometric altitude specifically
 		if vrs.Alt != 0 {
 			aircraft.BaroAltitude = vrs.Alt
 		}
-		
+
 		// Set geometric altitude if different from barometric
 		if vrs.GAlt != 0 {
 			aircraft.GeomAltitude = vrs.GAlt
 			aircraft.GeomAltitudeValid = true
 		}
 	}
-	
+
 	// Set speed if available
 	if vrs.Spd > 0 {
 		aircraft.GroundSpeed = int(vrs.Spd)
 		aircraft.GroundSpeedValid = true
 	}
-	
+
 	// Set heading/track if available
 	if vrs.Trak > 0 {
 		aircraft.Track = int(vrs.Trak)
 		aircraft.TrackValid = true
 	}
-	
+
 	// Set vertical rate if available
 	if vrs.Vsi != 0 {
 		aircraft.VerticalRate = vrs.Vsi
 		aircraft.VerticalRateValid = true
 	}
-	
+
 	// Set callsign if available
 	if vrs.Call != "" {
 		aircraft.Callsign = vrs.Call
 		aircraft.CallsignValid = true
 	}
-	
+
 	// Set squawk if available
 	if squawk, err := vrs.GetSquawk(); err == nil {
 		aircraft.Squawk = fmt.Sprintf("%04X", squawk) // Convert to hex string
 		aircraft.SquawkValid = true
 	}
-	
+
 	// Set ground status
 	aircraft.OnGround = vrs.IsOnGround()
 	aircraft.OnGroundValid = true
-	
+
 	// Set selected altitude if available
 	if vrs.TAlt != 0 {
 		aircraft.SelectedAltitude = vrs.TAlt
 	}
-	
+
 	// Set position source
 	switch vrs.GetPositionSource() {
 	case "MLAT":
@@ -334,7 +334,7 @@ func (c *VRSClient) convertVRSToAircraft(vrs *vrs.VRSAircraft) *modes.Aircraft {
 	case "TIS-B":
 		aircraft.PositionTISB = true
 	}
-	
+
 	// Set additional metadata if available
 	if vrs.Reg != "" {
 		aircraft.Registration = vrs.Reg
@@ -345,6 +345,6 @@ func (c *VRSClient) convertVRSToAircraft(vrs *vrs.VRSAircraft) *modes.Aircraft {
 	if vrs.Op != "" {
 		aircraft.Operator = vrs.Op
 	}
-	
+
 	return aircraft
-}
+}

internal/merger/merger.go

@@ -795,10 +795,13 @@ func (m *Merger) GetSources() []*Source {
 //
 // The statistics include:
 //   - total_aircraft: Current number of tracked aircraft
+//   - aircraft_with_position: Number of aircraft with valid position data
+//   - aircraft_without_position: Number of aircraft without position data
 //   - total_messages: Sum of all messages processed
 //   - active_sources: Number of currently connected sources
 //   - aircraft_by_sources: Distribution of aircraft by number of tracking sources
 //
+// The position statistics help assess data quality and tracking effectiveness.
 // The aircraft_by_sources map shows data quality - aircraft tracked by
 // multiple sources generally have better position accuracy and reliability.
 //
@@ -810,11 +813,22 @@ func (m *Merger) GetStatistics() map[string]interface{} {
 	totalMessages := int64(0)
 	activeSources := 0
 	aircraftBySources := make(map[int]int) // Count by number of sources
+	aircraftWithPosition := 0
+	aircraftWithoutPosition := 0
 
 	for _, state := range m.aircraft {
 		totalMessages += state.TotalMessages
 		numSources := len(state.Sources)
 		aircraftBySources[numSources]++
+
+		// Check if aircraft has valid position data
+		if state.Aircraft.PositionValid &&
+			state.Aircraft.Latitude != 0.0 &&
+			state.Aircraft.Longitude != 0.0 {
+			aircraftWithPosition++
+		} else {
+			aircraftWithoutPosition++
+		}
 	}
 
 	for _, src := range m.sources {
@@ -824,10 +838,12 @@ func (m *Merger) GetStatistics() map[string]interface{} {
 	}
 
 	return map[string]interface{}{
-		"total_aircraft":      len(m.aircraft),
+		"total_aircraft":            len(m.aircraft),
-		"total_messages":      totalMessages,
+		"aircraft_with_position":    aircraftWithPosition,
-		"active_sources":      activeSources,
+		"aircraft_without_position": aircraftWithoutPosition,
-		"aircraft_by_sources": aircraftBySources,
+		"total_messages":            totalMessages,
+		"active_sources":            activeSources,
+		"aircraft_by_sources":       aircraftBySources,
 	}
 }
 

internal/modes/decoder.go

@@ -157,10 +157,10 @@ type Aircraft struct {
 	BaroSetting      float64 // Barometric pressure setting (QNH) in millibars
 
 	// Additional fields from VRS JSON and extended sources
-	Registration      string // Aircraft registration (e.g., "N12345")
+	Registration string // Aircraft registration (e.g., "N12345")
-	AircraftType      string // Aircraft type (e.g., "B738")
+	AircraftType string // Aircraft type (e.g., "B738")
-	Operator          string // Airline or operator name
+	Operator     string // Airline or operator name
-	
+
 	// Validity flags for optional fields (used by VRS and other sources)
 	CallsignValid     bool // Whether callsign is valid
 	PositionValid     bool // Whether position is valid

internal/vrs/parser.go

@@ -34,30 +34,30 @@ type VRSMessage struct {
 
 // VRSAircraft represents a single aircraft in VRS JSON format
 type VRSAircraft struct {
-	Icao  string  `json:"Icao"`  // ICAO hex address (may have ~ prefix for non-ICAO)
+	Icao string  `json:"Icao"` // ICAO hex address (may have ~ prefix for non-ICAO)
-	Lat   float64 `json:"Lat"`   // Latitude
+	Lat  float64 `json:"Lat"`  // Latitude
-	Long  float64 `json:"Long"`  // Longitude
+	Long float64 `json:"Long"` // Longitude
-	Alt   int     `json:"Alt"`   // Barometric altitude in feet
+	Alt  int     `json:"Alt"`  // Barometric altitude in feet
-	GAlt  int     `json:"GAlt"`  // Geometric altitude in feet
+	GAlt int     `json:"GAlt"` // Geometric altitude in feet
-	Spd   float64 `json:"Spd"`   // Speed in knots
+	Spd  float64 `json:"Spd"`  // Speed in knots
-	Trak  float64 `json:"Trak"`  // Track/heading in degrees
+	Trak float64 `json:"Trak"` // Track/heading in degrees
-	Vsi   int     `json:"Vsi"`   // Vertical speed in feet/min
+	Vsi  int     `json:"Vsi"`  // Vertical speed in feet/min
-	Sqk   string  `json:"Sqk"`   // Squawk code
+	Sqk  string  `json:"Sqk"`  // Squawk code
-	Call  string  `json:"Call"`  // Callsign
+	Call string  `json:"Call"` // Callsign
-	Gnd   bool    `json:"Gnd"`   // On ground flag
+	Gnd  bool    `json:"Gnd"`  // On ground flag
-	TAlt  int     `json:"TAlt"`  // Target altitude
+	TAlt int     `json:"TAlt"` // Target altitude
-	Mlat  bool    `json:"Mlat"`  // MLAT position flag
+	Mlat bool    `json:"Mlat"` // MLAT position flag
-	Tisb  bool    `json:"Tisb"`  // TIS-B flag
+	Tisb bool    `json:"Tisb"` // TIS-B flag
-	Sat   bool    `json:"Sat"`   // Satellite (JAERO) position flag
+	Sat  bool    `json:"Sat"`  // Satellite (JAERO) position flag
-	
+
 	// Additional fields that may be present
-	Reg   string `json:"Reg"`   // Registration
+	Reg  string `json:"Reg"`  // Registration
-	Type  string `json:"Type"`  // Aircraft type
+	Type string `json:"Type"` // Aircraft type
-	Mdl   string `json:"Mdl"`   // Model
+	Mdl  string `json:"Mdl"`  // Model
-	Op    string `json:"Op"`    // Operator
+	Op   string `json:"Op"`   // Operator
-	From  string `json:"From"`  // Departure airport
+	From string `json:"From"` // Departure airport
-	To    string `json:"To"`    // Destination airport
+	To   string `json:"To"`   // Destination airport
-	
+
 	// Timing fields
 	PosTime int64 `json:"PosTime"` // Position timestamp (milliseconds)
 }
@@ -95,21 +95,21 @@ func (p *Parser) ReadMessage() (*VRSMessage, error) {
 	if err != nil {
 		return nil, err
 	}
-	
+
 	// Trim whitespace
 	line = strings.TrimSpace(line)
 	if line == "" {
 		// Empty line, try again
 		return p.ReadMessage()
 	}
-	
+
 	// Parse JSON
 	var msg VRSMessage
 	if err := json.Unmarshal([]byte(line), &msg); err != nil {
 		// Invalid JSON, skip and continue
 		return p.ReadMessage()
 	}
-	
+
 	return &msg, nil
 }
 
@@ -146,13 +146,13 @@ func (p *Parser) ParseStream(msgChan chan<- *VRSMessage, errChan chan<- error) {
 func (a *VRSAircraft) GetICAO24() (uint32, error) {
 	// Remove non-ICAO prefix if present
 	icaoStr := strings.TrimPrefix(a.Icao, "~")
-	
+
 	// Parse hex string
 	icao64, err := strconv.ParseUint(icaoStr, 16, 24)
 	if err != nil {
 		return 0, fmt.Errorf("invalid ICAO address: %s", a.Icao)
 	}
-	
+
 	return uint32(icao64), nil
 }
 
@@ -195,13 +195,13 @@ func (a *VRSAircraft) GetSquawk() (uint16, error) {
 	if a.Sqk == "" {
 		return 0, fmt.Errorf("no squawk code")
 	}
-	
+
 	// Parse hex squawk code
 	squawk64, err := strconv.ParseUint(a.Sqk, 16, 16)
 	if err != nil {
 		return 0, fmt.Errorf("invalid squawk code: %s", a.Sqk)
 	}
-	
+
 	return uint16(squawk64), nil
 }
 
@@ -231,4 +231,4 @@ func (a *VRSAircraft) GetTimestamp() time.Time {
 // IsOnGround returns true if the aircraft is on the ground
 func (a *VRSAircraft) IsOnGround() bool {
 	return a.Gnd
-}
+}