Show results for two-way traceroute, including SNR values between hops (#1248)

app/src/main/java/com/geeksville/mesh/service/MeshService.kt

@@ -17,6 +17,7 @@ import com.geeksville.mesh.*
 import com.geeksville.mesh.LocalOnlyProtos.LocalConfig
 import com.geeksville.mesh.LocalOnlyProtos.LocalModuleConfig
 import com.geeksville.mesh.MeshProtos.MeshPacket
+import com.geeksville.mesh.MeshProtos.RouteDiscovery
 import com.geeksville.mesh.MeshProtos.ToRadio
 import com.geeksville.mesh.android.hasLocationPermission
 import com.geeksville.mesh.database.MeshLogRepository
@@ -684,11 +685,7 @@ class MeshService : Service(), Logging {
                     Portnums.PortNum.TRACEROUTE_APP_VALUE -> {
                         if (data.wantResponse) return // ignore data from traceroute requests
                         val parsed = MeshProtos.RouteDiscovery.parseFrom(data.payload)
-                        radioConfigRepository.setTracerouteResponse(buildString {
-                            append("${getUserName(packet.to)} --> ")
-                            parsed.routeList.forEach { num -> append("${getUserName(num)} --> ") }
-                            append(getUserName(packet.from))
-                        })
+                        handleReceivedTraceroute(packet, parsed)
                     }
 
                     else -> debug("No custom processing needed for ${data.portnumValue}")
@@ -829,6 +826,49 @@ class MeshService : Service(), Logging {
         }
     }
 
+    @Suppress("MagicNumber")
+    private fun formatTraceroutePath(nodesList: List<Int>, snrList: List<Int>): String {
+        // nodesList should include both origin and destination nodes
+        // origin will not have an SNR value, but destination should
+        val snrStr = if (snrList.size == nodesList.size - 1) snrList else {
+            // use unknown SNR for entire route if snrList has invalid size
+            List(nodesList.size - 1) { -128 }
+        }.map { snr ->
+            val str = if (snr == -128) "?" else "${snr / 4}"
+            "⇊ $str dB"
+        }
+
+        return nodesList.map { nodeId ->
+            "■ ${getUserName(nodeId)}"
+        }.flatMapIndexed { i, nodeStr ->
+            if (i == 0) listOf(nodeStr) else listOf(snrStr[i-1], nodeStr)
+        }.joinToString("\n")
+    }
+
+    private fun handleReceivedTraceroute(packet: MeshPacket, trace: RouteDiscovery) {
+        val nodesToward = mutableListOf<Int>()
+        nodesToward.add(packet.to)
+        nodesToward += trace.routeList
+        nodesToward.add(packet.from)
+
+        val nodesBack = mutableListOf<Int>()
+        if (packet.hopStart > 0 && trace.snrBackList.size > 0) { // otherwise back route is invalid
+            nodesBack.add(packet.from)
+            nodesBack += trace.routeBackList
+            nodesBack.add(packet.to)
+        }
+
+        radioConfigRepository.setTracerouteResponse(buildString {
+            append("Route traced toward destination:\n\n")
+            append(formatTraceroutePath(nodesToward, trace.snrTowardsList))
+            if (nodesBack.size > 0) {
+                append("\n\n")
+                append("Route traced back to us:\n\n")
+                append(formatTraceroutePath(nodesBack, trace.snrBackList))
+            }
+        })
+    }
+
     // If apps try to send packets when our radio is sleeping, we queue them here instead
     private val offlineSentPackets = mutableListOf<DataPacket>()