AntennaRelay: Formalized the circular network check to check for circles of arbitrary length.
AntennaRelay: Formalized the circular network check to check for circles of arbitrary length.

--- a/ARMapRenderer.cs
+++ b/ARMapRenderer.cs
@@ -167,6 +167,7 @@
 
 						if (vesselRelay == null)
 						{
+							log.AppendFormat("\n\tGot null relay for vessel {0}", vessel.vesselName);
 							continue;
 						}
 
@@ -206,7 +207,7 @@
 		{
 			this.Cleanup();
 
-			print("ARMapRenderer: Destroyed.");
+			this.Log("Destroyed");
 		}
 		#endregion
 
@@ -273,18 +274,21 @@
 			if (relay.KerbinDirect)
 			{
 				nextPoint = ScaledSpace.LocalToScaledSpace(AntennaRelay.Kerbin.position);
-				relay = null;
 			}
 			else
 			{
-				if (relay.targetRelay == null)
-				{
+				if (relay.targetRelay == null || relay.targetRelay.vessel == null)
+				{
+					this.LogError(
+						"SetRelayVertices: relay {0} has null target relay or vessel when not KerbinDirect, bailing out!",
+						relay
+					);
+
 					renderer.enabled = false;
 					return;
 				}
 
 				nextPoint = ScaledSpace.LocalToScaledSpace(relay.targetRelay.vessel.GetWorldPos3D());
-				relay = relay.targetRelay;
 			}
 
 			renderer.SetColors(thisColor, thisColor);

--- a/AntennaRelay.cs
+++ b/AntennaRelay.cs
@@ -26,6 +26,8 @@
 // WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#define DEBUG
+
 using System;
 using System.Collections.Generic;
 using ToadicusTools;
@@ -198,6 +200,7 @@
 			this.KerbinDirect = true;
 
 			CelestialBody bodyOccludingBestOccludedRelay = null;
+			IAntennaRelay needle;
 
 			double nearestRelaySqrDistance = double.PositiveInfinity;
 			double bestOccludedSqrDistance = double.PositiveInfinity;
@@ -221,6 +224,7 @@
 				
 				if (potentialVessel == null)
 				{
+					Tools.PostErrorMessage("{0}: Skipping vessel at index {1} because it is null.", this, vIdx);
 					log.AppendFormat("\n\tSkipping vessel at index {0} because it is null.", vIdx);
 					log.Print();
 					return;
@@ -324,19 +328,49 @@
 
 				log.Append("\n\t\t...passed distance check");
 
-				if (
-					potentialBestRelay.CanTransmit() &&
-					(potentialBestRelay.targetRelay == null || potentialBestRelay.targetRelay.vessel != this.vessel))
-				{
-					// @TODO: Moved this here from outside the loop; why was it there?
-					nearestRelaySqrDistance = potentialSqrDistance;
-					this.nearestRelay = potentialBestRelay;
-
-					log.AppendFormat("\n\t{0}: found new nearest relay {1} ({2}m)",
-						this.ToString(),
-						this.nearestRelay.ToString(),
-						Math.Sqrt(nearestRelaySqrDistance)
-					);
+				if (potentialBestRelay.CanTransmit())
+				{
+					needle = potentialBestRelay;
+					bool isCircular = false;
+
+					while (needle != null)
+					{
+						if (needle.KerbinDirect)
+						{
+							break;
+						}
+
+						if (needle.targetRelay == null)
+						{
+							break;
+						}
+
+						if (needle.targetRelay.vessel == this.vessel || needle == this.moduleRef)
+						{
+							isCircular = true;
+							break;
+						}
+
+						needle = needle.targetRelay;
+					}
+
+					if (!isCircular)
+					{
+						nearestRelaySqrDistance = potentialSqrDistance;
+						this.nearestRelay = potentialBestRelay;
+
+						log.AppendFormat("\n\t{0}: found new nearest relay {1} ({2}m)",
+							this.ToString(),
+							this.nearestRelay.ToString(),
+							Math.Sqrt(nearestRelaySqrDistance)
+						);
+					}
+					else
+					{
+						log.AppendFormat("\n\t\t...connection to {0} would result in a circular network, skipping",
+							potentialBestRelay
+						);
+					}
 				}
 			}
 
@@ -346,6 +380,15 @@
 			kerbinSqrDistance *= kerbinSqrDistance;
 
 			log.AppendFormat("\n{0} ({1}): Search done, figuring status.", this.ToString(), this.GetType().Name);
+			log.AppendFormat(
+				"\n{0}: nearestRelay={1} ({2}m²)), bestOccludedRelay={3} ({4}m²), kerbinSqrDistance={5}m²)",
+				this,
+				this.nearestRelay == null ? "null" : this.nearestRelay.ToString(),
+				nearestRelaySqrDistance,
+				this.bestOccludedRelay == null ? "null" : this.bestOccludedRelay.ToString(),
+				bestOccludedSqrDistance,
+				kerbinSqrDistance
+			);
 
 			// If we don't have LOS to Kerbin, focus on relays
 			if (!this.vessel.hasLineOfSightTo(Kerbin, out bodyOccludingKerbin, ARConfiguration.RadiusRatio))
@@ -389,7 +432,7 @@
 							log.AppendFormat("\n\t\t\t\t...but the nearest relay is closer ({0} < {1}), so picking it.",
 								nearestRelaySqrDistance, bestOccludedSqrDistance);
 							
-							this.targetRelay = nearestRelay;
+							this.targetRelay = this.nearestRelay;
 							this.firstOccludingBody = null;
 						}
 						// Otherwise, target the best occluded relay.
@@ -419,7 +462,7 @@
 								nearestRelaySqrDistance, kerbinSqrDistance);
 							
 							this.KerbinDirect = false;
-							this.targetRelay = nearestRelay;
+							this.targetRelay = this.nearestRelay;
 						}
 						// Otherwise, pick Kerbin.
 						else
@@ -510,7 +553,7 @@
 								log.AppendFormat("\n\t\t\t\t...but the nearest relay is closer ({0} < {1}), so picking it.",
 									nearestRelaySqrDistance, bestOccludedSqrDistance);
 								
-								this.targetRelay = nearestRelay;
+								this.targetRelay = this.nearestRelay;
 								this.firstOccludingBody = null;
 							}
 							// Otherwise, target the best occluded relay.
@@ -540,7 +583,7 @@
 									nearestRelaySqrDistance, kerbinSqrDistance);
 								
 								this.KerbinDirect = false;
-								this.targetRelay = nearestRelay;
+								this.targetRelay = this.nearestRelay;
 							}
 							// Otherwise, pick Kerbin.
 							else

--- a/ModuleLimitedDataTransmitter.cs
+++ b/ModuleLimitedDataTransmitter.cs
@@ -145,13 +145,13 @@
 				{
 					return base.vessel;
 				}
-				else if (this.part != null)
+				else if (this.part != null && this.part.vessel != null)
 				{
 					return this.part.vessel;
 				}
-
 				else
 				{
+					this.LogError("Vessel and/or part reference are null, returning null vessel.");
 					return null;
 				}
 			}

--- a/ProtoAntennaRelay.cs
+++ b/ProtoAntennaRelay.cs
@@ -48,17 +48,24 @@
 		{
 			get
 			{
-				if (this.protoPart != null && this.protoPart.pVesselRef != null)
+				if (
+					this.protoPart != null &&
+					this.protoPart.pVesselRef != null &&
+					this.protoPart.pVesselRef.vesselRef != null
+				)
 				{
 					return this.protoPart.pVesselRef.vesselRef;
 				}
 				else
 				{
-					Tools.PostLogMessage("{0}: Could not fetch vessel!  {1}{2}{3}",
+					Tools.PostErrorMessage("{0}: Could not fetch vessel!  {1}{2}{3}",
 						this.ToString(),
-						this.protoPart == null ? "\n\tprotoPart=Null" : string.Empty,
-						this.protoPart != null && this.protoPart.pVesselRef == null ? "\n\tthis.protoPart.pVesselRef=Null" : string.Empty,
-						this.protoPart != null && this.protoPart.pVesselRef != null && this.protoPart.pVesselRef.vesselRef == null ? "\n\tthis.protoPart.pVesselRef.vesselRef=Null" : string.Empty
+						this.protoPart == null ? "\n\tprotoPart=null" : string.Empty,
+						this.protoPart != null && this.protoPart.pVesselRef == null ?
+							"\n\tthis.protoPart.pVesselRef=null" : string.Empty,
+						this.protoPart != null && this.protoPart.pVesselRef != null &&
+							this.protoPart.pVesselRef.vesselRef == null ?
+							"\n\tthis.protoPart.pVesselRef.vesselRef=null" : string.Empty
 					);
 					return null;
 				}

--- a/RelayDatabase.cs
+++ b/RelayDatabase.cs
@@ -72,9 +72,6 @@
 		// Vessel.id-keyed hash table of part counts, used for caching
 		private Dictionary<Guid, int> vesselPartCountTable;
 
-		// Vessel.id-keyed hash table of booleans to track what vessels have been checked so far this time.
-		public Dictionary<Guid, bool> CheckedVesselsTable;
-
 		private int cacheHits;
 		private int cacheMisses;
 
@@ -117,9 +114,25 @@
 		// Remove a vessel from the cache, if it exists.
 		public void DirtyVessel(Vessel vessel)
 		{
+			#if DEBUG
+			Tools.PostDebugMessage("RelayDatabase: Dirtying cache for vessel {0} in frame {1}",
+				vessel, new System.Diagnostics.StackTrace().ToString());
+			#else
+			Tools.PostLogMessage("RelayDatabase: Dirtying cache for vessel {0}", vessel.vesselName);
+			#endif
+
 			this.relayDatabase.Remove(vessel.id);
 			this.vesselPartCountTable.Remove(vessel.id);
-			this.relayDatabase.Remove(vessel.id);
+			this.bestRelayTable.Remove(vessel.id);
+		}
+
+		public void ClearCache()
+		{
+			Tools.PostLogMessage("RelayDatabase: onSceneChange clearing entire cache.");
+
+			this.relayDatabase.Clear();
+			this.bestRelayTable.Clear();
+			this.vesselPartCountTable.Clear();
 		}
 
 		// Returns true if both the relayDatabase and the vesselPartCountDB contain the vessel id.
@@ -228,12 +241,35 @@
 		// Runs when the player requests a scene change, such as when changing vessels or leaving flight.
 		private void onSceneChange(GameScenes scene)
 		{
-			// If the active vessel is a real thing...
-			if (FlightGlobals.ActiveVessel != null)
-			{
-				// ... dirty its cache
-				this.onVesselEvent(FlightGlobals.ActiveVessel);
-			}
+			Tools.PostDebugMessage(
+				"RelayDatabase: caught onSceneChangeRequested in scene {0} to scene {1}.  ActiveVessel is {2}",
+				HighLogic.LoadedScene,
+				scene,
+				FlightGlobals.ActiveVessel == null ? "null" : FlightGlobals.ActiveVessel.vesselName
+			);
+
+			if (scene == GameScenes.FLIGHT)
+			{
+				if (scene == HighLogic.LoadedScene)
+				{
+					if (FlightGlobals.ActiveVessel != null)
+					{
+						Tools.PostDebugMessage("RelayDatabase: onSceneChange clearing {0} from cache.",
+							FlightGlobals.ActiveVessel.vesselName);
+
+						this.onVesselEvent(FlightGlobals.ActiveVessel);
+					}
+				}
+				else
+				{
+					this.ClearCache();
+				}
+			}
+		}
+
+		private void onGameLoaded(object data)
+		{
+			this.ClearCache();
 		}
 
 		// Runs when parts are undocked
@@ -394,7 +430,6 @@
 			this.relayDatabase = new Dictionary<Guid, List<IAntennaRelay>>();
 			this.bestRelayTable = new Dictionary<Guid, IAntennaRelay>();
 			this.vesselPartCountTable = new Dictionary<Guid, int>();
-			this.CheckedVesselsTable = new Dictionary<Guid, bool>();
 
 			this.cacheHits = 0;
 			this.cacheMisses = 0;
@@ -406,6 +441,7 @@
 			GameEvents.onGameSceneLoadRequested.Add(this.onSceneChange);
 			GameEvents.onPartCouple.Add(this.onFromPartToPartEvent);
 			GameEvents.onPartUndock.Add(this.onPartEvent);
+			GameEvents.onGameStateLoad.Add(this.onGameLoaded);
 		}
 
 		~RelayDatabase()
@@ -417,6 +453,7 @@
 			GameEvents.onGameSceneLoadRequested.Remove(this.onSceneChange);
 			GameEvents.onPartCouple.Remove(this.onFromPartToPartEvent);
 			GameEvents.onPartUndock.Remove(this.onPartEvent);
+			GameEvents.onGameStateLoad.Remove(this.onGameLoaded);
 
 			Tools.PostDebugMessage(this.GetType().Name + " destroyed.");