Improve ComputerCraft integration of Train Stations

- Emit CC events train_imminent, train_arrival and train_departure when
  these occur on the station
- Add CC canTrainReach() function to test if the train stopped at the
  station can reach a (schedule-compatible) destination
- Add CC distanceTo() function to get the shortest distance to a
  (schedule-compatible) destination at the moment, using the train
  stopped in the station

src/main/java/com/simibubi/create/compat/computercraft/events/StationTrainPresenceEvent.java

@@ -0,0 +1,30 @@
+package com.simibubi.create.compat.computercraft.events;
+
+import org.jetbrains.annotations.NotNull;
+
+
+import com.simibubi.create.content.trains.entity.Train;
+
+public class StationTrainPresenceEvent implements ComputerEvent {
+
+	public enum Type {
+		IMMINENT("train_imminent"),
+		ARRIVAL("train_arrival"),
+		DEPARTURE("train_departure");
+
+		public final String name;
+
+		Type(String name) {
+			this.name = name;
+		}
+	}
+
+	public Type type;
+	public @NotNull Train train;
+
+	public StationTrainPresenceEvent(Type type, @NotNull Train train) {
+		this.type = type;
+		this.train = train;
+	}
+
+}

src/main/java/com/simibubi/create/compat/computercraft/implementation/peripherals/StationPeripheral.java

@@ -1,14 +1,19 @@
 package com.simibubi.create.compat.computercraft.implementation.peripherals;
 
+import java.util.ArrayList;
 import java.util.Map;
-
-import javax.annotation.Nullable;
+import java.util.regex.PatternSyntaxException;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import com.simibubi.create.AllPackets;
+import com.simibubi.create.compat.computercraft.events.ComputerEvent;
+import com.simibubi.create.compat.computercraft.events.StationTrainPresenceEvent;
 import com.simibubi.create.compat.computercraft.implementation.CreateLuaTable;
 import com.simibubi.create.content.trains.entity.Train;
+import com.simibubi.create.content.trains.graph.DiscoveredPath;
+import com.simibubi.create.content.trains.graph.EdgePointType;
 import com.simibubi.create.content.trains.schedule.Schedule;
 import com.simibubi.create.content.trains.station.GlobalStation;
 import com.simibubi.create.content.trains.station.StationBlockEntity;
@@ -18,6 +23,9 @@ import com.simibubi.create.foundation.utility.StringHelper;
 import dan200.computercraft.api.lua.IArguments;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.api.lua.MethodResult;
+import net.createmod.catnip.data.Glob;
+import net.createmod.catnip.data.Pair;
 import net.minecraft.nbt.ByteTag;
 import net.minecraft.nbt.CollectionTag;
 import net.minecraft.nbt.CompoundTag;
@@ -165,6 +173,45 @@ public class StationPeripheral extends SyncedPeripheral<StationBlockEntity> {
 		train.runtime.setSchedule(schedule, autoSchedule);
 	}
 
+	/**
+	 * @return Path (if available) and boolean indicating if destination exists at all.
+	 */
+	private Pair<@Nullable DiscoveredPath, @NotNull Boolean> findPath(String destinationFilter) throws LuaException {
+		Train train = getTrainOrThrow();
+		String regex = Glob.toRegexPattern(destinationFilter, "");
+		boolean anyMatch = false;
+		ArrayList<GlobalStation> validStations = new ArrayList<>();
+		try {
+			for (GlobalStation globalStation : train.graph.getPoints(EdgePointType.STATION)) {
+				if (!globalStation.name.matches(regex))
+					continue;
+				anyMatch = true;
+				validStations.add(globalStation);
+			}
+		} catch (PatternSyntaxException ignored) {}
+
+		DiscoveredPath best = train.navigation.findPathTo(validStations, Double.MAX_VALUE);
+		if (best == null)
+			return Pair.of(null, anyMatch);
+		return Pair.of(best, true);
+	}
+
+	@LuaFunction
+	public MethodResult canTrainReach(String destinationFilter) throws LuaException {
+		Pair<@Nullable DiscoveredPath, @NotNull Boolean> path = findPath(destinationFilter);
+		if (path.getFirst() != null)
+			return MethodResult.of(true, null);
+		return MethodResult.of(false, path.getSecond() ? "cannot-reach" : "no-target");
+	}
+
+	@LuaFunction
+	public MethodResult distanceTo(String destinationFilter) throws LuaException {
+		Pair<@Nullable DiscoveredPath, @NotNull Boolean> path = findPath(destinationFilter);
+		if (path.getFirst() != null)
+			return MethodResult.of(path.getFirst().distance, null);
+		return MethodResult.of(null, path.getSecond() ? "cannot-reach" : "no-target");
+	}
+
 	private @NotNull Train getTrainOrThrow() throws LuaException {
 		GlobalStation station = blockEntity.getStation();
 		if (station == null)
@@ -269,6 +316,13 @@ public class StationPeripheral extends SyncedPeripheral<StationBlockEntity> {
 		throw new LuaException("unknown object type " + value.getClass().getName());
 	}
 
+	@Override
+	public void prepareComputerEvent(@NotNull ComputerEvent event) {
+		if (event instanceof StationTrainPresenceEvent stpe) {
+			queueEvent(stpe.type.name, stpe.train.name.getString());
+		}
+	}
+
 	@NotNull
 	@Override
 	public String getType() {

src/main/java/com/simibubi/create/content/trains/station/StationBlockEntity.java

@@ -22,6 +22,7 @@ import com.simibubi.create.AllPackets;
 import com.simibubi.create.AllSoundEvents;
 import com.simibubi.create.Create;
 import com.simibubi.create.api.contraption.transformable.TransformableBlockEntity;
+import com.simibubi.create.compat.computercraft.events.StationTrainPresenceEvent;
 import com.simibubi.create.compat.computercraft.AbstractComputerBehaviour;
 import com.simibubi.create.compat.computercraft.ComputerCraftProxy;
 import com.simibubi.create.content.contraptions.AssemblyException;
@@ -267,6 +268,21 @@ public class StationBlockEntity extends SmartBlockEntity implements Transformabl
 			imminentTrain.runtime.displayLinkUpdateRequested = false;
 		}
 
+		if (!level.isClientSide && computerBehaviour.hasAttachedComputer()) {
+			if (this.imminentTrain == null && imminentTrain != null)
+				computerBehaviour.prepareComputerEvent(
+						new StationTrainPresenceEvent(StationTrainPresenceEvent.Type.IMMINENT, imminentTrain));
+			if (newlyArrived) {
+				if (trainPresent)
+					computerBehaviour.prepareComputerEvent(
+							new StationTrainPresenceEvent(StationTrainPresenceEvent.Type.ARRIVAL, imminentTrain));
+				else
+					computerBehaviour.prepareComputerEvent(
+							new StationTrainPresenceEvent(StationTrainPresenceEvent.Type.DEPARTURE,
+									Create.RAILWAYS.trains.get(this.imminentTrain)));
+			}
+		}
+
 		if (newlyArrived)
 			applyAutoSchedule();