Greatly improve cable network segment slicing and splicing

src/main/kotlin/ru/dbotthepony/mc/otm/block/entity/cable/EnergyCableGraph.kt

@@ -2,7 +2,7 @@ package ru.dbotthepony.mc.otm.block.entity.cable
 
 import it.unimi.dsi.fastutil.objects.Reference2ObjectOpenHashMap
 import it.unimi.dsi.fastutil.objects.ReferenceArraySet
-import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet
+import it.unimi.dsi.fastutil.objects.ReferenceLinkedOpenHashSet
 import net.minecraft.core.BlockPos
 import org.apache.logging.log4j.LogManager
 import ru.dbotthepony.mc.otm.SERVER_IS_LIVE
@@ -133,12 +133,24 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 		}
 
 		private val nodes = LinkedHashSet<EnergyCableBlockEntity.Node>()
-		private val paths = ReferenceOpenHashSet<SegmentPath>()
+		private var paths = ReferenceLinkedOpenHashSet<SegmentPath>()
 
 		operator fun contains(node: EnergyCableBlockEntity.Node): Boolean {
 			return node in nodes
 		}
 
+		fun missingNodes(from: Collection<EnergyCableBlockEntity.Node>): List<EnergyCableBlockEntity.Node> {
+			val missing = ArrayList<EnergyCableBlockEntity.Node>()
+
+			this.nodes.forEach {
+				if (it !in from) {
+					missing.add(it)
+				}
+			}
+
+			return missing
+		}
+
 		var throughput = Decimal.ZERO
 			private set
 
@@ -282,8 +294,9 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 		}
 
 		fun add(path: SegmentPath) {
-			check(paths.add(path)) { "Path $path shouldn't contain $this" }
+			if (paths.add(path)) {
-			check(path.segments.add(this)) { "Path set and Segment disagree whenever $this is absent from $path" }
+				check(path.segments.add(this)) { "Path set and Segment disagree whenever $this is absent from $path" }
+			}
 		}
 
 		fun remove(path: SegmentPath) {
@@ -293,35 +306,27 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 
 		// breaks "instant snapshots" of segments atm
 		// shouldn't cause major gameplay issues though
-		fun split(): List<Segment> {
+		fun split(nodes: Collection<EnergyCableBlockEntity.Node>): List<Segment> {
-			if (nodes.isEmpty()) {
+			for (node in nodes)
-				throw IllegalStateException("Empty segment somehow?")
+				require(node in this.nodes) { "$node does not belong to $this" }
-			} else if (nodes.size == 1) {
+
+			if (this.nodes.size == 1) {
 				return listOf(this)
 			} else {
-				lastPoweredStatus = 0
-				val list = ArrayList(nodes)
-				val itr = list.iterator()
-				itr.next()
 				val result = ArrayList<Segment>()
 				result.add(this)
 
-				for (v in itr) {
+				for (v in nodes) {
-					v._segment = Segment()
+					v.segment = Segment()
-					v.segment.nodes.add(v)
 					v.segment.throughput = v.energyThroughput
 					v.segment.throughputKnown = true
 					v.segment.transferredLastTick = transferredLastTick
-					v.segment.paths.addAll(paths)
+					v.segment.lastPoweredStatus = lastPoweredStatus
+					v.segment.paths = paths.clone()
 					paths.forEach { it.segments.add(v.segment) }
 					result.add(v.segment)
 				}
 
-				nodes.clear()
-				nodes.add(list[0])
-				throughput = list[0].energyThroughput
-				throughputKnown = true
-
 				return result
 			}
 		}
@@ -397,7 +402,7 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 
 			if (first.node === b) {
 				// solution found
-				val solution = ArrayList<EnergyCableBlockEntity.Node>()
+				val solution = LinkedHashSet<EnergyCableBlockEntity.Node>()
 
 				var last = first.parent
 				solution.add(first.node)
@@ -408,10 +413,23 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 				}
 
 				val touchedSegments = ReferenceArraySet<Segment>()
-				solution.forEach { touchedSegments.addAll(it.segment.split()) }
+
+				for (it in solution) {
+					if (it.segment in touchedSegments)
+						continue
+
+					val diff = it.segment.missingNodes(solution)
+
+					// segment satisfies new constraints
+					if (diff.isEmpty()) {
+						touchedSegments.add(it.segment)
+					} else {
+						touchedSegments.addAll(it.segment.split(diff))
+					}
+				}
+
 				val path = SegmentPath(a.blockEntity.blockPos, b.blockEntity.blockPos)
 				solution.forEach { it.segment.add(path) }
-
 				touchedSegments.forEach { it.tryCombine(touchedSegments) }
 
 				return path