If multiple paths exist to target, and they differ in throughput, now cables will combine their throughput

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

@@ -75,6 +75,14 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			return segments.any { node in it }
 		}
 
+		override fun equals(other: Any?): Boolean {
+			return this === other || other is SegmentPath && segments == other.segments
+		}
+
+		override fun hashCode(): Int {
+			return segments.hashCode()
+		}
+
 		fun transfer(amount: Decimal, simulate: Boolean, instantSnapshot: MutableMap<Segment, Decimal>): Decimal {
 			if (!amount.isPositive || shortCircuit) {
 				return Decimal.ZERO
@@ -90,16 +98,15 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 				}
 			}
 
-			var min = amount
+			val min = if (simulate) segments.minOf { it.throughput(instantSnapshot) } else segments.minOf { it.availableThroughput }
 
-			for (segment in segments) {
-				min = minOf(segment.transfer(amount, instantSnapshot), min)
-				if (!min.isPositive) return Decimal.ZERO
+			if (min.isPositive) {
+				if (simulate)
+					segments.forEach { it.transfer(min, instantSnapshot) }
+				else
+					segments.forEach { it.transfer(min) }
 			}
 
-			if (!simulate)
-				segments.forEach { it.transfer(min) }
-
 			return min
 		}
 
@@ -128,15 +135,18 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 		var throughput = Decimal.ZERO
 			private set
 
-		var transferredLastTick = Decimal.ZERO
-			private set
-
-		val availableThroughput: Decimal get() {
+		private fun checkThroughput() {
 			if (!throughputKnown) {
 				throughput = nodes.maxOf { it.energyThroughput }
 				throughputKnown = true
 			}
+		}
 
+		var transferredLastTick = Decimal.ZERO
+			private set
+
+		val availableThroughput: Decimal get() {
+			checkThroughput()
 			return throughput - transferredLastTick
 		}
 
@@ -173,6 +183,17 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			}
 		}
 
+		fun throughput(instantSnapshot: Map<Segment, Decimal>): Decimal {
+			if (lastTick != UNIVERSE_TICKS) {
+				transferredLastTick = Decimal.ZERO
+				lastTick = UNIVERSE_TICKS
+			}
+
+			checkThroughput()
+			val currentTransferred = instantSnapshot[this] ?: transferredLastTick
+			return throughput - currentTransferred
+		}
+
 		fun transfer(amount: Decimal, instantSnapshot: MutableMap<Segment, Decimal>): Decimal {
 			if (lastTick != UNIVERSE_TICKS) {
 				transferredLastTick = Decimal.ZERO
@@ -240,10 +261,7 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			check(paths.add(path)) { "Path $path should already contain $this" }
 			check(path.segments.add(this)) { "Path set and Segment disagree whenever $this is absent from $path" }
 
-			if (!throughputKnown) {
-				throughput = nodes.maxOf { it.energyThroughput }
-				throughputKnown = true
-			}
+			checkThroughput()
 		}
 
 		fun remove(path: SegmentPath) {
@@ -331,9 +349,9 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 		return null
 	}
 
-	private fun getPath(a: EnergyCableBlockEntity.Node, b: EnergyCableBlockEntity.Node, energyToTransfer: Decimal): SegmentPath? {
+	private fun getPath(a: EnergyCableBlockEntity.Node, b: EnergyCableBlockEntity.Node, energyToTransfer: Decimal): List<SegmentPath> {
 		if (!a.canTraverse || !b.canTraverse)
-			return null
+			return listOf()
 
 		val list = pathCache.computeIfAbsent(a to b) { CacheEntry() }
 
@@ -343,8 +361,8 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			while (maxThroughput < energyToTransfer && !list.saturated) {
 				val find = findPath(a, b, list.paths, maxThroughput)
 
-				if (find == null) {
-					list.saturated
+				if (find == null || find in list.paths) {
+					list.saturated = true
 				} else {
 					list.paths.add(find)
 					maxThroughput = maxOf(maxThroughput, find.availableThroughput)
@@ -352,9 +370,8 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			}
 		}
 
-		// TODO: Immediate load selection is bad because it can easily lead to oscillations and non optimal throughput
-		//  without user having any clue why their shit work suboptimally
-		return list.paths.maxByOrNull { it.availableThroughput }
+		list.paths.sortByDescending { it.availableThroughput }
+		return list.paths
 	}
 
 	override fun onNodeRemoved(node: EnergyCableBlockEntity.Node) {
@@ -383,31 +400,79 @@ class EnergyCableGraph : GraphNodeList<EnergyCableBlockEntity.Node, EnergyCableG
 			var hit = false
 
 			for (side in node.sides.values) {
-				if (side.isEnabled) {
-					if (fromNode === node && side.side === fromSide) {
-						hit = true
+				if (!side.isEnabled)
+					continue
+				else if (fromNode === node && side.side === fromSide) {
+					hit = true
+					continue
+				}
+
+				val it = side.neighbour.get() ?: continue
+				if (it is EnergyCableBlockEntity.CableSide) continue
+
+				val paths = getPath(fromNode, node, residue)
+				hit = true
+
+				if (paths.size == 1) {
+					// Single path, fast scenario
+					val path = paths[0]
+					val pathTransferred = path.transfer(residue, simulate, snapshot)
+					val thisReceived = it.receiveEnergy(pathTransferred, simulate)
+
+					// If cable transferred more than machine accepted, then "refund" energy
+					// so cables record actual value transferred through them
+					if (thisReceived != pathTransferred) {
+						path.refund(pathTransferred - thisReceived, simulate, snapshot)
+					}
+
+					received += thisReceived
+					residue -= thisReceived
+					if (!residue.isPositive) return received
+				} else if (paths.size >= 2) {
+					// Multiple paths, a bit more complicated
+					// Determine how much machine is likely to accept
+					val potentiallyAccepted = it.receiveEnergy(residue, true)
+
+					// Won't accept anything
+					if (potentiallyAccepted <= Decimal.ZERO)
+						continue
+
+					// Now determine combined available throughput
+					// Make a copy of snapshot, so we can freely write into it
+					val copy = snapshot.clone()
+					var calcResidue = potentiallyAccepted
+
+					// TODO: Currently, all transfers cause Braess's paradox, because of greedy selection of "fastest" cable
+					//  Need to implement heuristics to better distribute load across different paths/segments
+					for (path in paths) {
+						val passed = path.transfer(calcResidue, true, copy)
+						calcResidue -= passed
+						if (calcResidue <= Decimal.ZERO) break
+					}
+
+					if (calcResidue == potentiallyAccepted) {
+						// мда
 						continue
 					}
 
-					side.neighbour.get()?.let {
-						if (it !is EnergyCableBlockEntity.CableSide) {
-							val path = getPath(fromNode, node, residue)
-							hit = true
+					var thisReceived = it.receiveEnergy(potentiallyAccepted - calcResidue, simulate)
+					received += thisReceived
+					residue -= thisReceived
 
-							if (path != null) {
-								val thisReceived = it.receiveEnergy(path.transfer(residue, simulate, snapshot), simulate)
-								received += thisReceived
-								residue -= thisReceived
-								if (!residue.isPositive) return received
-							}
-						}
+					for (path in paths) {
+						val passed = path.transfer(thisReceived, simulate, snapshot)
+						thisReceived -= passed
+						if (thisReceived <= Decimal.ZERO) break
 					}
+
+					if (!residue.isPositive) return received
+					check(thisReceived <= Decimal.ZERO) { "Путом, алло, Путом, какого чёрта Путом? Путом почему ты заблокировал логику, а Путом?" }
 				}
 			}
 
 			if (!hit) {
 				itr.remove()
-				check(livelyNodes.remove(node))
+				check(livelyNodes.remove(node)) { "Lively nodes Set does not contain $node" }
 			}
 		}