PaperMC/patches/server/0808-Add-Alternate-Current-redstone-implementation.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Space Walker <spacedoesrs@gmail.com>
Date: Wed, 8 Jun 2022 18:47:18 +0200
Subject: [PATCH] Add Alternate Current redstone implementation

Author: Space Walker <spacedoesrs@gmail.com>

Original license: MIT
Original project: https://github.com/SpaceWalkerRS/alternate-current

This patch adds Alternate Current's redstone implementation as an alternative to vanilla and Eigencraft's.
Performance of (de)powering redstone dust is many times faster than vanilla, and even exceeds Eigencraft.
Similar to Eigencraft, Alternate Current heavily changes the update order of redstone dust. This means any contraption that
is location dependent in vanilla will either work everywhere or nowhere when using Alternate Current/Eigencraft. Beyond that
parity issues should be rare for both implementations, though Alternate Current has not been tested as thoroughly, so I
cannot comment on how the two compare in that aspect.

Alternate Current needs the following modifications:
* Level/ServerLevel: Each level has its own 'wire handler' that handles redstone dust power changes.
* RedStoneWireBlock: Replace calls to vanilla's or Eigencraft's methods for handling power changes with calls to
Alternate Current's wire handler.

diff --git a/src/main/java/alternate/current/wire/LevelHelper.java b/src/main/java/alternate/current/wire/LevelHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..f55c5c67b8461e9ef5614ea1a37f6e2866f39be3
--- /dev/null
+++ b/src/main/java/alternate/current/wire/LevelHelper.java
@@ -0,0 +1,65 @@
+package alternate.current.wire;
+
+import org.bukkit.event.block.BlockRedstoneEvent;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkStatus;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+
+public class LevelHelper {
+
+    static int doRedstoneEvent(ServerLevel level, BlockPos pos, int prevPower, int newPower) {
+        BlockRedstoneEvent event = new BlockRedstoneEvent(level.getWorld().getBlockAt(pos.getX(), pos.getY(), pos.getZ()), prevPower, newPower);
+        level.getCraftServer().getPluginManager().callEvent(event);
+
+        return event.getNewCurrent();
+    }
+
+    /**
+     * An optimized version of {@link net.minecraft.world.level.Level#setBlock
+     * Level.setBlock}. Since this method is only used to update redstone wire block
+     * states, lighting checks, height map updates, and block entity updates are
+     * omitted.
+     */
+    static boolean setWireState(ServerLevel level, BlockPos pos, BlockState state, boolean updateNeighborShapes) {
+        int y = pos.getY();
+
+        if (y < level.getMinBuildHeight() || y >= level.getMaxBuildHeight()) {
+            return false;
+        }
+
+        int x = pos.getX();
+        int z = pos.getZ();
+        int index = level.getSectionIndex(y);
+
+        ChunkAccess chunk = level.getChunk(x >> 4, z >> 4, ChunkStatus.FULL, true);
+        LevelChunkSection section = chunk.getSections()[index];
+
+        if (section == null) {
+            return false; // we should never get here
+        }
+
+        BlockState prevState = section.setBlockState(x & 15, y & 15, z & 15, state);
+
+        if (state == prevState) {
+            return false;
+        }
+
+        // notify clients of the BlockState change
+        level.getChunkSource().blockChanged(pos);
+        // mark the chunk for saving
+        chunk.setUnsaved(true);
+
+        if (updateNeighborShapes) {
+            prevState.updateIndirectNeighbourShapes(level, pos, Block.UPDATE_CLIENTS);
+            state.updateNeighbourShapes(level, pos, Block.UPDATE_CLIENTS);
+            state.updateIndirectNeighbourShapes(level, pos, Block.UPDATE_CLIENTS);
+        }
+
+        return true;
+    }
+}
diff --git a/src/main/java/alternate/current/wire/Node.java b/src/main/java/alternate/current/wire/Node.java
new file mode 100644
index 0000000000000000000000000000000000000000..8af6c69098e64945361d116b5fd6ac21e97fcd8d
--- /dev/null
+++ b/src/main/java/alternate/current/wire/Node.java
@@ -0,0 +1,113 @@
+package alternate.current.wire;
+
+import java.util.Arrays;
+
+import alternate.current.wire.WireHandler.Directions;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+
+/**
+ * A Node represents a block in the world. It also holds a few other pieces of
+ * information that speed up the calculations in the WireHandler class.
+ * 
+ * @author Space Walker
+ */
+public class Node {
+
+    // flags that encode the Node type
+    private static final int CONDUCTOR = 0b01;
+    private static final int SOURCE    = 0b10;
+
+    final ServerLevel level;
+    final Node[] neighbors;
+
+    BlockPos pos;
+    BlockState state;
+    boolean invalid;
+
+    private int flags;
+
+    /** The previous node in the priority queue. */
+    Node prev_node;
+    /** The next node in the priority queue. */
+    Node next_node;
+    /** The priority with which this node was queued. */
+    int priority;
+    /** The wire that queued this node for an update. */
+    WireNode neighborWire;
+
+    Node(ServerLevel level) {
+        this.level = level;
+        this.neighbors = new Node[Directions.ALL.length];
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof Node)) {
+            return false;
+        }
+
+        Node node = (Node)obj;
+
+        return level == node.level && pos.equals(node.pos);
+    }
+
+    @Override
+    public int hashCode() {
+        return pos.hashCode();
+    }
+
+    Node set(BlockPos pos, BlockState state, boolean clearNeighbors) {
+        if (state.is(Blocks.REDSTONE_WIRE)) {
+            throw new IllegalStateException("Cannot update a regular Node to a WireNode!");
+        }
+
+        if (clearNeighbors) {
+            Arrays.fill(neighbors, null);
+        }
+
+        this.pos = pos.immutable();
+        this.state = state;
+        this.invalid = false;
+
+        this.flags = 0;
+
+        if (this.state.isRedstoneConductor(this.level, this.pos)) {
+            this.flags |= CONDUCTOR;
+        }
+        if (this.state.isSignalSource()) {
+            this.flags |= SOURCE;
+        }
+
+        return this;
+    }
+
+    /**
+     * Determine the priority with which this node should be queued.
+     */
+    int priority() {
+        return neighborWire.priority;
+    }
+
+    public boolean isWire() {
+        return false;
+    }
+
+    public boolean isConductor() {
+        return (flags & CONDUCTOR) != 0;
+    }
+
+    public boolean isSignalSource() {
+        return (flags & SOURCE) != 0;
+    }
+
+    public WireNode asWire() {
+        throw new UnsupportedOperationException("Not a WireNode!");
+    }
+}
diff --git a/src/main/java/alternate/current/wire/PriorityQueue.java b/src/main/java/alternate/current/wire/PriorityQueue.java
new file mode 100644
index 0000000000000000000000000000000000000000..d71b4d0e4c44a2620b41b89475412db53bea20ed
--- /dev/null
+++ b/src/main/java/alternate/current/wire/PriorityQueue.java
@@ -0,0 +1,211 @@
+package alternate.current.wire;
+
+import java.util.AbstractQueue;
+import java.util.Arrays;
+import java.util.Iterator;
+
+import net.minecraft.world.level.redstone.Redstone;
+
+public class PriorityQueue extends AbstractQueue<Node> {
+
+    private static final int OFFSET = -Redstone.SIGNAL_MIN;
+
+    /** The last node for each priority value. */
+    private final Node[] tails;
+
+    private Node head;
+    private Node tail;
+
+    private int size;
+
+    PriorityQueue() {
+        this.tails = new Node[(Redstone.SIGNAL_MAX + OFFSET) + 1];
+    }
+
+    @Override
+    public boolean offer(Node node) {
+        if (node == null) {
+            throw new NullPointerException();
+        }
+
+        int priority = node.priority();
+
+        if (contains(node)) {
+            if (node.priority == priority) {
+                // already queued with this priority; exit
+                return false;
+            } else {
+                // already queued with different priority; move it
+                move(node, priority);
+            }
+        } else {
+            insert(node, priority);
+        }
+
+        return true;
+    }
+
+    @Override
+    public Node poll() {
+        if (head == null) {
+            return null;
+        }
+
+        Node node = head;
+        Node next = node.next_node;
+
+        if (next == null) {
+            clear(); // reset the tails array
+        } else {
+            if (node.priority != next.priority) {
+                // If the head is also a tail, its entry in the array
+                // can be cleared; there is no previous node with the
+                // same priority to take its place.
+                tails[node.priority + OFFSET] = null;
+            }
+
+            node.next_node = null;
+            next.prev_node = null;
+            head = next;
+
+            size--;
+        }
+
+        return node;
+    }
+
+    @Override
+    public Node peek() {
+        return head;
+    }
+
+    @Override
+    public void clear() {
+        for (Node node = head; node != null; ) {
+            Node n = node;
+            node = node.next_node;
+
+            n.prev_node = null;
+            n.next_node = null;
+        }
+
+        Arrays.fill(tails, null);
+
+        head = null;
+        tail = null;
+
+        size = 0;
+    }
+
+    @Override
+    public Iterator<Node> iterator() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    public boolean contains(Node node) {
+        return node == head || node.prev_node != null;
+    }
+
+    private void move(Node node, int priority) {
+        remove(node);
+        insert(node, priority);
+    }
+
+    private void remove(Node node) {
+        Node prev = node.prev_node;
+        Node next = node.next_node;
+
+        if (node == tail || node.priority != next.priority) {
+            // assign a new tail for this node's priority
+            if (node == head || node.priority != prev.priority) {
+                // there is no other node with the same priority; clear
+                tails[node.priority + OFFSET] = null;
+            } else {
+                // the previous node in the queue becomes the tail
+                tails[node.priority + OFFSET] = prev;
+            }
+        }
+
+        if (node == head) {
+            head = next;
+        } else {
+            prev.next_node = next;
+        }
+        if (node == tail) {
+            tail = prev;
+        } else {
+            next.prev_node = prev;
+        }
+
+        node.prev_node = null;
+        node.next_node = null;
+
+        size--;
+    }
+
+    private void insert(Node node, int priority) {
+        node.priority = priority;
+
+        // nodes are sorted by priority (highest to lowest)
+        // nodes with the same priority are ordered FIFO
+        if (head == null) {
+            // first element in this queue \o/
+            head = tail = node;
+        } else if (priority > head.priority) {
+            linkHead(node);
+        } else if (priority <= tail.priority) {
+            linkTail(node);
+        } else {
+            // since the node is neither the head nor the tail
+            // findPrev is guaranteed to find a non-null element
+            linkAfter(findPrev(node), node);
+        }
+
+        tails[priority + OFFSET] = node;
+
+        size++;
+    }
+
+    private void linkHead(Node node) {
+        node.next_node = head;
+        head.prev_node = node;
+        head = node;
+    }
+
+    private void linkTail(Node node) {
+        tail.next_node = node;
+        node.prev_node = tail;
+        tail = node;
+    }
+
+    private void linkAfter(Node prev, Node node) {
+        linkBetween(prev, node, prev.next_node);
+    }
+
+    private void linkBetween(Node prev, Node node, Node next) {
+        prev.next_node = node;
+        node.prev_node = prev;
+
+        node.next_node = next;
+        next.prev_node = node;
+    }
+
+    private Node findPrev(Node node) {
+        Node prev = null;
+
+        for (int i = node.priority + OFFSET; i < tails.length; i++) {
+            prev = tails[i];
+
+            if (prev != null) {
+                break;
+            }
+        }
+
+        return prev;
+    }
+}
diff --git a/src/main/java/alternate/current/wire/SimpleQueue.java b/src/main/java/alternate/current/wire/SimpleQueue.java
new file mode 100644
index 0000000000000000000000000000000000000000..2b30074252551e1dc55d5be17d26fb4a2d8eb2e4
--- /dev/null
+++ b/src/main/java/alternate/current/wire/SimpleQueue.java
@@ -0,0 +1,112 @@
+package alternate.current.wire;
+
+import java.util.AbstractQueue;
+import java.util.Iterator;
+
+public class SimpleQueue extends AbstractQueue<WireNode> {
+
+    private WireNode head;
+    private WireNode tail;
+
+    private int size;
+
+    SimpleQueue() {
+
+    }
+
+    @Override
+    public boolean offer(WireNode node) {
+        if (node == null) {
+            throw new NullPointerException();
+        }
+
+        if (tail == null) {
+            head = tail = node;
+        } else {
+            tail.next_wire = node;
+            tail = node;
+        }
+
+        size++;
+
+        return true;
+    }
+
+    @Override
+    public WireNode poll() {
+        if (head == null) {
+            return null;
+        }
+
+        WireNode node = head;
+        WireNode next = node.next_wire;
+
+        if (next == null) {
+            head = tail = null;
+        } else {
+            node.next_wire = null;
+            head = next;
+        }
+
+        size--;
+
+        return node;
+    }
+
+    @Override
+    public WireNode peek() {
+        return head;
+    }
+
+    @Override
+    public void clear() {
+        for (WireNode node = head; node != null; ) {
+            WireNode n = node;
+            node = node.next_wire;
+
+            n.next_wire = null;
+        }
+
+        head = null;
+        tail = null;
+
+        size = 0;
+    }
+
+    @Override
+    public Iterator<WireNode> iterator() {
+        return new SimpleIterator();
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    private class SimpleIterator implements Iterator<WireNode> {
+
+        private WireNode curr;
+        private WireNode next;
+
+        private SimpleIterator() {
+            next = head;
+        }
+
+        @Override
+        public boolean hasNext() {
+            if (next == null && curr != null) {
+                next = curr.next_wire;
+            }
+
+            return next != null;
+        }
+
+        @Override
+        public WireNode next() {
+            curr = next;
+            next = curr.next_wire;
+
+            return curr;
+        }
+    }
+}
diff --git a/src/main/java/alternate/current/wire/WireConnection.java b/src/main/java/alternate/current/wire/WireConnection.java
new file mode 100644
index 0000000000000000000000000000000000000000..4fd8cb29024330397cfe4cbc1f237d285bfb7b3e
--- /dev/null
+++ b/src/main/java/alternate/current/wire/WireConnection.java
@@ -0,0 +1,30 @@
+package alternate.current.wire;
+
+/**
+ * This class represents a connection between some WireNode (the 'owner') and a
+ * neighboring WireNode. Two wires are considered to be connected if power can
+ * flow from one wire to the other (and/or vice versa).
+ * 
+ * @author Space Walker
+ */
+public class WireConnection {
+
+    /** The connected wire. */
+    final WireNode wire;
+    /** Cardinal direction to the connected wire. */
+    final int iDir;
+    /** True if the owner of the connection can provide power to the connected wire. */
+    final boolean offer;
+    /** True if the connected wire can provide power to the owner of the connection. */
+    final boolean accept;
+
+    /** The next connection in the sequence. */
+    WireConnection next;
+
+    WireConnection(WireNode wire, int iDir, boolean offer, boolean accept) {
+        this.wire = wire;
+        this.iDir = iDir;
+        this.offer = offer;
+        this.accept = accept;
+    }
+}
diff --git a/src/main/java/alternate/current/wire/WireConnectionManager.java b/src/main/java/alternate/current/wire/WireConnectionManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..5a7209f05b549c222f6c9bc2af2a35790964947e
--- /dev/null
+++ b/src/main/java/alternate/current/wire/WireConnectionManager.java
@@ -0,0 +1,136 @@
+package alternate.current.wire;
+
+import java.util.Arrays;
+import java.util.function.Consumer;
+
+import alternate.current.wire.WireHandler.Directions;
+import alternate.current.wire.WireHandler.NodeProvider;
+
+public class WireConnectionManager {
+
+    /** The owner of these connections. */
+    final WireNode owner;
+
+    /** The first connection for each cardinal direction. */
+    private final WireConnection[] heads;
+
+    private WireConnection head;
+    private WireConnection tail;
+
+    /** The total number of connections. */
+    int total;
+
+    /**
+     * A 4 bit number that encodes in which direction(s) the owner has connections
+     * to other wires.
+     */
+    private int flowTotal;
+    /** The direction of flow based connections to other wires. */
+    int iFlowDir;
+
+    WireConnectionManager(WireNode owner) {
+        this.owner = owner;
+
+        this.heads = new WireConnection[Directions.HORIZONTAL.length];
+
+        this.total = 0;
+
+        this.flowTotal = 0;
+        this.iFlowDir = -1;
+    }
+
+    void set(NodeProvider nodes) {
+        if (total > 0) {
+            clear();
+        }
+
+        boolean belowIsConductor = nodes.getNeighbor(owner, Directions.DOWN).isConductor();
+        boolean aboveIsConductor = nodes.getNeighbor(owner, Directions.UP).isConductor();
+
+        for (int iDir = 0; iDir < Directions.HORIZONTAL.length; iDir++) {
+            Node neighbor = nodes.getNeighbor(owner, iDir);
+
+            if (neighbor.isWire()) {
+                add(neighbor.asWire(), iDir, true, true);
+
+                continue;
+            }
+
+            boolean sideIsConductor = neighbor.isConductor();
+
+            if (!sideIsConductor) {
+                Node node = nodes.getNeighbor(neighbor, Directions.DOWN);
+
+                if (node.isWire()) {
+                    add(node.asWire(), iDir, belowIsConductor, true);
+                }
+            }
+            if (!aboveIsConductor) {
+                Node node = nodes.getNeighbor(neighbor, Directions.UP);
+
+                if (node.isWire()) {
+                    add(node.asWire(), iDir, true, sideIsConductor);
+                }
+            }
+        }
+
+        if (total > 0) {
+            iFlowDir = WireHandler.FLOW_IN_TO_FLOW_OUT[flowTotal];
+        }
+    }
+
+    private void clear() {
+        Arrays.fill(heads, null);
+
+        head = null;
+        tail = null;
+
+        total = 0;
+
+        flowTotal = 0;
+        iFlowDir = -1;
+    }
+
+    private void add(WireNode wire, int iDir, boolean offer, boolean accept) {
+        add(new WireConnection(wire, iDir, offer, accept));
+    }
+
+    private void add(WireConnection connection) {
+        if (head == null) {
+            head = connection;
+            tail = connection;
+        } else {
+            tail.next = connection;
+            tail = connection;
+        }
+
+        total++;
+
+        if (heads[connection.iDir] == null) {
+            heads[connection.iDir] = connection;
+            flowTotal |= (1 << connection.iDir);
+        }
+    }
+
+    /**
+     * Iterate over all connections. Use this method if the iteration order is not
+     * important.
+     */
+    void forEach(Consumer<WireConnection> consumer) {
+        for (WireConnection c = head; c != null; c = c.next) {
+            consumer.accept(c);
+        }
+    }
+
+    /**
+     * Iterate over all connections. Use this method if the iteration order is
+     * important.
+     */
+    void forEach(Consumer<WireConnection> consumer, int iFlowDir) {
+        for (int iDir : WireHandler.CARDINAL_UPDATE_ORDERS[iFlowDir]) {
+            for (WireConnection c = heads[iDir]; c != null && c.iDir == iDir; c = c.next) {
+                consumer.accept(c);
+            }
+        }
+    }
+}
diff --git a/src/main/java/alternate/current/wire/WireHandler.java b/src/main/java/alternate/current/wire/WireHandler.java
new file mode 100644
index 0000000000000000000000000000000000000000..02d0a3c3edd36b636163c5c912b26336fe87d16c
--- /dev/null
+++ b/src/main/java/alternate/current/wire/WireHandler.java
@@ -0,0 +1,1150 @@
+package alternate.current.wire;
+
+import java.util.Iterator;
+import java.util.Queue;
+import java.util.function.Consumer;
+
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap.Entry;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMaps;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.redstone.Redstone;
+
+/**
+ * This class handles power changes for redstone wire. The algorithm was
+ * designed with the following goals in mind:
+ * <br>
+ * 1. Minimize the number of times a wire checks its surroundings to determine
+ * its power level.
+ * <br>
+ * 2. Minimize the number of block and shape updates emitted.
+ * <br>
+ * 3. Emit block and shape updates in a deterministic, non-locational order,
+ * fixing bug MC-11193.
+ * 
+ * <p>
+ * In Vanilla redstone wire is laggy because it fails on points 1 and 2.
+ * 
+ * <p>
+ * Redstone wire updates recursively and each wire calculates its power level in
+ * isolation rather than in the context of the network it is a part of. This
+ * means a wire in a grid can change its power level over half a dozen times
+ * before settling on its final value. This problem used to be worse in 1.13 and
+ * below, where a wire would only decrease its power level by 1 at a time.
+ * 
+ * <p>
+ * In addition to this, a wire emits 42 block updates and up to 22 shape updates
+ * each time it changes its power level.
+ * 
+ * <p>
+ * Of those 42 block updates, 6 are to itself, which are thus not only
+ * redundant, but a big source of lag, since those cause the wire to
+ * unnecessarily re-calculate its power level. A block only has 24 neighbors
+ * within a Manhattan distance of 2, meaning 12 of the remaining 36 block
+ * updates are duplicates and thus also redundant.
+ * 
+ * <p>
+ * Of the 22 shape updates, only 6 are strictly necessary. The other 16 are sent
+ * to blocks diagonally above and below. These are necessary if a wire changes
+ * its connections, but not when it changes its power level.
+ * 
+ * <p>
+ * Redstone wire in Vanilla also fails on point 3, though this is more of a
+ * quality-of-life issue than a lag issue. The recursive nature in which it
+ * updates, combined with the location-dependent order in which each wire
+ * updates its neighbors, makes the order in which neighbors of a wire network
+ * are updated incredibly inconsistent and seemingly random.
+ * 
+ * <p>
+ * Alternate Current fixes each of these problems as follows.
+ * 
+ * <p>
+ * 1. To make sure a wire calculates its power level as little as possible, we
+ * remove the recursive nature in which redstone wire updates in Vanilla.
+ * Instead, we build a network of connected wires, find those wires that receive
+ * redstone power from "outside" the network, and spread the power from there.
+ * This has a few advantages:
+ * <br>
+ * - Each wire checks for power from non-wire components at most once, and from
+ * nearby wires just twice.
+ * <br>
+ * - Each wire only sets its power level in the world once. This is important,
+ * because calls to Level.setBlock are even more expensive than calls to
+ * Level.getBlockState.
+ * 
+ * <p>
+ * 2. There are 2 obvious ways in which we can reduce the number of block and
+ * shape updates.
+ * <br>
+ * - Get rid of the 18 redundant block updates and 16 redundant shape updates,
+ * so each wire only emits 24 block updates and 6 shape updates whenever it
+ * changes its power level.
+ * <br>
+ * - Only emit block updates and shape updates once a wire reaches its final
+ * power level, rather than at each intermediary stage.
+ * <br>
+ * For an individual wire, these two optimizations are the best you can do, but
+ * for an entire grid, you can do better!
+ * 
+ * <p>
+ * Since we calculate the power of the entire network, sending block and shape
+ * updates to the wires in it is redundant. Removing those updates can reduce
+ * the number of block and shape updates by up to 20%.
+ * 
+ * <p>
+ * 3. To make the order of block updates to neighbors of a network
+ * deterministic, the first thing we must do is to replace the location-
+ * dependent order in which a wire updates its neighbors. Instead, we base it on
+ * the direction of power flow. This part of the algorithm was heavily inspired
+ * by theosib's 'RedstoneWireTurbo', which you can read more about in theosib's
+ * comment on Mojira <a href="https://bugs.mojang.com/browse/MC-81098?focusedCommentId=420777&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-420777">here</a>
+ * or by checking out its implementation in carpet mod <a href="https://github.com/gnembon/fabric-carpet/blob/master/src/main/java/carpet/helpers/RedstoneWireTurbo.java">here</a>.
+ * 
+ * <p>
+ * The idea is to determine the direction of power flow through a wire based on
+ * the power it receives from neighboring wires. For example, if the only power
+ * a wire receives is from a neighboring wire to its west, it can be said that
+ * the direction of power flow through the wire is east.
+ * 
+ * <p>
+ * We make the order of block updates to neighbors of a wire depend on what is
+ * determined to be the direction of power flow. This not only removes
+ * locationality entirely, it even removes directionality in a large number of
+ * cases. Unlike in 'RedstoneWireTurbo', however, I have decided to keep a
+ * directional element in ambiguous cases, rather than to introduce randomness,
+ * though this is trivial to change.
+ * 
+ * <p>
+ * While this change fixes the block update order of individual wires, we must
+ * still address the overall block update order of a network. This turns out to
+ * be a simple fix, because of a change we made earlier: we search through the
+ * network for wires that receive power from outside it, and spread the power
+ * from there. If we make each wire transmit its power to neighboring wires in
+ * an order dependent on the direction of power flow, we end up with a
+ * non-locational and largely non-directional wire update order.
+ * 
+ * @author Space Walker
+ */
+public class WireHandler {
+
+    public static class Directions {
+
+        public static final Direction[] ALL        = { Direction.WEST, Direction.NORTH, Direction.EAST, Direction.SOUTH, Direction.DOWN, Direction.UP };
+        public static final Direction[] HORIZONTAL = { Direction.WEST, Direction.NORTH, Direction.EAST, Direction.SOUTH };
+
+        // Indices for the arrays above.
+        // The cardinal directions are ordered clockwise. This allows
+        // for conversion between relative and absolute directions
+        // ('left' 'right' vs 'east' 'west') with simple arithmetic:
+        // If some Direction index 'iDir' is considered 'forward', then
+        // '(iDir + 1) & 0b11' is 'right', '(iDir + 2) & 0b11' is 'backward', etc.
+        public static final int WEST  = 0b000; // 0
+        public static final int NORTH = 0b001; // 1
+        public static final int EAST  = 0b010; // 2
+        public static final int SOUTH = 0b011; // 3
+        public static final int DOWN  = 0b100; // 4
+        public static final int UP    = 0b101; // 5
+
+        public static int iOpposite(int iDir) {
+            return iDir ^ (0b10 >>> (iDir >>> 2));
+        }
+
+        // Each array is placed at the index that encodes the direction that is missing
+        // from the array.
+        private static final int[][] I_EXCEPT = {
+            {       NORTH, EAST, SOUTH, DOWN, UP },
+            { WEST,        EAST, SOUTH, DOWN, UP },
+            { WEST, NORTH,       SOUTH, DOWN, UP },
+            { WEST, NORTH, EAST,        DOWN, UP },
+            { WEST, NORTH, EAST, SOUTH,       UP },
+            { WEST, NORTH, EAST, SOUTH, DOWN     }
+        };
+        private static final int[][] I_EXCEPT_CARDINAL = {
+            {       NORTH, EAST, SOUTH },
+            { WEST,        EAST, SOUTH },
+            { WEST, NORTH,       SOUTH },
+            { WEST, NORTH, EAST,       },
+            { WEST, NORTH, EAST, SOUTH },
+            { WEST, NORTH, EAST, SOUTH }
+        };
+    }
+
+    /**
+     * This conversion table takes in information about incoming flow, and outputs
+     * the determined outgoing flow.
+     * 
+     * <p>
+     * The input is a 4 bit number that encodes the incoming flow. Each bit
+     * represents a cardinal direction, and when it is 'on', there is flow in that
+     * direction.
+     * 
+     * <p>
+     * The output is a single Direction index, or -1 for ambiguous cases.
+     * 
+     * <p>
+     * The outgoing flow is determined as follows:
+     * 
+     * <p>
+     * If there is just 1 direction of incoming flow, that direction will be the
+     * direction of outgoing flow.
+     * 
+     * <p>
+     * If there are 2 directions of incoming flow, and these directions are not each
+     * other's opposites, the direction that is 'more clockwise' will be the
+     * direction of outgoing flow. More precisely, the direction that is 1 clockwise
+     * turn from the other is picked.
+     * 
+     * <p>
+     * If there are 3 directions of incoming flow, the two opposing directions
+     * cancel each other out, and the remaining direction will be the direction of
+     * outgoing flow.
+     * 
+     * <p>
+     * In all other cases, the flow is completely ambiguous.
+     */
+    static final int[] FLOW_IN_TO_FLOW_OUT = {
+        -1,               // 0b0000: -                     -> x
+        Directions.WEST,  // 0b0001: west                  -> west
+        Directions.NORTH, // 0b0010: north                 -> north
+        Directions.NORTH, // 0b0011: west/north            -> north
+        Directions.EAST,  // 0b0100: east                  -> east
+        -1,               // 0b0101: west/east             -> x
+        Directions.EAST,  // 0b0110: north/east            -> east
+        Directions.NORTH, // 0b0111: west/north/east       -> north
+        Directions.SOUTH, // 0b1000: south                 -> south
+        Directions.WEST,  // 0b1001: west/south            -> west
+        -1,               // 0b1010: north/south           -> x
+        Directions.WEST,  // 0b1011: west/north/south      -> west
+        Directions.SOUTH, // 0b1100: east/south            -> south
+        Directions.SOUTH, // 0b1101: west/east/south       -> south
+        Directions.EAST,  // 0b1110: north/east/south      -> east
+        -1,               // 0b1111: west/north/east/south -> x
+    };
+    /**
+     * Update orders of all directions. Given that the index encodes the direction
+     * that is to be considered 'forward', the resulting update order is
+     * { front, back, right, left, down, up }.
+     */
+    static final int[][] FULL_UPDATE_ORDERS = {
+        { Directions.WEST , Directions.EAST , Directions.NORTH, Directions.SOUTH, Directions.DOWN, Directions.UP },
+        { Directions.NORTH, Directions.SOUTH, Directions.EAST , Directions.WEST , Directions.DOWN, Directions.UP },
+        { Directions.EAST , Directions.WEST , Directions.SOUTH, Directions.NORTH, Directions.DOWN, Directions.UP },
+        { Directions.SOUTH, Directions.NORTH, Directions.WEST , Directions.EAST , Directions.DOWN, Directions.UP }
+    };
+    /**
+     * The default update order of all directions. It is equivalent to the order of
+     * shape updates in vanilla Minecraft.
+     */
+    static final int[] DEFAULT_FULL_UPDATE_ORDER = FULL_UPDATE_ORDERS[0];
+    /**
+     * Update orders of cardinal directions. Given that the index encodes the
+     * direction that is to be considered 'forward', the resulting update order is
+     * { front, back, right, left }.
+     */
+    static final int[][] CARDINAL_UPDATE_ORDERS = {
+        { Directions.WEST , Directions.EAST , Directions.NORTH, Directions.SOUTH },
+        { Directions.NORTH, Directions.SOUTH, Directions.EAST , Directions.WEST  },
+        { Directions.EAST , Directions.WEST , Directions.SOUTH, Directions.NORTH },
+        { Directions.SOUTH, Directions.NORTH, Directions.WEST , Directions.EAST  }
+    };
+    /**
+     * The default update order of all cardinal directions.
+     */
+    static final int[] DEFAULT_CARDINAL_UPDATE_ORDER = CARDINAL_UPDATE_ORDERS[0];
+
+    private static final int POWER_MIN = Redstone.SIGNAL_MIN;
+    private static final int POWER_MAX = Redstone.SIGNAL_MAX;
+    private static final int POWER_STEP = 1;
+
+    // If Vanilla will ever multi-thread the ticking of levels, there should
+    // be only one WireHandler per level, in case redstone updates in multiple
+    // levels at the same time. There are already mods that add multi-threading
+    // as well.
+    private final ServerLevel level;
+
+    /** Map of wires and neighboring blocks. */
+    private final Long2ObjectMap<Node> nodes;
+    /** Queue for the breadth-first search through the network. */
+    private final Queue<WireNode> search;
+    /** Queue of updates to wires and neighboring blocks. */
+    private final Queue<Node> updates;
+
+    // Rather than creating new nodes every time a network is updated we keep
+    // a cache of nodes that can be re-used.
+    private Node[] nodeCache;
+    private int nodeCount;
+
+    /** Is this WireHandler currently working through the update queue? */
+    private boolean updating;
+
+    public WireHandler(ServerLevel level) {
+        this.level = level;
+
+        this.nodes = new Long2ObjectOpenHashMap<>();
+        this.search = new SimpleQueue();
+        this.updates = new PriorityQueue();
+
+        this.nodeCache = new Node[16];
+        this.fillNodeCache(0, 16);
+    }
+
+    /**
+     * Retrieve the {@link Node Node} that represents the
+     * block at the given position in the level.
+     */
+    private Node getOrAddNode(BlockPos pos) {
+        return nodes.compute(pos.asLong(), (key, node) -> {
+            if (node == null) {
+                // If there is not yet a node at this position, retrieve and
+                // update one from the cache.
+                return getNextNode(pos);
+            }
+            if (node.invalid) {
+                return revalidateNode(node);
+            }
+
+            return node;
+        });
+    }
+
+    /**
+     * Remove and return the {@link Node Node} at the given
+     * position.
+     */
+    private Node removeNode(BlockPos pos) {
+        return nodes.remove(pos.asLong());
+    }
+
+    /**
+     * Return a {@link Node Node} that represents the block
+     * at the given position.
+     */
+    private Node getNextNode(BlockPos pos) {
+        return getNextNode(pos, level.getBlockState(pos));
+    }
+
+    /**
+     * Return a node that represents the given position and block state. If it is a
+     * wire, then create a new {@link WireNode WireNode}.
+     * Otherwise, grab the next {@link Node Node} from the
+     * cache and update it.
+     */
+    private Node getNextNode(BlockPos pos, BlockState state) {
+        return state.is(Blocks.REDSTONE_WIRE) ? new WireNode(level, pos, state) : getNextNode().set(pos, state, true);
+    }
+
+    /**
+     * Grab the first unused node from the cache. If all of the cache is already in
+     * use, increase it in size first.
+     */
+    private Node getNextNode() {
+        if (nodeCount == nodeCache.length) {
+            increaseNodeCache();
+        }
+
+        return nodeCache[nodeCount++];
+    }
+
+    private void increaseNodeCache() {
+        Node[] oldCache = nodeCache;
+        nodeCache = new Node[oldCache.length << 1];
+
+        for (int index = 0; index < oldCache.length; index++) {
+            nodeCache[index] = oldCache[index];
+        }
+
+        fillNodeCache(oldCache.length, nodeCache.length);
+    }
+
+    private void fillNodeCache(int start, int end) {
+        for (int index = start; index < end; index++) {
+            nodeCache[index] = new Node(level);
+        }
+    }
+
+    /**
+     * Try to revalidate the given node by looking at the block state that is
+     * occupying its position. If the given node is a wire but the block state is
+     * not, or vice versa, a new node must be created/grabbed from the cache.
+     * Otherwise, the node can be quickly revalidated with the new block state.
+     */
+    private Node revalidateNode(Node node) {
+        BlockPos pos = node.pos;
+        BlockState state = level.getBlockState(pos);
+
+        boolean wasWire = node.isWire();
+        boolean isWire = state.is(Blocks.REDSTONE_WIRE);
+
+        if (wasWire != isWire) {
+            return getNextNode(pos, state);
+        }
+
+        node.invalid = false;
+
+        if (isWire) {
+            // No need to update the block state of this wire - it will grab
+            // the current block state just before setting power anyway.
+            WireNode wire = node.asWire();
+
+            wire.root = false;
+            wire.discovered = false;
+            wire.searched = false;
+        } else {
+            node.set(pos, state, false);
+        }
+
+        return node;
+    }
+
+    /**
+     * Retrieve the neighbor of a node in the given direction and create a link
+     * between the two nodes if they are not yet linked. This link makes accessing
+     * neighbors of a node signficantly faster.
+     */
+    private Node getNeighbor(Node node, int iDir) {
+        Node neighbor = node.neighbors[iDir];
+
+        if (neighbor == null || neighbor.invalid) {
+            Direction dir = Directions.ALL[iDir];
+            BlockPos pos = node.pos.relative(dir);
+
+            Node oldNeighbor = neighbor;
+            neighbor = getOrAddNode(pos);
+
+            if (neighbor != oldNeighbor) {
+                int iOpp = Directions.iOpposite(iDir);
+
+                node.neighbors[iDir] = neighbor;
+                neighbor.neighbors[iOpp] = node;
+            }
+        }
+
+        return neighbor;
+    }
+
+    /**
+     * Iterate over all neighboring nodes of the given wire. The iteration order is
+     * designed to be an extension of the default block update order, and is
+     * determined as follows:
+     * <br>
+     * 1. The direction of power flow through the wire is to be considered
+     * 'forward'. The iteration order depends on the neighbors' relative positions
+     * to the wire.
+     * <br>
+     * 2. Each neighbor is identified by the step(s) you must take, starting at the
+     * wire, to reach it. Each step is 1 block, thus the position of a neighbor is
+     * encoded by the direction(s) of the step(s), e.g. (right), (down), (up, left),
+     * etc.
+     * <br>
+     * 3. Neighbors are iterated over in pairs that lie on opposite sides of the
+     * wire.
+     * <br>
+     * 4. Neighbors are iterated over in order of their distance from the wire. This
+     * means they are iterated over in 3 groups: direct neighbors first, then
+     * diagonal neighbors, and last are the far neighbors that are 2 blocks directly
+     * out.
+     * <br>
+     * 5. The order within each group is determined using the following basic order:
+     * { front, back, right, left, down, up }. This order was chosen because it
+     * converts to the following order of absolute directions when west is said to
+     * be 'forward': { west, east, north, south, down, up } - this is the order of
+     * shape updates.
+     */
+    private void forEachNeighbor(WireNode wire, Consumer<Node> consumer) {
+        int forward   = wire.iFlowDir;
+        int rightward = (forward + 1) & 0b11;
+        int backward  = (forward + 2) & 0b11;
+        int leftward  = (forward + 3) & 0b11;
+        int downward  = Directions.DOWN;
+        int upward    = Directions.UP;
+
+        Node front = getNeighbor(wire, forward);
+        Node right = getNeighbor(wire, rightward);
+        Node back  = getNeighbor(wire, backward);
+        Node left  = getNeighbor(wire, leftward);
+        Node below = getNeighbor(wire, downward);
+        Node above = getNeighbor(wire, upward);
+
+        // direct neighbors (6)
+        consumer.accept(front);
+        consumer.accept(back);
+        consumer.accept(right);
+        consumer.accept(left);
+        consumer.accept(below);
+        consumer.accept(above);
+
+        // diagonal neighbors (12)
+        consumer.accept(getNeighbor(front, rightward));
+        consumer.accept(getNeighbor(back, leftward));
+        consumer.accept(getNeighbor(front, leftward));
+        consumer.accept(getNeighbor(back, rightward));
+        consumer.accept(getNeighbor(front, downward));
+        consumer.accept(getNeighbor(back, upward));
+        consumer.accept(getNeighbor(front, upward));
+        consumer.accept(getNeighbor(back, downward));
+        consumer.accept(getNeighbor(right, downward));
+        consumer.accept(getNeighbor(left, upward));
+        consumer.accept(getNeighbor(right, upward));
+        consumer.accept(getNeighbor(left, downward));
+
+        // far neighbors (6)
+        consumer.accept(getNeighbor(front, forward));
+        consumer.accept(getNeighbor(back, backward));
+        consumer.accept(getNeighbor(right, rightward));
+        consumer.accept(getNeighbor(left, leftward));
+        consumer.accept(getNeighbor(below, downward));
+        consumer.accept(getNeighbor(above, upward));
+    }
+
+    /**
+     * This method should be called whenever a wire receives a block update.
+     */
+    public void onWireUpdated(BlockPos pos) {
+        invalidate();
+        findRoots(pos);
+        tryUpdate();
+    }
+
+    /**
+     * This method should be called whenever a wire is placed.
+     */
+    public void onWireAdded(BlockPos pos) {
+        Node node = getOrAddNode(pos);
+
+        if (!node.isWire()) {
+            return; // we should never get here
+        }
+
+        WireNode wire = node.asWire();
+        wire.added = true;
+
+        invalidate();
+        revalidateNode(wire);
+        findRoot(wire);
+        tryUpdate();
+    }
+
+    /**
+     * This method should be called whenever a wire is removed.
+     */
+    public void onWireRemoved(BlockPos pos, BlockState state) {
+        Node node = removeNode(pos);
+        WireNode wire;
+
+        if (node == null || !node.isWire()) {
+            wire = new WireNode(level, pos, state);
+        } else {
+            wire = node.asWire();
+        }
+
+        wire.invalid = true;
+        wire.removed = true;
+
+        // If these fields are set to 'true', the removal of this wire was part of
+        // already ongoing power changes, so we can exit early here.
+        if (updating && wire.shouldBreak) {
+            return;
+        }
+
+        invalidate();
+        revalidateNode(wire);
+        findRoot(wire);
+        tryUpdate();
+    }
+
+    /**
+     * The nodes map is a snapshot of the state of the world. It becomes invalid
+     * when power changes are carried out, since the block and shape updates can
+     * lead to block changes. If these block changes cause the network to be updated
+     * again every node must be invalidated, and revalidated before it is used
+     * again. This ensures the power calculations of the network are accurate.
+     */
+    private void invalidate() {
+        if (updating && !nodes.isEmpty()) {
+            Iterator<Entry<Node>> it = Long2ObjectMaps.fastIterator(nodes);
+
+            while (it.hasNext()) {
+                Entry<Node> entry = it.next();
+                Node node = entry.getValue();
+
+                node.invalid = true;
+            }
+        }
+    }
+
+    /**
+     * Look for wires at and around the given position that are in an invalid state
+     * and require power changes. These wires are called 'roots' because it is only
+     * when these wires change power level that neighboring wires must adjust as
+     * well.
+     * 
+     * <p>
+     * While it is strictly only necessary to check the wire at the given position,
+     * if that wire is part of a network, it is beneficial to check its surroundings
+     * for other wires that require power changes. This is because a network can
+     * receive power at multiple points. Consider the following setup:
+     * 
+     * <p>
+     * (top-down view, W = wire, L = lever, _ = air/other)
+     * <br> {@code _ _ W _ _ }
+     * <br> {@code _ W W W _ }
+     * <br> {@code W W L W W }
+     * <br> {@code _ W W W _ }
+     * <br> {@code _ _ W _ _ }
+     * 
+     * <p>
+     * The lever powers four wires in the network at once. If this is identified
+     * correctly, the entire network can (un)power at once. While it is not
+     * practical to cover every possible situation where a network is (un)powered
+     * from multiple points at once, checking for common cases like the one
+     * described above is relatively straight-forward.
+     */
+    private void findRoots(BlockPos pos) {
+        Node node = getOrAddNode(pos);
+
+        if (!node.isWire()) {
+            return; // we should never get here
+        }
+
+        WireNode wire = node.asWire();
+        findRoot(wire);
+
+        // If the wire at the given position is not in an invalid state
+        // we can exit early.
+        if (!wire.searched) {
+            return;
+        }
+
+        for (int iDir : FULL_UPDATE_ORDERS[wire.iFlowDir]) {
+            Node neighbor = getNeighbor(wire, iDir);
+
+            if (neighbor.isConductor() || neighbor.isSignalSource()) {
+                findRootsAround(neighbor, Directions.iOpposite(iDir));
+            }
+        }
+    }
+
+    /**
+     * Look for wires around the given node that require power changes.
+     */
+    private void findRootsAround(Node node, int except) {
+        for (int iDir : Directions.I_EXCEPT_CARDINAL[except]) {
+            Node neighbor = getNeighbor(node, iDir);
+
+            if (neighbor.isWire()) {
+                findRoot(neighbor.asWire());
+            }
+        }
+    }
+
+    /**
+     * Check if the given wire requires power changes. If it does, queue it for the
+     * breadth-first search as a root.
+     */
+    private void findRoot(WireNode wire) {
+        // Each wire only needs to be checked once.
+        if (wire.discovered) {
+            return;
+        }
+
+        discover(wire);
+        findExternalPower(wire);
+        findPower(wire, false);
+
+        if (needsUpdate(wire)) {
+            searchRoot(wire);
+        }
+    }
+
+    /**
+     * Prepare the given wire for the breadth-first search. This means:
+     * <br>
+     * - Check if the wire should break. Rather than breaking the wire right away,
+     * its effects are integrated into the power calculations.
+     * <br>
+     * - Reset the virtual and external power.
+     * <br>
+     * - Find connections to neighboring wires.
+     */
+    private void discover(WireNode wire) {
+        if (wire.discovered) {
+            return;
+        }
+
+        wire.discovered = true;
+        wire.searched = false;
+
+        if (!wire.removed && !wire.shouldBreak && !wire.state.canSurvive(level, wire.pos)) {
+            wire.shouldBreak = true;
+        }
+
+        wire.virtualPower = wire.currentPower;
+        wire.externalPower = POWER_MIN - 1;
+
+        wire.connections.set(this::getNeighbor);
+    }
+
+    /**
+     * Determine the power level the given wire receives from the blocks around it.
+     * Power from non-wire components only needs to be computed if power from
+     * neighboring wires has decreased, so as to determine how low the power of the
+     * wire can fall.
+     */
+    private void findPower(WireNode wire, boolean ignoreSearched) {
+        // As wire power is (re-)computed, flow information must be reset.
+        wire.virtualPower = wire.externalPower;
+        wire.flowIn = 0;
+
+        // If the wire is removed or going to break, its power level should always be
+        // the minimum value. This is because it (effectively) no longer exists, so
+        // cannot provide any power to neighboring wires.
+        if (wire.removed || wire.shouldBreak) {
+            return;
+        }
+
+        // Power received from neighboring wires will never exceed POWER_MAX -
+        // POWER_STEP, so if the external power is already larger than or equal to
+        // that, there is no need to check for power from neighboring wires.
+        if (wire.externalPower < (POWER_MAX - POWER_STEP)) {
+            findWirePower(wire, ignoreSearched);
+        }
+    }
+
+    /**
+     * Determine the power the given wire receives from connected neighboring wires
+     * and update the virtual power accordingly.
+     */
+    private void findWirePower(WireNode wire, boolean ignoreSearched) {
+        wire.connections.forEach(connection -> {
+            if (!connection.accept) {
+                return;
+            }
+
+            WireNode neighbor = connection.wire;
+
+            if (!ignoreSearched || !neighbor.searched) {
+                int power = Math.max(POWER_MIN, neighbor.virtualPower - POWER_STEP);
+                int iOpp = Directions.iOpposite(connection.iDir);
+
+                wire.offerPower(power, iOpp);
+            }
+        });
+    }
+
+    /**
+     * Determine the redstone signal the given wire receives from non-wire
+     * components and update the virtual power accordingly.
+     */
+    private void findExternalPower(WireNode wire) {
+        // If the wire is removed or going to break, its power level should always be
+        // the minimum value. Thus external power need not be computed.
+        // In other cases external power need only be computed once.
+        if (wire.removed || wire.shouldBreak || wire.externalPower >= POWER_MIN) {
+            return;
+        }
+
+        wire.externalPower = getExternalPower(wire);
+
+        if (wire.externalPower > wire.virtualPower) {
+            wire.virtualPower = wire.externalPower;
+        }
+    }
+
+    /**
+     * Determine the redstone signal the given wire receives from non-wire
+     * components.
+     */
+    private int getExternalPower(WireNode wire) {
+        int power = POWER_MIN;
+
+        for (int iDir = 0; iDir < Directions.ALL.length; iDir++) {
+            Node neighbor = getNeighbor(wire, iDir);
+
+            // Power from wires is handled separately.
+            if (neighbor.isWire()) {
+                continue;
+            }
+
+            // Since 1.16 there is a block that is both a conductor and a signal
+            // source: the target block!
+            if (neighbor.isConductor()) {
+                power = Math.max(power, getDirectSignalTo(wire, neighbor, Directions.iOpposite(iDir)));
+            }
+            if (neighbor.isSignalSource()) {
+                power = Math.max(power, neighbor.state.getSignal(level, neighbor.pos, Directions.ALL[iDir]));
+            }
+
+            if (power >= POWER_MAX) {
+                return POWER_MAX;
+            }
+        }
+
+        return power;
+    }
+
+    /**
+     * Determine the direct signal the given wire receives from neighboring blocks
+     * through the given conductor node.
+     */
+    private int getDirectSignalTo(WireNode wire, Node node, int except) {
+        int power = POWER_MIN;
+
+        for (int iDir : Directions.I_EXCEPT[except]) {
+            Node neighbor = getNeighbor(node, iDir);
+
+            if (neighbor.isSignalSource()) {
+                power = Math.max(power, neighbor.state.getDirectSignal(level, neighbor.pos, Directions.ALL[iDir]));
+
+                if (power >= POWER_MAX) {
+                    return POWER_MAX;
+                }
+            }
+        }
+
+        return power;
+    }
+
+    /**
+     * Check if the given wire needs to update its state in the world.
+     */
+    private boolean needsUpdate(WireNode wire) {
+        return wire.removed || wire.shouldBreak || wire.virtualPower != wire.currentPower;
+    }
+
+    /**
+     * Queue the given wire for the breadth-first search as a root.
+     */
+    private void searchRoot(WireNode wire) {
+        int iBackupFlowDir;
+
+        if (wire.connections.iFlowDir < 0) {
+            iBackupFlowDir = 0;
+        } else {
+            iBackupFlowDir = wire.connections.iFlowDir;
+        }
+
+        search(wire, true, iBackupFlowDir);
+    }
+
+    /**
+     * Queue the given wire for the breadth-first search and set a backup flow
+     * direction.
+     */
+    private void search(WireNode wire, boolean root, int iBackupFlowDir) {
+        search.offer(wire);
+
+        wire.root = root;
+        wire.searched = true;
+        // Normally the flow is not set until the power level is updated. However,
+        // in networks with multiple power sources the update order between them
+        // depends on which was discovered first. To make this less prone to
+        // directionality, each wire node is given a 'backup' flow. For roots, this
+        // is the determined flow of their connections. For non-roots this is the
+        // direction from which they were discovered.
+        wire.iFlowDir = iBackupFlowDir;
+    }
+
+    private void tryUpdate() {
+        if (!search.isEmpty()) {
+            update();
+        }
+        if (!updating) {
+            nodes.clear();
+            nodeCount = 0;
+        }
+    }
+
+    /**
+     * Update the network and neighboring blocks. This is done in 3 steps.
+     * 
+     * <p>
+     * <b>1. Search through the network</b>
+     * <br>
+     * Conduct a breadth-first search around the roots to find wires that are in an
+     * invalid state and need power changes.
+     * 
+     * <p>
+     * <b>2. Depower the network</b>
+     * <br>
+     * Depower all wires in the network. This allows power to be spread most
+     * efficiently.
+     * 
+     * <p>
+     * <b>3. Power the network</b>
+     * <br>
+     * Work through the update queue, setting the new power level of each wire and
+     * updating neighboring blocks. After a wire has updated its power level, it
+     * will emit shape updates and queue updates for neighboring wires and blocks.
+     */
+    private void update() {
+        // Search through the network for wires that need power changes. This includes
+        // the roots as well as any wires that will be affected by power changes to
+        // those roots.
+        searchNetwork();
+
+        // Depower all the wires in the network.
+        depowerNetwork();
+
+        // Bring each wire up to its new power level and update neighboring blocks.
+        try {
+            powerNetwork();
+        } catch (Throwable t) {
+            // If anything goes wrong while carrying out power changes, this field must
+            // be reset to 'false', or the wire handler will be locked out of carrying
+            // out power changes until the world is reloaded.
+            updating = false;
+
+            throw t;
+        }
+    }
+
+    /**
+     * Search through the network for wires that are in an invalid state and need
+     * power changes. These wires are added to the end of the queue, so that their
+     * neighbors can be searched next.
+     */
+    private void searchNetwork() {
+        for (WireNode wire : search) {
+            // The order in which wires are searched will influence the order in
+            // which they update their power levels.
+            wire.connections.forEach(connection -> {
+                if (!connection.offer) {
+                    return;
+                }
+
+                WireNode neighbor = connection.wire;
+
+                if (neighbor.searched) {
+                    return;
+                }
+
+                discover(neighbor);
+                findPower(neighbor, false);
+
+                // If power from neighboring wires has decreased, check for power
+                // from non-wire components so as to determine how low power can
+                // fall.
+                if (neighbor.virtualPower < neighbor.currentPower) {
+                    findExternalPower(neighbor);
+                }
+
+                if (needsUpdate(neighbor)) {
+                    search(neighbor, false, connection.iDir);
+                }
+            }, wire.iFlowDir);
+        }
+    }
+
+    /**
+     * Depower all wires in the network so that power can be spread from the power
+     * sources.
+     */
+    private void depowerNetwork() {
+        while (!search.isEmpty()) {
+            WireNode wire = search.poll();
+            findPower(wire, true);
+
+            if (wire.root || wire.removed || wire.shouldBreak || wire.virtualPower > POWER_MIN) {
+                queueWire(wire);
+            } else {
+                // Wires that do not receive any power do not queue power changes
+                // until they are offered power from a neighboring wire. To ensure
+                // that they accept any power from neighboring wires and thus queue
+                // their power changes, their virtual power is set to below the
+                // minimum.
+                wire.virtualPower--;
+            }
+        }
+    }
+
+    /**
+     * Work through the update queue, setting the new power level of each wire, then
+     * queueing updates to connected wires and neighboring blocks.
+     */
+    private void powerNetwork() {
+        // If an instantaneous update chain causes updates to another network
+        // (or the same network in another place), new power changes will be
+        // integrated into the already ongoing power queue, so we can exit early
+        // here.
+        if (updating) {
+            return;
+        }
+
+        updating = true;
+
+        while (!updates.isEmpty()) {
+            Node node = updates.poll();
+
+            if (node.isWire()) {
+                WireNode wire = node.asWire();
+
+                if (!needsUpdate(wire)) {
+                    continue;
+                }
+
+                findPowerFlow(wire);
+                transmitPower(wire);
+
+                if (wire.setPower()) {
+                    queueNeighbors(wire);
+
+                    // If the wire was newly placed or removed, shape updates have
+                    // already been emitted. However, unlike before 1.19, neighbor
+                    // updates are now queued, so to preserve behavior parity with
+                    // previous versions, we emit extra shape updates here to
+                    // notify neighboring observers.
+                    updateNeighborShapes(wire);
+                }
+            } else {
+                WireNode neighborWire = node.neighborWire;
+
+                if (neighborWire != null) {
+                    BlockPos neighborPos = neighborWire.pos;
+                    Block neighborBlock = neighborWire.state.getBlock();
+
+                    updateBlock(node, neighborPos, neighborBlock);
+                }
+            }
+        }
+
+        updating = false;
+    }
+
+    /**
+     * Use the information of incoming power flow to determine the direction of
+     * power flow through this wire. If that flow is ambiguous, try to use a flow
+     * direction based on connections to neighboring wires. If that is also
+     * ambiguous, use the backup value that was set when the wire was first added to
+     * the network.
+     */
+    private void findPowerFlow(WireNode wire) {
+        int flow = FLOW_IN_TO_FLOW_OUT[wire.flowIn];
+
+        if (flow >= 0) {
+            wire.iFlowDir = flow;
+        } else if (wire.connections.iFlowDir >= 0) {
+            wire.iFlowDir = wire.connections.iFlowDir;
+        }
+    }
+
+    /**
+     * Transmit power from the given wire to neighboring wires and queue updates to
+     * those wires.
+     */
+    private void transmitPower(WireNode wire) {
+        wire.connections.forEach(connection -> {
+            if (!connection.offer) {
+                return;
+            }
+
+            WireNode neighbor = connection.wire;
+
+            int power = Math.max(POWER_MIN, wire.virtualPower - POWER_STEP);
+            int iDir = connection.iDir;
+
+            if (neighbor.offerPower(power, iDir)) {
+                queueWire(neighbor);
+            }
+        }, wire.iFlowDir);
+    }
+
+    /**
+     * Emit shape updates around the given wire.
+     */
+    private void updateNeighborShapes(WireNode wire) {
+        BlockPos wirePos = wire.pos;
+        BlockState wireState = wire.state;
+
+        for (int iDir : DEFAULT_FULL_UPDATE_ORDER) {
+            Node neighbor = getNeighbor(wire, iDir);
+
+            if (!neighbor.isWire()) {
+                int iOpp = Directions.iOpposite(iDir);
+                Direction opp = Directions.ALL[iOpp];
+
+                updateShape(neighbor, opp, wirePos, wireState);
+            }
+        }
+    }
+
+    private void updateShape(Node node, Direction dir, BlockPos neighborPos, BlockState neighborState) {
+        BlockPos pos = node.pos;
+        BlockState state = level.getBlockState(pos);
+
+        // Shape updates to redstone wire are very expensive, and should never happen
+        // as a result of power changes anyway.
+        if (!state.isAir() && !state.is(Blocks.REDSTONE_WIRE)) {
+            BlockState newState = state.updateShape(dir, neighborState, level, pos, neighborPos);
+            Block.updateOrDestroy(state, newState, level, pos, Block.UPDATE_CLIENTS);
+        }
+    }
+
+    /**
+     * Queue block updates to nodes around the given wire.
+     */
+    private void queueNeighbors(WireNode wire) {
+        forEachNeighbor(wire, neighbor -> {
+            queueNeighbor(neighbor, wire);
+        });
+    }
+
+    /**
+     * Queue the given node for an update from the given neighboring wire.
+     */
+    private void queueNeighbor(Node node, WireNode neighborWire) {
+        // Updates to wires are queued when power is transmitted.
+        if (!node.isWire()) {
+            node.neighborWire = neighborWire;
+            updates.offer(node);
+        }
+    }
+
+    /**
+     * Queue the given wire for a power change. If the wire does not need a power
+     * change (perhaps because its power has already changed), transmit power to
+     * neighboring wires.
+     */
+    private void queueWire(WireNode wire) {
+        if (needsUpdate(wire)) {
+            updates.offer(wire);
+        } else {
+            findPowerFlow(wire);
+            transmitPower(wire);
+        }
+    }
+
+    /**
+     * Emit a block update to the given node.
+     */
+    private void updateBlock(Node node, BlockPos neighborPos, Block neighborBlock) {
+        BlockPos pos = node.pos;
+        BlockState state = level.getBlockState(pos);
+
+        // While this check makes sure wires in the network are not given block
+        // updates, it also prevents block updates to wires in neighboring networks.
+        // While this should not make a difference in theory, in practice, it is
+        // possible to force a network into an invalid state without updating it, even
+        // if it is relatively obscure.
+        // While I was willing to make this compromise in return for some significant
+        // performance gains in certain setups, if you are not, you can add all the
+        // positions of the network to a set and filter out block updates to wires in
+        // the network that way.
+        if (!state.isAir() && !state.is(Blocks.REDSTONE_WIRE)) {
+            state.neighborChanged(level, pos, neighborBlock, neighborPos, false);
+        }
+    }
+
+    @FunctionalInterface
+    public static interface NodeProvider {
+
+        public Node getNeighbor(Node node, int iDir);
+
+    }
+}
diff --git a/src/main/java/alternate/current/wire/WireNode.java b/src/main/java/alternate/current/wire/WireNode.java
new file mode 100644
index 0000000000000000000000000000000000000000..33cd90c30c22200a4e1ae64f40a0bf7864546b33
--- /dev/null
+++ b/src/main/java/alternate/current/wire/WireNode.java
@@ -0,0 +1,122 @@
+package alternate.current.wire;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.Mth;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.RedStoneWireBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.redstone.Redstone;
+
+/**
+ * A WireNode is a Node that represents a wire in the world. It stores all the
+ * information about the wire that the WireHandler needs to calculate power
+ * changes.
+ * 
+ * @author Space Walker
+ */
+public class WireNode extends Node {
+
+    final WireConnectionManager connections;
+
+    /** The power level this wire currently holds in the world. */
+    int currentPower;
+    /**
+     * While calculating power changes for a network, this field is used to keep
+     * track of the power level this wire should have.
+     */
+    int virtualPower;
+    /** The power level received from non-wire components. */
+    int externalPower;
+    /**
+     * A 4-bit number that keeps track of the power flow of the wires that give this
+     * wire its power level.
+     */
+    int flowIn;
+    /** The direction of power flow, based on the incoming flow. */
+    int iFlowDir;
+    boolean added;
+    boolean removed;
+    boolean shouldBreak;
+    boolean root;
+    boolean discovered;
+    boolean searched;
+
+    /** The next wire in the simple queue. */
+    WireNode next_wire;
+
+    WireNode(ServerLevel level, BlockPos pos, BlockState state) {
+        super(level);
+
+        this.pos = pos.immutable();
+        this.state = state;
+
+        this.connections = new WireConnectionManager(this);
+
+        this.virtualPower = this.currentPower = this.state.getValue(RedStoneWireBlock.POWER);
+        this.priority = priority();
+    }
+
+    @Override
+    Node set(BlockPos pos, BlockState state, boolean clearNeighbors) {
+        throw new UnsupportedOperationException("Cannot update a WireNode!");
+    }
+
+    @Override
+    int priority() {
+        return Mth.clamp(virtualPower, Redstone.SIGNAL_MIN, Redstone.SIGNAL_MAX);
+    }
+
+    @Override
+    public boolean isWire() {
+        return true;
+    }
+
+    @Override
+    public WireNode asWire() {
+        return this;
+    }
+
+    boolean offerPower(int power, int iDir) {
+        if (removed || shouldBreak) {
+            return false;
+        }
+        if (power == virtualPower) {
+            flowIn |= (1 << iDir);
+            return false;
+        }
+        if (power > virtualPower) {
+            virtualPower = power;
+            flowIn = (1 << iDir);
+
+            return true;
+        }
+
+        return false;
+    }
+
+    boolean setPower() {
+        if (removed) {
+            return true;
+        }
+
+        state = level.getBlockState(pos);
+
+        if (!state.is(Blocks.REDSTONE_WIRE)) {
+            return false; // we should never get here
+        }
+
+        if (shouldBreak) {
+            Block.dropResources(state, level, pos);
+            level.setBlock(pos, Blocks.AIR.defaultBlockState(), Block.UPDATE_CLIENTS);
+
+            return true;
+        }
+
+        currentPower = LevelHelper.doRedstoneEvent(level, pos, currentPower, Mth.clamp(virtualPower, Redstone.SIGNAL_MIN, Redstone.SIGNAL_MAX));
+        state = state.setValue(RedStoneWireBlock.POWER, currentPower);
+
+        return LevelHelper.setWireState(level, pos, state, added);
+    }
+}
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index a96aa3568453aa2da8b5cd5b269fc0b3fec13938..4cf7e66dfee34a29894f53d17e7e13c46fb4b85e 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -224,6 +224,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
     public final UUID uuid;
     public boolean hasPhysicsEvent = true; // Paper
     public boolean hasEntityMoveEvent = false; // Paper
+    private final alternate.current.wire.WireHandler wireHandler = new alternate.current.wire.WireHandler(this); // Paper - optimize redstone (Alternate Current)
     public static Throwable getAddToWorldStackTrace(Entity entity) {
         final Throwable thr = new Throwable(entity + " Added to world at " + new java.util.Date());
         io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateThrowable(thr);
@@ -2590,6 +2591,13 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return crashreportsystemdetails;
     }
 
+    // Paper start - optimize redstone (Alternate Current)
+    @Override
+    public alternate.current.wire.WireHandler getWireHandler() {
+        return wireHandler;
+    }
+    // Paper end
+
     private final class EntityCallbacks implements LevelCallback<Entity> {
 
         EntityCallbacks() {}
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 78fd63052f1eb5a650befecdad07cbc755658632..3a5bf6937a98d60be0d0142a15cf12d8de9b687f 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -1876,4 +1876,14 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         return ret;
     }
     // Paper end
+    // Paper start - optimize redstone (Alternate Current)
+    public alternate.current.wire.WireHandler getWireHandler() {
+        // This method is overridden in ServerLevel.
+        // Since Paper is a server platform there is no risk
+        // of this implementation being called. It is here
+        // only so this method can be called without casting
+        // an instance of Level to ServerLevel.
+        return null;
+    }
+    // Paper end - optimize redstone (Alternate Current)
 }
diff --git a/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java b/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
index 5ffb1453bf332e8035abacc97ab36d78e1248484..507be06ad51b7a212e28d3ca6680e0e4b00f4233 100644
--- a/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/RedStoneWireBlock.java
@@ -259,7 +259,7 @@ public class RedStoneWireBlock extends Block {
         return floor.isFaceSturdy(world, pos, Direction.UP) || floor.is(Blocks.HOPPER);
     }
 
-    // Paper start - Optimize redstone
+    // Paper start - Optimize redstone (Eigencraft)
     // The bulk of the new functionality is found in RedstoneWireTurbo.java
     com.destroystokyo.paper.util.RedstoneWireTurbo turbo = new com.destroystokyo.paper.util.RedstoneWireTurbo(this);
 
@@ -461,7 +461,13 @@ public class RedStoneWireBlock extends Block {
     @Override
     public void onPlace(BlockState state, Level world, BlockPos pos, BlockState oldState, boolean notify) {
         if (!oldState.is(state.getBlock()) && !world.isClientSide) {
-            this.updateSurroundingRedstone(world, pos, state, null); // Paper - Optimize redstone
+            // Paper start - optimize redstone - replace call to updatePowerStrength
+            if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+                world.getWireHandler().onWireAdded(pos); // Alternate Current
+            } else {
+                this.updateSurroundingRedstone(world, pos, state, null); // vanilla/Eigencraft
+            }
+            // Paper end
             Iterator iterator = Direction.Plane.VERTICAL.iterator();
 
             while (iterator.hasNext()) {
@@ -488,7 +494,13 @@ public class RedStoneWireBlock extends Block {
                     world.updateNeighborsAt(pos.relative(enumdirection), this);
                 }
 
-                this.updateSurroundingRedstone(world, pos, state, null); // Paper - Optimize redstone
+                // Paper start - optimize redstone - replace call to updatePowerStrength
+                if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+                    world.getWireHandler().onWireRemoved(pos, state); // Alternate Current
+                } else {
+                    this.updateSurroundingRedstone(world, pos, state, null); // vanilla/Eigencraft
+                }
+                // Paper end
                 this.updateNeighborsOfNeighboringWires(world, pos);
             }
         }
@@ -522,8 +534,14 @@ public class RedStoneWireBlock extends Block {
     @Override
     public void neighborChanged(BlockState state, Level world, BlockPos pos, Block sourceBlock, BlockPos sourcePos, boolean notify) {
         if (!world.isClientSide) {
+            // Paper start - optimize redstone (Alternate Current)
+            // Alternate Current handles breaking of redstone wires in the WireHandler.
+            if (world.paperConfig().misc.redstoneImplementation == io.papermc.paper.configuration.WorldConfiguration.Misc.RedstoneImplementation.ALTERNATE_CURRENT) {
+                world.getWireHandler().onWireUpdated(pos);
+            } else
+            // Paper end
             if (state.canSurvive(world, pos)) {
-                this.updateSurroundingRedstone(world, pos, state, sourcePos); // Paper - Optimize redstone
+                this.updateSurroundingRedstone(world, pos, state, sourcePos); // Paper - Optimize redstone (Eigencraft)
             } else {
                 dropResources(state, world, pos);
                 world.removeBlock(pos, false);