package mindustry.ai;

import arc.*;
import arc.graphics.*;
import arc.graphics.g2d.*;
import arc.math.*;
import arc.math.geom.*;
import arc.struct.*;
import arc.util.*;
import mindustry.annotations.Annotations.*;
import mindustry.content.*;
import mindustry.core.*;
import mindustry.game.EventType.*;
import mindustry.game.*;
import mindustry.gen.*;
import mindustry.graphics.*;
import mindustry.world.*;

import static mindustry.Vars.*;
import static mindustry.ai.Pathfinder.*;

//https://webdocs.cs.ualberta.ca/~mmueller/ps/hpastar.pdf
//https://www.gameaipro.com/GameAIPro/GameAIPro_Chapter23_Crowd_Pathfinding_and_Steering_Using_Flow_Field_Tiles.pdf
public class HierarchyPathFinder implements Runnable{
    private static final long maxUpdate = 100;//Time.millisToNanos(12);
    private static final int updateStepInterval = 20;//200;
    private static final int updateFPS = 30;
    private static final int updateInterval = 1000 / updateFPS, invalidateCheckInterval = 1000;

    static final int clusterSize = 12;

    static final boolean debug = OS.hasProp("mindustry.debug");

    static final int[] offsets = {
    1, 0, //right: bottom to top
    0, 1, //top: left to right
    0, 0, //left: bottom to top
    0, 0  //bottom: left to right
    };

    static final int[] moveDirs = {
    0, 1,
    1, 0,
    0, 1,
    1, 0
    };

    static final int[] nextOffsets = {
    1, 0,
    0, 1,
    -1, 0,
    0, -1
    };

    //maps team -> pathCost -> flattened array of clusters in 2D
    //(what about teams? different path costs?)
    Cluster[][][] clusters;

    int cwidth, cheight;

    //temporarily used for resolving connections for intra-edges
    IntSet usedEdges = new IntSet();
    //tasks to run on pathfinding thread
    TaskQueue queue = new TaskQueue();

    //individual requests based on unit - MAIN THREAD ONLY
    ObjectMap<Unit, PathRequest> unitRequests = new ObjectMap<>();

    Seq<PathRequest> threadPathRequests = new Seq<>(false);

    //TODO: very dangerous usage;
    //TODO - it is accessed from the main thread
    //TODO - it is written to on the pathfinding thread
    //maps position in world in (x + y * width format) to a cache of flow fields
    IntMap<FieldCache> fields = new IntMap<>();
    //MAIN THREAD ONLY
    Seq<FieldCache> fieldList = new Seq<>(false);

    //these are for inner edge A* (temporary!)
    IntFloatMap innerCosts = new IntFloatMap();
    PathfindQueue innerFrontier = new PathfindQueue();

    //ONLY modify on pathfinding thread.
    IntSet clustersToUpdate = new IntSet();
    IntSet clustersToInnerUpdate = new IntSet();

    //PATHFINDING THREAD - requests that should be recomputed
    ObjectSet<PathRequest> invalidRequests = new ObjectSet<>();

    /** Current pathfinding thread */
    @Nullable Thread thread;

    //path requests are per-unit
    static class PathRequest{
        final Unit unit;
        final int destination, team, costId;
        //resulting path of nodes
        final IntSeq resultPath = new IntSeq();

        //node index -> total cost
        @Nullable IntFloatMap costs = new IntFloatMap();
        //node index (NodeIndex struct) -> node it came from TODO merge them, make properties of FieldCache?
        @Nullable IntIntMap cameFrom = new IntIntMap();
        //frontier for A*
        @Nullable PathfindQueue frontier = new PathfindQueue();

        //main thread only!
        long lastUpdateId = state.updateId;

        //both threads
        volatile boolean notFound = false;
        volatile boolean invalidated = false;
        //old field assigned before everything was recomputed
        @Nullable volatile FieldCache oldCache;

        int lastTile;
        @Nullable Tile lastTargetTile;

        PathRequest(Unit unit, int team, int costId, int destination){
            this.unit = unit;
            this.costId = costId;
            this.team = team;
            this.destination = destination;
        }
    }

    static class FieldCache{
        final PathCost cost;
        final int team;
        final int goalPos;
        //frontier for flow fields
        final IntQueue frontier = new IntQueue();
        //maps cluster index to field weights; 0 means uninitialized
        final IntMap<int[]> fields = new IntMap<>();

        //main thread only!
        long lastUpdateId = state.updateId;

        //TODO: how are the nodes merged? CAN they be merged?

        FieldCache(PathCost cost, int team, int goalPos){
            this.cost = cost;
            this.team = team;
            this.goalPos = goalPos;
        }
    }

    public HierarchyPathFinder(){

        Events.on(ResetEvent.class, event -> stop());

        Events.on(WorldLoadEvent.class, event -> {
            stop();

            //TODO: can the pathfinding thread even see these?
            unitRequests = new ObjectMap<>();
            fields = new IntMap<>();
            fieldList = new Seq<>(false);

            clusters = new Cluster[256][][];
            cwidth = Mathf.ceil((float)world.width() / clusterSize);
            cheight = Mathf.ceil((float)world.height() / clusterSize);


            start();
        });

        Events.on(TileChangeEvent.class, e -> {

            e.tile.getLinkedTiles(t -> {
                int x = t.x, y = t.y, mx = x % clusterSize, my = y % clusterSize, cx = x / clusterSize, cy = y / clusterSize, cluster = cx + cy * cwidth;

                //is at the edge of a cluster; this means the portals may have changed.
                if(mx == 0 || my == 0 || mx == clusterSize - 1 || my == clusterSize - 1){

                    if(mx == 0) queueClusterUpdate(cx - 1, cy); //left
                    if(my == 0) queueClusterUpdate(cx, cy - 1); //bottom
                    if(mx == clusterSize - 1) queueClusterUpdate(cx + 1, cy); //right
                    if(my == clusterSize - 1) queueClusterUpdate(cx, cy + 1); //top

                    queueClusterUpdate(cx, cy);
                    //TODO: recompute edge clusters too.
                }else{
                    //there is no need to recompute portals for block updates that are not on the edge.
                    queue.post(() -> clustersToInnerUpdate.add(cluster));
                }
            });

            //TODO: recalculate affected flow fields? or just all of them? how to reflow?
        });

        //invalidate paths
        Events.run(Trigger.update, () -> {
            for(var req : unitRequests.values()){
                //skipped N update -> drop it
                if(req.lastUpdateId <= state.updateId - 10){
                    req.invalidated = true;
                    //concurrent modification!
                    queue.post(() -> threadPathRequests.remove(req));
                    Core.app.post(() -> unitRequests.remove(req.unit));
                }
            }

            for(var field : fieldList){
                //skipped N update -> drop it
                if(field.lastUpdateId <= state.updateId - 30){
                    //make sure it's only modified on the main thread...? but what about calling get() on this thread??
                    queue.post(() -> fields.remove(field.goalPos));
                    Core.app.post(() -> fieldList.remove(field));
                }
            }
        });

        if(debug){
            Events.run(Trigger.draw, () -> {
                int team = player.team().id;
                int cost = costGround;

                Draw.draw(Layer.overlayUI, () -> {
                    Lines.stroke(1f);

                    if(clusters[team] != null && clusters[team][cost] != null){
                        for(int cx = 0; cx < cwidth; cx++){
                            for(int cy = 0; cy < cheight; cy++){

                                var cluster = clusters[team][cost][cy * cwidth + cx];
                                if(cluster != null){
                                    Lines.stroke(0.5f);
                                    Draw.color(Color.gray);
                                    Lines.stroke(1f);

                                    Lines.rect(cx * clusterSize * tilesize - tilesize/2f, cy * clusterSize * tilesize - tilesize/2f, clusterSize * tilesize, clusterSize * tilesize);


                                    for(int d = 0; d < 4; d++){
                                        IntSeq portals = cluster.portals[d];
                                        if(portals != null){

                                            for(int i = 0; i < portals.size; i++){
                                                int pos = portals.items[i];
                                                int from = Point2.x(pos), to = Point2.y(pos);
                                                float width = tilesize * (Math.abs(from - to) + 1), height = tilesize;

                                                portalToVec(cluster, cx, cy, d, i, Tmp.v1);

                                                Draw.color(Color.brown);
                                                Lines.ellipse(30, Tmp.v1.x, Tmp.v1.y, width / 2f, height / 2f, d * 90f - 90f);

                                                LongSeq connections = cluster.portalConnections[d] == null ? null : cluster.portalConnections[d][i];

                                                if(connections != null){
                                                    Draw.color(Color.forest);
                                                    for(int coni = 0; coni < connections.size; coni ++){
                                                        long con = connections.items[coni];

                                                        portalToVec(cluster, cx, cy, IntraEdge.dir(con), IntraEdge.portal(con), Tmp.v2);

                                                        float
                                                        x1 = Tmp.v1.x, y1 = Tmp.v1.y,
                                                        x2 = Tmp.v2.x, y2 = Tmp.v2.y,
                                                        mx = (cx * clusterSize + clusterSize / 2f) * tilesize, my = (cy * clusterSize + clusterSize / 2f) * tilesize;
                                                        //Lines.curve(x1, y1, mx, my, mx, my, x2, y2, 20);
                                                        Lines.line(x1, y1, x2, y2);

                                                    }
                                                }
                                            }
                                        }
                                    }

                                    //TODO draw connections.

                                /*
                                Draw.color(Color.magenta);
                                for(var con : cluster.cons){
                                    float
                                    x1 = Point2.x(con.posFrom) * tilesize, y1 = Point2.y(con.posFrom) * tilesize,
                                    x2 = Point2.x(con.posTo) * tilesize, y2 = Point2.y(con.posTo) * tilesize,
                                    mx = (cx * clusterSize + clusterSize/2f) * tilesize, my = (cy * clusterSize + clusterSize/2f) * tilesize;
                                    //Lines.curve(x1, y1, mx, my, mx, my, x2, y2, 20);
                                    Lines.line(x1, y1, x2, y2);
                                }*/
                                }
                            }
                        }
                    }

                    for(var fields : fieldList){
                        try{
                            for(var entry : fields.fields){
                                int cx = entry.key % cwidth, cy = entry.key / cwidth;
                                for(int y = 0; y < clusterSize; y++){
                                    for(int x = 0; x < clusterSize; x++){
                                        int value = entry.value[x + y * clusterSize];
                                        Tmp.c1.a = 1f;
                                        Lines.stroke(0.8f, Tmp.c1.fromHsv(value * 3f, 1f, 1f));
                                        Draw.alpha(0.5f);
                                        Fill.square((x + cx * clusterSize) * tilesize, (y + cy * clusterSize) * tilesize, tilesize / 2f);
                                    }
                                }
                            }
                        }catch(Exception ignored){} //probably has some concurrency issues when iterating but I don't care, this is for debugging
                    }
                });
            });
        }
    }

    void queueClusterUpdate(int cx, int cy){
        if(cx >= 0 && cy >= 0 && cx < cwidth && cy < cheight){
            queue.post(() -> clustersToUpdate.add(cx + cy * cwidth));
        }
    }

    static void line(Vec2 a, Vec2 b){
        Fx.debugLine.at(a.x, a.y, 0f, Color.blue.cpy().a(0.1f), new Vec2[]{a.cpy(), b.cpy()});
    }

    static void line(Vec2 a, Vec2 b, Color color){
        Fx.debugLine.at(a.x, a.y, 0f, color, new Vec2[]{a.cpy(), b.cpy()});
    }

    //DEBUGGING ONLY
    Vec2 nodeToVec(int current, Vec2 out){
        portalToVec(0, NodeIndex.cluster(current), NodeIndex.dir(current), NodeIndex.portal(current), out);
        return out;
    }

    void portalToVec(int pathCost, int cluster, int direction, int portalIndex, Vec2 out){
        portalToVec(clusters[Team.sharded.id][pathCost][cluster], cluster % cwidth, cluster / cwidth, direction, portalIndex, out);
    }

    void portalToVec(Cluster cluster, int cx, int cy, int direction, int portalIndex, Vec2 out){
        int pos = cluster.portals[direction].items[portalIndex];
        int from = Point2.x(pos), to = Point2.y(pos);
        int addX = moveDirs[direction * 2], addY = moveDirs[direction * 2 + 1];
        float average = (from + to) / 2f;

        float
        x = (addX * average + cx * clusterSize + offsets[direction * 2] * (clusterSize - 1) + nextOffsets[direction * 2] / 2f) * tilesize,
        y = (addY * average + cy * clusterSize + offsets[direction * 2 + 1] * (clusterSize - 1) + nextOffsets[direction * 2 + 1] / 2f) * tilesize;

        out.set(x, y);
    }

    /** Starts or restarts the pathfinding thread. */
    private void start(){
        stop();
        if(net.client()) return;

        thread = new Thread(this, "Control Pathfinder");
        thread.setPriority(Thread.MIN_PRIORITY);
        thread.setDaemon(true);
        thread.start();
    }

    /** Stops the pathfinding thread. */
    private void stop(){
        if(thread != null){
            thread.interrupt();
            thread = null;
        }
        queue.clear();
    }

    /** @return a cluster at coordinates; can be null if not cluster was created yet*/
    @Nullable Cluster getCluster(int team, int pathCost, int cx, int cy){
        return getCluster(team, pathCost, cx + cy * cwidth);
    }

    /** @return a cluster at coordinates; can be null if not cluster was created yet*/
    @Nullable Cluster getCluster(int team, int pathCost, int clusterIndex){
        if(clusters == null) return null;

        Cluster[][] dim1 = clusters[team];

        if(dim1 == null) return null;

        Cluster[] dim2 = dim1[pathCost];

        if(dim2 == null) return null;

        return dim2[clusterIndex];
    }

    /** @return the cluster at specified coordinates; never null. */
    Cluster getCreateCluster(int team, int pathCost, int cx, int cy){
        return getCreateCluster(team, pathCost, cx + cy * cwidth);
    }

    /** @return the cluster at specified coordinates; never null. */
    Cluster getCreateCluster(int team, int pathCost, int clusterIndex){
        Cluster result = getCluster(team, pathCost, clusterIndex);
        if(result == null){
            return updateCluster(team, pathCost, clusterIndex % cwidth, clusterIndex / cwidth);
        }else{
            return result;
        }
    }

    Cluster updateCluster(int team, int pathCost, int cx, int cy){
        //TODO: what if clusters are null for thread visibility reasons?

        Cluster[][] dim1 = clusters[team];

        if(dim1 == null){
            dim1 = clusters[team] = new Cluster[Team.all.length][];
        }

        Cluster[] dim2 = dim1[pathCost];

        if(dim2 == null){
            dim2 = dim1[pathCost] = new Cluster[cwidth * cheight];
        }

        Cluster cluster = dim2[cy * cwidth + cx];
        if(cluster == null){
            cluster = dim2[cy * cwidth + cx] = new Cluster();
        }else{
            //reset data
            for(var p : cluster.portals){
                p.clear();
            }
        }

        PathCost cost = idToCost(pathCost);

        for(int direction = 0; direction < 4; direction++){
            int otherX = cx + Geometry.d4x(direction), otherY = cy + Geometry.d4y(direction);
            //out of bounds, no portals in this direction
            if(otherX < 0 || otherY < 0 || otherX >= cwidth || otherY >= cheight){
                continue;
            }

            Cluster other = dim2[otherX + otherY * cwidth];
            IntSeq portals;

            if(other == null){
                //create new portals at direction
                portals = cluster.portals[direction] = new IntSeq(4);
            }else{
                //share portals with the other cluster
                portals = cluster.portals[direction] = other.portals[(direction + 2) % 4];

                //clear the portals, they're being recalculated now
                portals.clear();
            }

            int addX = moveDirs[direction * 2], addY = moveDirs[direction * 2 + 1];
            int
            baseX = cx * clusterSize + offsets[direction * 2] * (clusterSize - 1),
            baseY = cy * clusterSize + offsets[direction * 2 + 1] * (clusterSize - 1),
            nextBaseX = baseX + Geometry.d4[direction].x,
            nextBaseY = baseY + Geometry.d4[direction].y;

            int lastPortal = -1;
            boolean prevSolid = true;

            for(int i = 0; i < clusterSize; i++){
                int x = baseX + addX * i, y = baseY + addY * i;

                //scan for portals
                if(solid(team, cost, x, y) || solid(team, cost, nextBaseX + addX * i, nextBaseY + addY * i)){
                    int previous = i - 1;
                    //hit a wall, create portals between the two points
                    if(!prevSolid && previous >= lastPortal){
                        //portals are an inclusive range
                        portals.add(Point2.pack(previous, lastPortal));
                    }
                    prevSolid = true;
                }else{
                    //empty area encountered, mark the location of portal start
                    if(prevSolid){
                        lastPortal = i;
                    }
                    prevSolid = false;
                }
            }

            //at the end of the loop, close any un-initialized portals; this is copy pasted code
            int previous = clusterSize - 1;
            if(!prevSolid && previous >= lastPortal){
                //portals are an inclusive range
                portals.add(Point2.pack(previous, lastPortal));
            }
        }

        updateInnerEdges(team, cost, cx, cy, cluster);

        return cluster;
    }

    void updateInnerEdges(int team, int cost, int cx, int cy, Cluster cluster){
        updateInnerEdges(team, idToCost(cost), cx, cy, cluster);
    }

    void updateInnerEdges(int team, PathCost cost, int cx, int cy, Cluster cluster){
        int minX = cx * clusterSize, minY = cy * clusterSize, maxX = Math.min(minX + clusterSize - 1, wwidth - 1), maxY = Math.min(minY + clusterSize - 1, wheight - 1);
        
        usedEdges.clear();

        //clear all connections, since portals changed, they need to be recomputed.
        cluster.portalConnections = new LongSeq[4][];

        for(int direction = 0; direction < 4; direction++){
            var portals = cluster.portals[direction];
            if(portals == null) continue;

            int addX = moveDirs[direction * 2], addY = moveDirs[direction * 2 + 1];

            for(int i = 0; i < portals.size; i++){
                usedEdges.add(Point2.pack(direction, i));
                
                int
                portal = portals.items[i],
                from = Point2.x(portal), to = Point2.y(portal),
                average = (from + to) / 2,
                x = (addX * average + cx * clusterSize + offsets[direction * 2] * (clusterSize - 1)),
                y = (addY * average + cy * clusterSize + offsets[direction * 2 + 1] * (clusterSize - 1));

                for(int otherDir = 0; otherDir < 4; otherDir++){
                    var otherPortals = cluster.portals[otherDir];
                    if(otherPortals == null) continue;

                    for(int j = 0; j < otherPortals.size; j++){

                        if(!usedEdges.contains(Point2.pack(otherDir, j))){

                            int
                            other = otherPortals.items[j],
                            otherFrom = Point2.x(other), otherTo = Point2.y(other),
                            otherAverage = (otherFrom + otherTo) / 2,
                            ox = cx * clusterSize + offsets[otherDir * 2] * (clusterSize - 1),
                            oy = cy * clusterSize + offsets[otherDir * 2 + 1] * (clusterSize - 1),
                            otherX = (moveDirs[otherDir * 2] * otherAverage + ox),
                            otherY = (moveDirs[otherDir * 2 + 1] * otherAverage + oy);

                            //duplicate portal; should never happen.
                            if(Point2.pack(x, y) == Point2.pack(otherX, otherY)){
                                continue;
                            }

                            float connectionCost = innerAstar(
                                team, cost,
                                minX, minY, maxX, maxY,
                                x + y * wwidth,
                                otherX + otherY * wwidth,
                                (moveDirs[otherDir * 2] * otherFrom + ox),
                                (moveDirs[otherDir * 2 + 1] * otherFrom + oy),
                                (moveDirs[otherDir * 2] * otherTo + ox),
                                (moveDirs[otherDir * 2 + 1] * otherTo + oy)
                            );

                            if(connectionCost != -1f){
                                if(cluster.portalConnections[direction] == null) cluster.portalConnections[direction] = new LongSeq[cluster.portals[direction].size];
                                if(cluster.portalConnections[otherDir] == null) cluster.portalConnections[otherDir] = new LongSeq[cluster.portals[otherDir].size];
                                if(cluster.portalConnections[direction][i] == null) cluster.portalConnections[direction][i] = new LongSeq(8);
                                if(cluster.portalConnections[otherDir][j] == null) cluster.portalConnections[otherDir][j] = new LongSeq(8);

                                //TODO: can there be duplicate edges??
                                cluster.portalConnections[direction][i].add(IntraEdge.get(otherDir, j, connectionCost));
                                cluster.portalConnections[otherDir][j].add(IntraEdge.get(direction, i, connectionCost));
                            }
                        }
                    }
                }
            }
        }
    }

    //distance heuristic: manhattan
    private static float heuristic(int a, int b){
        int x = a % wwidth, x2 = b % wwidth, y = a / wwidth, y2 = b / wwidth;
        return Math.abs(x - x2) + Math.abs(y - y2);
    }

    private static int tcost(int team, PathCost cost, int tilePos){
        return cost.getCost(team, pathfinder.tiles[tilePos]);
    }

    private static float tileCost(int team, PathCost type, int a, int b){
        //currently flat cost
        return cost(team, type, b);
    }

    /** @return -1 if no path was found */
    float innerAstar(int team, PathCost cost, int minX, int minY, int maxX, int maxY, int startPos, int goalPos, int goalX1, int goalY1, int goalX2, int goalY2){
        var frontier = innerFrontier;
        var costs = innerCosts;

        frontier.clear();
        costs.clear();

        //TODO: this can be faster and more memory efficient by making costs a NxN array... probably?
        costs.put(startPos, 0);
        frontier.add(startPos, 0);

        while(frontier.size > 0){
            int current = frontier.poll();

            int cx = current % wwidth, cy = current / wwidth;

            //found the goal (it's in the portal rectangle)
            //TODO portal rectangle approach does not work, making this slower than it should be
            if((cx >= goalX1 && cy >= goalY1 && cx <= goalX2 && cy <= goalY2) || current == goalPos){
                return costs.get(current);
            }

            for(Point2 point : Geometry.d4){
                int newx = cx + point.x, newy = cy + point.y;
                int next = newx + wwidth * newy;

                if(newx > maxX || newy > maxY || newx < minX || newy < minY) continue;

                //TODO fallback mode for enemy walls or whatever
                if(tcost(team, cost, next) == impassable) continue;

                float add = tileCost(team, cost, current, next);

                if(add < 0) continue;

                float newCost = costs.get(current) + add;

                if(newCost < costs.get(next, Float.POSITIVE_INFINITY)){
                    costs.put(next, newCost);
                    float priority = newCost + heuristic(next, goalPos);
                    frontier.add(next, priority);
                }
            }
        }

        return -1f;
    }

    int makeNodeIndex(int cx, int cy, int dir, int portal){
        //to make sure there's only one way to refer to each node, the direction must be 0 or 1 (referring to portals on the top or right edge)

        //direction can only be 2 if cluster X is 0 (left edge of map)
        if(dir == 2 && cx != 0){
            dir = 0;
            cx --;
        }

        //direction can only be 3 if cluster Y is 0 (bottom edge of map)
        if(dir == 3 && cy != 0){
            dir = 1;
            cy --;
        }

        return NodeIndex.get(cx + cy * cwidth, dir, portal);
    }

    //uses A* to find the closest node index to specified coordinates
    //this node is used in cluster A*
    /** @return MAX_VALUE if no node is found */
    private int findClosestNode(int team, int pathCost, int tileX, int tileY){
        int cx = tileX / clusterSize, cy = tileY / clusterSize;

        if(cx < 0 || cy < 0 || cx >= cwidth || cy >= cheight){
            return Integer.MAX_VALUE;
        }

        PathCost cost = idToCost(pathCost);
        Cluster cluster = getCreateCluster(team, pathCost, cx, cy);
        int minX = cx * clusterSize, minY = cy * clusterSize, maxX = Math.min(minX + clusterSize - 1, wwidth - 1), maxY = Math.min(minY + clusterSize - 1, wheight - 1);

        int bestPortalPair = Integer.MAX_VALUE;
        float bestCost = Float.MAX_VALUE;

        //A* to every node, find the best one (I know there's a better algorithm for this, probably dijkstra)
        for(int dir = 0; dir < 4; dir++){
            var portals = cluster.portals[dir];
            if(portals == null) continue;

            for(int j = 0; j < portals.size; j++){

                int
                other = portals.items[j],
                otherFrom = Point2.x(other), otherTo = Point2.y(other),
                otherAverage = (otherFrom + otherTo) / 2,
                ox = cx * clusterSize + offsets[dir * 2] * (clusterSize - 1),
                oy = cy * clusterSize + offsets[dir * 2 + 1] * (clusterSize - 1),
                otherX = (moveDirs[dir * 2] * otherAverage + ox),
                otherY = (moveDirs[dir * 2 + 1] * otherAverage + oy);

                float connectionCost = innerAstar(
                team, cost,
                minX, minY, maxX, maxY,
                tileX + tileY * wwidth,
                otherX + otherY * wwidth,
                //TODO these are wrong and never actually trigger
                (moveDirs[dir * 2] * otherFrom + ox),
                (moveDirs[dir * 2 + 1] * otherFrom + oy),
                (moveDirs[dir * 2] * otherTo + ox),
                (moveDirs[dir * 2 + 1] * otherTo + oy)
                );

                //better cost found, update and return
                if(connectionCost != -1f && connectionCost < bestCost){
                    bestPortalPair = Point2.pack(dir, j);
                    bestCost = connectionCost;
                }
            }
        }

        if(bestPortalPair != Integer.MAX_VALUE){
            return makeNodeIndex(cx, cy, Point2.x(bestPortalPair), Point2.y(bestPortalPair));
        }


        return Integer.MAX_VALUE;
    }

    //distance heuristic: manhattan
    private float clusterNodeHeuristic(int team, int pathCost, int nodeA, int nodeB){
        int
        clusterA = NodeIndex.cluster(nodeA),
        dirA = NodeIndex.dir(nodeA),
        portalA = NodeIndex.portal(nodeA),
        clusterB = NodeIndex.cluster(nodeB),
        dirB = NodeIndex.dir(nodeB),
        portalB = NodeIndex.portal(nodeB),
        rangeA = getCreateCluster(team, pathCost, clusterA).portals[dirA].items[portalA],
        rangeB = getCreateCluster(team, pathCost, clusterB).portals[dirB].items[portalB];

        float
        averageA = (Point2.x(rangeA) + Point2.y(rangeA)) / 2f,
        x1 = (moveDirs[dirA * 2] * averageA + (clusterA % cwidth) * clusterSize + offsets[dirA * 2] * (clusterSize - 1) + nextOffsets[dirA * 2] / 2f),
        y1 = (moveDirs[dirA * 2 + 1] * averageA + (clusterA / cwidth) * clusterSize + offsets[dirA * 2 + 1] * (clusterSize - 1) + nextOffsets[dirA * 2 + 1] / 2f),

        averageB = (Point2.x(rangeB) + Point2.y(rangeB)) / 2f,
        x2 = (moveDirs[dirB * 2] * averageB + (clusterB % cwidth) * clusterSize + offsets[dirB * 2] * (clusterSize - 1) + nextOffsets[dirB * 2] / 2f),
        y2 = (moveDirs[dirB * 2 + 1] * averageB + (clusterB / cwidth) * clusterSize + offsets[dirB * 2 + 1] * (clusterSize - 1) + nextOffsets[dirB * 2 + 1] / 2f);

        return Math.abs(x1 - x2) + Math.abs(y1 - y2);
    }

    @Nullable IntSeq clusterAstar(PathRequest request, int pathCost, int startNodeIndex, int endNodeIndex){
        var result = request.resultPath;

        if(startNodeIndex == endNodeIndex){
            result.clear();
            result.add(startNodeIndex);
            return result;
        }

        var team = request.team;

        if(request.costs == null) request.costs = new IntFloatMap();
        if(request.cameFrom == null) request.cameFrom = new IntIntMap();
        if(request.frontier == null) request.frontier = new PathfindQueue();

        //note: these are NOT cleared, it is assumed that this function cleans up after itself at the end
        //is this a good idea? don't know, might hammer the GC with unnecessary objects too
        var costs = request.costs;
        var cameFrom = request.cameFrom;
        var frontier = request.frontier;

        cameFrom.put(startNodeIndex, startNodeIndex);
        costs.put(startNodeIndex, 0);
        frontier.add(startNodeIndex, 0);

        boolean foundEnd = false;

        while(frontier.size > 0){
            int current = frontier.poll();

            if(current == endNodeIndex){
                foundEnd = true;
                break;
            }

            int cluster = NodeIndex.cluster(current), dir = NodeIndex.dir(current), portal = NodeIndex.portal(current);
            int cx = cluster % cwidth, cy = cluster / cwidth;
            Cluster clust = getCreateCluster(team, pathCost, cluster);
            LongSeq innerCons = clust.portalConnections[dir] == null || portal >= clust.portalConnections[dir].length ? null : clust.portalConnections[dir][portal];

            //edges for the cluster the node is 'in'
            if(innerCons != null){
                checkEdges(request, team, pathCost, current, endNodeIndex, cx, cy, innerCons);
            }

            //edges that this node 'faces' from the other side
            int nextCx = cx + Geometry.d4[dir].x, nextCy = cy + Geometry.d4[dir].y;
            if(nextCx >= 0 && nextCy >= 0 && nextCx < cwidth && nextCy < cheight){
                Cluster nextCluster = getCreateCluster(team, pathCost, nextCx, nextCy);
                int relativeDir = (dir + 2) % 4;
                LongSeq outerCons = nextCluster.portalConnections[relativeDir] == null ? null : nextCluster.portalConnections[relativeDir][portal];
                if(outerCons != null){
                    checkEdges(request, team, pathCost, current, endNodeIndex, nextCx, nextCy, outerCons);
                }
            }
        }

        //null them out, so they get GC'ed later
        //there's no reason to keep them around and waste memory, since this path may never be recalculated
        request.costs = null;
        request.cameFrom = null;
        request.frontier = null;

        if(foundEnd){
            result.clear();

            int cur = endNodeIndex;
            while(cur != startNodeIndex){
                result.add(cur);
                cur = cameFrom.get(cur);
            }

            result.reverse();

            return result;
        }
        return null;
    }

    private void checkEdges(PathRequest request, int team, int pathCost, int current, int goal, int cx, int cy, LongSeq connections){
        for(int i = 0; i < connections.size; i++){
            long con = connections.items[i];
            float cost = IntraEdge.cost(con);
            int otherDir = IntraEdge.dir(con), otherPortal = IntraEdge.portal(con);
            int next = makeNodeIndex(cx, cy, otherDir, otherPortal);

            float newCost = request.costs.get(current) + cost;

            if(newCost < request.costs.get(next, Float.POSITIVE_INFINITY)){
                request.costs.put(next, newCost);

                request.frontier.add(next, newCost + clusterNodeHeuristic(team, pathCost, next, goal));
                request.cameFrom.put(next, current);
            }
        }
    }

    private void updateFields(FieldCache cache, long nsToRun){
        var frontier = cache.frontier;
        var fields = cache.fields;
        var goalPos = cache.goalPos;
        var pcost = cache.cost;
        var team = cache.team;

        long start = Time.nanos();
        int counter = 0;

        //actually do the flow field part
        while(frontier.size > 0){
            int tile = frontier.removeLast();
            int baseX = tile % wwidth, baseY = tile / wwidth;
            int curWeightIndex = (baseX / clusterSize) + (baseY / clusterSize) * cwidth;

            //TODO: how can this be null??? serious problem!
            int[] curWeights = fields.get(curWeightIndex);
            if(curWeights == null) continue;

            int cost = curWeights[baseX % clusterSize + ((baseY % clusterSize) * clusterSize)];

            if(cost != impassable){
                for(Point2 point : Geometry.d4){

                    int
                    dx = baseX + point.x, dy = baseY + point.y,
                    clx = dx / clusterSize, cly = dy / clusterSize;

                    if(clx < 0 || cly < 0 || dx >= wwidth || dy >= wheight) continue;

                    int nextWeightIndex = clx + cly * cwidth;

                    int[] weights = nextWeightIndex == curWeightIndex ? curWeights : fields.get(nextWeightIndex);

                    //out of bounds; not allowed to move this way because no weights were registered here
                    if(weights == null) continue;

                    int newPos = tile + point.x + point.y * wwidth;

                    //can't move back to the goal
                    if(newPos == goalPos) continue;

                    if(dx - clx * clusterSize < 0 || dy - cly * clusterSize < 0) continue;

                    int newPosArray = (dx - clx * clusterSize) + (dy - cly * clusterSize) * clusterSize;

                    int otherCost = pcost.getCost(team, pathfinder.tiles[newPos]);
                    int oldCost = weights[newPosArray];

                    //a cost of 0 means uninitialized, OR it means we're at the goal position, but that's handled above
                    if((oldCost == 0 || oldCost > cost + otherCost) && otherCost != impassable){
                        frontier.addFirst(newPos);
                        weights[newPosArray] = cost + otherCost;
                    }
                }
            }

            //every N iterations, check the time spent - this prevents extra calls to nano time, which itself is slow
            if(nsToRun >= 0 && (counter++) >= updateStepInterval){
                counter = 0;
                if(Time.timeSinceNanos(start) >= nsToRun){
                    return;
                }
            }
        }
    }

    private void addFlowCluster(FieldCache cache, int cluster, boolean addingFrontier){
        addFlowCluster(cache, cluster % cwidth, cluster / cwidth, addingFrontier);
    }

    private void addFlowCluster(FieldCache cache, int cx, int cy, boolean addingFrontier){
        //out of bounds
        if(cx < 0 || cy < 0 || cx >= cwidth || cy >= cheight) return;

        var fields = cache.fields;
        int key = cx + cy * cwidth;

        if(!fields.containsKey(key)){
            fields.put(key, new int[clusterSize * clusterSize]);

            //TODO: now, scan d4 for nearby clusters.
            if(addingFrontier){

                for(int dir = 0; dir < 4; dir++){
                    int ox = cx + nextOffsets[dir * 2], oy = cy + nextOffsets[dir * 2 + 1];

                    if(ox < 0 || oy < 0 || ox >= cwidth || ox >= cheight) continue;

                    var otherField = cache.fields.get(ox + oy * cwidth);

                    if(otherField == null) continue;

                    int
                    relOffset = (dir + 2) % 4,
                    movex = moveDirs[relOffset * 2],
                    movey = moveDirs[relOffset * 2 + 1],
                    otherx1 = offsets[relOffset * 2] * (clusterSize - 1),
                    othery1 = offsets[relOffset * 2 + 1] * (clusterSize - 1);

                    //scan the edge of the cluster
                    for(int i = 0; i < clusterSize; i++){
                        int x = otherx1 + movex * i, y = othery1 + movey * i;

                        //check to make sure it's not 0 (uninitialized flowfield data)
                        if(otherField[x + y * clusterSize] > 0){
                            int worldX = x + ox * clusterSize, worldY = y + oy * clusterSize;

                            //add the world-relative position to the frontier, so it recalculates
                            cache.frontier.addFirst(worldX + worldY * wwidth);

                            if(debug){
                                Core.app.post(() -> Fx.placeBlock.at(worldX *tilesize, worldY * tilesize, 1f));
                            }
                        }
                    }
                }
            }
        }
    }

    private void initializePathRequest(PathRequest request, int team, int costId, int unitX, int unitY, int goalX, int goalY){
        PathCost pcost = idToCost(costId);

        int goalPos = (goalX + goalY * wwidth);

        int node = findClosestNode(team, costId, unitX, unitY);
        int dest = findClosestNode(team, costId, goalX, goalY);

        if(dest == Integer.MAX_VALUE){
            request.notFound = true;
            //no node found (TODO: invalid state??)
            return;
        }

        var nodePath = clusterAstar(request, costId, node, dest);

        //TODO: how to reuse properly. what if the flowfields don't go through this position (the fields are finished?) how to incrementally extend the flowfield?
        FieldCache cache = fields.get(goalPos);
        //if true, extra values are added on the sides of existing field cells that face new cells.
        boolean addingFrontier = true;

        //create the cache if it doesn't exist, and initialize it
        if(cache == null){
            fields.put(goalPos, cache = new FieldCache(pcost, team, goalPos));
            FieldCache fcache = cache;
            //register field in main thread for iteration
            Core.app.post(() -> fieldList.add(fcache));
            cache.frontier.addFirst(goalPos);
            addingFrontier = false; //when it's a new field, there is no need to add to the frontier to merge the flowfield
        }

        if(nodePath != null){
            int cx = unitX / clusterSize, cy = unitY / clusterSize;

            addFlowCluster(cache, cx, cy, addingFrontier);

            for(int i = -1; i < nodePath.size; i++){
                int
                current = i == -1 ? node : nodePath.items[i],
                cluster = NodeIndex.cluster(current),
                dir = NodeIndex.dir(current),
                dx = Geometry.d4[dir].x,
                dy = Geometry.d4[dir].y,
                ox = cluster % cwidth + dx,
                oy = cluster / cwidth + dy;

                addFlowCluster(cache, cluster, addingFrontier);

                //store directional/flipped version of cluster
                if(ox >= 0 && oy >= 0 && ox < cwidth && oy < cheight){
                    int other = ox + oy * cwidth;

                    addFlowCluster(cache, other, addingFrontier);
                }
            }
        }
    }

    private PathCost idToCost(int costId){
        return ControlPathfinder.costTypes.get(costId);
    }

    public boolean getPathPosition(Unit unit, Vec2 destination, Vec2 mainDestination, Vec2 out, @Nullable boolean[] noResultFound){
        int costId = unit.type.pathCostId;
        PathCost cost = idToCost(costId);

        int
        team = unit.team.id,
        tileX = unit.tileX(),
        tileY = unit.tileY(),
        destX = World.toTile(mainDestination.x),
        destY = World.toTile(mainDestination.y),
        actualDestX = World.toTile(destination.x),
        actualDestY = World.toTile(destination.y),
        destPos = destX + destY * wwidth;

        PathRequest request = unitRequests.get(unit);

        //if the destination can be trivially reached in a straight line, do that.
        if(!raycast(team, cost, tileX, tileY, actualDestX, actualDestY)){
            out.set(destination);
            return true;
        }

        boolean any = false;

        //use existing request if it exists.
        if(request != null && request.destination == destPos){
            request.lastUpdateId = state.updateId;

            Tile tileOn = unit.tileOn();
            //TODO: should fields be accessible from this thread?
            FieldCache fieldCache = fields.get(destPos);

            if(fieldCache != null && tileOn != null){
                FieldCache old = request.oldCache;
                //nullify the old field to be GCed, as it cannot be relevant anymore (this path is complete)
                if(fieldCache.frontier.isEmpty() && old != null){
                    request.oldCache = null;
                }

                fieldCache.lastUpdateId = state.updateId;
                int maxIterations = 30; //TODO higher/lower number?
                int i = 0;

                if(tileOn.pos() != request.lastTile || request.lastTargetTile == null){
                    //TODO tanks have weird behavior near edges of walls, as they try to avoid them
                    boolean anyNearSolid = false;

                    //find the next tile until one near a solid block is discovered
                    while(i ++ < maxIterations && !anyNearSolid){
                        int value = getCost(fieldCache, old, tileOn.x, tileOn.y);

                        Tile current = null;
                        int minCost = 0;
                        for(int dir = 0; dir < 8; dir ++){
                            Point2 point = Geometry.d8[dir];
                            int dx = tileOn.x + point.x, dy = tileOn.y + point.y;

                            Tile other = world.tile(dx, dy);

                            if(other == null) continue;

                            int packed = world.packArray(dx, dy);
                            int otherCost = getCost(fieldCache, old, dx, dy), relCost = otherCost - value;

                            if(relCost > 2 || otherCost <= 0){
                                anyNearSolid = true;
                            }

                            if(relCost == 7 || relCost == 8) otherCost = value + 1;

                            //check for corner preventing movement
                            if((checkCorner(unit, tileOn, other, dir - 1) || checkCorner(unit, tileOn, other, dir + 1)) &&
                                (checkSolid(unit, tileOn, dir - 2) || checkSolid(unit, tileOn, dir + 2))){ //there must be a tile to the left or right to keep the unit from going back and forth forever

                                //keep moving even if it's blocked
                                any = true;
                                continue;
                            }

                            if(otherCost < value && otherCost != impassable && (otherCost != 0 || packed == destPos) && (current == null || otherCost < minCost) && passable(cost, unit.team.id, packed) &&
                            //diagonal corner trap
                            !(
                            (!passable(cost, team, world.packArray(tileOn.x + point.x, tileOn.y)) ||
                            (!passable(cost, team, world.packArray(tileOn.x, tileOn.y + point.y))))
                            )
                            ){
                                current = other;
                                minCost = otherCost;
                            }
                        }

                        if(!(current == null || (costId == costGround && current.dangerous() && !tileOn.dangerous()))){
                            tileOn = current;
                            any = true;

                            if(current.array() == destPos){
                                break;
                            }
                        }else{
                            break;
                        }
                    }

                    //TODO: there are some serious issues with tileOn and the raycast position, intense vibration
                    request.lastTargetTile = any ? tileOn : null;
                    if(debug && tileOn != null && false){
                        Fx.placeBlock.at(tileOn.worldx(), tileOn.worldy(), 1);
                    }
                }

                if(request.lastTargetTile != null){
                    out.set(request.lastTargetTile);
                    return true;
                }
            }
        }else if(request == null){

            //queue new request.
            unitRequests.put(unit, request = new PathRequest(unit, team, costId, destPos));

            PathRequest f = request;

            //on the pathfinding thread: initialize the request
            queue.post(() -> {
                threadPathRequests.add(f);
                recalculatePath(f);
            });

            out.set(destination);

            return true;
        }

        if(noResultFound != null){
            noResultFound[0] = request.notFound;
        }
        return false;
    }

    private void recalculatePath(PathRequest request){
        initializePathRequest(request, request.team, request.costId, request.unit.tileX(), request.unit.tileY(), request.destination % wwidth, request.destination / wwidth);
    }

    private boolean checkSolid(Unit unit, Tile tile, int dir){
        var p = Geometry.d8[Mathf.mod(dir, 8)];
        return !unit.canPass(tile.x + p.x, tile.y + p.y);
    }

    private boolean checkCorner(Unit unit, Tile tile, Tile next, int dir){
        Tile other = tile.nearby(Geometry.d8[Mathf.mod(dir, 8)]);
        if(other == null){
            return true;
        }

        if(!unit.canPass(other.x, other.y)){
            return Geometry.raycastRect(unit.x, unit.y, next.worldx(), next.worldy(), Tmp.r1.setCentered(other.worldx(), other.worldy(), tilesize).grow(Math.min(unit.hitSize * 0.66f, 7.6f))) != null;
        }

        return false;
    }

    private int getCost(FieldCache cache, FieldCache old, int x, int y){
        //fall back to the old flowfield when possible - it's best not to use partial results from the base cache
        if(old != null){
            return getCost(old, x, y, false);
        }
        return getCost(cache, x, y, true);
    }

    private int getCost(FieldCache cache, int x, int y, boolean requeue){
        int[] field = cache.fields.get(x / clusterSize + (y / clusterSize) * cwidth);
        if(field == null){
            if(!requeue) return 0;
            //request a new flow cluster if one wasn't found; this may be a spammed a bit, but the function will return early once it's created the first time
            queue.post(() -> addFlowCluster(cache, x / clusterSize, y / clusterSize, true));
            return 0;
        }
        return field[(x % clusterSize) + (y % clusterSize) * clusterSize];
    }

    private static boolean raycast(int team, PathCost type, int x1, int y1, int x2, int y2){
        int ww = wwidth, wh = wheight;
        int x = x1, dx = Math.abs(x2 - x), sx = x < x2 ? 1 : -1;
        int y = y1, dy = Math.abs(y2 - y), sy = y < y2 ? 1 : -1;
        int e2, err = dx - dy;

        while(x >= 0 && y >= 0 && x < ww && y < wh){
            if(avoid(team, type, x + y * wwidth)) return true;
            if(x == x2 && y == y2) return false;

            //TODO no diagonals???? is this a good idea?
            /*
            //no diagonal ver
            if(2 * err + dy > dx - 2 * err){
                err -= dy;
                x += sx;
            }else{
                err += dx;
                y += sy;
            }*/

            //diagonal ver
            e2 = 2 * err;
            if(e2 > -dy){
                err -= dy;
                x += sx;
            }

            if(e2 < dx){
                err += dx;
                y += sy;
            }

        }

        return true;
    }

    private static boolean avoid(int team, PathCost type, int tilePos){
        int cost = cost(team, type, tilePos);
        return cost == impassable || cost >= 2;
    }

    private static boolean passable(PathCost cost, int team, int pos){
        int amount = cost.getCost(team, pathfinder.tiles[pos]);
        //edge case: naval reports costs of 6000+ for non-liquids, even though they are not technically passable
        return amount != impassable && !(cost == costTypes.get(costNaval) && amount >= 6000);
    }

    private static boolean solid(int team, PathCost type, int x, int y){
        return x < 0 || y < 0 || x >= wwidth || y >= wheight || solid(team, type, x + y * wwidth, true);
    }

    private static boolean solid(int team, PathCost type, int tilePos, boolean checkWall){
        int cost = cost(team, type, tilePos);
        return cost == impassable || (checkWall && cost >= 6000);
    }

    private static int cost(int team, PathCost cost, int tilePos){
        if(state.rules.limitMapArea && !Team.get(team).isAI()){
            int x = tilePos % wwidth, y = tilePos / wwidth;
            if(x < state.rules.limitX || y < state.rules.limitY || x > state.rules.limitX + state.rules.limitWidth || y > state.rules.limitY + state.rules.limitHeight){
                return impassable;
            }
        }
        return cost.getCost(team, pathfinder.tiles[tilePos]);
    }

    private void clusterChanged(int team, int pathCost, int cx, int cy){
        //TODO very important: invalidate paths!
        //reset all flowfields that contain this cluster
        //remove all paths that contain this cluster
        //VERY important: don't replace all the data.

        int index = cx + cy * cwidth;

        //TODO go through each path request:
        // - if it contains this cluster in its field:
        //   - DONE mark for it to be recomputed next frame in a Set (so it doesn't happen twice!)
        //   - DONE recomputing should invalidate the flowfield
        //   - recomputing should save the old flowfield Somewhere
        //   - DONE invalidations should be batched every few seconds (let's say, 2)
        for(var req : threadPathRequests){
            var field = fields.get(req.destination);
            if(field != null && field.fields.containsKey(index)){
                invalidRequests.add(req);
            }
        }

    }

    private void updateClustersComplete(int clusterIndex){
        for(int team = 0; team < clusters.length; team++){
            var dim1 = clusters[team];
            if(dim1 != null){
                for(int pathCost = 0; pathCost < dim1.length; pathCost++){
                    var dim2 = dim1[pathCost];
                    if(dim2 != null){
                        var cluster = dim2[clusterIndex];
                        if(cluster != null){
                            updateCluster(team, pathCost, clusterIndex % cwidth, clusterIndex / cwidth);
                            clusterChanged(team, pathCost, clusterIndex % cwidth, clusterIndex / cwidth);
                        }
                    }
                }
            }
        }
    }

    private void updateClustersInner(int clusterIndex){
        for(int team = 0; team < clusters.length; team++){
            var dim1 = clusters[team];
            if(dim1 != null){
                for(int pathCost = 0; pathCost < dim1.length; pathCost++){
                    var dim2 = dim1[pathCost];
                    if(dim2 != null){
                        var cluster = dim2[clusterIndex];
                        if(cluster != null){
                            updateInnerEdges(team, pathCost, clusterIndex % cwidth, clusterIndex / cwidth, cluster);
                            clusterChanged(team, pathCost, clusterIndex % cwidth, clusterIndex / cwidth);
                        }
                    }
                }
            }
        }
    }

    @Override
    public void run(){
        long lastInvalidCheck = Time.millis() + invalidateCheckInterval;

        while(true){
            if(net.client()) return;
            try{


                if(state.isPlaying()){
                    queue.run();

                    clustersToUpdate.each(cluster -> {
                        updateClustersComplete(cluster);

                        //just in case: don't redundantly update inner clusters after you've recalculated it entirely
                        clustersToInnerUpdate.remove(cluster);
                    });

                    clustersToInnerUpdate.each(cluster -> {
                        //only recompute the inner links
                        updateClustersInner(cluster);
                    });

                    clustersToInnerUpdate.clear();
                    clustersToUpdate.clear();

                    //periodically check for invalidated paths
                    if(Time.timeSinceMillis(lastInvalidCheck) > invalidateCheckInterval){
                        lastInvalidCheck = Time.millis();

                        var it = invalidRequests.iterator();
                        while(it.hasNext()){
                            var request = it.next();

                            //invalid request, ignore it
                            if(request.invalidated){
                                it.remove();
                                continue;
                            }

                            var field = fields.get(request.destination);

                            if(field != null){
                                //it's only worth recalculating a path when the current frontier has finished; otherwise the unit will be following something incomplete.
                                if(field.frontier.isEmpty()){

                                    //remove the field, to be recalculated next update one recalculatePath is processed
                                    fields.remove(field.goalPos);
                                    Core.app.post(() -> fieldList.remove(field));

                                    //once the field is invalidated, make sure that all the requests that have it stored in their 'old' field, so units don't stutter during recalculations
                                    for(var otherRequest : threadPathRequests){
                                        if(otherRequest.destination == request.destination){
                                            otherRequest.oldCache = field;
                                        }
                                    }

                                    //the recalculation is done next update, so multiple path requests in the same batch don't end up removing and recalculating the field multiple times.
                                    queue.post(() -> recalculatePath(request));
                                    //it has been processed.
                                    it.remove();
                                }
                            }else{ //there's no field, presumably because a previous request already invalidated it.
                                queue.post(() -> recalculatePath(request));
                                it.remove();
                            }
                        }
                    }

                    //each update time (not total!) no longer than maxUpdate
                    for(FieldCache cache : fields.values()){
                        updateFields(cache, maxUpdate);
                    }
                }

                try{
                    Thread.sleep(updateInterval);
                }catch(InterruptedException e){
                    //stop looping when interrupted externally
                    return;
                }
            }catch(Throwable e){
                e.printStackTrace();
            }
        }
    }

    static class Cluster{
        IntSeq[] portals = new IntSeq[4];
        //maps rotation + index of portal to list of IntraEdge objects
        LongSeq[][] portalConnections = new LongSeq[4][];
    }

    @Struct
    static class IntraEdgeStruct{
        @StructField(8)
        int dir;
        @StructField(8)
        int portal;

        float cost;
    }

    @Struct
    static class NodeIndexStruct{
        @StructField(22)
        int cluster;
        @StructField(2)
        int dir;
        @StructField(8)
        int portal;
    }
}