Create utility class to test the line of sight between Character and target point

api/src/main/java/com/bartlomiejpluta/base/lib/ai/FollowObjectAI.java

@@ -2,7 +2,7 @@ package com.bartlomiejpluta.base.lib.ai;
 
 import com.bartlomiejpluta.base.api.ai.AI;
 import com.bartlomiejpluta.base.api.ai.NPC;
-import com.bartlomiejpluta.base.api.location.Locationable;
+import com.bartlomiejpluta.base.api.entity.Entity;
 import com.bartlomiejpluta.base.api.map.layer.object.ObjectLayer;
 import com.bartlomiejpluta.base.api.move.MoveEvent;
 import com.bartlomiejpluta.base.util.path.MovementPath;
@@ -10,8 +10,10 @@ import com.bartlomiejpluta.base.util.path.PathExecutor;
 import com.bartlomiejpluta.base.util.pathfinder.PathFinder;
 import lombok.NonNull;
 import lombok.Setter;
+import lombok.extern.slf4j.Slf4j;
 
-public abstract class FollowObjectAI<N extends NPC, T extends Locationable> implements AI {
+@Slf4j
+public abstract class FollowObjectAI<N extends NPC, T extends Entity> implements AI {
 
    private final PathFinder finder;
    private final PathExecutor<N> executor;
@@ -22,55 +24,88 @@ public abstract class FollowObjectAI<N extends NPC, T extends Locationable> impl
 
    private MovementPath<N> path = null;
 
+   private boolean sees = false;
+
    protected FollowObjectAI(@NonNull PathFinder finder, @NonNull N npc, @NonNull T target) {
       this.finder = finder;
       this.npc = npc;
-      this.target = target;
       this.executor = new PathExecutor<>(npc);
+
+      setTarget(target);
+
+      npc.addEventListener(MoveEvent.TYPE, this::onMove);
    }
 
-   public void recomputePath() {
-      path = null;
-   }
+   private void onMove(MoveEvent event) {
+      if (npc.getStrategy() != this) {
+         return;
+      }
 
-   public void recomputePath(@NonNull MoveEvent event) {
       var movable = event.getMovable();
 
-      // Refresh only when target has been displaced
+      if (movable == npc) {
+         this.sees = sees(npc, target);
+         return;
+      }
+
+      // Recalculate path only when target has been displaced
       // or another object is blocking current path
-      if (movable == target || (path != null && path.contains(movable))) {
-         path = null;
+      if (movable == target) {
+         this.path = null;
+         this.sees = sees(npc, target);
+         return;
+      }
+
+      // Recalculate path when another object is blocking current path
+      if (path != null && path.contains(movable)) {
+         this.path = null;
       }
    }
 
    @Override
    public void nextActivity(ObjectLayer layer, float dt) {
-      if (!npc.isMoving()) {
-         var distance = npc.manhattanDistance(target);
-
-         if (distance == 1) {
-            npc.setFaceDirection(npc.getDirectionTowards(target));
-            interact(npc, target, layer, dt);
-         } else if (sees(npc, target, layer, distance)) {
-            follow(npc, target, layer, dt);
-
-            if (path == null || path.isEmpty()) {
-               path = finder.findPath(layer, npc, target.getCoordinates());
-               executor.setPath(path);
-            }
-
-            executor.execute(layer, dt);
-         } else {
-            idle(npc, target, layer, dt);
-         }
+      if (npc.isMoving()) {
+         return;
       }
+
+      var distance = npc.manhattanDistance(target);
+
+      if (distance == 1) {
+         npc.setFaceDirection(npc.getDirectionTowards(target));
+         interact(npc, target, layer, dt);
+         return;
+      }
+
+      if (sees) {
+         follow(npc, target, layer, dt);
+
+         // Calculate path
+         if (path == null || path.isEmpty()) {
+            path = finder.findPath(layer, npc, target.getCoordinates());
+            executor.setPath(path);
+         }
+
+         executor.execute(layer, dt);
+         return;
+      }
+
+
+      idle(npc, target, layer, dt);
    }
 
-   protected abstract boolean sees(N npc, T target, ObjectLayer layer, int distance);
 
-   protected abstract void interact(N npc, T target, ObjectLayer layer, float dt);
+   protected abstract boolean sees(N npc, T target);
 
-   protected abstract void follow(N npc, T target, ObjectLayer layer, float dt);
+   protected void interact(N npc, T target, ObjectLayer layer, float dt) {
 
-   protected abstract void idle(N npc, T target, ObjectLayer layer, float dt);
+   }
+
+   protected void follow(N npc, T target, ObjectLayer layer, float dt) {
+
+   }
+
+   protected void idle(N npc, T target, ObjectLayer layer, float dt) {
+
+   }
 }
+

api/src/main/java/com/bartlomiejpluta/base/util/math/BresenhamLine.java

@@ -0,0 +1,67 @@
+package com.bartlomiejpluta.base.util.math;
+
+import org.joml.Vector2i;
+import org.joml.Vector2ic;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.function.Function;
+
+public class BresenhamLine {
+   public static List<Vector2i> bresenhamLine(Vector2ic start, Vector2ic end) {
+      return bresenhamLine(start.x(), start.y(), end.x(), end.y());
+   }
+
+   public static List<Vector2i> bresenhamLine(int startX, int startY, int endX, int endY) {
+      var list = new LinkedList<Vector2i>();
+
+      bresenhamLine(startX, startY, endX, endY, v -> {
+         list.add(v);
+         return null;
+      });
+
+      return list;
+   }
+
+   public static <T> T bresenhamLine(Vector2ic start, Vector2ic end, Function<Vector2i, T> consumer) {
+      return bresenhamLine(start.x(), start.y(), end.x(), end.y(), consumer, null);
+   }
+
+   public static <T> T bresenhamLine(int startX, int startY, int endX, int endY, Function<Vector2i, T> consumer) {
+      return bresenhamLine(startX, startY, endX, endY, consumer, null);
+   }
+
+   public static <T> T bresenhamLine(Vector2ic start, Vector2ic end, Function<Vector2i, T> consumer, T defaultValue) {
+      return bresenhamLine(start.x(), start.y(), end.x(), end.y(), consumer, defaultValue);
+   }
+
+   public static <T> T bresenhamLine(int startX, int startY, int endX, int endY, Function<Vector2i, T> consumer, T defaultValue) {
+      int dx = Math.abs(endX - startX), dy = Math.abs(endY - startY);
+      int sx = startX < endX ? 1 : -1, sy = startY < endY ? 1 : -1;
+      int err = dx - dy;
+
+      while (true) {
+         var result = consumer.apply(new Vector2i(startX, startY));
+
+         if (result != null) {
+            return result;
+         }
+
+         if (startX == endX && startY == endY) break;
+
+         int e2 = err << 1;
+
+         if (e2 > -dy) {
+            err -= dy;
+            startX += sx;
+         }
+
+         if (e2 < dx) {
+            err += dx;
+            startY += sy;
+         }
+      }
+
+      return defaultValue;
+   }
+}

api/src/main/java/com/bartlomiejpluta/base/util/visibility/VisibilityChecker.java

@@ -0,0 +1,96 @@
+package com.bartlomiejpluta.base.util.visibility;
+
+
+import com.bartlomiejpluta.base.api.character.Character;
+import org.joml.Vector2ic;
+
+import static com.bartlomiejpluta.base.util.math.BresenhamLine.bresenhamLine;
+
+public class VisibilityChecker {
+   final int[][] DIRS = {{0, 1}, {-1, 0}, {0, -1}, {1, 0}}; // UP, LEFT, DOWN, RIGHT
+
+
+   public static boolean isInCone(Character observer, Vector2ic target, float angle, int maxDistance) {
+      var origin = observer.getCoordinates();
+      var direction = observer.getFaceDirection().vector;
+      return isInCone(origin.x(), origin.y(), direction.x(), direction.y(), target.x(), target.y(), angle, maxDistance);
+   }
+
+   /**
+    * Checks if a point (x, y) lies within a vision cone defined by an origin (x0, y0),
+    * a direction vector (dx, dy), a cone angle, and a maximum distance.
+    *
+    * @param x0          The x-coordinate of the origin point.
+    * @param y0          The y-coordinate of the origin point.
+    * @param dx          The x-component of the direction vector (should be normalized or non-zero).
+    * @param dy          The y-component of the direction vector (should be normalized or non-zero).
+    * @param x           The x-coordinate of the point to check.
+    * @param y           The y-coordinate of the point to check.
+    * @param angle       The full angle of the cone in radians.
+    * @param maxDistance The maximum distance from the origin to consider (points beyond are outside the cone).
+    * @return true if the point is within the cone and range, false otherwise.
+    */
+   public static boolean isInCone(int x0, int y0, int dx, int dy, int x, int y, float angle, int maxDistance) {
+      int vx = x - x0;
+      int vy = y - y0;
+      int lenSq = vx * vx + vy * vy;
+      if (lenSq == 0) return true; // point is exactly at origin
+      if (maxDistance > 0 && lenSq > maxDistance * maxDistance) return false; // outside max distance
+
+      // Compute dot product between direction and vector to point
+      int dot = dx * vx + dy * vy;
+
+      // Precompute cosine of half the cone angle
+      float halfAngle = angle * 0.5f;
+      float cosHalfAngle = (float) Math.cos(halfAngle);
+
+      // Normalize dot by length of vector to point (len)
+      float len = (float) Math.sqrt(lenSq);
+      float cosTheta = dot / len;
+
+      // Check if the point is within the cone
+      return cosTheta >= cosHalfAngle;
+   }
+
+   public static boolean canSee(Character observer, Character target, float angle, int range, boolean direction) {
+      var layer = observer.getLayer();
+
+      // Observer and target are on different layers
+      if (layer != target.getLayer()) {
+         return false;
+      }
+
+      // Target is out of observer's visibility area
+      if (observer.chebyshevDistance(target) > range) {
+         return false;
+      }
+
+      // Observer does not look at the target's direction
+      var targetCoords = target.getCoordinates();
+      if (direction && !isInCone(observer, targetCoords, angle, range)) {
+         return false;
+      }
+
+      var observerCoords = observer.getCoordinates();
+
+      // Checking line of sight
+      return bresenhamLine(observer.getCoordinates(), target.getCoordinates(), v -> {
+         // Don't check observer coords
+         if (observerCoords.equals(v)) {
+            return null;
+         }
+
+         // Target is visible
+         if (targetCoords.equals(v)) {
+            return true;
+         }
+
+         // Obstacle on the sight line
+         if (!layer.isTileReachable(v)) {
+            return false;
+         }
+
+         return null;
+      }, false);
+   }
+}