From 970988a5eb10b836db591ac8dc6d437fd569b684 Mon Sep 17 00:00:00 2001
From: Joshua Goins <josh@redstrate.com>
Date: Sat, 30 Apr 2022 19:52:28 -0400
Subject: [PATCH] Add A* pathing algorithm

I adapted the A* I had already implemented in a Realm of Chaos, now
adapted in Java and is used to calculate the player's path to their new
location.
---
 core/src/com/redstrate/watersymbol/AStar.java | 110 ++++++++++++++++++
 .../watersymbol/screens/GameScreen.java       |  20 ++++
 2 files changed, 130 insertions(+)
 create mode 100644 core/src/com/redstrate/watersymbol/AStar.java

diff --git a/core/src/com/redstrate/watersymbol/AStar.java b/core/src/com/redstrate/watersymbol/AStar.java
new file mode 100644
index 0000000..2204b1f
--- /dev/null
+++ b/core/src/com/redstrate/watersymbol/AStar.java
@@ -0,0 +1,110 @@
+package com.redstrate.watersymbol;
+
+import com.badlogic.gdx.math.Vector2;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/*
+This is a direct port of the A* pathing implementation in Realm of Chaos.
+ */
+public class AStar {
+    static class Node {
+        Vector2 position;
+        int g = 0;
+        int h = 0;
+        int f = 0;
+
+        Node parent;
+    }
+
+    private static final int maxOpenNodes = 200;
+
+    public static ArrayList<Vector2> path(Vector2 start, Vector2 end) {
+        Node startNode = new Node();
+        startNode.position = start;
+
+        Node endNode = new Node();
+        endNode.position = end;
+
+        ArrayList<Node> openList = new ArrayList<>();
+        openList.add(startNode);
+
+        ArrayList<Node> closedList = new ArrayList<>();
+        while(!openList.isEmpty() && openList.size() < maxOpenNodes) {
+            Node currentNode = openList.get(0);
+            int currentIndex = 0;
+            for(int i = 0; i < openList.size(); i++) {
+                if(openList.get(i).f < currentNode.f) {
+                    currentNode = openList.get(i);
+                    currentIndex = i;
+                }
+            }
+
+            openList.remove(currentIndex);
+            closedList.add(currentNode);
+
+            // check if we found the goal
+            if(currentNode.position.epsilonEquals(endNode.position)) {
+                ArrayList<Vector2> path = new ArrayList<>();
+                Node current = currentNode;
+                while(current != null) {
+                    path.add(current.position);
+                    current = current.parent;
+                }
+
+                System.out.println(path.toString());
+
+                return path;
+            }
+
+            ArrayList<Node> children = new ArrayList<>();
+
+            ArrayList<Vector2> adjacentPositions = new ArrayList<>();
+            adjacentPositions.add(new Vector2(0, -1));
+            adjacentPositions.add(new Vector2(0, 1));
+            adjacentPositions.add(new Vector2(-1, 0));
+            adjacentPositions.add(new Vector2(1, 0));
+            adjacentPositions.add(new Vector2(-1, -1));
+            adjacentPositions.add(new Vector2(-1, 1));
+            adjacentPositions.add(new Vector2(1, -1));
+            adjacentPositions.add(new Vector2(1, 1));
+            for (Vector2 position : adjacentPositions) {
+                Node newNode = new Node();
+                newNode.position = new Vector2(currentNode.position.x + position.x, currentNode.position.y + position.y);
+                newNode.parent = currentNode;
+
+                children.add(newNode);
+            }
+
+            for(Node child : children) {
+                boolean shouldContinue = false;
+                for(Node closedChild : closedList) {
+                    if(child.position.epsilonEquals(closedChild.position)) {
+                        shouldContinue = true;
+                    }
+                }
+
+                if(shouldContinue)
+                    continue;
+
+                child.g = currentNode.g + 1;
+                child.h = (int) (Math.pow(child.position.x - endNode.position.x, 2) + Math.pow(child.position.y - endNode.position.y, 2));
+                child.f = child.g + child.h;
+
+                for(Node openNode : openList) {
+                    if(child.position.epsilonEquals(openNode.position) && child.g > openNode.g) {
+                        shouldContinue = true;
+                    }
+                }
+
+                if(shouldContinue)
+                    continue;
+
+                openList.add(child);
+            }
+        }
+
+        return null;
+    }
+}
diff --git a/core/src/com/redstrate/watersymbol/screens/GameScreen.java b/core/src/com/redstrate/watersymbol/screens/GameScreen.java
index 2675b6a..9bee976 100644
--- a/core/src/com/redstrate/watersymbol/screens/GameScreen.java
+++ b/core/src/com/redstrate/watersymbol/screens/GameScreen.java
@@ -12,9 +12,12 @@ import com.badlogic.gdx.maps.tiled.renderers.OrthogonalTiledMapRenderer;
 import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.math.Vector3;
 import com.badlogic.gdx.utils.ScreenUtils;
+import com.redstrate.watersymbol.AStar;
 import com.redstrate.watersymbol.Player;
 import com.redstrate.watersymbol.WaterSymbol;
 
+import java.util.ArrayList;
+
 public class GameScreen implements Screen {
     private final WaterSymbol game;
     private boolean hasStartedMoving = false;
@@ -64,6 +67,23 @@ public class GameScreen implements Screen {
         // player is trying to move
         if(Gdx.input.isButtonPressed(0)) {
             hasStartedMoving = true;
+
+            Vector3 mousePos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);
+
+            camera.unproject(mousePos);
+
+            double newX = Math.floor(mousePos.x);
+            double newY = Math.floor(mousePos.y);
+
+            int newFixedX = (int) (newX / 32.0);
+            int newFixedY = (int) (newY / 32.0);
+
+            ArrayList<Vector2> path = AStar.path(new Vector2(player.positionX, player.positionY), new Vector2((float)newFixedX, (float)newFixedY));
+            if(path != null) {
+                for (Vector2 position : path) {
+                    game.batch.draw(playerTexture, position.x * 32, position.y * 32);
+                }
+            }
         } else if(hasStartedMoving) {
             Vector3 mousePos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);