From 13c0a66af0f2feff12257303579a7fb42b1a1d5b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Przemys=C5=82aw=20Pluta?=
 <noreply.git@mx.bartlomiejpluta.com>
Date: Sat, 3 Apr 2021 17:55:54 +0200
Subject: [PATCH] Create CameraController interface and following camera
 implementation

---
 .../base/lib/camera/CameraController.java     |  5 ++
 .../lib/camera/FollowingCameraController.java | 50 +++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 api/src/main/java/com/bartlomiejpluta/base/lib/camera/CameraController.java
 create mode 100644 api/src/main/java/com/bartlomiejpluta/base/lib/camera/FollowingCameraController.java

diff --git a/api/src/main/java/com/bartlomiejpluta/base/lib/camera/CameraController.java b/api/src/main/java/com/bartlomiejpluta/base/lib/camera/CameraController.java
new file mode 100644
index 00000000..0d5b1402
--- /dev/null
+++ b/api/src/main/java/com/bartlomiejpluta/base/lib/camera/CameraController.java
@@ -0,0 +1,5 @@
+package com.bartlomiejpluta.base.lib.camera;
+
+public interface CameraController {
+   void update();
+}
diff --git a/api/src/main/java/com/bartlomiejpluta/base/lib/camera/FollowingCameraController.java b/api/src/main/java/com/bartlomiejpluta/base/lib/camera/FollowingCameraController.java
new file mode 100644
index 00000000..bde6682f
--- /dev/null
+++ b/api/src/main/java/com/bartlomiejpluta/base/lib/camera/FollowingCameraController.java
@@ -0,0 +1,50 @@
+package com.bartlomiejpluta.base.lib.camera;
+
+import com.bartlomiejpluta.base.api.camera.Camera;
+import com.bartlomiejpluta.base.api.map.model.GameMap;
+import com.bartlomiejpluta.base.api.screen.Screen;
+import lombok.NonNull;
+import org.joml.Vector2fc;
+
+public class FollowingCameraController implements CameraController {
+   private final Vector2fc screenSize;
+   private final Vector2fc mapSize;
+   private final Camera camera;
+
+   private Vector2fc target;
+
+   private FollowingCameraController(@NonNull Screen screen, @NonNull Camera camera, @NonNull GameMap map) {
+      this.screenSize = screen.getSize();
+      this.camera = camera;
+      this.mapSize = map.getSize();
+   }
+
+   public FollowingCameraController follow(@NonNull Vector2fc target) {
+      this.target = target;
+      return this;
+   }
+
+   public FollowingCameraController stop() {
+      this.target = null;
+      return this;
+   }
+
+   @Override
+   public void update() {
+      if (target != null) {
+         final var bottomRightConstraintX = mapSize.x() - screenSize.x() / camera.getScaleX();
+         final var bottomRightConstraintY = mapSize.y() - screenSize.y() / camera.getScaleY();
+         final var newCameraPosX = target.x() - screenSize.x() / (2f * camera.getScaleX());
+         final var newCameraPosY = target.y() - screenSize.y() / (2f * camera.getScaleY());
+
+         camera.setPosition(
+               (newCameraPosX < bottomRightConstraintX) ? (newCameraPosX > 0 ? newCameraPosX : 0) : bottomRightConstraintX,
+               (newCameraPosY < bottomRightConstraintY) ? (newCameraPosY > 0 ? newCameraPosY : 0) : bottomRightConstraintY
+         );
+      }
+   }
+
+   public static FollowingCameraController on(Screen screen, Camera camera, GameMap map) {
+      return new FollowingCameraController(screen, camera, map);
+   }
+}