Physics Engine (#4)

* Add matter-js as a dependency

* Add body component

* Fix renderable node doc

* Add the physics node type

* Correct typo in physics enabled node types

* Update docs on render system

* Add physics system

* Update changelog

* Add physics engine to main app

* Tweak the gravity of the world

* Add body to sumo factory

* Add angle component

* Add angle to entity

* Add angle to the nodes

* Pass angle between systems

* Set default angle to 0

* Split systems and nodes

* Fix indentaion in physics world control

* Add third sumo entity

* Adjust values for constriants and physics

* Correct docs in new nodes

* Update built-in docs

1 files changed, 72 insertions, 0 deletions

diff --git a/lib/systems/physics_to_attributes.js b/lib/systems/physics_to_attributes.js
new file mode 100644
index 0000000..a49a16b
--- /dev/null
+++ b/lib/systems/physics_to_attributes.js
@@ -0,0 +1,72 @@
+import { System } from '@serpentity/serpentity';
+
+import PhysicalWithAttributesNode from '../nodes/physical_with_attributes';
+
+/**
+ * Distribuets physics data to the related components
+ *
+ * @extends {external:Serpentity.System}
+ * @class PhysicsToAttributesSystem
+ * @param {object} config a configuration object to extend.
+ */
+export default class PhysicsToAttributesSystem extends System {
+
+  constructor(config = {}) {
+
+    super();
+
+    /**
+     * The node collection of physics entities
+     *
+     * @property {external:Serpentity.NodeCollection} physicalEntities
+     * @instance
+     * @memberof PhysicsToAttributesSystem
+     */
+    this.physicalEntities = null;
+  }
+
+  /**
+   * Initializes system when added. Requests physics nodes
+   *
+   * @function added
+   * @memberof PhysicsToAttributesSystem
+   * @instance
+   * @param {external:Serpentity.Engine} engine the serpentity engine to
+   * which we are getting added
+   */
+  added(engine) {
+
+    this.physicalEntities = engine.getNodes(PhysicalWithAttributesNode);
+  }
+
+  /**
+   * Clears system resources when removed.
+   *
+   * @function removed
+   * @instance
+   * @memberof PhysicsToAttributesSystem
+   */
+  removed() {
+
+    this.physicalEntities = null;
+  }
+
+  /**
+   * Runs on every update of the loop. Updates the other components
+   * based on physics
+   *
+   * @function update
+   * @instance
+   * @param {Number} currentFrameDuration the duration of the current
+   * frame
+   * @memberof PhysicsToAttributesSystem
+   */
+  update(currentFrameDuration) {
+
+    for (const physicalEntity of this.physicalEntities) {
+      physicalEntity.position.x = physicalEntity.body.body.position.x;
+      physicalEntity.position.y = physicalEntity.body.body.position.y;
+      physicalEntity.angle.angle = physicalEntity.body.body.angle;
+    }
+  }
+};