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

5 files changed, 342 insertions, 10 deletions

diff --git a/lib/systems/attributes_to_renderable.js b/lib/systems/attributes_to_renderable.js
new file mode 100644
index 0000000..e5c66a0
--- /dev/null
+++ b/lib/systems/attributes_to_renderable.js
@@ -0,0 +1,73 @@
+import { System } from '@serpentity/serpentity';
+
+import RenderableWithAttributesNode from '../nodes/renderable_with_attributes';
+
+/**
+ * Updates the renderables based on their attribuets
+ *
+ * @extends {external:Serpentity.System}
+ * @class AttributesToRenderableSystem
+ * @param {object} config a configuration object to extend.
+ */
+export default class AttributesToRenderableSystem extends System {
+
+  constructor(config = {}) {
+
+    super();
+
+    /**
+     * The node collection of renderable entities
+     *
+     * @property {external:Serpentity.NodeCollection} renderables
+     * @instance
+     * @memberof AttributesToRenderableSystem
+     */
+    this.renderables = null;
+  }
+
+  /**
+   * Initializes system when added. Requests renderable nodes and
+   * attaches to event listeners to add / remove them to pixi stage
+   *
+   * @function added
+   * @memberof AttributesToRenderableSystem
+   * @instance
+   * @param {external:Serpentity.Engine} engine the serpentity engine to
+   * which we are getting added
+   */
+  added(engine) {
+
+    this.renderables = engine.getNodes(RenderableWithAttributesNode);
+  }
+
+  /**
+   * Clears system resources when removed.
+   *
+   * @function removed
+   * @instance
+   * @memberof AttributesToRenderableSystem
+   */
+  removed() {
+
+    this.renderables = null;
+  }
+
+  /**
+   * Runs on every update of the loop. Updates the graphics so they're
+   * rendered correctly
+   *
+   * @function update
+   * @instance
+   * @param {Number} currentFrameDuration the duration of the current
+   * frame
+   * @memberof AttributesToRenderableSystem
+   */
+  update(currentFrameDuration) {
+
+    for (const renderable of this.renderables) {
+      renderable.container.container.position.x = renderable.position.x;
+      renderable.container.container.position.y = renderable.position.y;
+      renderable.container.container.rotation = renderable.angle.angle;
+    }
+  }
+};
diff --git a/lib/systems/create_coupling_line.js b/lib/systems/create_coupling_line.js
new file mode 100644
index 0000000..8e5e9d7
--- /dev/null
+++ b/lib/systems/create_coupling_line.js
@@ -0,0 +1,96 @@
+import { System } from '@serpentity/serpentity';
+import { Graphics } from 'pixi.js';
+
+import PositionComponent from '@serpentity/components.position';
+
+import RenderableCoupleNode from '../nodes/renderable_couple';
+
+/**
+ * Renders renderable objects using pixi
+ *
+ * @extends {external:Serpentity.System}
+ * @class CreateCouplingLineSystem
+ * @param {object} config a configuration object to extend.
+ */
+export default class CreateCouplingLineSystem extends System {
+
+  constructor(config = {}) {
+
+    super();
+
+    /**
+     * The node collection of coupled entities entities
+     *
+     * @property {external:Serpentity.NodeCollection} coupledEntities
+     * @instance
+     * @memberof CreateCouplingLineSystem
+     */
+    this.coupledEntities = null;
+  }
+
+  /**
+   * Initializes system when added. Requests renderable nodes and
+   *
+   * @function added
+   * @memberof CreateCouplingLineSystem
+   * @instance
+   * @param {external:Serpentity.Engine} engine the serpentity engine to
+   * which we are getting added
+   */
+  added(engine) {
+
+    this.coupledEntities = engine.getNodes(RenderableCoupleNode);
+  }
+
+  /**
+   * Clears system resources when removed.
+   *
+   * @function removed
+   * @instance
+   * @memberof CreateCouplingLineSystem
+   */
+  removed() {
+
+    this.coupledEntities = null;
+  }
+
+  /**
+   * Runs on every update of the loop. Does nothing.
+   *
+   * @function update
+   * @instance
+   * @param {Number} currentFrameDuration the duration of the current
+   * frame
+   * @memberof CreateCouplingLineSystem
+   */
+  update(currentFrameDuration) {
+
+    for (const rootEntity of this.coupledEntities) {
+
+      const rootGraphic = rootEntity.container.container;
+      rootGraphic.removeChildren();
+
+      let lineGraphic = new Graphics();
+      lineGraphic = lineGraphic.lineStyle(5, 0xffffff, 0.9);
+
+      let initialPosition = false;
+
+      for (const coupledEntity of rootEntity.coupledEntities.coupledEntities) {
+        if (coupledEntity.hasComponent(PositionComponent)) {
+
+          const position = coupledEntity.getComponent(PositionComponent);
+
+          if (!initialPosition) {
+            lineGraphic = lineGraphic.moveTo(position.x, position.y);
+            initialPosition = true;
+            continue;
+          }
+          lineGraphic = lineGraphic.lineTo(position.x, position.y);
+        }
+      }
+
+      rootGraphic.addChild(lineGraphic);
+    }
+  }
+};
+
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;
+    }
+  }
+};
diff --git a/lib/systems/physics_world_control.js b/lib/systems/physics_world_control.js
new file mode 100644
index 0000000..daa39c1
--- /dev/null
+++ b/lib/systems/physics_world_control.js
@@ -0,0 +1,98 @@
+import { System } from '@serpentity/serpentity';
+import { Engine, World } from 'matter-js';
+
+import PhysicalNode from '../nodes/physical';
+
+const internals = {
+  kNoEngine: 'No matter js physics engine found. Make sure you set the `engine` key in the config object when initializing.'
+};
+
+/**
+ * Adds and removes objects to the physics world and calls update
+ *
+ * @extends {external:Serpentity.System}
+ * @class PhysicsWorldControlSystem
+ * @param {object} config a configuration object to extend.
+ */
+export default class PhysicsWorldControlSystem extends System {
+
+  constructor(config = {}) {
+
+    super();
+
+    /**
+     * The node collection of physics entities
+     *
+     * @property {external:Serpentity.NodeCollection} physicalEntities
+     * @instance
+     * @memberof PhysicsWorldControlSystem
+     */
+    this.physicalEntities = null;
+
+    /**
+     * The matter-js engine we will use to process physics
+     *
+     * @property {external:MatterJs.Engine} engine
+     * @instance
+     * @memberof PhysicsWorldControlSystem
+     */
+    this.engine = config.engine;
+
+    if (!this.engine) {
+      throw new Error(internals.kNoEngine);
+    }
+  }
+
+  /**
+   * Initializes system when added. Requests physics nodes and
+   * attaches to event listeners to add / remove them to pixi stage
+   *
+   * @function added
+   * @memberof PhysicsWorldControlSystem
+   * @instance
+   * @param {external:Serpentity.Engine} engine the serpentity engine to
+   * which we are getting added
+   */
+  added(engine) {
+
+    this.physicalEntities = engine.getNodes(PhysicalNode);
+    this.physicalEntities.on('nodeAdded', (event) => {
+
+      World.add(this.engine.world, [event.node.body.body]);
+    });
+    this.physicalEntities.on('nodeRemoved', (event) => {
+
+      World.remove(this.engine.world, [event.node.body.body]);
+    });
+  }
+
+  /**
+   * Clears system resources when removed.
+   *
+   * @function removed
+   * @instance
+   * @memberof PhysicsWorldControlSystem
+   */
+  removed() {
+
+    this.physicalEntities.removeAllListeners('nodeAdded');
+    this.physicalEntities.removeAllListeners('nodeRemoved');
+    this.physicalEntities = null;
+  }
+
+  /**
+   * Runs on every update of the loop. Updates the physics
+   *
+   * @function update
+   * @instance
+   * @param {Number} currentFrameDuration the duration of the current
+   * frame
+   * @memberof PhysicsWorldControlSystem
+   */
+  update(currentFrameDuration) {
+
+    Engine.run(this.engine);
+  }
+};
+
+
diff --git a/lib/systems/render.js b/lib/systems/render.js
index 8d3d446..a2e3020 100644
--- a/lib/systems/render.js
+++ b/lib/systems/render.js
@@ -7,7 +7,7 @@ const internals = {
 };
 
 /**
- * Renders renderable objects to console
+ * Renders renderable objects using pixi
  *
  * @extends {external:Serpentity.System}
  * @class RenderSystem
@@ -80,8 +80,7 @@ export default class RenderSystem extends System {
   }
 
   /**
-   * Runs on every update of the loop. Prints the location of every
-   * renderable
+   * Runs on every update of the loop. Does nothing.
    *
    * @function update
    * @instance
@@ -89,11 +88,5 @@ export default class RenderSystem extends System {
    * frame
    * @memberof RenderSystem
    */
-  update(currentFrameDuration) {
-
-    for (const renderable of this.renderables) {
-      renderable.container.container.position.x = renderable.position.x;
-      renderable.container.container.position.y = renderable.position.y;
-    }
-  }
+  update(currentFrameDuration) {}
 };