add a piston

1 files changed, 48 insertions, 0 deletions

diff --git a/src/engine/entities/Piston.ts b/src/engine/entities/Piston.ts
new file mode 100644
index 0000000..18b761b
--- /dev/null
+++ b/src/engine/entities/Piston.ts
@@ -0,0 +1,48 @@
+import { Entity, EntityNames } from ".";
+import { Colliding, ComponentNames, FacingDirection, Grid, RadialObserve } from "../components";
+import { Game } from "../Game";
+import { Coord2D, Direction } from "../interfaces";
+
+export class Piston extends Entity {
+  constructor(gridPosition: Coord2D, direction: Direction) {
+    super(EntityNames.Piston);
+
+    const radius = 1 + .001;
+    this.addComponent(new RadialObserve(this.onObservation.bind(this), radius));
+
+    this.addComponent(new FacingDirection(direction));
+
+    this.addComponent(new Grid(gridPosition));
+
+    this.addComponent(new Colliding());
+  }
+
+  private onObservation(_game: Game, entity: Entity) {
+    const facingDirection = this.getComponent<FacingDirection>(ComponentNames.FacingDirection);
+
+    const myPosition = this.getComponent<Grid>(ComponentNames.Grid).gridPosition;
+    const observingGrid = entity.getComponent<Grid>(ComponentNames.Grid);
+    const observingPosition = observingGrid.gridPosition;
+
+    const [dx, dy] = [myPosition.x - observingPosition.x, myPosition.y - observingPosition.y].map(x => Math.round(x));
+    const v: Record<typeof dx, Record<typeof dy, Direction>> = {
+      [-1]: {
+	[dy]: Direction.RIGHT,
+      },
+      [1]: {
+	[dy]: Direction.LEFT,
+      },
+      [0]: {
+	[-1]: Direction.UP,
+	[1]: Direction.DOWN,
+      }
+    };
+
+    if (facingDirection.currentDirection !== v[dx][dy]) {
+      return;
+    }
+
+    observingGrid.movingDirection = facingDirection.currentDirection;
+    entity.addComponent(observingGrid);
+  }
+}