feat(Gamepad class): implement stick() method

src/inputs/gamepad.spec.ts

@@ -120,7 +120,7 @@ describe('The `Gamepad` class', () => {
             pressed: false,
           },
         ],
-        axes: [],
+        axes: [0, 0, 0, 0],
         connected: true,
         timestamp: 0,
       }
@@ -163,6 +163,30 @@ describe('The `Gamepad` class', () => {
 
     })
 
+    describe('should have a `stick()` method that returns a component that', () => {
+
+      it('throws an error when initialized with an invalid stick', () => {
+        expect(() => gamepad.stick('lol')).to.throw(Error, 'Gamepad stick "lol" not found!')
+      })
+
+      it('returns a (0, 0) vector when initially queried', () => {
+        expect(gamepad.stick('left')).to.deep.equal(new Vector2())
+      })
+
+      it('returns the correct vector when queried after change', () => {
+        nav.gamepads[0].axes[0] = .56
+        nav.gamepads[0].axes[1] = .31
+        expect(gamepad.stick('left')).to.deep.equal(new Vector2(.56, .31))
+      })
+
+      it('also works with custom axis numbers', () => {
+        nav.gamepads[0].axes[2] = .42
+        nav.gamepads[0].axes[3] = .69
+        expect(gamepad.stick({ xAxis: 2, yAxis: 3 })).to.deep.equal(new Vector2(.42, .69))
+      })
+
+    })
+
   })
 
 })

src/inputs/gamepad.ts

@@ -2,6 +2,19 @@ import { IGamepad, INavigator, IWindow  } from '../apis'
 import { Control  } from '../core/control'
 import { store } from '../index'
 import { findButtonNumber, getButtonLabel } from '../maps/gamepad'
+import { Vector2 } from '../utils/math'
+
+export interface GamepadStick {
+
+  xAxis: number
+  yAxis: number
+
+}
+
+const gamepadSticks: { [id: string]: GamepadStick } = {
+  left: { xAxis: 0, yAxis: 1 },
+  right: { xAxis: 2, yAxis: 3 },
+}
 
 export class Gamepad {
 
@@ -71,4 +84,15 @@ export class Gamepad {
     }
   }
 
+  public stick(stick: string | GamepadStick): Vector2 {
+    if (typeof stick === 'string') {
+      if (stick in gamepadSticks) {
+        stick = gamepadSticks[stick]
+      } else {
+        throw new Error(`Gamepad stick "${stick}" not found!`)
+      }
+    }
+    return new Vector2(this.gamepad.axes[stick.xAxis], this.gamepad.axes[stick.yAxis])
+  }
+
 }