feat: add <Tween> component

src/Tween/easing.ts

@@ -0,0 +1,59 @@
+export type TEasing = (time: number) => number;
+
+export interface IEasingMap {
+  linear: TEasing;
+  inQuad: TEasing;
+  outQuad: TEasing;
+  inOutQuad: TEasing;
+  inCubic: TEasing;
+  outCubic: TEasing;
+  inOutCubic: TEasing;
+  inQuart: TEasing;
+  outQuart: TEasing;
+  inOutQuart: TEasing;
+  inQuint: TEasing;
+  outQuint: TEasing;
+  inOutQuint: TEasing;
+}
+
+// From: https://gist.github.com/gre/1650294
+export const easing: IEasingMap = {
+  // no easing, no acceleration
+  linear: (t) => t,
+
+  // accelerating from zero velocity
+  inQuad: (t) => t*t,
+
+  // decelerating to zero velocity
+  outQuad: (t) => t*(2-t),
+
+  // acceleration until halfway, then deceleration
+  inOutQuad: (t) => t<.5 ? 2*t*t : -1+(4-2*t)*t,
+
+  // accelerating from zero velocity
+  inCubic: (t) => t*t*t,
+
+  // decelerating to zero velocity
+  outCubic: (t) => (--t)*t*t+1,
+
+  // acceleration until halfway, then deceleration
+  inOutCubic: (t) => t<.5 ? 4*t*t*t : (t-1)*(2*t-2)*(2*t-2)+1,
+
+  // accelerating from zero velocity
+  inQuart: (t) => t*t*t*t,
+
+  // decelerating to zero velocity
+  outQuart: (t) => 1-(--t)*t*t*t,
+
+  // acceleration until halfway, then deceleration
+  inOutQuart: (t) => t<.5 ? 8*t*t*t*t : 1-8*(--t)*t*t*t,
+
+  // accelerating from zero velocity
+  inQuint: (t) => t*t*t*t*t,
+
+  // decelerating to zero velocity
+  outQuint: (t) => 1+(--t)*t*t*t*t,
+
+  // acceleration until halfway, then deceleration
+  inOutQuint: (t) => t<.5 ? 16*t*t*t*t*t : 1+16*(--t)*t*t*t*t
+};

src/Tween/index.ts

@@ -0,0 +1,45 @@
+import {render, createEnhancer} from 'react-universal-interface';
+import {Render, IRenderProps} from '../Render';
+import {h} from '../util';
+import {easing, TEasing, IEasingMap} from './easing';
+
+export interface ITweenProps extends IRenderProps {
+  easing: (keyof IEasingMap) | [number, number, number, number] | ((time: number) => number);
+  Render: React.SFC<IRenderProps> | React.ComponentClass<IRenderProps>;
+}
+
+export const Tween: React.SFC<ITweenProps> = (props) => {
+  let {easing: fn} = props;
+
+  switch (typeof props.easing) {
+    case 'string':
+      fn = easing[fn as string];
+      break;
+    case 'object':
+      // TODO: Implement cubic-bezier
+  }
+
+  if (process.env.NODE_ENV !== 'production') {
+    if (typeof fn !== 'function') {
+      console.error(
+        '<Tween> expected "easing" property to be a valid easing function or a 4-tuple array or numbers ' +
+        'specifying a Cubic Bezier curve, or a string specifying one of the built-int easing functions: ' +
+        '"' + Object.keys(easing).join('", "') + '".'
+      );
+      console.trace();
+
+      return null;
+    }
+  }
+
+  return h(props.Render, props,
+    ({value}) => render(props, {value: (fn as TEasing)(value)})
+  );
+};
+
+Tween.defaultProps = {
+  easing: 'linear',
+  Render
+};
+
+export const withTween = createEnhancer(Tween, 'tween');