added missing files

src/internal/constants.ts

@@ -0,0 +1,8 @@
+export const pi = Math.PI;
+export const tau = 2 * pi;
+export const epsilon = 0.0001;
+export const c1 = 1.70158;
+export const c2 = c1 * 1.525;
+export const c3 = c1 + 1;
+export const c4 = tau / 3;
+export const c5 = tau / 4.5;

src/internal/cssEasings.ts

@@ -0,0 +1,35 @@
+const c = `cubic-bezier`;
+const s = `step`;
+
+export const ease = c + `(.25,.1,.25,1)`;
+export const easeIn = c + `(.42,0,1,1)`;
+export const easeInBack = c + `(.6,-.28,.735,.045)`;
+export const easeInCirc = c + `(.6,.04,.98,.335)`;
+export const easeInCubic = c + `(.55,.055,.675,.19)`;
+export const easeInExpo = c + `(.95,.05,.795,.035)`;
+export const easeInOut = c + `(.42,0,.58,1)`;
+export const easeInOutBack = c + `(.68,-.55,.265,1.55)`;
+export const easeInOutCirc = c + `(.785,.135,.15,.86)`;
+export const easeInOutCubic = c + `(.645,.045,.355,1)`;
+export const easeInOutExpo = c + `(1,0,0,1)`;
+export const easeInOutQuad = c + `(.455,.03,.515,.955)`;
+export const easeInOutQuart = c + `(.77,0,.175,1)`;
+export const easeInOutQuint = c + `(.86,0,.07,1)`;
+export const easeInOutSine = c + `(.445,.05,.55,.95)`;
+export const easeInQuad = c + `(.55,.085,.68,.53)`;
+export const easeInQuart = c + `(.895,.03,.685,.22)`;
+export const easeInQuint = c + `(.755,.05,.855,.06)`;
+export const easeInSine = c + `(.47,0,.745,.715)`;
+export const easeOut = c + `(0,0,.58,1)`;
+export const easeOutBack = c + `(.175,.885,.32,1.275)`;
+export const easeOutCirc = c + `(.075,.82,.165,1)`;
+export const easeOutCubic = c + `(.215,.61,.355,1)`;
+export const easeOutExpo = c + `(.19,1,.22,1)`;
+export const easeOutQuad = c + `(.25,.46,.45,.94)`;
+export const easeOutQuart = c + `(.165,.84,.44,1)`;
+export const easeOutQuint = c + `(.23,1,.32,1)`;
+export const easeOutSine = c + `(.39,.575,.565,1)`;
+export const elegantSlowStartEnd = c + `(.175,.885,.32,1.275)`;
+export const linear = c + `(0,0,1,1)`;
+export const stepEnd = s + `(1,0)`;
+export const stepStart = s + `(1,1)`;

src/internal/cssFunction.ts

@@ -0,0 +1,34 @@
+import { EasingFunction } from '../types';
+import { cubicBezier, ease, easeIn, easeOut, easeInOut, stepStart, stepEnd, linear, step } from './index';
+
+const camelCaseRegex = /([a-z])[- ]([a-z])/ig;
+const cssFunctionRegex = /([a-z-]+)\(([^\)]+)\)/ig;
+const cssEasings = { ease, easeIn, easeOut, easeInOut, stepStart, stepEnd, linear };
+
+const camelCaseMatcher = (match: string, p1: string, p2: string) => p1 + p2.toUpperCase();
+
+const toCamelCase = (value: string | undefined): string => typeof value === 'string'
+  ? (value as string).replace(camelCaseRegex, camelCaseMatcher) : '';
+
+const find = (nameOrCssFunction: string) => {
+  // search for a compatible known easing
+  const easingName = toCamelCase(nameOrCssFunction);
+  const easing = cssEasings[easingName] || nameOrCssFunction;
+  const matches = cssFunctionRegex.exec(easing);
+  if (!matches || !matches.length) {
+    throw new Error('could not parse css function');
+  }
+  return [matches[1]].concat(matches[2].split(','));
+};
+
+export const cssFunction = (easingString: string): EasingFunction => {
+  const p = find(easingString);
+  const fnName = p[0];
+  if (fnName === 'step') {
+    return step(+p[1], p[2] as number | 'start' | 'end');
+  }
+  if (fnName === 'cubic-bezier') {
+    return cubicBezier(+p[1], +p[2], +p[3], +p[4]);
+  }
+  throw new Error('could not parse css function');
+};

src/internal/cubicBezier.ts

@@ -0,0 +1,38 @@
+import { abs, epsilon } from './index';
+import { EasingFunction } from '../types';
+
+const bezier = (n1: number, n2: number, t: number) =>
+  3 * n1 * (1 - t) * (1 - t) * t + 3 * n2 * (1 - t) * t * t + t * t * t;
+
+export const cubicBezier = (p0: number, p1: number, p2: number, p3: number): EasingFunction => {
+  if (p0 < 0 || p0 > 1 || p2 < 0 || p2 > 1) {
+    return (x: number) => x;
+  }
+
+  return (x: number): number => {
+    if (x === 0 || x === 1) {
+      return x;
+    }
+
+    let start = 0;
+    let end = 1;
+    let limit = 19;
+
+    do {
+      const mid = (start + end) * .5;
+      const xEst = bezier(p0, p2, mid);
+
+      if (abs(x - xEst) < epsilon) {
+        return bezier(p1, p3, mid);
+      }
+      if (xEst < x) {
+        start = mid;
+      } else {
+        end = mid;
+      }
+    } while (--limit);
+
+    // limit is reached
+    return x;
+  };
+};

src/internal/index.ts

@@ -0,0 +1,6 @@
+export * from './constants';
+export * from './cssEasings';
+export * from './cssFunction';
+export * from './cubicBezier';
+export * from './math';
+export * from './step';

src/internal/math.ts

@@ -0,0 +1,5 @@
+export const abs = Math.abs;
+export const cos = Math.cos;
+export const pow = Math.pow;
+export const sin = Math.sin;
+export const sqrt = Math.sqrt;

src/internal/step.ts

@@ -0,0 +1,9 @@
+import { EasingFunction } from '../types';
+
+export const step = (count: number, pos?: number | 'end' | 'start'): EasingFunction => {
+  const q = count / 1;
+  const p: number = pos === 'end'
+    ? 0 : pos === 'start'
+      ? 1 : pos || 0;
+  return (x: number): number => x >= 1 ? 1 : (p * q + x) - (p * q + x) % q;
+};