export type Easing = (t: number) => number;

export const EasingFunctions: { [name: string]: Easing } = {
  linear: (t) => t,
  quadratic: (t) => t * t,
  cubic: (t) => t * t * t,
  quartric: (t) => t * t * t * t,
  quintic: (t) => t * t * t * t * t,
  sine: (t) => 1 - Math.cos((t * Math.PI) / 2),
  exponential: (t) => Math.pow(2, 10 * (t - 1)),
  circle: (t) => 1 - Math.sqrt(1 - t * t),
  back: (t) => {
    const s = 1.70158;
    return t * t * ((s + 1) * t - s);
  },
  elastic: (t) =>
    1 - Math.pow(Math.cos((t * Math.PI) / 2), 3) * Math.cos(t * Math.PI),
  bounce: (t) => {
    if (t < 1 / 2.75) {
      return 7.5625 * t * t;
    }
    if (t < 2 / 2.75) {
      const t2 = t - 1.5 / 2.75;
      return 7.5625 * t2 * t2 + 0.75;
    }
    if (t < 2.5 / 2.75) {
      const t2 = t - 2.25 / 2.75;
      return 7.5625 * t2 * t2 + 0.9375;
    }
    const t2 = t - 2.625 / 2.75;
    return 7.5625 * t2 * t2 + 0.984375;
  }
};

export const EasingModes: { [name: string]: (easing: Easing) => Easing } = {
  in: (easing: Easing) => {
    return easing;
  },
  out: (easing: Easing) => {
    return (t) => 1 - easing(1 - t);
  },
  inOut: (easing: Easing) => {
    return (t) => {
      if (t < 0.5) {
        return easing(t * 2) / 2;
      }
      return 1 - easing((1 - t) * 2) / 2;
    };
  }
};