import type { NodeDef } from '../../NodeRegistry';
import { asNumber } from '../../values';
import { curvesOf, easingOfParams, easingParams, idleEasing } from '../easing';
import { num, withDefault } from '../shared';

import { easedShare } from '../../../model/animation';
import { LERP } from '../../../model/curve';

export const Lerp: NodeDef = {
  type: LERP,
  label: 'Lerp',
  category: 'data',
  description:
    'Blends from a to b as t runs from 0 to 1, along the chosen easing – the same ones an animation ' +
    'key offers. t is held in 0…1. Step stays at a until t reaches 1. Back, Elastic and a Curve ' +
    'asset may overshoot b.',
  inputs: [withDefault(num('a'), 0), withDefault(num('b'), 1), withDefault(num('t'), 0)],
  outputs: [num('result')],
  params: easingParams(),
  idleParams: idleEasing,
  run: (_ctx, inputs, params, _def, _entry, lookup) => {
    const a = asNumber(inputs.a);
    const t = Math.min(Math.max(asNumber(inputs.t), 0), 1);
    const share = easedShare(easingOfParams(params), t, curvesOf(lookup));
    return { outputs: { result: a + (asNumber(inputs.b) - a) * share } };
  },
};