import { Interpolant } from '../Interpolant.js';
import { Quaternion } from '../Quaternion.js';

/**
 * Spherical linear unit quaternion interpolant.
 */

class QuaternionLinearInterpolant extends Interpolant {

	constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

		super( parameterPositions, sampleValues, sampleSize, resultBuffer );

	}

	interpolate_( i1, t0, t, t1 ) {

		const result = this.resultBuffer,
			values = this.sampleValues,
			stride = this.valueSize,

			alpha = ( t - t0 ) / ( t1 - t0 );

		let offset = i1 * stride;

		for ( let end = offset + stride; offset !== end; offset += 4 ) {

			Quaternion.slerpFlat( result, 0, values, offset - stride, values, offset, alpha );

		}

		return result;

	}

}


export { QuaternionLinearInterpolant };