import { Vector3 } from '../math/Vector3.js';
import { Object3D } from '../core/Object3D.js';

const _v1 = /*@__PURE__*/ new Vector3();
const _v2 = /*@__PURE__*/ new Vector3();

class LOD extends Object3D {

	constructor() {

		super();

		this._currentLevel = 0;

		this.type = 'LOD';

		Object.defineProperties( this, {
			levels: {
				enumerable: true,
				value: []
			},
			isLOD: {
				value: true,
			}
		} );

		this.autoUpdate = true;

	}

	copy( source ) {

		super.copy( source, false );

		const levels = source.levels;

		for ( let i = 0, l = levels.length; i < l; i ++ ) {

			const level = levels[ i ];

			this.addLevel( level.object.clone(), level.distance, level.hysteresis );

		}

		this.autoUpdate = source.autoUpdate;

		return this;

	}

	addLevel( object, distance = 0, hysteresis = 0 ) {

		distance = Math.abs( distance );

		const levels = this.levels;

		let l;

		for ( l = 0; l < levels.length; l ++ ) {

			if ( distance < levels[ l ].distance ) {

				break;

			}

		}

		levels.splice( l, 0, { distance: distance, hysteresis: hysteresis, object: object } );

		this.add( object );

		return this;

	}

	getCurrentLevel() {

		return this._currentLevel;

	}



	getObjectForDistance( distance ) {

		const levels = this.levels;

		if ( levels.length > 0 ) {

			let i, l;

			for ( i = 1, l = levels.length; i < l; i ++ ) {

				let levelDistance = levels[ i ].distance;

				if ( levels[ i ].object.visible ) {

					levelDistance -= levelDistance * levels[ i ].hysteresis;

				}

				if ( distance < levelDistance ) {

					break;

				}

			}

			return levels[ i - 1 ].object;

		}

		return null;

	}

	raycast( raycaster, intersects ) {

		const levels = this.levels;

		if ( levels.length > 0 ) {

			_v1.setFromMatrixPosition( this.matrixWorld );

			const distance = raycaster.ray.origin.distanceTo( _v1 );

			this.getObjectForDistance( distance ).raycast( raycaster, intersects );

		}

	}

	update( camera ) {

		const levels = this.levels;

		if ( levels.length > 1 ) {

			_v1.setFromMatrixPosition( camera.matrixWorld );
			_v2.setFromMatrixPosition( this.matrixWorld );

			const distance = _v1.distanceTo( _v2 ) / camera.zoom;

			levels[ 0 ].object.visible = true;

			let i, l;

			for ( i = 1, l = levels.length; i < l; i ++ ) {

				let levelDistance = levels[ i ].distance;

				if ( levels[ i ].object.visible ) {

					levelDistance -= levelDistance * levels[ i ].hysteresis;

				}

				if ( distance >= levelDistance ) {

					levels[ i - 1 ].object.visible = false;
					levels[ i ].object.visible = true;

				} else {

					break;

				}

			}

			this._currentLevel = i - 1;

			for ( ; i < l; i ++ ) {

				levels[ i ].object.visible = false;

			}

		}

	}

	toJSON( meta ) {

		const data = super.toJSON( meta );

		if ( this.autoUpdate === false ) data.object.autoUpdate = false;

		data.object.levels = [];

		const levels = this.levels;

		for ( let i = 0, l = levels.length; i < l; i ++ ) {

			const level = levels[ i ];

			data.object.levels.push( {
				object: level.object.uuid,
				distance: level.distance,
				hysteresis: level.hysteresis
			} );

		}

		return data;

	}

}


export { LOD };