@polygonjs/polygonjs/src/engine/expressions/methods/point.ts

node-based WebGL 3D engine https://polygonjs.com

/**
 * Returns the value of a vertex attribute
 *
 * @remarks
 * It takes 3 arguments.
 *
 * `point(input_index_or_node_path, attrib_name, point_index)`
 *
 * - `input_index_or_node_path` is a number or a string
 * - `attrib_name` is a string, the name of the attribute
 * - `point_index` index of the point to fetch
 *
 * ## Usage
 *
 * - `point(0, 'position', 0)` - returns the position of the first point of the first input, as a THREE.Vector3
 *
 */
import {BaseMethodFindDependencyArgs} from './_Base';
import {BaseMethod} from './_Base';
import {MethodDependency} from '../MethodDependency';
import {GeometryContainer} from '../../containers/Geometry';
import {CoreObjectType} from '../../../core/geometry/ObjectContent';
import {CorePoint} from '../../../core/geometry/entities/point/CorePoint';

const EXPECTED_ARGS_COUNT = 3;
const _pointsSrc: CorePoint<CoreObjectType>[] = [];
export class PointExpression extends BaseMethod {
	static override requiredArguments() {
		return [
			['string', 'path to node'],
			['string', 'attribute name'],
			['index', 'point index'],
		];
	}

	override findDependency(args: BaseMethodFindDependencyArgs): MethodDependency | null {
		return this.createDependencyFromIndexOrPath(args);
	}

	override processArguments(args: any[]): Promise<any> {
		return new Promise(async (resolve, reject) => {
			if (args.length == EXPECTED_ARGS_COUNT) {
				const index_or_path = args[0];
				const attrib_name = args[1];
				const point_index = args[2];
				let container: GeometryContainer | null = null;
				try {
					container = (await this.getReferencedNodeContainer(index_or_path)) as GeometryContainer;
				} catch (e) {
					reject(e);
				}
				if (container) {
					const value = this._get_value_from_container(container, attrib_name, point_index);
					resolve(value);
				}
			} else {
				console.warn(`${args.length} given when expected ${EXPECTED_ARGS_COUNT}`);
				resolve(0);
			}
		});
	}

	_get_value_from_container(container: GeometryContainer, attrib_name: string, point_index: number) {
		const coreGroup = container.coreContent();
		if (coreGroup) {
			coreGroup.points(_pointsSrc);
			const point = _pointsSrc[point_index];

			if (point) {
				return point.attribValue(attrib_name);
			} else {
				return 0;
			}
		} else {
			return null;
		}
	}
}