import { Geometry } from "../Geometry.ts";

/** Flat ring (annulus) geometry on the XY plane. */
export class RingGeometry extends Geometry {
	constructor(
		innerRadius = 0.5,
		outerRadius = 1,
		thetaSegments = 32,
		phiSegments = 1,
		thetaStart = 0,
		thetaLength: number = Math.PI * 2,
	) {
		super();

		this.type = "RingGeometry";
		this.parameters = {
			innerRadius,
			outerRadius,
			thetaSegments,
			phiSegments,
			thetaStart,
			thetaLength,
		};

		const ts = Math.max(3, Math.floor(thetaSegments));
		const ps = Math.max(1, Math.floor(phiSegments));

		const positions: number[] = [];
		const normals: number[] = [];
		const uvs: number[] = [];
		const indices: number[] = [];

		let index = 0;
		const grid: number[][] = [];

		for (let j = 0; j <= ps; j++) {
			const row: number[] = [];
			const r = innerRadius + (j / ps) * (outerRadius - innerRadius);
			for (let i = 0; i <= ts; i++) {
				const theta = thetaStart + (i / ts) * thetaLength;
				positions.push(r * Math.cos(theta), r * Math.sin(theta), 0);
				normals.push(0, 0, 1);
				uvs.push(
					(r * Math.cos(theta) + outerRadius) / (2 * outerRadius),
					(r * Math.sin(theta) + outerRadius) / (2 * outerRadius),
				);
				row.push(index++);
			}
			grid.push(row);
		}

		for (let j = 0; j < ps; j++) {
			for (let i = 0; i < ts; i++) {
				const a = grid[j][i];
				const b = grid[j + 1][i];
				const c = grid[j + 1][i + 1];
				const d = grid[j][i + 1];
				indices.push(a, b, d);
				indices.push(b, c, d);
			}
		}

		const IndexArray = index > 65535 ? Uint32Array : Uint16Array;

		this.setPositions(new Float32Array(positions));
		this.setNormals(new Float32Array(normals));
		this.setUVs(new Float32Array(uvs));
		this.setIndex(new IndexArray(indices));
	}
}