import type { Geometry } from "../geometry/Geometry.ts";
import type { Material } from "../materials/Material.ts";
import type { Matrix4 } from "../math/Matrix4.ts";
import { Mesh } from "./Mesh.ts";

interface ColorLike {
	r: number;
	g: number;
	b: number;
}

/** Mesh rendered multiple times with per-instance transforms. */
export class InstancedMesh extends Mesh {
	override type = "InstancedMesh";

	#count: number;

	#instanceMatrix: Float32Array;

	#instanceColor: Float32Array | undefined = undefined;

	override frustumCulled = true;

	constructor(
		geometry: Geometry | undefined = undefined,
		material: Material | undefined = undefined,
		count = 0,
	) {
		super(geometry, material);
		this.#count = count;
		this.#instanceMatrix = new Float32Array(count * 16);

		for (let i = 0; i < count; i++) {
			const offset = i * 16;
			this.#instanceMatrix[offset + 0] = 1;
			this.#instanceMatrix[offset + 5] = 1;
			this.#instanceMatrix[offset + 10] = 1;
			this.#instanceMatrix[offset + 15] = 1;
		}
	}

	get count(): number {
		return this.#count;
	}

	set count(value: number) {
		this.#count = value;
	}

	get instanceMatrix(): Float32Array {
		return this.#instanceMatrix;
	}

	get instanceColor(): Float32Array | undefined {
		return this.#instanceColor;
	}

	set instanceColor(value: Float32Array | undefined) {
		this.#instanceColor = value;
	}

	getMatrixAt(index: number, matrix: Matrix4): void {
		const offset = index * 16;
		const te = matrix.elements;
		for (let i = 0; i < 16; i++) {
			te[i] = this.#instanceMatrix[offset + i];
		}
	}

	setMatrixAt(index: number, matrix: Matrix4): void {
		const offset = index * 16;
		const te = matrix.elements;
		for (let i = 0; i < 16; i++) {
			this.#instanceMatrix[offset + i] = te[i];
		}
	}

	getColorAt(index: number, color: ColorLike): void {
		if (this.#instanceColor === undefined) return;
		const offset = index * 3;
		color.r = this.#instanceColor[offset + 0];
		color.g = this.#instanceColor[offset + 1];
		color.b = this.#instanceColor[offset + 2];
	}

	setColorAt(index: number, color: ColorLike): void {
		if (this.#instanceColor === undefined) {
			this.#instanceColor = new Float32Array(this.#count * 3);
		}
		const offset = index * 3;
		this.#instanceColor[offset + 0] = color.r;
		this.#instanceColor[offset + 1] = color.g;
		this.#instanceColor[offset + 2] = color.b;
	}

	override clone(): InstancedMesh {
		const cloned = new InstancedMesh(this.geometry, this.material, this.#count);
		cloned.copy(this);
		cloned.#instanceMatrix = this.#instanceMatrix.slice();
		if (this.#instanceColor !== undefined) {
			cloned.#instanceColor = this.#instanceColor.slice();
		}
		return cloned;
	}

	dispose(): void {
		this.#instanceMatrix = new Float32Array(0);
		this.#instanceColor = undefined;
	}
}