import { MathUtils } from "../../math/MathUtils.ts";

interface Vec3Like {
	x: number;
	y: number;
	z: number;
}

interface Settable3 {
	set(x: number, y: number, z: number): Settable3;
}

/** Projects view-space coordinates to screen-space pixel positions. */
export class ViewToScreen {
	#width: number;
	#height: number;

	constructor(width: number, height: number) {
		this.#width = width;
		this.#height = height;
	}

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

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

	setSize(width: number, height: number): void {
		this.#width = width;
		this.#height = height;
	}

	/** Projects NDC coordinates to integer screen-space pixel coordinates. */
	project(
		ndcX: number,
		ndcY: number,
		ndcZ: number,
		target: Settable3,
	): Settable3 {
		const screenX = MathUtils.fastTrunc(((ndcX + 1) * this.#width) >> 1);
		const screenY = MathUtils.fastTrunc(((1 - ndcY) * this.#height) >> 1);
		const clampedX = MathUtils.clamp(screenX, 0, this.#width - 1);
		const clampedY = MathUtils.clamp(screenY, 0, this.#height - 1);
		return target.set(clampedX, clampedY, ndcZ);
	}

	/** Convenience wrapper: projects a point's x/y/z via project(). */
	projectPoint(point: Vec3Like, target: Settable3): Settable3 {
		return this.project(point.x, point.y, point.z, target);
	}
}