import type { Node } from "../core/Node.ts";
import type { Material } from "../materials/Material.ts";
import { Vector3 } from "../math/Vector3.ts";

export interface Centroid {
	x: number;
	y: number;
	z: number;
}

const _pos = new Vector3();

/** Single polygon draw operation with material, depth, and vertex data. */
export class DrawCall {
	mesh: Node;

	/**
	 * Flat Float32Array of projected vertex data, stride 4.
	 * Layout per vertex: [x, y, z, w] (NDC xyz, clip-space w).
	 */
	projectedVerts: Float32Array = new Float32Array(0);

	vertCount = 0;

	material: Material;

	faceIndices: number[] | Uint16Array | Uint32Array = [];

	centroid: Centroid = { x: 0, y: 0, z: 0 };

	triangles: unknown = undefined;

	worldPositions: Float32Array = new Float32Array(0);

	/**
	 * Flat typed array for baked shading colors.
	 * Flat shading: stride 3 (r,g,b per face). Gouraud: stride 9 (r,g,b x 3 vertices).
	 */
	shadedColorData: Float32Array = new Float32Array(0);

	/** Stride into shadedColorData: 3 for flat, 9 for gouraud, 0 when unset. */
	shadedColorStride = 0;

	_tileDistance = 0;

	constructor(
		mesh: Node,
		material: Material,
		centroidX?: number,
		centroidY?: number,
		centroidZ?: number,
	) {
		this.mesh = mesh;
		this.material = material;
		if (
			centroidX !== undefined &&
			centroidY !== undefined &&
			centroidZ !== undefined
		) {
			this.centroid.x = centroidX;
			this.centroid.y = centroidY;
			this.centroid.z = centroidZ;
		} else {
			this.#computeCentroid();
		}
	}

	/**
	 * Computes the draw call's centroid from the mesh's bounding sphere
	 * center (world-space). Falls back to mesh origin when no bounding
	 * sphere is available.
	 */
	#computeCentroid(): void {
		const mesh = this.mesh as Node & {
			geometry?: { boundingSphere?: { centre: Vector3 } };
		};
		const bs = mesh.geometry?.boundingSphere;
		if (bs) {
			_pos.copy(bs.centre).applyMatrix4(this.mesh.matrixWorld);
		} else {
			_pos.setFromMatrixPosition(this.mesh.matrixWorld);
		}
		this.centroid.x = _pos.x;
		this.centroid.y = _pos.y;
		this.centroid.z = _pos.z;
	}
}