function painterSortStable(a, b) {
	if (a.groupOrder !== b.groupOrder) {
		return a.groupOrder - b.groupOrder;
	} else if (a.renderOrder !== b.renderOrder) {
		return a.renderOrder - b.renderOrder;
	} else if (a.material.id !== b.material.id) {
		return a.material.id - b.material.id;
	} else if (a.z !== b.z) {
		return a.z - b.z;
	} else {
		return a.id - b.id;
	}
}

function reversePainterSortStable(a, b) {
	if (a.groupOrder !== b.groupOrder) {
		return a.groupOrder - b.groupOrder;
	} else if (a.renderOrder !== b.renderOrder) {
		return a.renderOrder - b.renderOrder;
	} else if (a.z !== b.z) {
		return b.z - a.z;
	} else {
		return a.id - b.id;
	}
}

function WebGLRenderList() {
	const renderItems = [];
	let renderItemsIndex = 0;

	const opaque = [];
	const transmissive = [];
	const transparent = [];

	function init() {
		renderItemsIndex = 0;

		opaque.length = 0;
		transmissive.length = 0;
		transparent.length = 0;
	}

	function getNextRenderItem(object, geometry, material, groupOrder, z, group) {
		let renderItem = renderItems[renderItemsIndex];

		if (renderItem === undefined) {
			renderItem = {
				id: object.id,
				object: object,
				geometry: geometry,
				material: material,
				groupOrder: groupOrder,
				renderOrder: object.renderOrder,
				z: z,
				group: group,
			};

			renderItems[renderItemsIndex] = renderItem;
		} else {
			renderItem.id = object.id;
			renderItem.object = object;
			renderItem.geometry = geometry;
			renderItem.material = material;
			renderItem.groupOrder = groupOrder;
			renderItem.renderOrder = object.renderOrder;
			renderItem.z = z;
			renderItem.group = group;
		}

		renderItemsIndex++;

		return renderItem;
	}

	function push(object, geometry, material, groupOrder, z, group) {
		const renderItem = getNextRenderItem(object, geometry, material, groupOrder, z, group);

		if (material.transmission > 0.0) {
			transmissive.push(renderItem);
		} else if (material.transparent === true) {
			transparent.push(renderItem);
		} else {
			opaque.push(renderItem);
		}
	}

	function unshift(object, geometry, material, groupOrder, z, group) {
		const renderItem = getNextRenderItem(object, geometry, material, groupOrder, z, group);

		if (material.transmission > 0.0) {
			transmissive.unshift(renderItem);
		} else if (material.transparent === true) {
			transparent.unshift(renderItem);
		} else {
			opaque.unshift(renderItem);
		}
	}

	function sort(customOpaqueSort, customTransparentSort) {
		if (opaque.length > 1) opaque.sort(customOpaqueSort || painterSortStable);
		if (transmissive.length > 1) transmissive.sort(customTransparentSort || reversePainterSortStable);
		if (transparent.length > 1) transparent.sort(customTransparentSort || reversePainterSortStable);
	}

	function finish() {
		// Clear references from inactive renderItems in the list

		for (let i = renderItemsIndex, il = renderItems.length; i < il; i++) {
			const renderItem = renderItems[i];

			if (renderItem.id === null) break;

			renderItem.id = null;
			renderItem.object = null;
			renderItem.geometry = null;
			renderItem.material = null;
			renderItem.group = null;
		}
	}

	return {
		opaque: opaque,
		transmissive: transmissive,
		transparent: transparent,

		init: init,
		push: push,
		unshift: unshift,
		finish: finish,

		sort: sort,
	};
}

function WebGLRenderLists() {
	let lists = new WeakMap();

	function get(scene, renderCallDepth) {
		let list;

		if (lists.has(scene) === false) {
			list = new WebGLRenderList();
			lists.set(scene, [list]);
		} else {
			if (renderCallDepth >= lists.get(scene).length) {
				list = new WebGLRenderList();
				lists.get(scene).push(list);
			} else {
				list = lists.get(scene)[renderCallDepth];
			}
		}

		return list;
	}

	function dispose() {
		lists = new WeakMap();
	}

	return {
		get: get,
		dispose: dispose,
	};
}

export { WebGLRenderLists, WebGLRenderList };