import LayeringError from "../../errors/graph/layering/LayeringError.js";
import Edge from "../Edge.js";
import Node from "../Node.js";
import Layer from "./Layer.js";

export default class Layering<TNode extends Node, TEdge extends Edge<TNode>> {
	private readonly _layers: Map<number, Layer<TNode>>;

	public constructor() {
		this._layers = new Map();
	}

	public assign(node: TNode, layerIndex: number) : this {
		if(!this._layers.has(layerIndex))
			this._layers.set(layerIndex, new Layer(layerIndex));

		this._layers.get(layerIndex)!.addNodes([node.id]);

		return this;
	}

	public getLayers(): Layer<TNode>[] {
		return Array.from(this._layers.values()).sort((a, b) => a.index - b.index);
	}

	public getLayerOf(nodeId: TNode["id"]) : number | null {
		for(const [layerIndex, layer] of this._layers)
			if(layer.nodes.some((id) => id == nodeId))
				return layerIndex;

		return null;
	}

	public setLayerOf(nodeId: TNode["id"], newLayerIndex: number) : this {
		const oldIndex = this.getLayerOf(nodeId);
		if(oldIndex !== null) {
			const oldLayer = this._layers.get(oldIndex);
			oldLayer?.removeNodes([nodeId])
		}

		if(!this._layers.has(newLayerIndex))
			this._layers.set(newLayerIndex, new Layer(newLayerIndex));
		this._layers.get(newLayerIndex)!.addNodes([nodeId]);

		return this;
	}

	public isEdgeTight(edge: TEdge) : boolean {
		const { from, to } = edge;
		const fromLayerIndex = this.getLayerOf(from), toLayerIndex = this.getLayerOf(to);

		if(fromLayerIndex == null || toLayerIndex == null)
			throw new LayeringError(`Node from edge ${edge.id} is not assigned to any layer`);

		return Math.abs(fromLayerIndex - toLayerIndex) === 1;
	}

	public getEdgeSpan(edge: TEdge) : number {
		const fromLayer = this.getLayerOf(edge.from);
		const toLayer = this.getLayerOf(edge.to);

		if(fromLayer === null || toLayer === null)
			throw new LayeringError(`Node from edge ${edge.id} is not assigned to any layer`);

		return Math.abs(fromLayer - toLayer);
	}

	public normalize() : this {
		const minLayerIndex = Math.min(...Array.from(this._layers.keys()));
		if(minLayerIndex === 0) 
			return this;

		const newLayers = new Map<number, Layer<TNode>>();
		for(const [index, layer] of this._layers) {
			const newLayerIndex = index - minLayerIndex;
			const newLayer = new Layer<TNode>(newLayerIndex);
			newLayer.addNodes(layer.nodes);
			newLayers.set(newLayerIndex, newLayer);
		}

		this._layers.clear();
		newLayers.forEach((layer, index) => this._layers.set(index, layer));
	
		return this;
	}


	public get height() : number {
		return this._layers.size;
	}

	public get width() : number {
		return Math.max(...Array.from(this._layers.values()).map((layer) => layer.width));
	}
}