import {AnyMenuItem, MenuItemType} from "./MenuRenderer.types";
import {TraversalMap, StringifiedTraversalPath, TraversalPath, TraversalKey} from "./MenuTraversal.types";
import {InvalidTraversalRouteError} from "./InvalidTraversalRouteError";

export class MenuTraversal {
  private readonly traversalMap: TraversalMap
  private currentPath: TraversalPath = [];
  
  public get path() {
    return this.currentPath;
  }
  
  public get stringifiedPath(): StringifiedTraversalPath {
    return this.stringifyTraversalPath(this.currentPath);
  }
  
  public get currentMenuItem(): AnyMenuItem {
    const path = this.stringifiedPath;
    if (!this.traversalMap.has(path)) {
      throw new InvalidTraversalRouteError(this.currentPath);
    }
    
    return <AnyMenuItem>this.traversalMap.get(path);
  }
  
  public get isRoot(): boolean {
    return this.currentPath.length === 0;
  }
  
  constructor(
    private readonly menu: AnyMenuItem[],
    private readonly rootLabel: string = "",
    private readonly rootDescription: string = ''
  ) {
    this.traversalMap = this.generateTraversalMap();
    
  }
  
  public travelForward(next: TraversalKey) {
    const nextPath = [
      ...this.currentPath,
      next
    ];
    
    if (!this.traversalMap.has(this.stringifyTraversalPath(nextPath))) {
      throw new InvalidTraversalRouteError(nextPath);
    }
    
    this.currentPath = nextPath;
  }
  
  public travelBack() {
    this.currentPath.pop();
  }
  
  public getMenuItem(path: StringifiedTraversalPath): AnyMenuItem 
  {
    if (!this.traversalMap.has(path)) {
      throw new InvalidTraversalRouteError([path]);
    }
    
    return <AnyMenuItem>this.traversalMap.get(path);
  }
  
  public static unstringifyTraversalPath(path: StringifiedTraversalPath): TraversalPath {
    return path.split('/');
  }

  private generateTraversalMap(): TraversalMap {
    const map = new Map<StringifiedTraversalPath, AnyMenuItem>();

    map.set('', {
      traversalKey: '',
      label: this.rootLabel,
      description: this.rootDescription,
      type: MenuItemType.Collection,
      children: this.menu
    });

    const that = this;

    function traversePath(path: TraversalPath, menuItem: AnyMenuItem) {
      path = [...path, menuItem.traversalKey];
      map.set(that.stringifyTraversalPath(path), menuItem);

      if (menuItem.type !== MenuItemType.Collection) {
        return;
      }

      menuItem.children.forEach((nextMenuItem) => {
        traversePath(path, nextMenuItem);
      })
    }

    this.menu.forEach((menuItem) => {
      traversePath([], menuItem);
    })

    return map;
  }
  
  private stringifyTraversalPath(path: TraversalPath): StringifiedTraversalPath {
    return path.join('/');
  }
}