import { TreeWalker } from './TreeWalker';

export abstract class ArrayChildrenTreeWalker<T> extends TreeWalker<T>
{
  _parentMap = new Map<T,T>();
  
  abstract getChildren( t:T ):T[];

  clearParentMap()
  {
    this._parentMap.clear();
  }

  updateParentMap( root:T, ...otherRoots:T[] )
  {
    let stack = [ root ].concat( otherRoots );

    while ( stack.length > 0 )
    {
      let parent = stack.shift();
      let children = this.getChildren( parent );

      for ( let child of children )
      {
        this._parentMap.set( child, parent );
        stack.push( child );
      }
      
    }
  }

  childAt( t:T, index:number )
  {
    return this.getChildren( t )[ index ];
  }

  parent( t:T ):T
  {
    return this._parentMap.get( t );
  }

  numChildren( t:T )
  {
    return this.getChildren( t ).length;
  }


}