/**
 * A `PriorityListElement` has a priority to assist in sorting. The idea is that the items in a
 * grouped priority list will not modify their priority during processing to such an amount, that
 * they will change into another group. Smaller lists are smaller to sort, and in case of resource
 * limitation (maximum number of rendered objects reached), not all items have to be sorted at all.
 */ export interface PriorityListElement { /**
     * The integer value of this priority is used to group objects of "same" priority.
     */ priority : number ; } /**
 * The `PriorityListGroup` contains a list of  PriorityListElement s that all have the same
 * (integer) priority.
  export class PriorityListGroup < T extends PriorityListElement > { constructor ( readonly priority , public elements = new Array ( ) ) { } returns clone ( ) { return new PriorityListGroup < T > ( this . priority , this . elements . slice ( ) ) ; } param element returns remove ( element ) { const foundIndex = this . elements . indexOf ( element ) ; if ( foundIndex === - 1 ) { return false ; } this . elements . splice ( foundIndex , 1 ) ; return true ; } } /**
 * The `PriorityListGroupMap` is a map to map the (integer) priority to a  PriorityListGroup .
  export type PriorityListGroupMap < T extends PriorityListElement > = Map < number , PriorityListGroup < T > > ; /**
 * The `GroupedPriorityList` contains a [[PriorityListGroupMap]] to manage a larger number of items
 * in priority groups.
 */ export class GroupedPriorityList < T extends PriorityListElement > { readonly groups : PriorityListGroupMap < T > = new Map ( ) ; param element add ( element ) { this . getGroup ( element . priority ) . elements . push ( element ) ; } param element returns remove ( element ) { const group = this . findGroup ( element . priority ) ; if ( group !== undefined && group . remove ( element ) ) { if ( group . elements . length === 0 ) { this . groups . delete ( group . priority ) ; } return true ; } return false ; } /**
     * Remove all internal  PriorityListGroup s.
      clear ( ) { this . groups . clear ( ) ; } /**
     * Merge another  GroupedPriorityList into this one.
     *
     *  param other merge ( other ) { for ( const otherGroup of other . groups ) { const group = this . findGroup ( otherGroup [ 1 ] . priority ) ; if ( group === undefined ) { this . groups . set ( Math . floor ( otherGroup [ 1 ] . priority ) , otherGroup [ 1 ] . clone ( ) ) ; continue ; } group . elements = group . elements . concat ( otherGroup [ 1 ] . elements ) ; } return this ; } clone ( ) { const clone = new GroupedPriorityList < T > ( ) ; for ( const [ priority , group ] of this . groups ) { clone . groups . set ( priority , group . clone ( ) ) ; } return clone ; } param { ( element : T ) => void } fun forEach ( fun ) { for ( const group of this . groups ) { group [ 1 ] . elements . forEach ( fun ) ; } } /**
     * Count the number of elements in this `GroupedPriorityList`.
     */ count ( ) { let n = 0 ; for ( const group of this . groups ) { n += group [ 1 ] . elements . length ; } return n ; } param priority private findGroup ( priority ) { const normalizedPriority = Math . floor ( priority ) ; const group = this . groups . get ( normalizedPriority ) ; return group ; } param priority private getGroup ( priority ) { let group = this . findGroup ( priority ) ; if ( group === undefined ) { const normalizedPriority = Math . floor ( priority ) ; group = new PriorityListGroup < T > ( normalizedPriority ) ; this . groups . set ( group . priority , group ) ; } return group ; } }