// Wrap the tree of events.

import {BinaryHeapWithComparer} from '../../structs/BinaryHeapWithComparer'

import {SweepEvent} from '../spline/coneSpanner/SweepEvent'
import {BasicReflectionEvent} from './basicReflectionEvent'
import {ScanDirection} from './ScanDirection'

export class EventQueue {
  scanDirection: ScanDirection

  eventTree: BinaryHeapWithComparer<SweepEvent>

  constructor() {
    this.eventTree = new BinaryHeapWithComparer<SweepEvent>((a, b) => this.Compare(a, b))
  }

  Reset(scanDir: ScanDirection) {
    /*Assert.assert(0 === this.eventTree.Count, 'Stray events in EventQueue.Reset')*/
    this.scanDirection = scanDir
  }

  Enqueue(evt: SweepEvent) {
    this.eventTree.Enqueue(evt)
  }

  Dequeue(): SweepEvent {
    const evt: SweepEvent = this.eventTree.Dequeue()
    return evt
  }

  get Count(): number {
    return this.eventTree.Count
  }

  public Compare(lhs: SweepEvent, rhs: SweepEvent): number {
    if (lhs === rhs) {
      return 0
    }

    if (lhs == null) {
      return -1
    }

    if (rhs == null) {
      return 1
    }

    // First see if it's at the same scanline level (perpendicular coordinate).
    let cmp = this.scanDirection.ComparePerpCoord(lhs.Site, rhs.Site)
    if (cmp) return cmp
    // Event sites are at the same scanline level. Make sure that any reflection events are lowest (come before
    // any side events, which could remove the side the reflection event was queued for).  We may have two
    // reflection events at same coordinate, because we enqueue in two situations: when a side is opened,
    // and when a side that is within that side's scanline-parallel span is closed.
    const lhsIsNotReflection = !(lhs instanceof BasicReflectionEvent) ? 1 : 0
    const rhsIsNotReflection = !(rhs instanceof BasicReflectionEvent) ? 1 : 0
    cmp = lhsIsNotReflection - rhsIsNotReflection
    // If the scanline-parallel coordinate is the same these events are at the same point.
    if (cmp) return cmp
    return this.scanDirection.CompareScanCoord(lhs.Site, rhs.Site)
  }
}