{
  "version": 3,
  "sources": ["src/app/shared/scroll/intersection-observer.service.ts"],
  "sourcesContent": ["import { Injectable, NgZone, ElementRef } from '@angular/core';\r\nimport { ScrollBarService } from '@shared/scroll/scrollbar.service';\r\nimport { NgScrollbar } from 'ngx-scrollbar';\r\n\r\n\r\nexport interface IntersectionTarget {\r\n  elRef: ElementRef;\r\n  updateVisibility?: (isVisible: boolean, ratio: number) => void;\r\n}\r\n\r\n@Injectable()\r\nexport class IntersectionObserverService {\r\n\r\n  private observer: IntersectionObserver;\r\n  private targets: Map<Element, IntersectionTarget>;\r\n\r\n  // I initialize the lazy-viewport service.\r\n  constructor(\r\n    private zone: NgZone,\r\n    private scrollBarService: ScrollBarService\r\n  ) {\r\n\r\n    this.observer = null;\r\n\r\n    // The IntersectionObserver watches Elements. However, when an element visibility\r\n    // changes, we have to alert an Angular Directive instance. As such, we're going\r\n    // to keep a map of Elements-to-Directives. This way, when our observer callback\r\n    // is invoked, we'll be able to extract the appropriate Directive from the\r\n    // Element-based observer entries collection.\r\n    this.targets = new Map();\r\n\r\n  }\r\n\r\n  // ---\r\n  // PUBLIC METHODS.\r\n  // ---\r\n\r\n  // I add the given IntersectionTarget implementation to the collection of objects being\r\n  // tracked by the IntersectionObserver.\r\n  public addTarget(target: IntersectionTarget): void {\r\n\r\n    if (this.observer) {\r\n      const el = target.elRef.nativeElement;\r\n      if (el instanceof Element === false) {\r\n        throw new Error('Intersection Observer service: Invalid target element');\r\n      }\r\n\r\n      this.targets.set(el, target);\r\n      this.observer.observe(el);\r\n\r\n      // provvedere polyfill https://github.com/w3c/IntersectionObserver/tree/master/polyfill\r\n      // If we don't actually have an observer (lacking browser support), then we're\r\n      // going to punt on the feature for now and just immediately tell the target\r\n      // that it is visible on the page.\r\n    } else {\r\n\r\n      target.updateVisibility(true, 1.0);\r\n\r\n    }\r\n\r\n  }\r\n\r\n\r\n  // I setup the IntersectionObserver with the given element as the root.\r\n  public setup(scrollbar: NgScrollbar | string = null, rootMargin?: string, threshold?: number): void {\r\n\r\n    // While the IntersectionObserver is supported in the modern browsers, it will\r\n    // never be added to Internet Explorer (IE) and is not in my version of Safari\r\n    // (at the time of this post). As such, we'll only use it if it's available.\r\n    // And, if it's not, we'll fall-back to non-lazy behaviors.\r\n    let sb: NgScrollbar;\r\n    if (!global['IntersectionObserver']) {\r\n\r\n      return;\r\n\r\n    }\r\n    if (scrollbar) {\r\n      sb = typeof scrollbar === 'string' ? this.scrollBarService.getById(scrollbar) : scrollbar;\r\n    } else {\r\n      sb = this.scrollBarService.mainScrollbar;\r\n    }\r\n\r\n\r\n    this.zone.runOutsideAngular(\r\n      () => {\r\n        this.observer = new IntersectionObserver(\r\n          this.handleIntersectionUpdate,\r\n          {\r\n            root: sb.viewport.nativeElement,\r\n            rootMargin: rootMargin ? rootMargin : '0px 0px 0px 0px',\r\n            threshold: threshold ? threshold : 0\r\n          }\r\n        );\r\n      });\r\n\r\n  }\r\n\r\n\r\n  // I remove the given LazyTarget implementation from the collection of objects being\r\n  // tracked by the IntersectionObserver.\r\n  public removeTarget(target: ElementRef): void {\r\n\r\n    // If the IntersectionObserver isn't supported, we never started tracking the\r\n    // given target in the first place.\r\n    if (this.observer) {\r\n      const el = target.nativeElement;\r\n      this.targets.delete(el);\r\n      this.observer.unobserve(el);\r\n    }\r\n\r\n  }\r\n\r\n\r\n  // I teardown this service instance.\r\n  public teardown(): void {\r\n\r\n    if (this.observer) {\r\n\r\n      this.observer.disconnect();\r\n      this.observer = null;\r\n\r\n    }\r\n\r\n    this.targets.clear();\r\n    this.targets = null;\r\n\r\n  }\r\n\r\n  // ---\r\n  // PRIVATE METHODS.\r\n  // ---\r\n\r\n  // I handle changes in the visibility for elements being tracked by the intersection\r\n  // observer.\r\n  // --\r\n  // CAUTION: Using fat-arrow binding for method.\r\n  private handleIntersectionUpdate = (entries: IntersectionObserverEntry[]): void => {\r\n\r\n    for (const entry of entries) {\r\n\r\n      const intersectionTarget = this.targets.get(entry.target);\r\n\r\n      if (intersectionTarget) {\r\n        intersectionTarget.updateVisibility(\r\n          entry.isIntersecting,\r\n          entry.intersectionRatio\r\n        );\r\n      }\r\n    }\r\n\r\n  }\r\n\r\n}\r\n"],
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  "names": ["IntersectionObserverService", "constructor", "zone", "scrollBarService", "handleIntersectionUpdate", "entries", "entry", "intersectionTarget", "targets", "get", "target", "updateVisibility", "isIntersecting", "intersectionRatio", "observer", "Map", "addTarget", "el", "elRef", "nativeElement", "Element", "Error", "set", "observe", "setup", "scrollbar", "rootMargin", "threshold", "sb", "global", "getById", "mainScrollbar", "runOutsideAngular", "IntersectionObserver", "root", "viewport", "removeTarget", "delete", "unobserve", "teardown", "disconnect", "clear", "\u0275\u0275inject", "NgZone", "ScrollBarService", "factory", "\u0275fac", "_IntersectionObserverService"]
}