import { NgZone } from '@angular/core';
import { IgxOverlayService } from '../overlay';
import { ScrollStrategy } from './scroll-strategy';

/**
 * On scroll reposition the overlay content.
 */
export class AbsoluteScrollStrategy extends ScrollStrategy {
    private _initialized = false;
    private _document: Document;
    private _overlayService: IgxOverlayService;
    private _id: string;
    private _scrollContainer: HTMLElement;
    private _zone: NgZone;

    constructor(scrollContainer?: HTMLElement) {
        super();
        this._scrollContainer = scrollContainer;
    }

    /**
     * Initializes the strategy. Should be called once
     *
     * @param document reference to Document object.
     * @param overlayService IgxOverlay service to use in this strategy.
     * @param id Unique id for this strategy.
     * ```typescript
     * settings.scrollStrategy.initialize(document, overlay, id);
     * ```
     */
    public initialize(document: Document, overlayService: IgxOverlayService, id: string) {
        if (this._initialized) {
            return;
        }
        this._overlayService = overlayService;
        this._id = id;
        this._document = document;
        this._zone = overlayService.getOverlayById(id).ngZone;
        this._initialized = true;
    }

    /**
     * Attaches the strategy
     * ```typescript
     * settings.scrollStrategy.attach();
     * ```
     */
    public attach(): void {
        if (this._zone) {
            this._zone.runOutsideAngular(() => {
                this.addScrollEventListener();
            });
        } else {
            this.addScrollEventListener();
        }
    }

    /**
     * Detaches the strategy
     * ```typescript
     * settings.scrollStrategy.detach();
     * ```
     */
    public detach(): void {
        if (this._scrollContainer) {
            this._scrollContainer.removeEventListener('scroll', this.onScroll, true);
        } else {
            // Tired of this thing throwing every other time. Fix it ffs!
            this._document?.removeEventListener('scroll', this.onScroll, true);
        }

        this._initialized = false;
    }

    private addScrollEventListener() {
        if (this._scrollContainer) {
            this._scrollContainer.addEventListener('scroll', this.onScroll, true);
        } else {
            this._document.addEventListener('scroll', this.onScroll, true);
        }
    }

    private onScroll = (e: Event) => {
        const overlayInfo = this._overlayService.getOverlayById(this._id);
        if (!overlayInfo) {
            return;
        }
        if (!overlayInfo.elementRef.nativeElement.contains(e.target)) {
            this._overlayService.reposition(this._id);
        }
    };
}