Virtual Repeat Model for angular-materials Virtual Repeat

virtual-repeat-model.ts

class VirtualRepeatModel {
	PAGE_SIZE: number = 20;
	totalItems: number = 0;
	totalPages: number;
	loadedItems = {};
	currentIndex: number;
	extraParams = {};

	constructor(public api: restangular.IElement, public initialPage?: number) {

	}

	refresh() {
		this.loadedItems = {};
		this.getItemAtIndex(0);
	}

	getItemAtIndex(index: number) {
		if (this.initialPage > 1) {
			index = index + this.initialPage * this.PAGE_SIZE;
		}
		this.currentIndex = index;
		var pageNumber = Math.floor(index / this.PAGE_SIZE);
		var page = this.loadedItems[pageNumber];
		if (page) {
			return page[index % this.PAGE_SIZE];
		} else if (page !== null) {
			this.fetchPage(pageNumber);
		}
	}

	fetchPage(pageNumber: number) {
		this.loadedItems[pageNumber] = null;
		let request = {
			page: pageNumber === 0 ? 1 : pageNumber,
			pageSize: this.PAGE_SIZE
		};
		angular.extend(request, this.extraParams);
		return this.api.getList(request).then((data) => {
			this.totalItems = data.meta.totalRecords;
			this.totalPages = data.meta.totalPages;
			this.loadedItems[pageNumber] = data.plain();
		}).catch((err) => {
			return null;
		});
	}

	getLength(): number {
		return this.totalItems;
	}
}