import { Component, OnInit, Input } from '@angular/core';

@Component({
  selector: 'scrolltotop',
  templateUrl: './scrolltotop.component.html',
  styleUrls: ['./scrolltotop.component.css']
})
export class ScrolltotopComponent implements OnInit {

  @Input() ngStyle: { [key: string]: string; }

  btn = {
    "position": "fixed",
    "bottom": "2%",
    "right": "5%",
    "padding": "15px",
    "background-color": "#888",
    "transition": "all 1s ease-in-out"
  }

  arrow = {
    "padding": "5px",
    "border-top": "4px solid #fff",
    "border-left": "4px solid #fff",
    "transform": "rotate(45deg) translate(15%, 15%)",
    "transition": "all 1s ease-in-out"
  }

  constructor() { }

  ngOnInit() {

    var elem = document.body || document.documentElement;

    function runScroll() {
      scrollTo(elem, 0, 600);
    }

    var scrollme;

    scrollme = document.querySelector("#top");
    scrollme.addEventListener("click", runScroll, false)

    function scrollTo(element, to, duration) {

      if (duration <= 0) return;

      var difference = to - element.scrollTop;
      var perTick = difference / duration * 10;

      setTimeout(function () {

        element.scrollTop = element.scrollTop + perTick;

        if (element.scrollTop == to) return;

        scrollTo(element, to, duration - 10);

      }, 10);

    }

    window.onscroll = function () { scrollFunction() };

    function scrollFunction() {

      if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {

        document.getElementById("top").style.display = "block";

      } else {

        document.getElementById("top").style.display = "none";

      }

    }

  }

}