import { Component, Input, OnInit, OnDestroy, ElementRef, Output,  EventEmitter  } from '@angular/core';


@Component({
  selector: 'countdown-timer',
  template: `{{ displayTime }}`
})
export class CountdownTimer implements OnInit, OnDestroy{
 
  @Input() start;
  @Input() end;
  @Output() zeroTrigger;
  @Input() timeOnly;
  timer: any;
  displayTime: any;
  constructor(
    private el: ElementRef
  ) {
    this.zeroTrigger = new EventEmitter(true);

  }

  ngOnInit(): void {
    this.timer = setInterval(() => {
      
        if (this.start) {
            this.displayTime = this.getTimeDiff(this.start, true);
        } else {
            this.displayTime = this.getTimeDiff(this.end);
        }
      }, 1000);
  }

  ngOnDestroy() {
    this.stopTimer();
  }

  private getTimeDiff( datetime, useAsTimer = false ) {
      datetime = new Date( datetime ).getTime();
      var now = new Date().getTime();
  
      if( isNaN(datetime) )
      {
          return "";
      }

      var milisec_diff = datetime - now;
      if (useAsTimer) {
          milisec_diff = now - datetime;
      } 

      // Zero Time Trigger
      if (milisec_diff <= 0) {
        this.zeroTrigger.emit("reached zero");
        return "00:00:00:00";
      }

      var days = Math.floor(milisec_diff / 1000 / 60 / (60 * 24));
      var date_diff = new Date( milisec_diff );
      // var day_string = (days) ? this.twoDigit(days) + ":" : "";
      var day_string = this.twoDigit(days) + ":";
      var day_hours = days * 24;


      if (this.timeOnly) {
        let hours = date_diff.getUTCHours() + day_hours;
        return  this.twoDigit(hours) +
        ":" + this.twoDigit(date_diff.getMinutes()) + ":" 
        + this.twoDigit(date_diff.getSeconds());
      } else {
        // Date() takes a UTC timestamp – getHours() gets hours in local time not in UTC. therefore we have to use getUTCHours()
        return day_string + this.twoDigit(date_diff.getUTCHours()) +
           ":" + this.twoDigit(date_diff.getMinutes()) + ":" 
           + this.twoDigit(date_diff.getSeconds());

      }
  }


  private twoDigit(number: number) {
      return number > 9 ? "" + number: "0" + number;
  }

  private stopTimer() {
    clearInterval(this.timer);
    this.timer = undefined;
  }
  
}