import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'relativeTime',
  standalone: true,
  pure: false
})
export class RelativeTimePipe implements PipeTransform {

  transform(value: string): string {
    if (!value) {
      return '';
    }

    const now = new Date();
    const past = new Date(value);
    const elapsed = now.getTime() - past.getTime();

    const msPerSecond = 1000;
    const msPerMinute = msPerSecond * 60;
    const msPerHour = msPerMinute * 60;
    const msPerDay = msPerHour * 24;
    const msPerWeek = msPerDay * 7;
    const msPerMonth = msPerDay * 30;
    const msPerYear = msPerDay * 365;

    if (elapsed < msPerSecond) {
      return 'just now';
    } else if (elapsed < msPerMinute) {
      return `${Math.round(elapsed / msPerSecond)} seconds ago`;
    } else if (elapsed < msPerHour) {
      return `${Math.round(elapsed / msPerMinute)} minutes ago`;
    } else if (elapsed < msPerDay) {
      return `${Math.round(elapsed / msPerHour)} hours ago`;
    } else if (elapsed < msPerWeek) {
      return `${Math.round(elapsed / msPerDay)} days ago`;
    } else if (elapsed < msPerMonth) {
      return `${Math.round(elapsed / msPerWeek)} weeks ago`;
    } else if (elapsed < msPerYear) {
      return `${Math.round(elapsed / msPerMonth)} months ago`;
    } else {
      return `${Math.round(elapsed / msPerYear)} years ago`;
    }
  }
}