1 files changed, 121 insertions, 0 deletions
diff --git a/gui/src/shared/date-helper.ts b/gui/src/shared/date-helper.ts
new file mode 100644
index 0000000000..0011ed8fc2
--- /dev/null
+++ b/gui/src/shared/date-helper.ts
@@ -0,0 +1,121 @@
+import { sprintf } from 'sprintf-js';
+import { messages } from './gettext';
+
+export type DateType = Date | string;
+
+export enum DateComponent {
+  day,
+  hour,
+  minute,
+}
+
+export function dateByAddingComponent(date: DateType, component: DateComponent, value: number) {
+  const modifiedDate = new Date(date);
+  switch (component) {
+    case DateComponent.day:
+      modifiedDate.setDate(modifiedDate.getDate() + value);
+      break;
+    case DateComponent.hour:
+      modifiedDate.setHours(modifiedDate.getHours() + value);
+      break;
+    case DateComponent.minute:
+      modifiedDate.setMinutes(modifiedDate.getMinutes() + value);
+      break;
+  }
+
+  return modifiedDate;
+}
+
+export class DateDiff {
+  private readonly fromDate: Date;
+  private readonly toDate: Date;
+
+  public constructor(fromDate: DateType, toDate: DateType) {
+    this.fromDate = new Date(fromDate);
+    this.toDate = new Date(toDate);
+  }
+
+  get milliseconds(): number {
+    return this.toDate.getTime() - this.fromDate.getTime();
+  }
+
+  get seconds(): number {
+    return this.floor(this.milliseconds / 1000);
+  }
+
+  get minutes(): number {
+    return this.floor(this.seconds / 60);
+  }
+
+  get hours(): number {
+    return this.floor(this.minutes / 60);
+  }
+
+  get days(): number {
+    return this.floor(this.hours / 24);
+  }
+
+  get months(): number {
+    const months = new Date(Math.abs(this.milliseconds)).getUTCMonth();
+    const monthsWithSign = this.milliseconds >= 0 ? months : -months;
+    return this.years * 12 + monthsWithSign;
+  }
+
+  get years(): number {
+    const years = new Date(Math.abs(this.milliseconds)).getUTCFullYear() - 1970;
+    return this.milliseconds >= 0 ? years : -years;
+  }
+
+  private floor(n: number): number {
+    return n >= 0 ? Math.floor(n) : Math.ceil(n);
+  }
+}
+
+export function formatRelativeDate(
+  fromDate: DateType,
+  toDate: DateType,
+  withSuffix = false,
+): string {
+  const diff = new DateDiff(fromDate, toDate);
+  const years = Math.abs(diff.years);
+  const months = Math.abs(diff.months);
+  const days = Math.abs(diff.days);
+  const hours = Math.abs(diff.hours);
+  const minutes = Math.abs(diff.minutes);
+
+  if (!withSuffix) {
+    if (years > 0) {
+      return sprintf(messages.ngettext('1 year', '%d years', years), years);
+    } else if (months >= 3) {
+      return sprintf(messages.ngettext('1 month', '%d months', months), months);
+    } else if (days > 0) {
+      return sprintf(messages.ngettext('1 day', '%d days', days), days);
+    } else {
+      return messages.gettext('less than a day');
+    }
+  } else if (diff.milliseconds > 0) {
+    if (years > 0) {
+      return sprintf(messages.ngettext('1 year left', '%d years left', years), years);
+    } else if (months >= 3) {
+      return sprintf(messages.ngettext('1 month left', '%d months left', months), months);
+    } else if (days > 0) {
+      return sprintf(messages.ngettext('1 day left', '%d days left', days), days);
+    } else {
+      return messages.gettext('less than a day left');
+    }
+  } else {
+    if (years > 0) {
+      return sprintf(messages.ngettext('a year ago', '%d years ago', years), years);
+    } else if (months > 0) {
+      return sprintf(messages.ngettext('a month ago', '%d months ago', months), months);
+    } else if (days > 0) {
+      return sprintf(messages.ngettext('a day ago', '%d days ago', days), days);
+    } else if (hours > 0) {
+      return sprintf(messages.ngettext('an hour ago', '%d hours ago', hours), hours);
+    } else if (minutes > 0) {
+      return sprintf(messages.ngettext('a minute ago', '%d minutes ago', minutes), minutes);
+    } else {
+      return messages.gettext('less than a minute ago');
+    }
+  }
+}