const DRAFT_KEY = "qa-draft";
const relativeTime = new Intl.RelativeTimeFormat(undefined, {
  numeric: "auto",
});

function getValidDate(dateString: string): Date | null {
  const date = new Date(dateString);
  return Number.isNaN(date.getTime()) ? null : date;
}

export function readQuestionDraft(): string {
  try {
    return localStorage.getItem(DRAFT_KEY) ?? "";
  } catch {
    return "";
  }
}

export function writeQuestionDraft(value: string) {
  try {
    localStorage.setItem(DRAFT_KEY, value);
  } catch {
    // Ignore storage failures.
  }
}

export function clearQuestionDraft() {
  try {
    localStorage.removeItem(DRAFT_KEY);
  } catch {
    // Ignore storage failures.
  }
}

export function formatExactTimestamp(dateString: string): string {
  const date = getValidDate(dateString);
  if (!date) return dateString;

  return new Intl.DateTimeFormat(undefined, {
    dateStyle: "medium",
    timeStyle: "short",
  }).format(date);
}

export function formatRelativeTimestamp(dateString: string): string {
  const date = getValidDate(dateString);
  if (!date) return dateString;

  const diffMs = date.getTime() - Date.now();
  const diffMinutes = Math.round(diffMs / 60000);
  const diffHours = Math.round(diffMs / 3600000);
  const diffDays = Math.round(diffMs / 86400000);

  if (Math.abs(diffMinutes) < 60)
    return relativeTime.format(diffMinutes, "minute");
  if (Math.abs(diffHours) < 24) return relativeTime.format(diffHours, "hour");
  if (Math.abs(diffDays) < 30) return relativeTime.format(diffDays, "day");

  return new Intl.DateTimeFormat(undefined, { dateStyle: "medium" }).format(
    date,
  );
}