/**
 * Date formatting utilities for the Antaram app.
 *
 * Uses date-fns for absolute formats and a hand-rolled relative time
 * function to avoid pulling in too many locale files.
 */
import { format, isToday, isYesterday, isThisYear, parseISO } from 'date-fns';

// ─── Relative Time ───────────────────────────────────────────────────────────

/**
 * Returns a human-friendly relative time string.
 *
 * Examples:
 *   - "just now"           (< 60 seconds)
 *   - "2 min ago"          (< 60 minutes)
 *   - "1 hr ago"           (< 24 hours)
 *   - "Yesterday"          (yesterday)
 *   - "3 days ago"         (< 7 days)
 *   - "Mar 15"             (same year, >= 7 days)
 *   - "Mar 15, 2024"       (different year)
 */
export function formatRelativeTime(dateStr: string): string {
  const date = parseISO(dateStr);
  const now = new Date();
  const diffMs = now.getTime() - date.getTime();
  const diffSec = Math.floor(diffMs / 1000);
  const absDiffSec = Math.abs(diffSec);

  // Future dates (shouldn't happen often, but handle gracefully)
  if (diffSec < 0) {
    if (absDiffSec < 60) return 'in a moment';
    if (absDiffSec < 3600) {
      const mins = Math.floor(absDiffSec / 60);
      return `in ${mins} min`;
    }
    if (absDiffSec < 86400) {
      const hrs = Math.floor(absDiffSec / 3600);
      return `in ${hrs} hr${hrs > 1 ? 's' : ''}`;
    }
    return formatDate(dateStr);
  }

  // Past dates
  if (diffSec < 60) return 'just now';

  const diffMin = Math.floor(diffSec / 60);
  if (diffMin < 60) return `${diffMin} min ago`;

  const diffHr = Math.floor(diffMin / 60);
  if (diffHr < 24) return `${diffHr} hr${diffHr > 1 ? 's' : ''} ago`;

  if (isYesterday(date)) return 'Yesterday';

  const diffDays = Math.floor(diffHr / 24);
  if (diffDays < 7) return `${diffDays} day${diffDays > 1 ? 's' : ''} ago`;

  // Fall back to short date format
  if (isThisYear(date)) return format(date, 'MMM d');
  return format(date, 'MMM d, yyyy');
}

// ─── Absolute Date ───────────────────────────────────────────────────────────

/**
 * Format as "Mar 29, 2026"
 */
export function formatDate(dateStr: string): string {
  const date = parseISO(dateStr);
  return format(date, 'MMM d, yyyy');
}

/**
 * Format as "Mar 29, 2026 at 10:42 AM"
 */
export function formatDateTime(dateStr: string): string {
  const date = parseISO(dateStr);
  if (isThisYear(date)) {
    return format(date, 'MMM d \'at\' h:mm a');
  }
  return format(date, 'MMM d, yyyy \'at\' h:mm a');
}

// ─── Time Only ───────────────────────────────────────────────────────────────

/**
 * Format as "10:42 AM"
 */
export function formatTime(dateStr: string): string {
  const date = parseISO(dateStr);
  return format(date, 'h:mm a');
}

/**
 * Format as "10:42:03 AM" (with seconds)
 */
export function formatTimeWithSeconds(dateStr: string): string {
  const date = parseISO(dateStr);
  return format(date, 'h:mm:ss a');
}

// ─── Short Helpers ───────────────────────────────────────────────────────────

/**
 * Returns "Today", "Yesterday", or the formatted date.
 */
export function formatDayLabel(dateStr: string): string {
  const date = parseISO(dateStr);
  if (isToday(date)) return 'Today';
  if (isYesterday(date)) return 'Yesterday';
  if (isThisYear(date)) return format(date, 'EEEE, MMM d');
  return format(date, 'EEEE, MMM d, yyyy');
}

/**
 * Format as "10 Mar 2026 14:30" (for chat message timestamps)
 */
export function formatChatTimestamp(dateStr: string): string {
  const date = parseISO(dateStr);
  if (isToday(date)) return format(date, 'HH:mm');
  if (isYesterday(date)) return 'Yesterday';
  if (isThisYear(date)) return format(date, 'd MMM');
  return format(date, 'd MMM yyyy');
}

/**
 * Duration in minutes to human-readable string.
 * Example: 125 → "2 hr 5 min"
 */
export function formatDuration(minutes: number): string {
  if (minutes < 1) return '< 1 min';
  const hrs = Math.floor(minutes / 60);
  const mins = Math.round(minutes % 60);
  if (hrs === 0) return `${mins} min`;
  if (mins === 0) return `${hrs} hr`;
  return `${hrs} hr ${mins} min`;
}