import { type ClassValue, clsx } from "clsx";
import { twMerge } from "tailwind-merge";

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

export function formatDate(dateString: string): string {
  if (!dateString) return 'N/A';
  const date = new Date(dateString);
  return date.toLocaleDateString('en-ZA', {
    day: '2-digit',
    month: 'short',
    year: 'numeric',
  });
}

export function formatDateTime(dateString: string): string {
  if (!dateString) return 'N/A';
  const date = new Date(dateString);
  return date.toLocaleString('en-ZA', {
    day: '2-digit',
    month: 'short',
    year: 'numeric',
    hour: '2-digit',
    minute: '2-digit',
  });
}

export function formatCurrency(amount: number): string {
  return new Intl.NumberFormat('en-ZA', {
    style: 'currency',
    currency: 'ZAR',
  }).format(amount);
}

export function getRelativeTime(dateString: string): string {
  const date = new Date(dateString);
  const now = new Date();
  const diffInSeconds = Math.floor((now.getTime() - date.getTime()) / 1000);

  if (diffInSeconds < 60) return 'Just now';
  if (diffInSeconds < 3600) return `${Math.floor(diffInSeconds / 60)}m ago`;
  if (diffInSeconds < 86400) return `${Math.floor(diffInSeconds / 3600)}h ago`;
  if (diffInSeconds < 604800) return `${Math.floor(diffInSeconds / 86400)}d ago`;
  return formatDate(dateString);
}

export function debounce<T extends (...args: unknown[]) => unknown>(
  func: T,
  wait: number
): (...args: Parameters<T>) => void {
  let timeout: ReturnType<typeof setTimeout>;
  return (...args: Parameters<T>) => {
    clearTimeout(timeout);
    timeout = setTimeout(() => func(...args), wait);
  };
}

export function groupBy<T>(array: T[], key: keyof T): Record<string, T[]> {
  return array.reduce((result, item) => {
    const groupKey = String(item[key]);
    if (!result[groupKey]) {
      result[groupKey] = [];
    }
    result[groupKey].push(item);
    return result;
  }, {} as Record<string, T[]>);
}

export function calculateDistance(
  lat1: number,
  lon1: number,
  lat2: number,
  lon2: number
): number {
  const R = 6371; // Earth's radius in km
  const dLat = (lat2 - lat1) * Math.PI / 180;
  const dLon = (lon2 - lon1) * Math.PI / 180;
  const a =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
    Math.sin(dLon / 2) * Math.sin(dLon / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  return R * c;
}

/**
 * Parse coordinates from a text field.
 * Supports formats like:
 *   "-33.9249, 18.4241"
 *   "-33.9249 18.4241"
 *   "lat: -33.9249, lng: 18.4241"
 * Returns null if parsing fails.
 */
export function parseCoordinates(coordString: string | undefined): { latitude: number; longitude: number } | null {
  if (!coordString) return null;

  const matches = coordString.match(/-?\d+\.?\d*/g);
  if (matches && matches.length >= 2) {
    const lat = parseFloat(matches[0]);
    const lng = parseFloat(matches[1]);
    if (!isNaN(lat) && !isNaN(lng)) {
      return { latitude: lat, longitude: lng };
    }
  }

  return null;
}

export interface ProximityCluster<T> {
  id: string;
  items: T[];
  center: { latitude: number; longitude: number };
  label: string;
}

export function clusterByProximity<T extends { id: string; expand?: { supplier?: { coordinates?: string; suppliername?: string } } }>(
  items: T[],
  radiusKm: number = 2
): ProximityCluster<T>[] {
  const withCoords: Array<{ item: T; coords: { latitude: number; longitude: number } }> = [];
  const withoutCoords: T[] = [];

  for (const item of items) {
    const coords = parseCoordinates(item.expand?.supplier?.coordinates);
    if (coords) {
      withCoords.push({ item, coords });
    } else {
      withoutCoords.push(item);
    }
  }

  const assigned = new Set<string>();
  const clusters: ProximityCluster<T>[] = [];

  for (const seed of withCoords) {
    if (assigned.has(seed.item.id)) continue;

    const clusterItems: Array<{ item: T; coords: { latitude: number; longitude: number } }> = [seed];
    assigned.add(seed.item.id);

    for (const candidate of withCoords) {
      if (assigned.has(candidate.item.id)) continue;
      const dist = calculateDistance(
        seed.coords.latitude, seed.coords.longitude,
        candidate.coords.latitude, candidate.coords.longitude
      );
      if (dist <= radiusKm) {
        clusterItems.push(candidate);
        assigned.add(candidate.item.id);
      }
    }

    const centerLat = clusterItems.reduce((s, p) => s + p.coords.latitude, 0) / clusterItems.length;
    const centerLng = clusterItems.reduce((s, p) => s + p.coords.longitude, 0) / clusterItems.length;

    const supplierNames = Array.from(
      new Set(
        clusterItems
          .map(c => c.item.expand?.supplier?.suppliername)
          .filter((n): n is string => !!n)
      )
    );

    clusters.push({
      id: `cluster-${clusters.length}`,
      items: clusterItems.map(c => c.item),
      center: { latitude: centerLat, longitude: centerLng },
      label: supplierNames.length === 1
        ? supplierNames[0]
        : supplierNames.length > 1
          ? `${supplierNames[0]} +${supplierNames.length - 1}`
          : `Stop ${clusters.length + 1}`,
    });
  }

  if (withoutCoords.length > 0) {
    clusters.push({
      id: 'cluster-no-coords',
      items: withoutCoords,
      center: { latitude: 0, longitude: 0 },
      label: 'No location',
    });
  }

  return clusters;
}