/**
 * Generate a deterministic offset based on a unique identifier.
 * This ensures the same ID always gets the same offset,
 * allowing multiple users in the same city to be spread out
 * while maintaining consistent positions.
 *
 * @param id - Unique identifier (e.g., claw ID)
 * @param maxOffsetKm - Maximum offset in kilometers (default: 15km)
 * @returns Object with lat and lng offsets in degrees
 */
export function generateDeterministicOffset(
  id: string,
  maxOffsetKm: number = 15
): { latOffset: number; lngOffset: number } {
  // Simple hash function to convert string to number
  let hash = 0;
  for (let i = 0; i < id.length; i++) {
    const char = id.charCodeAt(i);
    hash = ((hash << 5) - hash) + char;
    hash = hash & hash; // Convert to 32-bit integer
  }

  // Use the hash to generate two pseudo-random values between -1 and 1
  // Using simple modulo arithmetic for determinism
  const seed1 = Math.abs(hash % 10000) / 10000; // 0 to 1
  const seed2 = Math.abs((hash >> 8) % 10000) / 10000; // 0 to 1

  // Convert to -1 to 1 range with better distribution
  const factor1 = (seed1 * 2 - 1);
  const factor2 = (seed2 * 2 - 1);

  // Convert km to degrees (approximate)
  // 1 degree latitude ≈ 111km
  // 1 degree longitude varies by latitude (cos(lat) * 111km)
  // We use a rough average here
  const kmPerDegree = 111;
  const maxOffsetDegrees = maxOffsetKm / kmPerDegree;

  return {
    latOffset: factor1 * maxOffsetDegrees,
    lngOffset: factor2 * maxOffsetDegrees,
  };
}

/**
 * Apply deterministic offset to coordinates.
 * This spreads out users in the same city while keeping
 * each user's position consistent.
 *
 * @param lat - Original latitude
 * @param lng - Original longitude
 * @param id - Unique identifier for deterministic offset
 * @param maxOffsetKm - Maximum offset in kilometers
 * @returns New coordinates with offset applied
 */
export function applyDeterministicOffset(
  lat: number,
  lng: number,
  id: string,
  maxOffsetKm: number = 15
): { lat: number; lng: number } {
  const { latOffset, lngOffset } = generateDeterministicOffset(id, maxOffsetKm);

  // Adjust longitude offset based on latitude
  // (longitude degrees get smaller towards poles)
  const lngCorrection = Math.cos((lat * Math.PI) / 180);

  return {
    lat: lat + latOffset,
    lng: lng + lngOffset * lngCorrection,
  };
}