export function formatDistance(meters: number): string {
  if (meters < 1000) return `${Math.round(meters)}m`
  return `${(meters / 1000).toFixed(1)}km`
}

export function formatTime(isoString: string): string {
  const date = new Date(isoString)
  const now = new Date()
  const diffMs = now.getTime() - date.getTime()
  const diffMin = Math.floor(diffMs / 60000)
  const diffHour = Math.floor(diffMin / 60)
  const diffDay = Math.floor(diffHour / 24)

  if (diffMin < 1) return '刚刚'
  if (diffMin < 60) return `${diffMin}分钟前`
  if (diffHour < 24) return `${diffHour}小时前`
  if (diffDay < 7) return `${diffDay}天前`

  const month = date.getMonth() + 1
  const day = date.getDate()
  return `${month}月${day}日`
}

export function formatLastSeen(isoString: string): string {
  const diffMin = Math.floor((Date.now() - new Date(isoString).getTime()) / 60000)
  if (diffMin < 2) return '刚刚在线'
  if (diffMin < 60) return `${diffMin}分钟前`
  const diffHour = Math.floor(diffMin / 60)
  if (diffHour < 24) return `${diffHour}小时前`
  return '昨天在线'
}

export function formatCount(n: number): string {
  if (n < 1000) return String(n)
  if (n < 10000) return `${(n / 1000).toFixed(1)}k`
  return `${Math.floor(n / 10000)}w`
}

export function getAvatarGradient(seed: string): string {
  const gradients = [
    'linear-gradient(135deg, #ffd6e8, #fff1a6)',
    'linear-gradient(135deg, #ffe7a0, #b7f4d2)',
    'linear-gradient(135deg, #c9f7df, #d9d2ff)',
    'linear-gradient(135deg, #cfe8ff, #ffd6e8)',
    'linear-gradient(135deg, #e3d8ff, #c9f7df)',
  ]
  let hash = 0
  for (let i = 0; i < seed.length; i++) hash = (hash * 31 + seed.charCodeAt(i)) & 0xffffffff
  return gradients[Math.abs(hash) % gradients.length]
}

export function getPetEmoji(species: string, breed?: string): string {
  if (species === 'cat') return '🐱'
  if (species === 'other') return '🐾'
  const dogBreedEmoji: Record<string, string> = {
    '比熊': '🐩',
    '柴犬': '🐕',
    '金毛': '🦮',
    '哈士奇': '🐺',
    '萨摩耶': '🐕‍🦺',
  }
  return (breed && dogBreedEmoji[breed]) || '🐶'
}

export function calcDistance(lat1: number, lng1: number, lat2: number, lng2: number): number {
  const R = 6371000
  const dLat = (lat2 - lat1) * Math.PI / 180
  const dLng = (lng2 - lng1) * Math.PI / 180
  const a = Math.sin(dLat / 2) ** 2 +
    Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) * Math.sin(dLng / 2) ** 2
  return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a))
}