/**
 * 通用工具类
 * 此代码由AI生成
 */

/**
 * 格式化时间
 * @param {string|Date} time 
 * @param {string} pattern 
 */
export function formatTime(time, pattern = 'yyyy-MM-dd HH:mm:ss') {
  if (!time) return ''
  const date = new Date(time)
  const o = {
    'M+': date.getMonth() + 1,
    'd+': date.getDate(),
    'H+': date.getHours(),
    'm+': date.getMinutes(),
    's+': date.getSeconds()
  }
  if (/(y+)/.test(pattern)) {
    pattern = pattern.replace(RegExp.$1, (date.getFullYear() + '').substr(4 - RegExp.$1.length))
  }
  for (const k in o) {
    if (new RegExp('(' + k + ')').test(pattern)) {
      pattern = pattern.replace(RegExp.$1, RegExp.$1.length === 1 ? o[k] : ('00' + o[k]).substr(('' + o[k]).length))
    }
  }
  return pattern
}

/**
 * 日期格式化展示（5分钟前，今天 HH:mm 等）
 */
export function displayTime(time) {
  if (!time) return ''
  const date = new Date(time)
  const now = new Date()
  const diff = now.getTime() - date.getTime()
  
  if (diff < 60000) return '刚刚'
  if (diff < 3600000) return Math.floor(diff / 60000) + '分钟前'
  if (now.toDateString() === date.toDateString()) return '今天 ' + formatTime(date, 'HH:mm')
  
  const yesterday = new Date(now.getTime() - 86400000)
  if (yesterday.toDateString() === date.toDateString()) return '昨天 ' + formatTime(date, 'HH:mm')
  
  return formatTime(date, 'MM-dd HH:mm')
}

/**
 * 解密/解码 Base64 字符串为 UTF-8 字符串
 * @param {string} str - Base64 编码的字符串
 * @returns {string}
 */
export function decodeBase64(str) {
  if (!str) return ''
  const cleanStr = String(str).trim().replace(/\s+/g, '')
  // 检查是否为 base64 格式
  const isBase64 = /^[A-Za-z0-9+/=]+$/.test(cleanStr)
  if (!isBase64) return str

  try {
    // 1. Base64 解码为二进制字符串
    const atobPolyfill = (s) => {
      if (typeof atob === 'function') return atob(s)
      const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
      let output = ''
      const clean = s.replace(/=+$/, '')
      for (let bc = 0, bs, buffer, idx = 0; idx < clean.length; ) {
        const char = clean.charAt(idx++)
        const buffer = chars.indexOf(char)
        if (buffer === -1) throw new Error('Invalid base64 character')
        bs = bc % 4 ? bs * 64 + buffer : buffer
        if (bc++ % 4) {
          output += String.fromCharCode(255 & bs >> (-2 * bc & 6))
        }
      }
      return output
    }

    const decodedBinary = atobPolyfill(cleanStr)

    // 2. 将二进制字符串解码为 UTF-8 字符串
    const decodeUtf8 = (bin) => {
      let result = ''
      let i = 0
      while (i < bin.length) {
        const c1 = bin.charCodeAt(i++)
        if (c1 < 128) {
          result += String.fromCharCode(c1)
        } else if (c1 > 191 && c1 < 224) {
          const c2 = bin.charCodeAt(i++)
          result += String.fromCharCode(((c1 & 31) << 6) | (c2 & 63))
        } else if (c1 > 223 && c1 < 240) {
          const c2 = bin.charCodeAt(i++)
          const c3 = bin.charCodeAt(i++)
          result += String.fromCharCode(((c1 & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63))
        } else {
          const c2 = bin.charCodeAt(i++)
          const c3 = bin.charCodeAt(i++)
          const c4 = bin.charCodeAt(i++)
          const codepoint = ((c1 & 7) << 18) | ((c2 & 63) << 12) | ((c3 & 63) << 6) | (c4 & 63)
          if (codepoint > 0xffff) {
            const offset = codepoint - 0x10000
            result += String.fromCharCode((offset >> 10) + 0xd800, (offset & 0x3ff) + 0xdc00)
          } else {
            result += String.fromCharCode(codepoint)
          }
        }
      }
      return result
    }

    return decodeUtf8(decodedBinary)
  } catch (e) {
    console.error('Base64 decode failed:', e)
    return str
  }
}