export function bytesToBase64(bytes) {
  let binary = ''
  for (let i = 0; i < bytes.length; i++) binary += String.fromCharCode(bytes[i])
  return btoa(binary)
}

export function base64ToBytes(str) {
  const clean = str.replace(/\s/g, '')
  const binary = atob(clean)
  const bytes = new Uint8Array(binary.length)
  for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i)
  return bytes
}

export function encodeBase64(text) {
  return btoa(unescape(encodeURIComponent(text)))
}

export function decodeBase64(text) {
  return decodeURIComponent(escape(atob(text)))
}

export function encodeUrl(text) {
  return encodeURIComponent(text)
}

export function decodeUrl(text) {
  return decodeURIComponent(text)
}

export function encodeUnicode(text) {
  let result = ''
  let i = 0
  
  while (i < text.length) {
    const codePoint = text.codePointAt(i)
    
    if (codePoint > 0xFFFF) {
      // 超出 BMP 的字符，使用代理对表示
      const high = Math.floor((codePoint - 0x10000) / 0x400) + 0xD800
      const low = ((codePoint - 0x10000) % 0x400) + 0xDC00
      result += '\\u' + high.toString(16).toUpperCase().padStart(4, '0')
      result += '\\u' + low.toString(16).toUpperCase().padStart(4, '0')
      i += 2 // 代理对占用两个字符位置
    } else {
      // BMP 字符
      result += '\\u' + codePoint.toString(16).toUpperCase().padStart(4, '0')
      i++
    }
  }
  
  return result
}

export function decodeUnicode(text) {
  try {
    let result = ''
    let i = 0
    
    while (i < text.length) {
      // 匹配 \uXXXX 格式
      if (text[i] === '\\' && i + 1 < text.length && text[i + 1] === 'u' && i + 5 < text.length) {
        const hex = text.substring(i + 2, i + 6)
        if (/^[0-9a-fA-F]{4}$/.test(hex)) {
          const code1 = parseInt(hex, 16)
          
          // 检查是否是高代理（surrogate high）
          if (code1 >= 0xD800 && code1 <= 0xDBFF && i + 11 < text.length) {
            // 检查下一个是否是低代理
            if (text[i + 6] === '\\' && text[i + 7] === 'u') {
              const hex2 = text.substring(i + 8, i + 12)
              if (/^[0-9a-fA-F]{4}$/.test(hex2)) {
                const code2 = parseInt(hex2, 16)
                // 检查是否是低代理（surrogate low）
                if (code2 >= 0xDC00 && code2 <= 0xDFFF) {
                  // 组合代理对
                  const codePoint = 0x10000 + ((code1 - 0xD800) << 10) + (code2 - 0xDC00)
                  result += String.fromCodePoint(codePoint)
                  i += 12
                  continue
                }
              }
            }
          }
          
          // 普通字符或单独的代理
          result += String.fromCharCode(code1)
          i += 6
          continue
        }
      }
      
      // 匹配 \UXXXXXXXX 格式（8位十六进制）
      if (text[i] === '\\' && i + 1 < text.length && text[i + 1] === 'U' && i + 9 < text.length) {
        const hex = text.substring(i + 2, i + 10)
        if (/^[0-9a-fA-F]{8}$/.test(hex)) {
          const code = parseInt(hex, 16)
          if (code > 0x10FFFF) {
            throw new Error('无效的 Unicode 码点：超出范围')
          }
          result += String.fromCodePoint(code)
          i += 10
          continue
        }
      }
      
      // 普通字符
      result += text[i]
      i++
    }
    
    return result
  } catch (e) {
    throw new Error('Unicode 解码失败：' + e.message)
  }
}