Base64URL.swift

//
//  Base64URLUtils.swift
//  CodeRepo
//
//  Created by tramp on 23/04/2018.
//  Copyright © 2018 tramp. All rights reserved.
//

import Foundation


/// 转换base64URL编码的字符串为base64编码的字符串
///
/// - Parameter base64URL: base64URL编码的字符串
/// - Returns: base64编码的字符串
func convertBase64URLToBase64(_ base64URL: String) -> String {
    
    var result = base64URL
        .then(from: "-", to: "+")
        .then(from: "_", to: "/")
        .then(from: "\n", to: "")
        .then(from: "\r", to: "")
    var equalsToBeAdded = base64URL.count % 4
    /// 根据base64编码规则，末尾的=只有0， 1，2三种可能
    if equalsToBeAdded > 0 {
        if equalsToBeAdded == 3 {
            equalsToBeAdded = 1
        }
        (0..<equalsToBeAdded).forEach{ _ in result.append("=")}
    }
    return result
}


/// 转换base64编码的字符串为base64URL编码的字符串
///
/// - Parameter base64: base64编码的字符串
/// - Returns: base64URL编码的字符串

func convertBase64ToBase64URL(_ base64: String) -> String {
    let result = base64
        .then(from: "+", to: "-")
        .then(from: "/", to: "_")
        .then(from: "=", to: "")
    return result
}

extension String {
    func then(from: String, to: String) -> String {
        return self.replacingOccurrences(of: from, with: to, options: .literal, range: range(of: self))
    }
}

base64 ⇋ base64URL