OTP/OTPKit/TOTPKey.swift

//
//  TOTPKey.swift
//  OTPKit
//
//  Created by Shadowfacts on 8/21/21.
//

import Foundation

public struct TOTPKey: OTPKey, Equatable, Hashable, Codable {
    public let secret: Data
    public let period: Int
    public let digits: Int
    public let algorithm: OTPAlgorithm
    public let label: String?
    public let issuer: String
//    let image: Data?
    
    public init(secret: Data, period: Int, digits: Int, label: String?, issuer: String) {
        self.secret = secret
        self.period = period
        self.digits = digits
        self.algorithm = .SHA1
        self.label = label
        self.issuer = issuer
    }
}

public extension TOTPKey {
    
    init?(urlComponents: URLComponents) {
        guard urlComponents.scheme == "otpauth",
              urlComponents.host == "totp",
              let queryItems = urlComponents.queryItems else {
            return nil
        }
        
        var label: String?
        var issuer: String
        var secret: Data?
        var period: Int = 30
        var digits = 6
        
        let path = urlComponents.path.drop(while: { $0 == "/" })
        let components = path.components(separatedBy: ":")
        if components.count > 1 {
            issuer = components[0]
            label = components[1]
        } else {
            issuer = components[0]
        }
        
        for item in queryItems {
            guard let value = item.value else { continue }
            switch item.name.lowercased() {
            case "algorithm":
                if value.lowercased() != "sha1" {
                    return  nil
                }
            case "digits":
                if let newDigits = Int(value) {
                    digits = newDigits
                }
            case "issuer":
                issuer = value
            case "period":
                if let newPeriod = Int(value) {
                    period = newPeriod
                }
            case "secret":
                if let data = value.base32DecodedData {
                    secret = data
                }
            default:
                continue
            }
        }
        
        guard let secret = secret else { return nil }
        self.issuer = issuer
        self.label = label
        self.secret = secret
        self.period = period
        self.digits = digits
        self.algorithm = .SHA1
    }
    
    var url: URL {
        var components = URLComponents()
        
        components.scheme = "otpauth"
        components.host = "totp"
        
        if let label = label, !label.isEmpty {
            components.path = "/\(issuer):\(label)"
        } else {
            components.path = "/\(issuer)"
        }
        components.queryItems = [
            URLQueryItem(name: "algorithm", value: "SHA1"),
            URLQueryItem(name: "digits", value: digits.description),
            URLQueryItem(name: "issuer", value: issuer),
            URLQueryItem(name: "period", value: period.description),
            URLQueryItem(name: "secret", value: secret.base32EncodedString),
        ]
        
        return components.url!
    }
    
}