//
//  CardData.swift
//  PSCB-OOS-iOS
//
//  Created by Antonov Ilia on 21.10.2020.
//

import Foundation
import PassKit

public enum CardDataError: Error {
    case invalidExiryDate(String)
    case invalidCvCode
    case invalidPan
}

/// Billing info.
/// Detailed card information
public struct CardData {
    let pan: String
    let expiryYear: Int
    let expiryMonth: Int
    let cardholder: String?
    let cvCode: String
    
    /// Constructs card data from all necessary for billing fields
    ///
    /// - Parameters:
    ///     - pan: Card number
    ///     - expiryYear: A full year number (e.g: `2020`). For production cannot be in the past
    ///     - expiryMonth: A month number from 1 to 12.
    ///     - cvCode: CVC/CVV number
    ///     - cardholder: (Optional) Cardholder name in latin.
    ///
    /// - Returns: optional instance of a new card. If validation fails returns nil
    public init?(pan: String, expiryYear: Int, expiryMonth: Int, cvCode: String, cardholder: String? = nil) {
        guard expiryMonth >= 1 && expiryMonth <= 12 else {
            print("Month can be between 1 and 12")
            return nil
        }
        
        #if !DEBUG
        // todo check year + month in the past
        let currentYear = Calendar.current.component(.year, from: Date())
        guard expiryYear >= currentYear else {
            print("Year must be current or in the future")
            return nil
        }
        #endif
        
        self.pan = pan
        self.expiryMonth = expiryMonth
        self.expiryYear = expiryYear
        self.cvCode = cvCode
        self.cardholder = cardholder
    }
    
    /// - Returns: A last 2 digits of the expiry year
    public func getExpYearString() -> String {
        return String(String(expiryYear).dropFirst(2))
    }
    
    /// - Returns: A zero padded expiry month string
    public func getExpMonthString() -> String {
        return expiryMonth < 10 ? "0\(self.expiryMonth)" : String(self.expiryMonth)
    }
    
}

extension CardData {
    
    internal static let pubKey: Data = {
        let key = "MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAPQsWyHaynwoc2tuMbengf1SFase9tPnwtPh4o1tR+94xsWztADdhhUaUBk/68ipaoZE8uSnM9UgdEPmOotFXyUCAwEAAQ=="
        
        return Data(base64Encoded: key)!
    }()
    
    
    /// Produces a cryptogram string from given `CardData`
    /// See: https://docs.pscb.ru/oos/shpa.html#shlyuz-prozrachnoj-avtorizacii-sozdanie-platezha-otvet
    ///
    /// - Returns: a Base64 encoded cryptogram string
    public func toCryptgramString() throws -> String {
        let month = self.getExpMonthString()
        let year  = self.getExpYearString()
        let joinedString = "\(self.pan)|\(month)|\(year)|\(cvCode)\(self.cardholder ?? "")"
        let base64Encode = try RSAHelper.encryptEncodeBase64(message: joinedString)
        
        return base64Encode
    }

}