CBU Validator

CBUValidator.swift

//
//  CBUValidator.swift
//  CBU Scanner
//
//  Created by Fernando Zafe on 21/08/2023.
//

import Foundation

class CBUValidator {
    
    typealias CBU = [UInt8]
    typealias BankNumber = [UInt8]
    typealias BranchNumber = [UInt8]
    typealias AccountNumber = [UInt8]
    typealias BlockOneVerificationNumber = UInt8
    typealias BlockTwoVerificationNumber = UInt8
    typealias BlockOneIsValid = Bool
    typealias BlockTwoIsValid = Bool
    typealias CBUIsValid = Bool
    
    private func cutNumber(from text: String) -> String {
        let start = text.index(text.startIndex, offsetBy: 0)
        let end = text.index(text.startIndex, offsetBy: 22)
        let range = start..<end
        return String(text[range])
    }
    
    private func transformToCBU(from text: String) -> CBU {
        let cbu = text.map { UInt8(String($0))! }
        return cbu
    }
    
    private func getBankNumber(from cbu: CBU) -> BankNumber {
        Array(cbu[0..<3])
    }
    
    private func getBranchNumber(from cbu: CBU) -> BranchNumber {
        Array(cbu[3..<7])
    }
    
    private func getBlockOneVerificationNumber(from cbu: CBU) -> BlockOneVerificationNumber {
        cbu[7]
    }
    
    private func getAccountNumber(from cbu: CBU) -> AccountNumber {
        Array(cbu[8..<21])
    }
    
    private func getBlockTwoVerificationNumber(from cbu: CBU) -> BlockTwoVerificationNumber {
        cbu[21]
    }
    
    private func verifyFirstBlock(bankNumber: BankNumber, branchNumber: BranchNumber, blockOneVerificationNumber: BlockOneVerificationNumber) -> BlockOneIsValid {
        
        let sumBank: UInt8 =
            bankNumber[0] * 7 +
            bankNumber[1] * 1 +
            bankNumber[2] * 3
        
        let sumBranch: UInt8 =
            branchNumber[0] * 9 +
            branchNumber[1] * 7 +
            branchNumber[2] * 1 +
            branchNumber[3] * 3
        
        let sum = sumBank + sumBranch
        
        let remainder = sum % 10
        
        let substract = 10 - remainder
        
        return
            blockOneVerificationNumber == 0 ?
            substract == 10 :
            substract == blockOneVerificationNumber
    }
    
    private func verifySecondBlock(accountNumber: AccountNumber, blockTwoVerificationNumber: BlockTwoVerificationNumber) -> BlockTwoIsValid {
        
        var sum : UInt =  UInt(3 * (accountNumber[0] + accountNumber[4] + accountNumber[8] + accountNumber[12]))
            sum = sum + UInt(9 * (accountNumber[1] + accountNumber[5] + accountNumber[9]))
            sum = sum + UInt(7 * (accountNumber[2] + accountNumber[6] + accountNumber[10]))
            sum = sum + UInt(accountNumber[3] + accountNumber[7] + accountNumber[11])
        
        let remainder = sum % 10
        
        let substract = 10 - remainder
        
        return
            blockTwoVerificationNumber == 0 ?
            substract == 10 :
            substract == blockTwoVerificationNumber
        
    }
    
    public func verifyCBU(_ text: String) -> CBUIsValid {
        
        let cbu = transformToCBU(from: text)
        
        let bankNumber = getBankNumber(from: cbu)
        let branchNumber = getBranchNumber(from: cbu)
        let blockOneVerificationNumber = getBlockOneVerificationNumber(from: cbu)
        let accountNumber = getAccountNumber(from: cbu)
        let blockTwoVerificationNumber = getBlockTwoVerificationNumber(from: cbu)
        
        let blockOneIsValid = verifyFirstBlock(bankNumber: bankNumber, branchNumber: branchNumber, blockOneVerificationNumber: blockOneVerificationNumber)
        let blockTwoIsValid = verifySecondBlock(accountNumber: accountNumber, blockTwoVerificationNumber: blockTwoVerificationNumber)
        
        return blockOneIsValid && blockTwoIsValid
    }
    
}