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58 lines
1.8 KiB
Kotlin
58 lines
1.8 KiB
Kotlin
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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package org.mozilla.fenix.settings.creditcards
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import androidx.annotation.VisibleForTesting
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import mozilla.components.support.utils.creditCardIIN
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// Number of last digits to be shown when credit card number is obfuscated.
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private const val LAST_VISIBLE_DIGITS_COUNT = 4
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/**
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* Strips characters other than digits from a string.
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* Used to strip a credit card number user input of spaces and separators.
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*/
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fun String.toCreditCardNumber(): String {
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return this.filter { it.isDigit() }
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}
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/**
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* Returns the last 4 digits from a formatted credit card number string.
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*/
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fun String.last4Digits(): String {
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return this.takeLast(LAST_VISIBLE_DIGITS_COUNT)
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}
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/**
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* Returns true if the provided string is a valid credit card by checking if it has a matching
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* credit card issuer network passes the Luhn Algorithm, and false otherwise.
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*/
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fun String.validateCreditCardNumber(): Boolean {
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val creditCardNumber = this.toCreditCardNumber()
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if (creditCardNumber != this || creditCardNumber.creditCardIIN() == null) {
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return false
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}
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return luhnAlgorithmValidation(creditCardNumber)
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}
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/**
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* Implementation of Luhn Algorithm validation (https://en.wikipedia.org/wiki/Luhn_algorithm)
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*/
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@Suppress("MagicNumber")
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@VisibleForTesting
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internal fun luhnAlgorithmValidation(creditCardNumber: String): Boolean {
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var checksum = 0
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val reversedCardNumber = creditCardNumber.reversed()
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for (index in reversedCardNumber.indices) {
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val digit = Character.getNumericValue(reversedCardNumber[index])
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checksum += if (index % 2 == 0) digit else (digit * 2).let { (it / 10) + (it % 10) }
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}
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return (checksum % 10) == 0
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}
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