/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.service.autofill;
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import static android.view.autofill.Helper.sDebug;
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import android.annotation.NonNull;
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import android.annotation.TestApi;
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import android.os.Parcel;
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import android.os.Parcelable;
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import android.util.Log;
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import android.view.autofill.AutofillId;
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import com.android.internal.util.Preconditions;
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import java.util.Arrays;
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/**
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* Validator that returns {@code true} if the number created by concatenating all given fields
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* pass a Luhn algorithm checksum. All non-digits are ignored.
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*
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* <p>See {@link SaveInfo.Builder#setValidator(Validator)} for examples.
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*/
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public final class LuhnChecksumValidator extends InternalValidator implements Validator,
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Parcelable {
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private static final String TAG = "LuhnChecksumValidator";
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private final AutofillId[] mIds;
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/**
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* Default constructor.
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*
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* @param ids id of fields that comprises the number to be checked.
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*/
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public LuhnChecksumValidator(@NonNull AutofillId... ids) {
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mIds = Preconditions.checkArrayElementsNotNull(ids, "ids");
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}
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/**
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* Checks if the Luhn checksum is valid.
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*
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* @param number The number including the checksum
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*/
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private static boolean isLuhnChecksumValid(@NonNull String number) {
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int sum = 0;
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boolean isDoubled = false;
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for (int i = number.length() - 1; i >= 0; i--) {
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final int digit = number.charAt(i) - '0';
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if (digit < 0 || digit > 9) {
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// Ignore non-digits
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continue;
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}
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int addend;
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if (isDoubled) {
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addend = digit * 2;
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if (addend > 9) {
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addend -= 9;
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}
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} else {
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addend = digit;
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}
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sum += addend;
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isDoubled = !isDoubled;
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}
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return sum % 10 == 0;
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}
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/** @hide */
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@Override
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@TestApi
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public boolean isValid(@NonNull ValueFinder finder) {
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if (mIds == null || mIds.length == 0) return false;
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final StringBuilder builder = new StringBuilder();
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for (AutofillId id : mIds) {
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final String partialNumber = finder.findByAutofillId(id);
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if (partialNumber == null) {
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if (sDebug) Log.d(TAG, "No partial number for id " + id);
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return false;
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}
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builder.append(partialNumber);
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}
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final String number = builder.toString();
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boolean valid = isLuhnChecksumValid(number);
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if (sDebug) Log.d(TAG, "isValid(" + number.length() + " chars): " + valid);
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return valid;
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}
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@Override
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public String toString() {
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if (!sDebug) return super.toString();
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return "LuhnChecksumValidator: [ids=" + Arrays.toString(mIds) + "]";
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}
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/////////////////////////////////////
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// Parcelable "contract" methods. //
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/////////////////////////////////////
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@Override
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public int describeContents() {
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return 0;
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}
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@Override
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public void writeToParcel(Parcel parcel, int flags) {
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parcel.writeParcelableArray(mIds, flags);
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}
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public static final @android.annotation.NonNull Parcelable.Creator<LuhnChecksumValidator> CREATOR =
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new Parcelable.Creator<LuhnChecksumValidator>() {
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@Override
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public LuhnChecksumValidator createFromParcel(Parcel parcel) {
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return new LuhnChecksumValidator(parcel.readParcelableArray(null, AutofillId.class));
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}
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@Override
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public LuhnChecksumValidator[] newArray(int size) {
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return new LuhnChecksumValidator[size];
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}
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};
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}
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