1 /*
2  * Copyright (C) 2019 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package android.ext.services.autofill;
17 
18 import android.os.Bundle;
19 import android.view.autofill.AutofillValue;
20 
21 import androidx.annotation.Nullable;
22 import androidx.annotation.VisibleForTesting;
23 
24 final class CreditCardMatcher {
25 
26     /**
27      * Required arg for {@link #calculateScore} that provides the min and max lengths for
28      * credit card number.
29      *
30      * <p>must be non-negative and less than or equal to
31      * {@link #REQUIRED_ARG_MAX_CREDIT_CARD_LENGTH}.</p>
32      *
33      * <p>Must supply an int.</p>
34      */
35     public static final String REQUIRED_ARG_MIN_CREDIT_CARD_LENGTH = "REQUIRED_ARG_MIN_CC_LENGTH";
36 
37     /**
38      * Required arg for {@link #calculateScore} that provides the max length for
39      * credit card number.
40      *
41      * <p>must be non-negative and greater or equal to
42      * {@link #REQUIRED_ARG_MIN_CREDIT_CARD_LENGTH}.</p>
43      *
44      * <p>Must supply an int.</p>
45      */
46     public static final String REQUIRED_ARG_MAX_CREDIT_CARD_LENGTH = "REQUIRED_ARG_MAX_CC_LENGTH";
47 
48     /**
49      * Optional arg for {@link #calculateScore} that provides the suffix length e.g. last N digits
50      * of the credit card number.
51      *
52      * <p>If argument is not provided, the suffix length defaults to 4.</p>
53      *
54      * <p>Must supply an int.</p>
55      */
56     public static final String OPTIONAL_ARG_SUFFIX_LENGTH = "OPTIONAL_ARG_SUFFIX_LENGTH";
57 
58     /**
59      * Gets the field classification score of a credit card number string and a string representing
60      * the last four digits of the credit card.
61      *
62      * @return {@code 1.0} if the last four digits of the credit card matches with the given four
63      * digits, and the length of the credit card number is within the given requirements,
64      * {@code 0.0} otherwise.
65      *
66      * @param actualValue credit card number.
67      * @param userDataValue four digit string.
68      */
69     @VisibleForTesting
calculateScore(@ullable AutofillValue actualValue, @Nullable String userDataValue, @Nullable Bundle args)70     static float calculateScore(@Nullable AutofillValue actualValue,
71             @Nullable String userDataValue, @Nullable Bundle args) {
72         if (actualValue == null || !actualValue.isText() || userDataValue == null || args == null) {
73             return 0;
74         }
75         final String actualValueText = actualValue.getTextValue().toString();
76 
77         final int minCreditCardLength = args.getInt(REQUIRED_ARG_MIN_CREDIT_CARD_LENGTH, -1);
78         final int maxCreditCardLength = args.getInt(REQUIRED_ARG_MAX_CREDIT_CARD_LENGTH, -1);
79         if (minCreditCardLength < 0 || maxCreditCardLength < minCreditCardLength) {
80             throw new IllegalArgumentException("bad length arguments");
81         }
82 
83         final int actualValueLength = actualValueText.length();
84         final int userDataLength = userDataValue.length();
85         final int suffixLength = args.getInt(OPTIONAL_ARG_SUFFIX_LENGTH, 4);
86         if (suffixLength <= 0) {
87             throw new IllegalArgumentException("bad suffix length argument");
88         }
89 
90         // Satisfies length checks.
91         if (actualValueLength != suffixLength || userDataLength < minCreditCardLength
92                 || userDataLength > maxCreditCardLength || userDataLength < actualValueLength) {
93             return 0;
94         }
95         final String userDataLastN = userDataValue.substring(
96                 userDataLength - suffixLength);
97 
98         // Last 4 digits are equal.
99         return actualValueText.equalsIgnoreCase(userDataLastN) ? 1 : 0;
100     }
101 }
102