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      1 /*
      2  * Copyright (C) 2015 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 
     17 package com.android.statementservice.retriever;
     18 
     19 import android.annotation.NonNull;
     20 
     21 /**
     22  * An immutable value type representing a statement, consisting of a source, target, and relation.
     23  * This reflects an assertion that the relation holds for the source, target pair. For example, if a
     24  * web site has the following in its assetlinks.json file:
     25  *
     26  * <pre>
     27  * {
     28  * "relation": ["delegate_permission/common.handle_all_urls"],
     29  * "target"  : {"namespace": "android_app", "package_name": "com.example.app",
     30  *              "sha256_cert_fingerprints": ["00:11:22:33"] }
     31  * }
     32  * </pre>
     33  *
     34  * Then invoking {@link AbstractStatementRetriever#retrieveStatements(AbstractAsset)} will return a
     35  * {@link Statement} with {@link #getSource} equal to the input parameter, {@link #getRelation}
     36  * equal to
     37  *
     38  * <pre>Relation.create("delegate_permission", "common.get_login_creds");</pre>
     39  *
     40  * and with {@link #getTarget} equal to
     41  *
     42  * <pre>AbstractAsset.create("{\"namespace\" : \"android_app\","
     43  *                           + "\"package_name\": \"com.example.app\"}"
     44  *                           + "\"sha256_cert_fingerprints\": \"[\"00:11:22:33\"]\"}");
     45  * </pre>
     46  */
     47 public final class Statement {
     48 
     49     private final AbstractAsset mTarget;
     50     private final Relation mRelation;
     51     private final AbstractAsset mSource;
     52 
     53     private Statement(AbstractAsset source, AbstractAsset target, Relation relation) {
     54         mSource = source;
     55         mTarget = target;
     56         mRelation = relation;
     57     }
     58 
     59     /**
     60      * Returns the source asset of the statement.
     61      */
     62     @NonNull
     63     public AbstractAsset getSource() {
     64         return mSource;
     65     }
     66 
     67     /**
     68      * Returns the target asset of the statement.
     69      */
     70     @NonNull
     71     public AbstractAsset getTarget() {
     72         return mTarget;
     73     }
     74 
     75     /**
     76      * Returns the relation of the statement.
     77      */
     78     @NonNull
     79     public Relation getRelation() {
     80         return mRelation;
     81     }
     82 
     83     /**
     84      * Creates a new Statement object for the specified target asset and relation. For example:
     85      * <pre>
     86      *   Asset asset = Asset.Factory.create(
     87      *       "{\"namespace\" : \"web\",\"site\": \"https://www.test.com\"}");
     88      *   Relation relation = Relation.create("delegate_permission", "common.get_login_creds");
     89      *   Statement statement = Statement.create(asset, relation);
     90      * </pre>
     91      */
     92     public static Statement create(@NonNull AbstractAsset source, @NonNull AbstractAsset target,
     93                                    @NonNull Relation relation) {
     94         return new Statement(source, target, relation);
     95     }
     96 
     97     @Override
     98     public boolean equals(Object o) {
     99         if (this == o) {
    100             return true;
    101         }
    102         if (o == null || getClass() != o.getClass()) {
    103             return false;
    104         }
    105 
    106         Statement statement = (Statement) o;
    107 
    108         if (!mRelation.equals(statement.mRelation)) {
    109             return false;
    110         }
    111         if (!mTarget.equals(statement.mTarget)) {
    112             return false;
    113         }
    114         if (!mSource.equals(statement.mSource)) {
    115             return false;
    116         }
    117 
    118         return true;
    119     }
    120 
    121     @Override
    122     public int hashCode() {
    123         int result = mTarget.hashCode();
    124         result = 31 * result + mRelation.hashCode();
    125         result = 31 * result + mSource.hashCode();
    126         return result;
    127     }
    128 
    129     @Override
    130     public String toString() {
    131         StringBuilder statement = new StringBuilder();
    132         statement.append("Statement: ");
    133         statement.append(mSource);
    134         statement.append(", ");
    135         statement.append(mTarget);
    136         statement.append(", ");
    137         statement.append(mRelation);
    138         return statement.toString();
    139     }
    140 }
    141