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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.util.JsonReader;
     20 
     21 import org.json.JSONArray;
     22 import org.json.JSONException;
     23 import org.json.JSONObject;
     24 
     25 import java.io.IOException;
     26 import java.io.StringReader;
     27 import java.util.ArrayList;
     28 import java.util.List;
     29 
     30 /**
     31  * Utility class that parses JSON-formatted statements.
     32  */
     33 /* package private */ final class StatementParser {
     34 
     35     private static final String FIELD_NOT_STRING_FORMAT_STRING = "Expected %s to be string.";
     36     private static final String FIELD_NOT_ARRAY_FORMAT_STRING = "Expected %s to be array.";
     37 
     38     /**
     39      * Parses a JSON array of statements.
     40      */
     41     static ParsedStatement parseStatementList(String statementList, AbstractAsset source)
     42             throws JSONException, IOException {
     43         List<Statement> statements = new ArrayList<Statement>();
     44         List<String> delegates = new ArrayList<String>();
     45 
     46         JsonReader reader = new JsonReader(new StringReader(statementList));
     47         reader.setLenient(false);
     48 
     49         reader.beginArray();
     50         while (reader.hasNext()) {
     51             ParsedStatement result;
     52             try {
     53                 result = parseStatement(reader, source);
     54             } catch (AssociationServiceException e) {
     55                 // The element in the array is well formatted Json but not a well-formed Statement.
     56                 continue;
     57             }
     58             statements.addAll(result.getStatements());
     59             delegates.addAll(result.getDelegates());
     60         }
     61         reader.endArray();
     62 
     63         return new ParsedStatement(statements, delegates);
     64     }
     65 
     66     /**
     67      * Parses a single JSON statement.
     68      */
     69     static ParsedStatement parseStatement(String statementString, AbstractAsset source)
     70             throws AssociationServiceException, IOException, JSONException {
     71         JsonReader reader = new JsonReader(new StringReader(statementString));
     72         reader.setLenient(false);
     73         return parseStatement(reader, source);
     74     }
     75 
     76     /**
     77      * Parses a single JSON statement. This method guarantees that exactly one JSON object
     78      * will be consumed.
     79      */
     80     static ParsedStatement parseStatement(JsonReader reader, AbstractAsset source)
     81             throws JSONException, AssociationServiceException, IOException {
     82         List<Statement> statements = new ArrayList<Statement>();
     83         List<String> delegates = new ArrayList<String>();
     84 
     85         JSONObject statement = JsonParser.parse(reader);
     86 
     87         if (statement.optString(Utils.DELEGATE_FIELD_DELEGATE, null) != null) {
     88             delegates.add(statement.optString(Utils.DELEGATE_FIELD_DELEGATE));
     89         } else {
     90             JSONObject targetObject = statement.optJSONObject(Utils.ASSET_DESCRIPTOR_FIELD_TARGET);
     91             if (targetObject == null) {
     92                 throw new AssociationServiceException(String.format(
     93                         FIELD_NOT_STRING_FORMAT_STRING, Utils.ASSET_DESCRIPTOR_FIELD_TARGET));
     94             }
     95 
     96             JSONArray relations = statement.optJSONArray(Utils.ASSET_DESCRIPTOR_FIELD_RELATION);
     97             if (relations == null) {
     98                 throw new AssociationServiceException(String.format(
     99                         FIELD_NOT_ARRAY_FORMAT_STRING, Utils.ASSET_DESCRIPTOR_FIELD_RELATION));
    100             }
    101 
    102             AbstractAsset target = AssetFactory.create(targetObject);
    103             for (int i = 0; i < relations.length(); i++) {
    104                 statements.add(Statement
    105                         .create(source, target, Relation.create(relations.getString(i))));
    106             }
    107         }
    108 
    109         return new ParsedStatement(statements, delegates);
    110     }
    111 }
    112