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
17package com.android.statementservice.retriever;
18
19import android.util.JsonReader;
20import android.util.JsonToken;
21
22import org.json.JSONArray;
23import org.json.JSONException;
24import org.json.JSONObject;
25
26import java.io.IOException;
27import java.util.ArrayList;
28import java.util.List;
29
30/**
31 * A helper class that creates a {@link JSONObject} from a {@link JsonReader}.
32 */
33public final class JsonParser {
34
35    private JsonParser() {}
36
37    /**
38     * Consumes and parses exactly one JSON object from the {@link JsonReader}.
39     * The object's fields can only be objects, strings or arrays of strings.
40     */
41    public static JSONObject parse(JsonReader reader) throws IOException, JSONException {
42        JSONObject output = new JSONObject();
43        String errorMsg = null;
44
45        reader.beginObject();
46        while (reader.hasNext()) {
47            String fieldName = reader.nextName();
48
49            if (output.has(fieldName)) {
50                errorMsg = "Duplicate field name.";
51                reader.skipValue();
52                continue;
53            }
54
55            JsonToken token = reader.peek();
56            if (token.equals(JsonToken.BEGIN_ARRAY)) {
57                output.put(fieldName, new JSONArray(parseArray(reader)));
58            } else if (token.equals(JsonToken.STRING)) {
59                output.put(fieldName, reader.nextString());
60            } else if (token.equals(JsonToken.BEGIN_OBJECT)) {
61                try {
62                    output.put(fieldName, parse(reader));
63                } catch (JSONException e) {
64                    errorMsg = e.getMessage();
65                }
66            } else {
67                reader.skipValue();
68                errorMsg = "Unsupported value type.";
69            }
70        }
71        reader.endObject();
72
73        if (errorMsg != null) {
74            throw new JSONException(errorMsg);
75        }
76
77        return output;
78    }
79
80    /**
81     * Parses one string array from the {@link JsonReader}.
82     */
83    public static List<String> parseArray(JsonReader reader) throws IOException {
84        ArrayList<String> output = new ArrayList<>();
85
86        reader.beginArray();
87        while (reader.hasNext()) {
88            output.add(reader.nextString());
89        }
90        reader.endArray();
91
92        return output;
93    }
94}
95