1// Copyright (c) 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef BASE_PREFS_JSON_PREF_STORE_H_
6#define BASE_PREFS_JSON_PREF_STORE_H_
7
8#include <set>
9#include <string>
10
11#include "base/basictypes.h"
12#include "base/callback_forward.h"
13#include "base/compiler_specific.h"
14#include "base/files/file_path.h"
15#include "base/files/important_file_writer.h"
16#include "base/memory/scoped_ptr.h"
17#include "base/memory/weak_ptr.h"
18#include "base/message_loop/message_loop_proxy.h"
19#include "base/observer_list.h"
20#include "base/prefs/base_prefs_export.h"
21#include "base/prefs/persistent_pref_store.h"
22#include "base/threading/non_thread_safe.h"
23
24class PrefFilter;
25
26namespace base {
27class DictionaryValue;
28class FilePath;
29class SequencedTaskRunner;
30class SequencedWorkerPool;
31class Value;
32}
33
34// A writable PrefStore implementation that is used for user preferences.
35class BASE_PREFS_EXPORT JsonPrefStore
36    : public PersistentPrefStore,
37      public base::ImportantFileWriter::DataSerializer,
38      public base::SupportsWeakPtr<JsonPrefStore>,
39      public base::NonThreadSafe {
40 public:
41  struct ReadResult;
42
43  // Returns instance of SequencedTaskRunner which guarantees that file
44  // operations on the same file will be executed in sequenced order.
45  static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(
46      const base::FilePath& pref_filename,
47      base::SequencedWorkerPool* worker_pool);
48
49  // Same as the constructor below with no alternate filename.
50  JsonPrefStore(
51      const base::FilePath& pref_filename,
52      const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
53      scoped_ptr<PrefFilter> pref_filter);
54
55  // |sequenced_task_runner| must be a shutdown-blocking task runner, ideally
56  // created by the GetTaskRunnerForFile() method above.
57  // |pref_filename| is the path to the file to read prefs from.
58  // |pref_alternate_filename| is the path to an alternate file which the
59  // desired prefs may have previously been written to. If |pref_filename|
60  // doesn't exist and |pref_alternate_filename| does, |pref_alternate_filename|
61  // will be moved to |pref_filename| before the read occurs.
62  JsonPrefStore(
63      const base::FilePath& pref_filename,
64      const base::FilePath& pref_alternate_filename,
65      const scoped_refptr<base::SequencedTaskRunner>& sequenced_task_runner,
66      scoped_ptr<PrefFilter> pref_filter);
67
68  // PrefStore overrides:
69  virtual bool GetValue(const std::string& key,
70                        const base::Value** result) const OVERRIDE;
71  virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
72  virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
73  virtual bool HasObservers() const OVERRIDE;
74  virtual bool IsInitializationComplete() const OVERRIDE;
75
76  // PersistentPrefStore overrides:
77  virtual bool GetMutableValue(const std::string& key,
78                               base::Value** result) OVERRIDE;
79  virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
80  virtual void SetValueSilently(const std::string& key,
81                                base::Value* value) OVERRIDE;
82  virtual void RemoveValue(const std::string& key) OVERRIDE;
83  virtual bool ReadOnly() const OVERRIDE;
84  virtual PrefReadError GetReadError() const OVERRIDE;
85  // Note this method may be asynchronous if this instance has a |pref_filter_|
86  // in which case it will return PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE.
87  // See details in pref_filter.h.
88  virtual PrefReadError ReadPrefs() OVERRIDE;
89  virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) OVERRIDE;
90  virtual void CommitPendingWrite() OVERRIDE;
91  virtual void ReportValueChanged(const std::string& key) OVERRIDE;
92
93  // Just like RemoveValue(), but doesn't notify observers. Used when doing some
94  // cleanup that shouldn't otherwise alert observers.
95  void RemoveValueSilently(const std::string& key);
96
97  // Registers |on_next_successful_write| to be called once, on the next
98  // successful write event of |writer_|.
99  void RegisterOnNextSuccessfulWriteCallback(
100      const base::Closure& on_next_successful_write);
101
102 private:
103  virtual ~JsonPrefStore();
104
105  // This method is called after the JSON file has been read.  It then hands
106  // |value| (or an empty dictionary in some read error cases) to the
107  // |pref_filter| if one is set. It also gives a callback pointing at
108  // FinalizeFileRead() to that |pref_filter_| which is then responsible for
109  // invoking it when done. If there is no |pref_filter_|, FinalizeFileRead()
110  // is invoked directly.
111  void OnFileRead(scoped_ptr<ReadResult> read_result);
112
113  // ImportantFileWriter::DataSerializer overrides:
114  virtual bool SerializeData(std::string* output) OVERRIDE;
115
116  // This method is called after the JSON file has been read and the result has
117  // potentially been intercepted and modified by |pref_filter_|.
118  // |initialization_successful| is pre-determined by OnFileRead() and should
119  // be used when reporting OnInitializationCompleted().
120  // |schedule_write| indicates whether a write should be immediately scheduled
121  // (typically because the |pref_filter_| has already altered the |prefs|) --
122  // this will be ignored if this store is read-only.
123  void FinalizeFileRead(bool initialization_successful,
124                        scoped_ptr<base::DictionaryValue> prefs,
125                        bool schedule_write);
126
127  const base::FilePath path_;
128  const base::FilePath alternate_path_;
129  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
130
131  scoped_ptr<base::DictionaryValue> prefs_;
132
133  bool read_only_;
134
135  // Helper for safely writing pref data.
136  base::ImportantFileWriter writer_;
137
138  scoped_ptr<PrefFilter> pref_filter_;
139  ObserverList<PrefStore::Observer, true> observers_;
140
141  scoped_ptr<ReadErrorDelegate> error_delegate_;
142
143  bool initialized_;
144  bool filtering_in_progress_;
145  PrefReadError read_error_;
146
147  std::set<std::string> keys_need_empty_value_;
148
149  DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
150};
151
152#endif  // BASE_PREFS_JSON_PREF_STORE_H_
153