1// Copyright 2014 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 SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
6#define SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
7
8#include "base/basictypes.h"
9#include "base/callback.h"
10#include "base/memory/scoped_ptr.h"
11#include "base/memory/weak_ptr.h"
12#include "base/sequenced_task_runner.h"
13#include "base/task_runner.h"
14#include "sync/api/attachments/attachment.h"
15#include "sync/base/sync_export.h"
16#include "sync/internal_api/public/attachments/attachment_service.h"
17
18namespace syncer {
19
20// AttachmentServiceProxy wraps an AttachmentService allowing multiple threads
21// to share the wrapped AttachmentService and invoke its methods in the
22// appropriate thread.
23//
24// Callbacks passed to methods on this class will be invoked in the same thread
25// from which the method was called.
26//
27// This class does not own its wrapped AttachmentService object.  This class
28// holds a WeakPtr to the wrapped object.  Once the the wrapped object is
29// destroyed, method calls on this object will be no-ops.
30//
31// Users of this class should take care to destroy the wrapped object on the
32// correct thread (wrapped_task_runner).
33//
34// This class is thread-safe and is designed to be passed by const-ref.
35class SYNC_EXPORT AttachmentServiceProxy : public AttachmentService {
36 public:
37  // Default copy and assignment are welcome.
38
39  // Construct an invalid AttachmentServiceProxy.
40  AttachmentServiceProxy();
41
42  // Construct an AttachmentServiceProxy that forwards calls to |wrapped| on the
43  // |wrapped_task_runner| thread.
44  //
45  // Note, this object does not own |wrapped|.  When |wrapped| is destroyed,
46  // calls to this object become no-ops.
47  AttachmentServiceProxy(
48      const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
49      const base::WeakPtr<syncer::AttachmentService>& wrapped);
50
51  virtual ~AttachmentServiceProxy();
52
53  // AttachmentService implementation.
54  //
55  // GetStore always returns NULL.
56  virtual AttachmentStore* GetStore() OVERRIDE;
57  virtual void GetOrDownloadAttachments(
58      const AttachmentIdList& attachment_ids,
59      const GetOrDownloadCallback& callback) OVERRIDE;
60  virtual void DropAttachments(const AttachmentIdList& attachment_ids,
61                               const DropCallback& callback) OVERRIDE;
62  virtual void UploadAttachments(
63      const AttachmentIdSet& attachment_ids) OVERRIDE;
64
65 protected:
66  // Core does the work of proxying calls to AttachmentService methods from one
67  // thread to another so AttachmentServiceProxy can be an easy-to-use,
68  // non-ref-counted A ref-counted class.
69  //
70  // Callback from AttachmentService are proxied back using free functions
71  // defined in the .cc file (ProxyFooCallback functions).
72  //
73  // Core is ref-counted because we want to allow AttachmentServiceProxy to be
74  // copy-constructable while allowing for different implementations of Core
75  // (e.g. one type of core might own the wrapped AttachmentService).
76  //
77  // Calls to objects of this class become no-ops once its wrapped object is
78  // destroyed.
79  class SYNC_EXPORT Core : public AttachmentService,
80                           public base::RefCountedThreadSafe<Core> {
81   public:
82    // Construct an AttachmentServiceProxyCore that forwards calls to |wrapped|.
83    Core(const base::WeakPtr<syncer::AttachmentService>& wrapped);
84
85    // AttachmentService implementation.
86    virtual AttachmentStore* GetStore() OVERRIDE;
87    virtual void GetOrDownloadAttachments(
88        const AttachmentIdList& attachment_ids,
89        const GetOrDownloadCallback& callback) OVERRIDE;
90    virtual void DropAttachments(const AttachmentIdList& attachment_ids,
91                                 const DropCallback& callback) OVERRIDE;
92    virtual void UploadAttachments(
93        const AttachmentIdSet& attachment_ids) OVERRIDE;
94
95   protected:
96    friend class base::RefCountedThreadSafe<Core>;
97    virtual ~Core();
98
99   private:
100    base::WeakPtr<AttachmentService> wrapped_;
101
102    DISALLOW_COPY_AND_ASSIGN(Core);
103  };
104
105  // Used in tests to create an AttachmentServiceProxy with a custom Core.
106  AttachmentServiceProxy(
107      const scoped_refptr<base::SequencedTaskRunner>& wrapped_task_runner,
108      const scoped_refptr<Core>& core);
109
110 private:
111  scoped_refptr<base::SequencedTaskRunner> wrapped_task_runner_;
112  scoped_refptr<Core> core_;
113};
114
115}  // namespace syncer
116
117#endif  // SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_PROXY_H_
118