Add a Model to the download component.

components/download/internal/model_impl.cc

Index: components/download/internal/model_impl.cc
diff --git a/components/download/internal/model_impl.cc b/components/download/internal/model_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d8137fcc8bf6063fa34ae11726bef563effbea6f
--- /dev/null
+++ b/components/download/internal/model_impl.cc
@@ -0,0 +1,118 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/download/internal/model_impl.h"
+
+#include "base/bind.h"
+#include "base/memory/ptr_util.h"
+#include "components/download/internal/entry.h"
+
+namespace download {
+
+ModelImpl::ModelImpl(Client* client, std::unique_ptr<Store> store)
+    : client_(client), store_(std::move(store)), weak_ptr_factory_(this) {
+  DCHECK(client_);
+  DCHECK(store_);
+}
+
+ModelImpl::~ModelImpl() = default;
+
+void ModelImpl::Initialize() {
+  DCHECK(!store_->IsInitialized());
+  store_->Initialize(base::Bind(&ModelImpl::OnInitializedFinished,
+                                weak_ptr_factory_.GetWeakPtr()));
+}
+
+void ModelImpl::Destroy() {
+  store_->Destroy(base::Bind(&ModelImpl::OnDestroyFinished,
+                             weak_ptr_factory_.GetWeakPtr()));
+}
+
+void ModelImpl::Add(const Entry& entry) {
+  DCHECK(entries_.find(entry.guid) == entries_.end());
+
+  entries_.insert(OwnedEntryPair(entry.guid, base::MakeUnique<Entry>(entry)));

[xingliu, 2017/05/09 06:11:41]

nit: maybe consider std::map::emplace.

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

Done.

+  store_->Update(entry, base::Bind(&ModelImpl::OnAddFinished,
+                                   weak_ptr_factory_.GetWeakPtr(), entry.client,
+                                   entry.guid));
+}
+
+void ModelImpl::Update(const Entry& entry) {
+  // TODO(dtrainor): Should we validate that no updates can occur to an entry
+  // that is currently in the process of being added?

[Peter Beverloo, 2017/05/10 12:44:45]

While the Client definitely should wait for the acknowledgements, in practice
this does little harm. The ProtoDB will run on a sequenced task runner so
there's a guarantee that the update will run after the add.

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

Yeah I can probably remove this now that it's simpler.  Thanks!

+  DCHECK(entries_.find(entry.guid) != entries_.end());
+
+  entries_[entry.guid] = base::MakeUnique<Entry>(entry);
+  store_->Update(entry, base::Bind(&ModelImpl::OnUpdateFinished,
+                                   weak_ptr_factory_.GetWeakPtr(), entry.client,
+                                   entry.guid));
+}
+
+void ModelImpl::Remove(const std::string& guid) {
+  const auto& it = entries_.find(guid);
+  DCHECK(it != entries_.end());
+
+  DownloadClient client = it->second->client;
+  entries_.erase(it);
+  store_->Remove(guid,
+                 base::Bind(&ModelImpl::OnRemoveFinished,
+                            weak_ptr_factory_.GetWeakPtr(), client, guid));
+}
+
+Entry* ModelImpl::Get(const std::string& guid) {
+  const auto& it = entries_.find(guid);
+  return it == entries_.end() ? nullptr : it->second.get();
+}
+
+Model::EntryList ModelImpl::PeekEntries() {
+  EntryList entries;
+  for (const auto& it : entries_)
+    entries.push_back(it.second.get());
+
+  return entries;
+}
+
+void ModelImpl::OnInitializedFinished(
+    bool success,
+    std::unique_ptr<std::vector<Entry>> entries) {
+  if (!success) {
+    client_->OnInitialized(false);
+    return;
+  }
+
+  for (const auto& entry : *entries) {
+    entries_.insert(OwnedEntryPair(entry.guid, base::MakeUnique<Entry>(entry)));
+  }
+  client_->OnInitialized(true);
+}
+
+void ModelImpl::OnDestroyFinished(bool success) {
+  store_.reset();
+  entries_.clear();
+  client_->OnDestroyed(success);
+}
+
+void ModelImpl::OnAddFinished(DownloadClient client,
+                              const std::string& guid,
+                              bool success) {
+  // TODO(dtrainor): If the add fails, should we automatically remove it from
+  // this map?

[Peter Beverloo, 2017/05/10 12:44:45]

I'd argue so. Current behaviour is:

auto model = base::MakeUnique<ModelImpl>(..);
model->Add(entry) --> false
model->Get(entry.guid) --> it was added??

[David Trainor- moved to gerrit, 2017/05/15 15:59:51]

I think the hard part is:
model->Add(entry) --> async write starts
model->Get(entry.guid) --> Has the value before the async returns
model->OnAddFinished(false) --> We remove it

I guess as long as I'm 100% clear on the semantics of the operation it should be
ok.  Either that or notifying OnEntryRemoved() on the client to clear it up.

+  client_->OnItemAdded(success, client, guid);
+}
+
+void ModelImpl::OnUpdateFinished(DownloadClient client,
+                                 const std::string& guid,
+                                 bool success) {
+  if (!success)
+    client_->OnStoreUpdateFailed(client, guid);
+}
+
+void ModelImpl::OnRemoveFinished(DownloadClient client,
+                                 const std::string& guid,
+                                 bool success) {
+  if (!success)
+    client_->OnStoreUpdateFailed(client, guid);
+}
+
+}  // namespace download