chromium/components/feed/core/v2/stream_model/feature_tree.h

// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_
#define COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_

#include <map>
#include <string>
#include <utility>
#include <vector>

#include "base/memory/raw_ptr.h"
#include "base/types/id_type.h"
#include "components/feed/core/proto/v2/store.pb.h"
#include "components/feed/core/v2/proto_util.h"
#include "components/feed/core/v2/types.h"

namespace feed {
namespace stream_model {

// Uniquely identifies a feedwire::ContentId. Provided by |ContentMap|.
ContentTag;
ContentRevision;

// Owns instances of feedstore::Content pointed to by the feature tree, and
// maps ContentId into ContentTag.
class ContentMap { … };

// A node in FeatureTree.
struct StreamNode { … };

// The feature tree which underlies StreamModel.
// This tree is different than most, the rules are as follows:
// * A node may or may not have a parent, so this is more of a forest than a
//   tree.
// * When nodes are removed, their set of children are remembered. If the node
//   is added again, it retains its old children.
// * A node can be added multiple times, but subsequent adds will not change
//   the node's parent.
// * There is only one 'stream root' acknowledged, even though there can be many
//   roots. The stream root is the last root node added of type STREAM. The
//   stream root identifies the tree whose nodes are used to compute
//   |GetVisibleContent()|.
// * A tree can be constructed with a base tree. This copies features from base,
//   but refers to content stored in base by reference.
class FeatureTree { … };

}  // namespace stream_model
}  // namespace feed

#endif  // COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_