tdesktop/Telegram/SourceFiles/data/data_abstract_sparse_ids.h

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/*
This file is part of Telegram Desktop,
the official desktop application for the Telegram messaging service.
For license and copyright information please follow this link:
https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
*/
#pragma once
template <typename IdsContainer>
class AbstractSparseIds {
public:
using Id = typename IdsContainer::value_type;
AbstractSparseIds() = default;
AbstractSparseIds(
const IdsContainer &ids,
std::optional<int> fullCount,
std::optional<int> skippedBefore,
std::optional<int> skippedAfter)
: _ids(ids)
, _fullCount(fullCount)
, _skippedBefore(skippedBefore)
, _skippedAfter(skippedAfter) {
}
[[nodiscard]] std::optional<int> fullCount() const {
return _fullCount;
}
[[nodiscard]] std::optional<int> skippedBefore() const {
return _skippedBefore;
}
[[nodiscard]] std::optional<int> skippedAfter() const {
return _skippedAfter;
}
[[nodiscard]] std::optional<int> indexOf(Id id) const {
const auto it = ranges::find(_ids, id);
if (it != _ids.end()) {
return (it - _ids.begin());
}
return std::nullopt;
}
[[nodiscard]] int size() const {
return _ids.size();
}
[[nodiscard]] Id operator[](int index) const {
Expects(index >= 0 && index < size());
return *(_ids.begin() + index);
}
[[nodiscard]] std::optional<int> distance(Id a, Id b) const {
if (const auto i = indexOf(a)) {
if (const auto j = indexOf(b)) {
return *j - *i;
}
}
return std::nullopt;
}
[[nodiscard]] std::optional<Id> nearest(Id id) const {
static_assert(std::is_same_v<IdsContainer, base::flat_set<MsgId>>);
if (const auto it = ranges::lower_bound(_ids, id); it != _ids.end()) {
return *it;
} else if (_ids.empty()) {
return std::nullopt;
}
return _ids.back();
}
void reverse() {
ranges::reverse(_ids);
std::swap(_skippedBefore, _skippedAfter);
}
private:
IdsContainer _ids;
std::optional<int> _fullCount;
std::optional<int> _skippedBefore;
std::optional<int> _skippedAfter;
};