request_context.hpp

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#pragma once
 
/// @file userver/server/request/request_context.hpp
/// @brief @copybrief server::request::RequestContext
 
#include <string>
#include <string_view>
#include <type_traits>
 
#include <userver/utils/any_movable.hpp>
#include <userver/utils/fast_pimpl.hpp>
#include <userver/utils/statistics/labels.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace server::request {
 
namespace impl {
class InternalRequestContext;
}
 
/// @brief Stores request-specific data during request processing.
///
/// For example: you can store some data in `HandleRequestThrow()` method
/// and access this data in `GetResponseDataForLogging()` method.
class RequestContext final {
public:
    RequestContext();
 
    RequestContext(RequestContext&&) noexcept;
 
    RequestContext(const RequestContext&) = delete;
 
    ~RequestContext();
 
    /// @brief Stores user data if it was not previously stored in this.
    /// @throw std::runtime_error if user data was already stored.
    template <typename Data>
    Data& SetUserData(Data data);
 
    /// @brief Emplaces user data if it was not previously stored in this.
    /// @throw std::runtime_error if user data was already stored.
    template <typename Data, typename... Args>
    Data& EmplaceUserData(Args&&... args);
 
    /// @returns Stored user data
    /// @throws std::runtime_error if no data was stored
    /// @throws std::bad_any_cast if data of different type was stored
    template <typename Data>
    Data& GetUserData();
 
    /// @returns Stored user data
    /// @throws std::runtime_error if no data was stored
    /// @throws std::bad_any_cast if data of different type was stored
    template <typename Data>
    const Data& GetUserData() const;
 
    /// @returns A pointer to data of type Data if it was stored before during
    /// current request processing or nullptr otherwise
    template <typename Data>
    std::remove_reference_t<Data>* GetUserDataOptional();
 
    /// @returns A pointer to data of type Data if it was stored before during
    /// current request processing or nullptr otherwise
    template <typename Data>
    const std::remove_reference_t<Data>* GetUserDataOptional() const;
 
    /// @brief Erases the user data.
    void EraseUserData() noexcept;
 
    /// @brief Stores the data with specified name if it was not previously stored
    /// in this.
    /// @throw std::runtime_error if data with such name was already stored.
    template <typename Data>
    Data& SetData(std::string name, Data data);
 
    /// @brief Emplaces the data with specified name if it was not previously
    /// stored in this.
    /// @throw std::runtime_error if data with such name was already stored.
    template <typename Data, typename... Args>
    Data& EmplaceData(std::string name, Args&&... args);
 
    /// @returns Stored data with specified name.
    /// @throws std::runtime_error if no data was stored
    /// @throws std::bad_any_cast if data of different type was stored
    template <typename Data>
    Data& GetData(std::string_view name);
 
    /// @returns Stored data with specified name.
    /// @throws std::runtime_error if no data was stored
    /// @throws std::bad_any_cast if data of different type was stored
    template <typename Data>
    const Data& GetData(std::string_view name) const;
 
    /// @returns Stored data with specified name or nullptr if no data found.
    /// @throws std::bad_any_cast if data of different type was stored.
    template <typename Data>
    std::remove_reference_t<Data>* GetDataOptional(std::string_view name);
 
    /// @returns Stored data with specified name or nullptr if no data found.
    /// @throws std::bad_any_cast if data of different type was stored.
    template <typename Data>
    const std::remove_reference_t<Data>* GetDataOptional(std::string_view name) const;
 
    /// @brief Erase data with specified name.
    void EraseData(std::string_view name) noexcept;
 
    /// @brief Set the metrics shard (path + labels) for this request.
    /// When set, handler metrics will be accumulated on a new subpath "http.handler.path.*"
    /// and the provided labels would be set to each metric
    /// @note If something (e.g. middleware) interrupts the request before this method is called
    /// then the sharded metrics won't be written
    void SetHandlerMetricsShard(std::string_view path, utils::statistics::LabelsSpan labels);
 
    // TODO : TAXICOMMON-8252
    impl::InternalRequestContext& GetInternalContext() noexcept;
 
private:
    utils::AnyMovable& SetUserAnyData(utils::AnyMovable&& data);
    utils::AnyMovable& GetUserAnyData();
    utils::AnyMovable* GetUserAnyDataOptional() noexcept;
    void EraseUserAnyData() noexcept;
 
    utils::AnyMovable& SetAnyData(std::string&& name, utils::AnyMovable&& data);
    utils::AnyMovable& GetAnyData(std::string_view name);
    utils::AnyMovable* GetAnyDataOptional(std::string_view name) noexcept;
    void EraseAnyData(std::string_view name) noexcept;
 
    class Impl;
    static constexpr std::size_t kPimplSize = 120;
    utils::FastPimpl<Impl, kPimplSize, alignof(void*)> impl_;
};
 
template <typename Data>
Data& RequestContext::SetUserData(Data data) {
    static_assert(
        !std::is_const_v<Data>,
        "Data stored in RequestContext is mutable if RequestContext is "
        "not `const`. Remove the `const` from the template parameter "
        "of SetUserData as it makes no sense"
    );
    static_assert(
        !std::is_reference_v<Data>,
        "Data in RequestContext is stored by copy. Remove the reference "
        "from the template parameter of SetUserData as it makes no sense"
    );
    return utils::AnyCast<Data&>(SetUserAnyData(std::move(data)));
}
 
template <typename Data, typename... Args>
Data& RequestContext::EmplaceUserData(Args&&... args) {
    // NOLINTNEXTLINE(google-readability-casting)
    auto& data = SetUserAnyData(Data(std::forward<Args>(args)...));
    return utils::AnyCast<Data&>(data);
}
 
template <typename Data>
Data& RequestContext::GetUserData() {
    return utils::AnyCast<Data&>(GetUserAnyData());
}
 
template <typename Data>
const Data& RequestContext::GetUserData() const {
    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
    return const_cast<RequestContext*>(this)->GetUserData<Data>();
}
 
template <typename Data>
std::remove_reference_t<Data>* RequestContext::GetUserDataOptional() {
    auto* data = GetUserAnyDataOptional();
    return data ? &utils::AnyCast<Data&>(*data) : nullptr;
}
 
template <typename Data>
const std::remove_reference_t<Data>* RequestContext::GetUserDataOptional() const {
    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
    return const_cast<RequestContext*>(this)->GetUserDataOptional<Data>();
}
 
inline void RequestContext::EraseUserData() noexcept { EraseUserAnyData(); }
 
template <typename Data>
Data& RequestContext::SetData(std::string name, Data data) {
    static_assert(
        !std::is_const_v<Data>,
        "Data stored in RequestContext is mutable if RequestContext is "
        "not `const`. Remove the `const` from the template parameter "
        "of SetData as it makes no sense"
    );
    static_assert(
        !std::is_reference_v<Data>,
        "Data in RequestContext is stored by copy. Remove the reference "
        "from the template parameter of SetData as it makes no sense"
    );
    return utils::AnyCast<Data&>(SetAnyData(std::move(name), std::move(data)));
}
 
template <typename Data, typename... Args>
Data& RequestContext::EmplaceData(std::string name, Args&&... args) {
    // NOLINTNEXTLINE(google-readability-casting)
    auto& data = SetAnyData(std::move(name), Data(std::forward<Args>(args)...));
    return utils::AnyCast<Data&>(data);
}
 
template <typename Data>
Data& RequestContext::GetData(std::string_view name) {
    return utils::AnyCast<Data&>(GetAnyData(name));
}
 
template <typename Data>
const Data& RequestContext::GetData(std::string_view name) const {
    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
    return const_cast<RequestContext*>(this)->GetData<Data>(name);
}
 
template <typename Data>
std::remove_reference_t<Data>* RequestContext::GetDataOptional(std::string_view name) {
    auto* data = GetAnyDataOptional(name);
    return data ? &utils::AnyCast<Data&>(*data) : nullptr;
}
 
template <typename Data>
const std::remove_reference_t<Data>* RequestContext::GetDataOptional(std::string_view name) const {
    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
    return const_cast<RequestContext*>(this)->GetDataOptional<Data>(name);
}
 
inline void RequestContext::EraseData(std::string_view name) noexcept { EraseAnyData(name); }
 
}  // namespace server::request
 
USERVER_NAMESPACE_END