http_response.hpp

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#pragma once
 
/// @file userver/server/http/http_response.hpp
/// @brief @copybrief server::http::HttpResponse
 
#include <chrono>
#include <string>
#include <variant>
 
#include <userver/compiler/impl/lifetime.hpp>
#include <userver/concurrent/queue.hpp>
#include <userver/engine/single_consumer_event.hpp>
#include <userver/http/content_type.hpp>
#include <userver/http/header_map.hpp>
#include <userver/server/http/http_response_cookie.hpp>
#include <userver/server/request/response_base.hpp>
#include <userver/utils/impl/projecting_view.hpp>
#include <userver/utils/str_icase.hpp>
 
#include "http_status.hpp"
 
USERVER_NAMESPACE_BEGIN
 
namespace server::http {
 
// RFC 9110 states that in case of missing Content-Type it may be assumed to be
// application/octet-stream.
//
// text/plain was our first guess, but we should provide an encoding with that
// type, which we do not know for sure. "application/octet-stream" has no
// charset https://www.iana.org/assignments/media-types/application/octet-stream
inline constexpr std::string_view kDefaultContentType = "application/octet-stream";
 
class Http2ResponseWriter;
 
namespace impl {
 
void OutputHeader(USERVER_NAMESPACE::http::headers::HeadersString& header, std::string_view key, std::string_view val);
 
/// @brief Event-like helper for waiting until HTTP headers can be sent.
///
/// For streamed responses this happens on the first body chunk (or when the
/// handler finishes). It does not wait for the full response body.
class HeadersEndEvent final {
public:
    explicit HeadersEndEvent(engine::SingleConsumerEvent& event) noexcept : event_(event) {}
 
    [[nodiscard]] bool IsReady() const noexcept { return event_.IsReady(); }
 
    /// @brief Satisfies @ref engine::Awaitable, for use with @ref engine::WaitAny.
    [[nodiscard]] engine::AwaitableToken GetAwaitableToken() noexcept USERVER_IMPL_LIFETIME_BOUND {
        return event_.GetAwaitableToken();
    }
 
    /// @returns whether headers became ready before deadline or cancellation.
    [[nodiscard]] bool Wait() { return event_.WaitForEvent(); }
 
private:
    engine::SingleConsumerEvent& event_;
};
 
}  // namespace impl
 
class HttpRequest;
 
/// @brief HTTP Response data
class HttpResponse final : public request::ResponseBase {
public:
    using HeadersMap = USERVER_NAMESPACE::http::headers::HeaderMap;
 
    using HeadersMapKeys = decltype(utils::impl::MakeKeysView(HeadersMap()));
 
    using CookiesMap = Cookie::CookiesMap;
 
    using CookiesMapKeys = decltype(utils::impl::MakeKeysView(CookiesMap()));
 
    /// @cond
    HttpResponse(const HttpRequest& request, request::ResponseDataAccounter& data_accounter);
    HttpResponse(
        const HttpRequest& request,
        request::ResponseDataAccounter& data_accounter,
        std::chrono::steady_clock::time_point now,
        utils::StrCaseHash hasher
    );
    ~HttpResponse() override;
 
    void SetSendFailed(std::chrono::steady_clock::time_point failure_time) override;
    /// @endcond
 
    /// @brief Add a new response header or rewrite an existing one.
    /// @returns true if the header was set. Returns false if headers
    /// were already sent for stream'ed response and the new header was not set,
    /// or the header overrides system header.
    bool SetHeader(std::string name, std::string value);
 
    /// @brief Add a new response header or rewrite an existing one.
    /// @returns true if the header was set. Returns false if headers
    /// were already sent for stream'ed response and the new header was not set,
    /// or the header overrides system header.
    bool SetHeader(std::string_view name, std::string value);
 
    /// @overload
    bool SetHeader(const USERVER_NAMESPACE::http::headers::PredefinedHeader& header, std::string value);
 
    /// @brief Add or rewrite the Content-Type header.
    void SetContentType(const USERVER_NAMESPACE::http::ContentType& type);
 
    /// @brief Add or rewrite the Content-Encoding header.
    void SetContentEncoding(std::string encoding);
 
    /// @brief Set the HTTP response status code.
    /// @returns true if the status was set. Returns false if headers
    /// were already sent for stream'ed response and the new status was not set.
    bool SetStatus(HttpStatus status) noexcept;
 
    /// @brief Set the end of system headers.
    /// All headers written before this call are considered system; after - user.
    /// User headers can't overwrite system headers.
    void SetSystemHeadersEnd();
 
    /// @brief Remove all headers from response, except system headers.
    /// @returns true if the headers were cleared. Returns false if headers
    /// were already sent for stream'ed response and the headers were not cleared.
    bool ClearUserHeaders();
 
    /// @brief Sets a cookie if it was not set before.
    void SetCookie(Cookie cookie);
 
    /// @brief Remove all cookies from response.
    void ClearCookies();
 
    /// @return HTTP response status
    HttpStatus GetStatus() const { return status_; }
 
    /// @return List of HTTP system headers names.
    HeadersMapKeys GetSystemHeaderNames() const;
 
    /// @return List of HTTP user headers names.
    HeadersMapKeys GetUserHeaderNames() const;
 
    /// @return Value of the header with case insensitive name header_name, or an
    /// empty string if no such header.
    const std::string& GetHeader(std::string_view header_name) const;
    /// @overload
    const std::string& GetHeader(const USERVER_NAMESPACE::http::headers::PredefinedHeader& header_name) const;
 
    /// @return true if header with case insensitive name header_name exists,
    /// false otherwise.
    bool HasHeader(std::string_view header_name) const;
    /// @overload
    bool HasHeader(const USERVER_NAMESPACE::http::headers::PredefinedHeader& header_name) const;
 
    /// @return List of cookies names.
    CookiesMapKeys GetCookieNames() const;
 
    /// @return Value of the cookie with case sensitive name cookie_name, or an
    /// empty string if no such cookie exists.
    const Cookie& GetCookie(std::string_view cookie_name) const;
 
    /// @cond
    // TODO: server internals. remove from public interface
 
    [[nodiscard]] impl::HeadersEndEvent FinishedSendingHeadersEvent() noexcept USERVER_IMPL_LIFETIME_BOUND {
        return impl::HeadersEndEvent{headers_end_};
    }
 
    void SendResponse(engine::io::RwBase& socket) override;
    /// @endcond
 
    void SetStatusServiceUnavailable() override { SetStatus(HttpStatus::kServiceUnavailable); }
    void SetStatusOk() override { SetStatus(HttpStatus::kOk); }
    void SetStatusNotFound() override { SetStatus(HttpStatus::kNotFound); }
 
    bool WaitForHeadersEnd() override;
    void SetHeadersEnd() override;
 
    /// @returns true if response headers were committed and cannot be changed.
    [[nodiscard]] bool IsHeadersEnd() const noexcept { return headers_end_.IsReady(); }
 
    using Queue = concurrent::StringStreamQueue;
    using Producer = std::variant<std::monostate, Queue::Producer, impl::Http2StreamEventProducer>;
 
    void SetStreamBody();
    bool IsBodyStreamed() const override;
    // Can be called only once
    Producer GetBodyProducer();
 
private:
    friend class Http2ResponseWriter;
 
    // Returns total size of the response
    std::size_t SetBodyStreamed(engine::io::RwBase& socket, USERVER_NAMESPACE::http::headers::HeadersString& header);
 
    // Returns total size of the response
    std::size_t SetBodyNotStreamed(engine::io::RwBase& socket, USERVER_NAMESPACE::http::headers::HeadersString& header);
 
    const HttpRequest& request_;
    HttpStatus status_ = HttpStatus::kOk;
    HeadersMap system_headers_;
    HeadersMap user_headers_;
    CookiesMap cookies_;
 
    bool system_headers_ended_ = false;
    engine::SingleConsumerEvent headers_end_{engine::SingleConsumerEvent::NoAutoReset()};
    std::optional<Queue::Consumer> body_stream_;
    Producer body_stream_producer_;
    bool is_stream_body_{false};
};
 
void SetThrottleReason(http::HttpResponse& http_response, std::string log_reason, std::string http_header_reason);
 
}  // namespace server::http
 
USERVER_NAMESPACE_END