ClickHouse/src/Server/HTTPHandlerFactory.h

#pragma once

#include <Interpreters/AsynchronousMetrics.h>
#include <Server/HTTP/HTMLForm.h>
#include <Server/HTTP/HTTPRequestHandlerFactory.h>
#include <Server/HTTPHandlerRequestFilter.h>
#include <Common/StringUtils/StringUtils.h>
#include <common/logger_useful.h>

#include <Poco/Util/LayeredConfiguration.h>

namespace DB
{

namespace ErrorCodes
{
    extern const int UNKNOWN_ELEMENT_IN_CONFIG;
}

class IServer;

/// Handle request using child handlers
class HTTPRequestHandlerFactoryMain : public HTTPRequestHandlerFactory
{
public:
    explicit HTTPRequestHandlerFactoryMain(const std::string & name_);

    void addHandler(HTTPRequestHandlerFactoryPtr child_factory) { child_factories.emplace_back(child_factory); }

    std::unique_ptr<HTTPRequestHandler> createRequestHandler(const HTTPServerRequest & request) override;

private:
    Poco::Logger * log;
    std::string name;

    std::vector<HTTPRequestHandlerFactoryPtr> child_factories;
};

template <typename TEndpoint>
class HandlingRuleHTTPHandlerFactory : public HTTPRequestHandlerFactory
{
public:
    using Filter = std::function<bool(const HTTPServerRequest &)>;

    template <typename... TArgs>
    explicit HandlingRuleHTTPHandlerFactory(TArgs &&... args)
    {
        creator = [args = std::tuple<TArgs...>(std::forward<TArgs>(args) ...)]()
        {
            return std::apply([&](auto && ... endpoint_args)
            {
                return std::make_unique<TEndpoint>(std::forward<decltype(endpoint_args)>(endpoint_args)...);
            }, std::move(args));
        };
    }

    void addFilter(Filter cur_filter)
    {
        Filter prev_filter = filter;
        filter = [prev_filter, cur_filter](const auto & request)
        {
            return prev_filter ? prev_filter(request) && cur_filter(request) : cur_filter(request);
        };
    }

    void addFiltersFromConfig(Poco::Util::AbstractConfiguration & config, const std::string & prefix)
    {
        Poco::Util::AbstractConfiguration::Keys filters_type;
        config.keys(prefix, filters_type);

        for (const auto & filter_type : filters_type)
        {
            if (filter_type == "handler")
                continue;
            else if (filter_type == "url")
                addFilter(urlFilter(config, prefix + ".url"));
            else if (filter_type == "headers")
                addFilter(headersFilter(config, prefix + ".headers"));
            else if (filter_type == "methods")
                addFilter(methodsFilter(config, prefix + ".methods"));
            else
                throw Exception("Unknown element in config: " + prefix + "." + filter_type, ErrorCodes::UNKNOWN_ELEMENT_IN_CONFIG);
        }
    }

    void attachStrictPath(const String & strict_path)
    {
        addFilter([strict_path](const auto & request) { return request.getURI() == strict_path; });
    }

    void attachNonStrictPath(const String & non_strict_path)
    {
        addFilter([non_strict_path](const auto & request) { return startsWith(request.getURI(), non_strict_path); });
    }

    /// Handle GET or HEAD endpoint on specified path
    void allowGetAndHeadRequest()
    {
        addFilter([](const auto & request)
        {
            return request.getMethod() == Poco::Net::HTTPRequest::HTTP_GET
                || request.getMethod() == Poco::Net::HTTPRequest::HTTP_HEAD;
        });
    }

    /// Handle POST or GET with params
    void allowPostAndGetParamsRequest()
    {
        addFilter([](const auto & request)
        {
            return request.getURI().find('?') != std::string::npos
                || request.getMethod() == Poco::Net::HTTPRequest::HTTP_POST;
        });
    }

    std::unique_ptr<HTTPRequestHandler> createRequestHandler(const HTTPServerRequest & request) override
    {
        return filter(request) ? creator() : nullptr;
    }

private:
    Filter filter;
    std::function<std::unique_ptr<HTTPRequestHandler> ()> creator;
};

HTTPRequestHandlerFactoryPtr createStaticHandlerFactory(IServer & server, const std::string & config_prefix);

HTTPRequestHandlerFactoryPtr createDynamicHandlerFactory(IServer & server, const std::string & config_prefix);

HTTPRequestHandlerFactoryPtr createPredefinedHandlerFactory(IServer & server, const std::string & config_prefix);

HTTPRequestHandlerFactoryPtr createReplicasStatusHandlerFactory(IServer & server, const std::string & config_prefix);

HTTPRequestHandlerFactoryPtr
createPrometheusHandlerFactory(IServer & server, AsynchronousMetrics & async_metrics, const std::string & config_prefix);

HTTPRequestHandlerFactoryPtr createHandlerFactory(IServer & server, AsynchronousMetrics & async_metrics, const std::string & name);
}