/*
 * Copyright 2019-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
 */

#pragma once

#include "alternator/executor.hh"
#include "utils/scoped_item_list.hh"
#include <seastar/core/future.hh>
#include <seastar/core/condition-variable.hh>
#include <seastar/http/httpd.hh>
#include <seastar/net/tls.hh>
#include <optional>
#include "alternator/auth.hh"
#include "service/qos/service_level_controller.hh"
#include "utils/small_vector.hh"
#include "utils/updateable_value.hh"
#include <seastar/core/units.hh>

struct client_data;

namespace alternator {

using chunked_content = rjson::chunked_content;

class server : public peering_sharded_service<server> {
    // The maximum size of a request body that Alternator will accept,
    // in bytes. This is a safety measure to prevent Alternator from
    // running out of memory when a client sends a very large request.
    // DynamoDB also has the same limit set to 16 MB.
    static constexpr size_t request_content_length_limit = 16*MB;
    using alternator_callback = std::function<future<executor::request_return_type>(executor&, executor::client_state&,
            tracing::trace_state_ptr, service_permit, rjson::value, std::unique_ptr<http::request>)>;
    using alternator_callbacks_map = std::unordered_map<std::string_view, alternator_callback>;

    httpd::http_server _http_server;
    httpd::http_server _https_server;
    executor& _executor;
    service::storage_proxy& _proxy;
    gms::gossiper& _gossiper;
    auth::service& _auth_service;
    qos::service_level_controller& _sl_controller;

    key_cache _key_cache;
    utils::updateable_value<bool> _enforce_authorization;
    utils::updateable_value<bool> _warn_authorization;
    utils::updateable_value<uint64_t> _max_users_query_size_in_trace_output;
    utils::small_vector<std::reference_wrapper<seastar::httpd::http_server>, 2> _enabled_servers;
    named_gate _pending_requests;
    // In some places we will need a CQL updateable_timeout_config object even
    // though it isn't really relevant for Alternator which defines its own
    // timeouts separately. We can create this object only once.
    updateable_timeout_config _timeout_config;

    alternator_callbacks_map _callbacks;

    semaphore* _memory_limiter;
    utils::updateable_value<uint32_t> _max_concurrent_requests;

    ::shared_ptr<seastar::tls::server_credentials> _credentials;

    class json_parser {
        static constexpr size_t yieldable_parsing_threshold = 16*KB;
        chunked_content _raw_document;
        rjson::value _parsed_document;
        std::exception_ptr _current_exception;
        semaphore _parsing_sem{1};
        condition_variable _document_waiting;
        condition_variable _document_parsed;
        abort_source _as;
        future<> _run_parse_json_thread;
    public:
        json_parser();
        // Moving a chunked_content into parse() allows parse() to free each
        // chunk as soon as it is parsed, so when chunks are relatively small,
        // we don't need to store the sum of unparsed and parsed sizes.
        future<rjson::value> parse(chunked_content&& content);
        future<> stop();
    };
    json_parser _json_parser;

    // The server maintains a list of ongoing requests, that are being handled
    // by handle_api_request(). It uses this list in get_client_data(), which
    // is called when reading the "system.clients" virtual table.
    struct ongoing_request {
        socket_address _client_address;
        sstring _user_agent;
        sstring _username;
        scheduling_group _scheduling_group;
        bool _is_https;
        client_data make_client_data() const;
    };
    utils::scoped_item_list<ongoing_request> _ongoing_requests;

public:
    server(executor& executor, service::storage_proxy& proxy, gms::gossiper& gossiper, auth::service& service, qos::service_level_controller& sl_controller);

    future<> init(net::inet_address addr, std::optional<uint16_t> port, std::optional<uint16_t> https_port, std::optional<tls::credentials_builder> creds,
            utils::updateable_value<bool> enforce_authorization, utils::updateable_value<bool> warn_authorization, utils::updateable_value<uint64_t> max_users_query_size_in_trace_output,
            semaphore* memory_limiter, utils::updateable_value<uint32_t> max_concurrent_requests);
    future<> stop();
    // get_client_data() is called (on each shard separately) when the virtual
    // table "system.clients" is read. It is expected to generate a list of
    // clients connected to this server (on this shard). This function is
    // called by alternator::controller::get_client_data().
    future<utils::chunked_vector<client_data>> get_client_data();
private:
    void set_routes(seastar::httpd::routes& r);
    // If verification succeeds, returns the authenticated user's username
    future<std::string> verify_signature(const seastar::http::request&, const chunked_content&);
    future<executor::request_return_type> handle_api_request(std::unique_ptr<http::request> req);
};

}