// Copyright (c) 2015-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <httpserver.h>

#include <chainparamsbase.h>

#include <common/args.h>

#include <common/messages.h>

#include <compat/compat.h>

#include <logging.h>

#include <netbase.h>

#include <node/interface_ui.h>

#include <rpc/protocol.h>

#include <sync.h>

#include <util/check.h>

#include <util/signalinterrupt.h>

#include <util/strencodings.h>

#include <util/threadnames.h>

#include <util/threadpool.h>

#include <util/translation.h>

#include <condition_variable>

#include <cstdio>

#include <cstdlib>

#include <deque>

#include <memory>

#include <optional>

#include <span>

#include <string>

#include <thread>

#include <unordered_map>

#include <vector>

#include <sys/types.h>

#include <sys/stat.h>

#include <event2/buffer.h>

#include <event2/bufferevent.h>

#include <event2/http.h>

#include <event2/http_struct.h>

#include <event2/keyvalq_struct.h>

#include <event2/thread.h>

#include <event2/util.h>

#include <support/events.h>

using common::InvalidPortErrMsg;

/** Maximum size of http request (request line + headers) */

static const size_t MAX_HEADERS_SIZE = 8192;

struct HTTPPathHandler

{

    HTTPPathHandler(std::string _prefix, bool _exactMatch, HTTPRequestHandler _handler):

        prefix(_prefix), exactMatch(_exactMatch), handler(_handler)

    {

    }

    std::string prefix;

    bool exactMatch;

    HTTPRequestHandler handler;

};

/** HTTP module state */

//! libevent event loop

static struct event_base* eventBase = nullptr;

//! HTTP server

static struct evhttp* eventHTTP = nullptr;

//! List of subnets to allow RPC connections from

static std::vector<CSubNet> rpc_allow_subnets;

//! Handlers for (sub)paths

static GlobalMutex g_httppathhandlers_mutex;

static std::vector<HTTPPathHandler> pathHandlers GUARDED_BY(g_httppathhandlers_mutex);

//! Bound listening sockets

static std::vector<evhttp_bound_socket *> boundSockets;

/// \anchor http_pool

//! Http thread pool - future: encapsulate in HttpContext

static ThreadPool g_threadpool_http("http");

static int g_max_queue_depth{100};

/**

 * @brief Helps keep track of open `evhttp_connection`s with active `evhttp_requests`

 *

 */

class HTTPRequestTracker

{

private:

    mutable Mutex m_mutex;

    mutable std::condition_variable m_cv;

    //! For each connection, keep a counter of how many requests are open

    std::unordered_map<const evhttp_connection*, size_t> m_tracker GUARDED_BY(m_mutex);

    void RemoveConnectionInternal(const decltype(m_tracker)::iterator it) EXCLUSIVE_LOCKS_REQUIRED(m_mutex)

    {

        m_tracker.erase(it);

        if (m_tracker.empty()) m_cv.notify_all();

    }

public:

    //! Increase request counter for the associated connection by 1

    void AddRequest(evhttp_request* req) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

    {

        const evhttp_connection* conn{Assert(evhttp_request_get_connection(Assert(req)))};

        WITH_LOCK(m_mutex, ++m_tracker[conn]);

    }

    //! Decrease request counter for the associated connection by 1, remove connection if counter is 0

    void RemoveRequest(evhttp_request* req) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

    {

        const evhttp_connection* conn{Assert(evhttp_request_get_connection(Assert(req)))};

        LOCK(m_mutex);

        auto it{m_tracker.find(conn)};

        if (it != m_tracker.end() && it->second > 0) {

            if (--(it->second) == 0) RemoveConnectionInternal(it);

        }

    }

    //! Remove a connection entirely

    void RemoveConnection(const evhttp_connection* conn) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

    {

        LOCK(m_mutex);

        auto it{m_tracker.find(Assert(conn))};

        if (it != m_tracker.end()) RemoveConnectionInternal(it);

    }

    size_t CountActiveConnections() const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

    {

        return WITH_LOCK(m_mutex, return m_tracker.size());

    }

    //! Wait until there are no more connections with active requests in the tracker

    void WaitUntilEmpty() const EXCLUSIVE_LOCKS_REQUIRED(!m_mutex)

    {

        WAIT_LOCK(m_mutex, lock);

        m_cv.wait(lock, [this]() EXCLUSIVE_LOCKS_REQUIRED(m_mutex) { return m_tracker.empty(); });

    }

};

//! Track active requests

static HTTPRequestTracker g_requests;

/** Check if a network address is allowed to access the HTTP server */

static bool ClientAllowed(const CNetAddr& netaddr)

{

    if (!netaddr.IsValid())

        return false;

    for(const CSubNet& subnet : rpc_allow_subnets)

        if (subnet.Match(netaddr))

            return true;

    return false;

}

/** Initialize ACL list for HTTP server */

static bool InitHTTPAllowList()

{

    rpc_allow_subnets.clear();

    rpc_allow_subnets.emplace_back(LookupHost("127.0.0.1", false).value(), 8);  // always allow IPv4 local subnet

    rpc_allow_subnets.emplace_back(LookupHost("::1", false).value());  // always allow IPv6 localhost

    for (const std::string& strAllow : gArgs.GetArgs("-rpcallowip")) {

        const CSubNet subnet{LookupSubNet(strAllow)};

        if (!subnet.IsValid()) {

            uiInterface.ThreadSafeMessageBox(

                Untranslated(strprintf("Invalid -rpcallowip subnet specification: %s. Valid values are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0), a network/CIDR (e.g. 1.2.3.4/24), all ipv4 (0.0.0.0/0), or all ipv6 (::/0). RFC4193 is allowed only if -cjdnsreachable=0.", strAllow)),

                CClientUIInterface::MSG_ERROR);

            return false;

        }

        rpc_allow_subnets.push_back(subnet);

    }

    std::string strAllowed;

    for (const CSubNet& subnet : rpc_allow_subnets)

        strAllowed += subnet.ToString() + " ";

    LogDebug(BCLog::HTTP, "Allowing HTTP connections from: %s\n", strAllowed);

    return true;

}

/** HTTP request method as string - use for logging only */

std::string RequestMethodString(HTTPRequest::RequestMethod m)

{

    switch (m) {

    case HTTPRequest::GET:

        return "GET";

    case HTTPRequest::POST:

        return "POST";

    case HTTPRequest::HEAD:

        return "HEAD";

    case HTTPRequest::PUT:

        return "PUT";

    case HTTPRequest::UNKNOWN:

        return "unknown";

    } // no default case, so the compiler can warn about missing cases

    assert(false);

}

/** HTTP request callback */

static void http_request_cb(struct evhttp_request* req, void* arg)

{

    evhttp_connection* conn{evhttp_request_get_connection(req)};

    // Track active requests

    {

        g_requests.AddRequest(req);

        evhttp_request_set_on_complete_cb(req, [](struct evhttp_request* req, void*) {

            g_requests.RemoveRequest(req);

        }, nullptr);

        evhttp_connection_set_closecb(conn, [](evhttp_connection* conn, void* arg) {

            g_requests.RemoveConnection(conn);

        }, nullptr);

    }

    // Disable reading to work around a libevent bug, fixed in 2.1.9

    // See https://github.com/libevent/libevent/commit/5ff8eb26371c4dc56f384b2de35bea2d87814779

    // and https://github.com/bitcoin/bitcoin/pull/11593.

    if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02010900) {

        if (conn) {

            bufferevent* bev = evhttp_connection_get_bufferevent(conn);

            if (bev) {

                bufferevent_disable(bev, EV_READ);

            }

        }

    }

    auto hreq{std::make_shared<HTTPRequest>(req, *static_cast<const util::SignalInterrupt*>(arg))};

    // Early address-based allow check

    if (!ClientAllowed(hreq->GetPeer())) {

        LogDebug(BCLog::HTTP, "HTTP request from %s rejected: Client network is not allowed RPC access\n",

                 hreq->GetPeer().ToStringAddrPort());

        hreq->WriteReply(HTTP_FORBIDDEN);

        return;

    }

    // Early reject unknown HTTP methods

    if (hreq->GetRequestMethod() == HTTPRequest::UNKNOWN) {

        LogDebug(BCLog::HTTP, "HTTP request from %s rejected: Unknown HTTP request method\n",

                 hreq->GetPeer().ToStringAddrPort());

        hreq->WriteReply(HTTP_BAD_METHOD);

        return;

    }

    LogDebug(BCLog::HTTP, "Received a %s request for %s from %s\n",

             RequestMethodString(hreq->GetRequestMethod()), SanitizeString(hreq->GetURI(), SAFE_CHARS_URI).substr(0, 100), hreq->GetPeer().ToStringAddrPort());

    // Find registered handler for prefix

    std::string strURI = hreq->GetURI();

    std::string path;

    LOCK(g_httppathhandlers_mutex);

    std::vector<HTTPPathHandler>::const_iterator i = pathHandlers.begin();

    std::vector<HTTPPathHandler>::const_iterator iend = pathHandlers.end();

    for (; i != iend; ++i) {

        bool match = false;

        if (i->exactMatch)

            match = (strURI == i->prefix);

        else

            match = strURI.starts_with(i->prefix);

        if (match) {

            path = strURI.substr(i->prefix.size());

            break;

        }

    }

    // Dispatch to worker thread

    if (i != iend) {

        if (static_cast<int>(g_threadpool_http.WorkQueueSize()) >= g_max_queue_depth) {

            LogWarning("Request rejected because http work queue depth exceeded, it can be increased with the -rpcworkqueue= setting");

            hreq->WriteReply(HTTP_SERVICE_UNAVAILABLE, "Work queue depth exceeded");

            return;

        }

        auto item = [req = hreq, in_path = std::move(path), fn = i->handler]() {

            std::string err_msg;

            try {

                fn(req.get(), in_path);

                return;

            } catch (const std::exception& e) {

                LogWarning("Unexpected error while processing request for '%s'. Error msg: '%s'", req->GetURI(), e.what());

                err_msg = e.what();

            } catch (...) {

                LogWarning("Unknown error while processing request for '%s'", req->GetURI());

                err_msg = "unknown error";

            }

            // Reply so the client doesn't hang waiting for the response.

            req->WriteHeader("Connection", "close");

            // TODO: Implement specific error formatting for the REST and JSON-RPC servers responses.

            req->WriteReply(HTTP_INTERNAL_SERVER_ERROR, err_msg);

        };

        if (auto res = g_threadpool_http.Submit(std::move(item)); !res.has_value()) {

            Assume(hreq.use_count() == 1); // ensure request will be deleted

            // Both SubmitError::Inactive and SubmitError::Interrupted mean shutdown

            LogWarning("HTTP request rejected during server shutdown: '%s'", SubmitErrorString(res.error()));

            hreq->WriteReply(HTTP_SERVICE_UNAVAILABLE, "Request rejected during server shutdown");

            return;

        }

    } else {

        hreq->WriteReply(HTTP_NOT_FOUND);

    }

}

/** Callback to reject HTTP requests after shutdown. */

static void http_reject_request_cb(struct evhttp_request* req, void*)

{

    LogDebug(BCLog::HTTP, "Rejecting request while shutting down\n");

    evhttp_send_error(req, HTTP_SERVUNAVAIL, nullptr);

}

/// \anchor http

/** Event dispatcher thread */

static void ThreadHTTP(struct event_base* base)

{

    util::ThreadRename("http");

    LogDebug(BCLog::HTTP, "Entering http event loop\n");

    event_base_dispatch(base);

    // Event loop will be interrupted by InterruptHTTPServer()

    LogDebug(BCLog::HTTP, "Exited http event loop\n");

}

/** Bind HTTP server to specified addresses */

static bool HTTPBindAddresses(struct evhttp* http)

{

    uint16_t http_port{static_cast<uint16_t>(gArgs.GetIntArg("-rpcport", BaseParams().RPCPort()))};

    std::vector<std::pair<std::string, uint16_t>> endpoints;

    // Determine what addresses to bind to

    // To prevent misconfiguration and accidental exposure of the RPC

    // interface, require -rpcallowip and -rpcbind to both be specified

    // together. If either is missing, ignore both values, bind to localhost

    // instead, and log warnings.

    if (gArgs.GetArgs("-rpcallowip").empty() || gArgs.GetArgs("-rpcbind").empty()) { // Default to loopback if not allowing external IPs

        endpoints.emplace_back("::1", http_port);

        endpoints.emplace_back("127.0.0.1", http_port);

        if (!gArgs.GetArgs("-rpcallowip").empty()) {

            LogWarning("Option -rpcallowip was specified without -rpcbind; this doesn't usually make sense");

        }

        if (!gArgs.GetArgs("-rpcbind").empty()) {

            LogWarning("Option -rpcbind was ignored because -rpcallowip was not specified, refusing to allow everyone to connect");

        }

    } else { // Specific bind addresses

        for (const std::string& strRPCBind : gArgs.GetArgs("-rpcbind")) {

            uint16_t port{http_port};

            std::string host;

            if (!SplitHostPort(strRPCBind, port, host)) {

                LogError("%s\n", InvalidPortErrMsg("-rpcbind", strRPCBind).original);

                return false;

            }

            endpoints.emplace_back(host, port);

        }

    }

    // Bind addresses

    for (std::vector<std::pair<std::string, uint16_t> >::iterator i = endpoints.begin(); i != endpoints.end(); ++i) {

        LogInfo("Binding RPC on address %s port %i", i->first, i->second);

        evhttp_bound_socket *bind_handle = evhttp_bind_socket_with_handle(http, i->first.empty() ? nullptr : i->first.c_str(), i->second);

        if (bind_handle) {

            const std::optional<CNetAddr> addr{LookupHost(i->first, false)};

            if (i->first.empty() || (addr.has_value() && addr->IsBindAny())) {

                LogWarning("The RPC server is not safe to expose to untrusted networks such as the public internet");

            }

            // Set the no-delay option (disable Nagle's algorithm) on the TCP socket.

            evutil_socket_t fd = evhttp_bound_socket_get_fd(bind_handle);

            int one = 1;

            if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, reinterpret_cast<char*>(&one), sizeof(one)) == SOCKET_ERROR) {

                LogInfo("WARNING: Unable to set TCP_NODELAY on RPC server socket, continuing anyway\n");

            }

            boundSockets.push_back(bind_handle);

        } else {

            LogWarning("Binding RPC on address %s port %i failed.", i->first, i->second);

        }

    }

    return !boundSockets.empty();

}

/** libevent event log callback */

static void libevent_log_cb(int severity, const char *msg)

{

    switch (severity) {

    case EVENT_LOG_DEBUG:

        LogDebug(BCLog::LIBEVENT, "%s", msg);

        break;

    case EVENT_LOG_MSG:

        LogInfo("libevent: %s", msg);

        break;

    case EVENT_LOG_WARN:

        LogWarning("libevent: %s", msg);

        break;

    default: // EVENT_LOG_ERR and others are mapped to error

        LogError("libevent: %s", msg);

        break;

    }

}

bool InitHTTPServer(const util::SignalInterrupt& interrupt)

{

    if (!InitHTTPAllowList())

        return false;

    // Redirect libevent's logging to our own log

    event_set_log_callback(&libevent_log_cb);

    // Update libevent's log handling.

    UpdateHTTPServerLogging(LogInstance().WillLogCategory(BCLog::LIBEVENT));

#ifdef WIN32

    evthread_use_windows_threads();

#else

    evthread_use_pthreads();

#endif

    raii_event_base base_ctr = obtain_event_base();

    /* Create a new evhttp object to handle requests. */

    raii_evhttp http_ctr = obtain_evhttp(base_ctr.get());

    struct evhttp* http = http_ctr.get();

    if (!http) {

        LogError("Couldn't create evhttp. Exiting.");

        return false;

    }

    evhttp_set_timeout(http, gArgs.GetIntArg("-rpcservertimeout", DEFAULT_HTTP_SERVER_TIMEOUT));

    evhttp_set_max_headers_size(http, MAX_HEADERS_SIZE);

    evhttp_set_max_body_size(http, MAX_SIZE);

    evhttp_set_gencb(http, http_request_cb, (void*)&interrupt);

    if (!HTTPBindAddresses(http)) {

        LogError("Unable to bind any endpoint for RPC server");

        return false;

    }

    LogDebug(BCLog::HTTP, "Initialized HTTP server\n");

    g_max_queue_depth = std::max(gArgs.GetArg("-rpcworkqueue", DEFAULT_HTTP_WORKQUEUE), 1);

    LogDebug(BCLog::HTTP, "set work queue of depth %d", g_max_queue_depth);

    // transfer ownership to eventBase/HTTP via .release()

    eventBase = base_ctr.release();

    eventHTTP = http_ctr.release();

    return true;

}

void UpdateHTTPServerLogging(bool enable) {

    if (enable) {

        event_enable_debug_logging(EVENT_DBG_ALL);

    } else {

        event_enable_debug_logging(EVENT_DBG_NONE);

    }

}

static std::thread g_thread_http;

void StartHTTPServer()

{

    int rpcThreads = std::max(gArgs.GetArg("-rpcthreads", DEFAULT_HTTP_THREADS), 1);

    LogInfo("Starting HTTP server with %d worker threads", rpcThreads);

    g_threadpool_http.Start(rpcThreads);

    g_thread_http = std::thread(ThreadHTTP, eventBase);

}

void InterruptHTTPServer()

{

    LogDebug(BCLog::HTTP, "Interrupting HTTP server\n");

    if (eventHTTP) {

        // Reject requests on current connections

        evhttp_set_gencb(eventHTTP, http_reject_request_cb, nullptr);

    }

    // Interrupt pool after disabling requests

    g_threadpool_http.Interrupt();

}

void StopHTTPServer()

{

    LogDebug(BCLog::HTTP, "Stopping HTTP server\n");

    LogDebug(BCLog::HTTP, "Waiting for HTTP worker threads to exit\n");

    g_threadpool_http.Stop();

    // Unlisten sockets, these are what make the event loop running, which means

    // that after this and all connections are closed the event loop will quit.

    for (evhttp_bound_socket *socket : boundSockets) {

        evhttp_del_accept_socket(eventHTTP, socket);

    }

    boundSockets.clear();

    {

        if (const auto n_connections{g_requests.CountActiveConnections()}; n_connections != 0) {

            LogDebug(BCLog::HTTP, "Waiting for %d connections to stop HTTP server\n", n_connections);

        }

        g_requests.WaitUntilEmpty();

    }

    if (eventHTTP) {

        // Schedule a callback to call evhttp_free in the event base thread, so

        // that evhttp_free does not need to be called again after the handling

        // of unfinished request connections that follows.

        event_base_once(eventBase, -1, EV_TIMEOUT, [](evutil_socket_t, short, void*) {

            evhttp_free(eventHTTP);

            eventHTTP = nullptr;

        }, nullptr, nullptr);

    }

    if (eventBase) {

        LogDebug(BCLog::HTTP, "Waiting for HTTP event thread to exit\n");

        if (g_thread_http.joinable()) g_thread_http.join();

        event_base_free(eventBase);

        eventBase = nullptr;

    }

    LogDebug(BCLog::HTTP, "Stopped HTTP server\n");

}

struct event_base* EventBase()

{

    return eventBase;

}

static void httpevent_callback_fn(evutil_socket_t, short, void* data)

{

    // Static handler: simply call inner handler

    HTTPEvent *self = static_cast<HTTPEvent*>(data);

    self->handler();

    if (self->deleteWhenTriggered)

        delete self;

}

HTTPEvent::HTTPEvent(struct event_base* base, bool _deleteWhenTriggered, const std::function<void()>& _handler):

    deleteWhenTriggered(_deleteWhenTriggered), handler(_handler)

{

    ev = event_new(base, -1, 0, httpevent_callback_fn, this);

    assert(ev);

}

HTTPEvent::~HTTPEvent()

{

    event_free(ev);

}

void HTTPEvent::trigger(struct timeval* tv)

{

    if (tv == nullptr)

        event_active(ev, 0, 0); // immediately trigger event in main thread

    else

        evtimer_add(ev, tv); // trigger after timeval passed

}

HTTPRequest::HTTPRequest(struct evhttp_request* _req, const util::SignalInterrupt& interrupt, bool _replySent)

    : req(_req), m_interrupt(interrupt), replySent(_replySent)

{

}

HTTPRequest::~HTTPRequest()

{

    if (!replySent) {

        // Keep track of whether reply was sent to avoid request leaks

        LogWarning("Unhandled HTTP request");

        WriteReply(HTTP_INTERNAL_SERVER_ERROR, "Unhandled request");

    }

    // evhttpd cleans up the request, as long as a reply was sent.

}

std::pair<bool, std::string> HTTPRequest::GetHeader(const std::string& hdr) const

{

    const struct evkeyvalq* headers = evhttp_request_get_input_headers(req);

    assert(headers);

    const char* val = evhttp_find_header(headers, hdr.c_str());

    if (val)

        return std::make_pair(true, val);

    else

        return std::make_pair(false, "");

}

std::string HTTPRequest::ReadBody()

{

    struct evbuffer* buf = evhttp_request_get_input_buffer(req);

    if (!buf)

        return "";

    size_t size = evbuffer_get_length(buf);

    /** Trivial implementation: if this is ever a performance bottleneck,

     * internal copying can be avoided in multi-segment buffers by using

     * evbuffer_peek and an awkward loop. Though in that case, it'd be even

     * better to not copy into an intermediate string but use a stream

     * abstraction to consume the evbuffer on the fly in the parsing algorithm.

     */

    const char* data = (const char*)evbuffer_pullup(buf, size);

    if (!data) // returns nullptr in case of empty buffer

        return "";

    std::string rv(data, size);

    evbuffer_drain(buf, size);

    return rv;

}

void HTTPRequest::WriteHeader(const std::string& hdr, const std::string& value)

{

    struct evkeyvalq* headers = evhttp_request_get_output_headers(req);

    assert(headers);

    evhttp_add_header(headers, hdr.c_str(), value.c_str());

}

/** Closure sent to main thread to request a reply to be sent to

 * a HTTP request.

 * Replies must be sent in the main loop in the main http thread,

 * this cannot be done from worker threads.

 */

void HTTPRequest::WriteReply(int nStatus, std::span<const std::byte> reply)

{

    assert(!replySent && req);

    if (m_interrupt) {

        WriteHeader("Connection", "close");

    }

    // Send event to main http thread to send reply message

    struct evbuffer* evb = evhttp_request_get_output_buffer(req);

    assert(evb);

    evbuffer_add(evb, reply.data(), reply.size());

    auto req_copy = req;

    HTTPEvent* ev = new HTTPEvent(eventBase, true, [req_copy, nStatus]{

        evhttp_send_reply(req_copy, nStatus, nullptr, nullptr);

        // Re-enable reading from the socket. This is the second part of the libevent

        // workaround above.

        if (event_get_version_number() >= 0x02010600 && event_get_version_number() < 0x02010900) {

            evhttp_connection* conn = evhttp_request_get_connection(req_copy);

            if (conn) {

                bufferevent* bev = evhttp_connection_get_bufferevent(conn);

                if (bev) {

                    bufferevent_enable(bev, EV_READ | EV_WRITE);

                }

            }

        }

    });

    ev->trigger(nullptr);

    replySent = true;

    req = nullptr; // transferred back to main thread

}

CService HTTPRequest::GetPeer() const

{

    evhttp_connection* con = evhttp_request_get_connection(req);

    CService peer;

    if (con) {

        // evhttp retains ownership over returned address string

        const char* address = "";

        uint16_t port = 0;

#ifdef HAVE_EVHTTP_CONNECTION_GET_PEER_CONST_CHAR

        evhttp_connection_get_peer(con, &address, &port);

#else

        evhttp_connection_get_peer(con, (char**)&address, &port);

#endif // HAVE_EVHTTP_CONNECTION_GET_PEER_CONST_CHAR

        peer = MaybeFlipIPv6toCJDNS(LookupNumeric(address, port));

    }

    return peer;

}

std::string HTTPRequest::GetURI() const

{

    return evhttp_request_get_uri(req);

}

HTTPRequest::RequestMethod HTTPRequest::GetRequestMethod() const

{

    switch (evhttp_request_get_command(req)) {

    case EVHTTP_REQ_GET:

        return GET;

    case EVHTTP_REQ_POST:

        return POST;

    case EVHTTP_REQ_HEAD:

        return HEAD;

    case EVHTTP_REQ_PUT:

        return PUT;

    default:

        return UNKNOWN;

    }

}

std::optional<std::string> HTTPRequest::GetQueryParameter(const std::string& key) const

{

    const char* uri{evhttp_request_get_uri(req)};

    return GetQueryParameterFromUri(uri, key);

}

std::optional<std::string> GetQueryParameterFromUri(const char* uri, const std::string& key)

{

    evhttp_uri* uri_parsed{evhttp_uri_parse(uri)};

    if (!uri_parsed) {

        throw std::runtime_error("URI parsing failed, it likely contained RFC 3986 invalid characters");

    }

    const char* query{evhttp_uri_get_query(uri_parsed)};

    std::optional<std::string> result;

    if (query) {

        // Parse the query string into a key-value queue and iterate over it

        struct evkeyvalq params_q;

        evhttp_parse_query_str(query, &params_q);

        for (struct evkeyval* param{params_q.tqh_first}; param != nullptr; param = param->next.tqe_next) {

            if (param->key == key) {

                result = param->value;

                break;

            }

        }

        evhttp_clear_headers(&params_q);

    }

    evhttp_uri_free(uri_parsed);

    return result;

}

void RegisterHTTPHandler(const std::string &prefix, bool exactMatch, const HTTPRequestHandler &handler)

{

    LogDebug(BCLog::HTTP, "Registering HTTP handler for %s (exactmatch %d)\n", prefix, exactMatch);

    LOCK(g_httppathhandlers_mutex);

    pathHandlers.emplace_back(prefix, exactMatch, handler);

}

void UnregisterHTTPHandler(const std::string &prefix, bool exactMatch)

{

    LOCK(g_httppathhandlers_mutex);

    std::vector<HTTPPathHandler>::iterator i = pathHandlers.begin();

    std::vector<HTTPPathHandler>::iterator iend = pathHandlers.end();

    for (; i != iend; ++i)

        if (i->prefix == prefix && i->exactMatch == exactMatch)

            break;

    if (i != iend)

    {

        LogDebug(BCLog::HTTP, "Unregistering HTTP handler for %s (exactmatch %d)\n", prefix, exactMatch);

        pathHandlers.erase(i);

    }

}