/*
 * Copyright (C) 2004-2025 ZNC, see the NOTICE file for details.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <znc/IRCNetwork.h>
#include <znc/IRCSock.h>

struct reply {
    const char* szReply;
    bool bLastResponse;
};

// TODO this list is far from complete, no errors are handled
static const struct {
    const char* szRequest;
    struct reply vReplies[21];
} vRouteReplies[] = {
      {"WHO",
       {{"402", true},   /* rfc1459 ERR_NOSUCHSERVER */
        {"352", false},  /* rfc1459 RPL_WHOREPLY */
        {"315", true},   /* rfc1459 RPL_ENDOFWHO */
        {"354", false},  // e.g. Quaknet uses this for WHO #chan %n
        {"403", true},   // No such chan
        {nullptr, true}}},
      {"LIST",
       {{"402", true},  /* rfc1459 ERR_NOSUCHSERVER */
        {"321", false}, /* rfc1459 RPL_LISTSTART */
        {"322", false}, /* rfc1459 RPL_LIST */
        {"323", true},  /* rfc1459 RPL_LISTEND */
        {nullptr, true}}},
      {"NAMES",
       {
        {"353", false}, /* rfc1459 RPL_NAMREPLY */
        {"366", true},  /* rfc1459 RPL_ENDOFNAMES */
        {"401", true},  /* rfc1459 ERR_NOSUCHNICK */
        {"403", true},  /* rfc1459 ERR_NOSUCHCHANNEL */
        {nullptr, true},
       }},
      {"LUSERS",
       {{"251", false}, /* rfc1459 RPL_LUSERCLIENT */
        {"252", false}, /* rfc1459 RPL_LUSEROP */
        {"253", false}, /* rfc1459 RPL_LUSERUNKNOWN */
        {"254", false}, /* rfc1459 RPL_LUSERCHANNELS */
        {"255", false}, /* rfc1459 RPL_LUSERME */
        {"265", false},
        {"266", true},
        // We don't handle 250 here since some IRCds don't sent it
        //{"250", true},
        {nullptr, true}}},
      {"WHOIS",
       {{"311", false}, /* rfc1459 RPL_WHOISUSER */
        {"312", false}, /* rfc1459 RPL_WHOISSERVER */
        {"313", false}, /* rfc1459 RPL_WHOISOPERATOR */
        {"317", false}, /* rfc1459 RPL_WHOISIDLE */
        {"319", false}, /* rfc1459 RPL_WHOISCHANNELS */
        {"320", false}, /* unreal RPL_WHOISSPECIAL */
        {"301", false}, /* rfc1459 RPL_AWAY */
        {"276", false}, /* oftc-hybrid RPL_WHOISCERTFP */
        {"330", false}, /* ratbox RPL_WHOISLOGGEDIN
                           aka ircu RPL_WHOISACCOUNT */
        {"337", false}, /* solanum RPL_WHOISTEXT -- "is hiding their idle time" */
        {"338", false}, /* ircu RPL_WHOISACTUALLY -- "actually using host" */
        {"378", false}, /* RPL_WHOISHOST -- real address of vhosts */
        {"671", false}, /* RPL_WHOISSECURE */
        {"307", false}, /* RPL_WHOISREGNICK */
        {"379", false}, /* RPL_WHOISMODES */
        {"760", false}, /* ircv3.2 RPL_WHOISKEYVALUE */
        {"318", true},  /* rfc1459 RPL_ENDOFWHOIS */
        {"401", true},  /* rfc1459 ERR_NOSUCHNICK */
        {"402", true},  /* rfc1459 ERR_NOSUCHSERVER */
        {"431", true},  /* rfc1459 ERR_NONICKNAMEGIVEN */
        {nullptr, true}}},
      {"PING",
       {{"PONG", true},
        {"402", true}, /* rfc1459 ERR_NOSUCHSERVER */
        {"409", true}, /* rfc1459 ERR_NOORIGIN */
        {nullptr, true}}},
      {"USERHOST",
       {{"302", true},
        {"461", true}, /* rfc1459 ERR_NEEDMOREPARAMS */
        {nullptr, true}}},
      {"TIME",
       {{"391", true}, /* rfc1459 RPL_TIME */
        {"402", true}, /* rfc1459 ERR_NOSUCHSERVER */
        {nullptr, true}}},
      {"WHOWAS",
       {{"406", false}, /* rfc1459 ERR_WASNOSUCHNICK */
        {"312", false}, /* rfc1459 RPL_WHOISSERVER */
        {"314", false}, /* rfc1459 RPL_WHOWASUSER */
        {"330", false}, /* ratbox RPL_WHOISLOGGEDIN
                           aka ircu RPL_WHOISACCOUNT */
        {"338", false}, /* ircu RPL_WHOISACTUALLY -- "actually using host" */
        {"369", true},  /* rfc1459 RPL_ENDOFWHOWAS */
        {"431", true},  /* rfc1459 ERR_NONICKNAMEGIVEN */
        {nullptr, true}}},
      {"ISON",
       {{"303", true}, /* rfc1459 RPL_ISON */
        {"461", true}, /* rfc1459 ERR_NEEDMOREPARAMS */
        {nullptr, true}}},
      {"LINKS",
       {{"364", false}, /* rfc1459 RPL_LINKS */
        {"365", true},  /* rfc1459 RPL_ENDOFLINKS */
        {"402", true},  /* rfc1459 ERR_NOSUCHSERVER */
        {nullptr, true}}},
      {"MAP",
       {{"006", false},
        // inspircd
        {"270", false},
        // SilverLeo wants this two added
        {"015", false},
        {"017", true},
        {"007", true},
        {"481", true}, /* rfc1459 ERR_NOPRIVILEGES */
        {nullptr, true}}},
      {"TRACE",
       {{"200", false}, /* rfc1459 RPL_TRACELINK */
        {"201", false}, /* rfc1459 RPL_TRACECONNECTING */
        {"202", false}, /* rfc1459 RPL_TRACEHANDSHAKE */
        {"203", false}, /* rfc1459 RPL_TRACEUNKNOWN */
        {"204", false}, /* rfc1459 RPL_TRACEOPERATOR */
        {"205", false}, /* rfc1459 RPL_TRACEUSER */
        {"206", false}, /* rfc1459 RPL_TRACESERVER */
        {"208", false}, /* rfc1459 RPL_TRACENEWTYPE */
        {"261", false}, /* rfc1459 RPL_TRACELOG */
        {"262", true},
        {"402", true}, /* rfc1459 ERR_NOSUCHSERVER */
        {nullptr, true}}},
      {"USERS",
       {
        {"265", false},
        {"266", true},
        {"392", false}, /* rfc1459 RPL_USERSSTART */
        {"393", false}, /* rfc1459 RPL_USERS */
        {"394", true},  /* rfc1459 RPL_ENDOFUSERS */
        {"395", false}, /* rfc1459 RPL_NOUSERS */
        {"402", true},  /* rfc1459 ERR_NOSUCHSERVER */
        {"424", true},  /* rfc1459 ERR_FILEERROR */
        {"446", true},  /* rfc1459 ERR_USERSDISABLED */
        {nullptr, true},
       }},
      {"METADATA",
       {
        {"761", false}, /* ircv3.2 RPL_KEYVALUE */
        {"762", true},  /* ircv3.2 RPL_METADATAEND */
        {"765", true},  /* ircv3.2 ERR_TARGETINVALID */
        {"766", true},  /* ircv3.2 ERR_NOMATCHINGKEYS */
        {"767", true},  /* ircv3.2 ERR_KEYINVALID */
        {"768", true},  /* ircv3.2 ERR_KEYNOTSET */
        {"769", true},  /* ircv3.2 ERR_KEYNOPERMISSION */
        {nullptr, true},
       }},
      // This is just a list of all possible /mode replies stuffed together.
      // Since there should never be more than one of these going on, this
      // should work fine and makes the code simpler.
      {"MODE",
       {// "You're not a channel operator"
        {"482", true},
        // MODE I
        {"346", false},
        {"347", true},
        // MODE b
        {"367", false},
        {"368", true},
        // MODE e
        {"348", false},
        {"349", true},
        {"403", true}, /* rfc1459 ERR_NOSUCHCHANNEL */
        {"442", true}, /* rfc1459 ERR_NOTONCHANNEL */
        {"467", true}, /* rfc1459 ERR_KEYSET */
        {"472", true}, /* rfc1459 ERR_UNKNOWNMODE */
        {"501", true}, /* rfc1459 ERR_UMODEUNKNOWNFLAG */
        {"502", true}, /* rfc1459 ERR_USERSDONTMATCH */
        {nullptr, true},
       }},
       {"TOPIC",
        {
         {"461", true}, /* rfc1459 ERR_NEEDMOREPARAMS */
         {"403", true}, /* rfc1459 ERR_NOSUCHCHANNEL */
         {"442", true}, /* rfc1459 ERR_NOTONCHANNEL */
         {"482", true}, /* rfc1459 ERR_CHANOPRIVSNEEDED */
         {"331", true}, /* rfc1459 RPL_NOTOPIC */
         {"332", false}, /* rfc1459 RPL_TOPIC */
         {"333", true}, /* ircu? RPL_TOPICWHOTIME */
         {nullptr, true},
       }},

      // END (last item!)
      {nullptr, {{nullptr, true}}}};

class CRouteTimeout : public CTimer {
  public:
    CRouteTimeout(CModule* pModule, unsigned int uInterval,
                  unsigned int uCycles, const CString& sLabel,
                  const CString& sDescription)
        : CTimer(pModule, uInterval, uCycles, sLabel, sDescription) {}
    ~CRouteTimeout() override {}

  protected:
    void RunJob() override;
};

struct queued_req {
    CMessage msg;
    const struct reply* reply;
};

typedef std::map<CClient*, std::vector<struct queued_req>> requestQueue;

class CRouteRepliesMod : public CModule {
  public:
    MODCONSTRUCTOR(CRouteRepliesMod) {
        m_pDoing = nullptr;
        m_pReplies = nullptr;

        AddHelpCommand();
        AddCommand("Silent", t_d("[yes|no]"),
                   t_d("Decides whether to show the timeout messages or not"),
                   [=](const CString& sLine) { SilentCommand(sLine); });
    }

    ~CRouteRepliesMod() override {
        requestQueue::iterator it;

        while (!m_vsPending.empty()) {
            it = m_vsPending.begin();

            while (!it->second.empty()) {
                PutIRC(it->second[0].msg);
                it->second.erase(it->second.begin());
            }

            m_vsPending.erase(it);
        }
    }

    void OnIRCConnected() override {
        m_pDoing = nullptr;
        m_pReplies = nullptr;
        m_vsPending.clear();

        // No way we get a reply, so stop the timer (If it's running)
        RemTimer("RouteTimeout");
    }

    void OnIRCDisconnected() override {
        OnIRCConnected();  // Let's keep it in one place
    }

    void OnClientDisconnect() override {
        requestQueue::iterator it;

        if (GetClient() == m_pDoing) {
            // The replies which aren't received yet will be
            // broadcasted to everyone, but at least nothing breaks
            RemTimer("RouteTimeout");
            m_pDoing = nullptr;
            m_pReplies = nullptr;
        }

        it = m_vsPending.find(GetClient());

        if (it != m_vsPending.end()) m_vsPending.erase(it);

        SendRequest();
    }

    EModRet OnRawMessage(CMessage& msg) override {
        CString sCmd = msg.GetCommand().AsUpper();
        size_t i = 0;

        if (!m_pReplies) return CONTINUE;

        // Is this a "not enough arguments" error?
        if (sCmd == "461") {
            // :server 461 nick WHO :Not enough parameters
            CString sOrigCmd = msg.GetParam(1);

            if (m_LastRequest.GetCommand().Equals(sOrigCmd)) {
                // This is the reply to the last request
                if (RouteReply(msg, true)) return HALTCORE;
                return CONTINUE;
            }
        }

        while (m_pReplies[i].szReply != nullptr) {
            if (m_pReplies[i].szReply == sCmd) {
                if (RouteReply(msg, m_pReplies[i].bLastResponse))
                    return HALTCORE;
                return CONTINUE;
            }
            i++;
        }

        // TODO HALTCORE is wrong, it should not be passed to
        // the clients, but the core itself should still handle it!

        return CONTINUE;
    }

    EModRet OnUserRawMessage(CMessage& Message) override {
        const CString& sCmd = Message.GetCommand();

        if (!GetNetwork()->GetIRCSock() ||
            !GetNetwork()->GetIRCSock()->IsConnected())
            return CONTINUE;

        if (Message.GetType() == CMessage::Type::Mode) {
            // Check if this is a mode request that needs to be handled

            // If there are arguments to a mode change,
            // we must not route it.
            if (!Message.GetParamsColon(2).empty()) return CONTINUE;

            // Grab the mode change parameter
            CString sMode = Message.GetParam(1);

            // If this is a channel mode request, znc core replies to it
            if (sMode.empty()) return CONTINUE;

            // Check if this is a mode change or a specific
            // mode request (the later needs to be routed).
            sMode.TrimPrefix("+");
            if (sMode.length() != 1) return CONTINUE;

            // Now just check if it's one of the supported modes
            switch (sMode[0]) {
                case 'I':
                case 'b':
                case 'e':
                    break;
                default:
                    return CONTINUE;
            }

            // Ok, this looks like we should route it.
            // Fall through to the next loop
        } else if (Message.GetType() == CMessage::Type::Topic) {
            // Check if this is a topic request that needs to be handled

            // If there are arguments to a topic we must not route it.
            // Topic change message may result in TOPIC change to go to every client
            if (!Message.GetParamsColon(1).empty()) return CONTINUE;
        }

        for (size_t i = 0; vRouteReplies[i].szRequest != nullptr; i++) {
            if (vRouteReplies[i].szRequest == sCmd) {
                struct queued_req req = {Message, vRouteReplies[i].vReplies};
                m_vsPending[GetClient()].push_back(req);
                SendRequest();

                return HALTCORE;
            }
        }

        return CONTINUE;
    }

    void Timeout() {
        // The timer will be deleted after this by the event loop

        if (!GetNV("silent_timeouts").ToBool()) {
            PutModule(
                t_s("This module hit a timeout which is probably a "
                    "connectivity issue."));
            PutModule(
                t_s("However, if you can provide steps to reproduce this "
                    "issue, please do report a bug."));
            PutModule(
                t_f("To disable this message, do \"/msg {1} silent yes\"")(
                    GetModNick()));
            PutModule(t_f("Last request: {1}")(m_LastRequest.ToString()));
            PutModule(t_s("Expected replies:"));

            for (size_t i = 0; m_pReplies[i].szReply != nullptr; i++) {
                if (m_pReplies[i].bLastResponse)
                    PutModule(t_f("{1} (last)")(m_pReplies[i].szReply));
                else
                    PutModule(m_pReplies[i].szReply);
            }
        }

        m_pDoing = nullptr;
        m_pReplies = nullptr;
        SendRequest();
    }

  private:
    bool RouteReply(const CMessage& msg, bool bFinished = false) {
        if (!m_pDoing) return false;

        // TODO: RouteReply(const CMessage& Message, bool bFinished = false)
        m_pDoing->PutClient(msg);

        if (bFinished) {
            // Stop the timeout
            RemTimer("RouteTimeout");

            m_pDoing = nullptr;
            m_pReplies = nullptr;
            SendRequest();
        }

        return true;
    }

    void SendRequest() {
        requestQueue::iterator it;

        if (m_pDoing || m_pReplies) return;

        if (m_vsPending.empty()) return;

        it = m_vsPending.begin();

        if (it->second.empty()) {
            m_vsPending.erase(it);
            SendRequest();
            return;
        }

        // When we are called from the timer, we need to remove it.
        // We can't delete it (segfault on return), thus we
        // just stop it. The main loop will delete it.
        CTimer* pTimer = FindTimer("RouteTimeout");
        if (pTimer) {
            pTimer->Stop();
            UnlinkTimer(pTimer);
        }
        AddTimer(
            new CRouteTimeout(this, 60, 1, "RouteTimeout",
                              "Recover from missing / wrong server replies"));

        m_pDoing = it->first;
        m_pReplies = it->second[0].reply;
        m_LastRequest = it->second[0].msg;
        PutIRC(it->second[0].msg);
        it->second.erase(it->second.begin());
    }

    void SilentCommand(const CString& sLine) {
        const CString sValue = sLine.Token(1);

        if (!sValue.empty()) {
            SetNV("silent_timeouts", sValue);
        }

        PutModule(GetNV("silent_timeouts").ToBool()
                      ? t_s("Timeout messages are disabled.")
                      : t_s("Timeout messages are enabled."));
    }

    CClient* m_pDoing;
    const struct reply* m_pReplies;
    requestQueue m_vsPending;
    // This field is only used for display purpose.
    CMessage m_LastRequest;
};

void CRouteTimeout::RunJob() {
    CRouteRepliesMod* pMod = (CRouteRepliesMod*)GetModule();
    pMod->Timeout();
}

template <>
void TModInfo<CRouteRepliesMod>(CModInfo& Info) {
    Info.SetWikiPage("route_replies");
}

NETWORKMODULEDEFS(CRouteRepliesMod,
                  t_s("Send replies (e.g. to /who) to the right client only"))