/*
 * =====================================================================================
 *
 *       Filename:  center.cpp
 *
 *    Description:  
 *
 *        Version:  1.0
 *        Created:  2021年03月30日 16时19分37秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Li Chao (), 
 *   Organization:  
 *
 * =====================================================================================
 */
#include "center.h"
#include "bh_util.h"
#include "defs.h"
#include "log.h"
#include "shm.h"
#include <chrono>
#include <unordered_map>

using namespace std::chrono;
using namespace std::chrono_literals;

using namespace bhome_shm;
using namespace bhome_msg;
typedef BHCenter::MsgHandler Handler;

namespace
{

typedef std::string ProcId;
typedef size_t ProcIndex; // max local procs.
const int kMaxProcs = 65536;

// record all procs ever registered, always grow, never remove.
// mainly for node to request msg allocation.
// use index instead of MQId to save some bits.
class ProcRecords
{
public:
	struct ProcRec {
		ProcId proc_;
		MQId ssn_ = 0;
	};

	ProcRecords() { procs_.reserve(kMaxProcs); }

	ProcIndex Put(const ProcId &proc_id, const MQId ssn)
	{
		if (procs_.size() >= kMaxProcs) {
			return -1;
		}
		auto pos_isnew = proc_index_.emplace(proc_id, procs_.size());
		int index = pos_isnew.first->second;
		if (pos_isnew.second) {
			procs_.emplace_back(ProcRec{proc_id, ssn});
		} else { // update ssn
			procs_[index].ssn_ = ssn;
		}
		return index;
	}
	const ProcRec &Get(const ProcIndex index) const
	{
		static ProcRec empty_rec;
		return (index < procs_.size()) ? procs_[index] : empty_rec;
	}

private:
	std::unordered_map<ProcId, size_t> proc_index_;
	std::vector<ProcRec> procs_;
};

class MsgRecords
{
	typedef int64_t MsgId;
	typedef int64_t Offset;

public:
	void RecordMsg(const MsgI &msg) { msgs_.emplace(msg.id(), msg.Offset()); }
	void FreeMsg(MsgId id)
	{
		auto pos = msgs_.find(id);
		if (pos != msgs_.end()) {
			ShmMsg(pos->second).Free();
			msgs_.erase(pos);
		} else {
			LOG_TRACE() << "ignore late free request.";
		}
	}
	void AutoRemove()
	{
		auto now = NowSec();
		if (now < time_to_clean_) {
			return;
		}
		// LOG_FUNCTION;
		time_to_clean_ = now + 1;
		int64_t limit = std::max(10000ul, msgs_.size() / 10);
		int64_t n = 0;
		auto it = msgs_.begin();
		while (it != msgs_.end() && --limit > 0) {
			ShmMsg msg(it->second);
			auto Free = [&]() {
				msg.Free();
				it = msgs_.erase(it);
				++n;
			};
			int n = now - msg.timestamp();
			if (n < 10) {
				++it;
			} else if (msg.Count() == 0) {
				Free();
			} else if (n > 60) {
				Free();
			}
		}
		if (n > 0) {
			LOG_DEBUG() << "~~~~~~~~~~~~~~~~ auto release msgs: " << n;
		}
	}
	size_t size() const { return msgs_.size(); }
	void DebugPrint() const
	{
		LOG_DEBUG() << "msgs : " << size();
		int i = 0;
		int total_count = 0;
		for (auto &kv : msgs_) {
			MsgI msg(kv.second);
			total_count += msg.Count();
			LOG_TRACE() << "  " << i++ << ": msg id: " << kv.first << ", offset: " << kv.second << ", count: " << msg.Count() << ", size: " << msg.Size();
		}
		LOG_DEBUG() << "total count: " << total_count;
	}

private:
	std::unordered_map<MsgId, Offset> msgs_;
	int64_t time_to_clean_ = 0;
};

//TODO check proc_id
class NodeCenter
{
public:
	typedef MQId Address;
	typedef bhome_msg::ProcInfo ProcInfo;
	typedef std::function<void(Address const)> Cleaner;

private:
	enum {
		kStateInvalid,
		kStateNormal,
		kStateOffline,
		kStateKillme,
	};

	struct ProcState {
		int64_t timestamp_ = 0;
		uint32_t flag_ = 0; // reserved
		void PutOffline(const int64_t offline_time)
		{
			timestamp_ = NowSec() - offline_time;
			flag_ = kStateOffline;
		}
		void UpdateState(const int64_t now, const int64_t offline_time, const int64_t kill_time)
		{
			auto diff = now - timestamp_;
			LOG_DEBUG() << "state " << this << " diff: " << diff;
			if (diff < offline_time) {
				flag_ = kStateNormal;
			} else if (diff < kill_time) {
				flag_ = kStateOffline;
			} else {
				flag_ = kStateKillme;
			}
		}
	};
	typedef std::unordered_map<Address, std::set<Topic>> AddressTopics;

	struct NodeInfo {
		ProcState state_;               // state
		std::map<MQId, int64_t> addrs_; // registered mqs
		ProcInfo proc_;                 //
		AddressTopics services_;        // address: topics
		AddressTopics subscriptions_;   // address: topics
	};
	typedef std::shared_ptr<NodeInfo> Node;
	typedef std::weak_ptr<NodeInfo> WeakNode;

	struct TopicDest {
		MQId mq_id_;
		int64_t mq_abs_addr_;
		WeakNode weak_node_;
		bool operator<(const TopicDest &a) const { return mq_id_ < a.mq_id_; }
	};
	inline MQId SrcAddr(const BHMsgHead &head) { return head.route(0).mq_id(); }
	inline int64_t SrcAbsAddr(const BHMsgHead &head) { return head.route(0).abs_addr(); }
	inline bool MatchAddr(std::map<Address, int64_t> const &addrs, const Address &addr) { return addrs.find(addr) != addrs.end(); }

	NodeCenter(const std::string &id, const Cleaner &cleaner, const int64_t offline_time, const int64_t kill_time) :
	    id_(id), cleaner_(cleaner), offline_time_(offline_time), kill_time_(kill_time), last_check_time_(0) {}

public:
	typedef std::set<TopicDest> Clients;

	NodeCenter(const std::string &id, const Cleaner &cleaner, const steady_clock::duration offline_time, const steady_clock::duration kill_time) :
	    NodeCenter(id, cleaner, duration_cast<seconds>(offline_time).count(), duration_cast<seconds>(kill_time).count()) {}

	// center name, no relative to shm.
	const std::string &id() const { return id_; }
	int64_t OnNodeInit(ShmSocket &socket, const int64_t val)
	{
		LOG_FUNCTION;
		SharedMemory &shm = socket.shm();
		MQId ssn = (val >> 4) & MaskBits(56);
		int reply = EncodeCmd(eCmdNodeInitReply);

		if (nodes_.find(ssn) != nodes_.end()) {
			return reply; // ignore if exists.
		}

		auto UpdateRegInfo = [&](Node &node) {
			node->state_.timestamp_ = NowSec() - offline_time_;
			node->state_.UpdateState(NowSec(), offline_time_, kill_time_);

			// create sockets.
			try {
				ShmSocket tmp(shm, true, ssn, 16);
				node->addrs_.emplace(ssn, tmp.AbsAddr());
				return true;
			} catch (...) {
				return false;
			}
		};

		auto PrepareProcInit = [&](Node &node) {
			bool r = false;
			ShmMsg init_msg;
			DEFER1(init_msg.Release());
			MsgProcInit body;
			auto head = InitMsgHead(GetType(body), id(), ssn);
			return init_msg.Make(GetAllocSize(CalcAllocIndex(900))) &&
			       init_msg.Fill(ShmMsg::Serialize(head, body)) &&
			       SendAllocMsg(socket, {ssn, node->addrs_[ssn]}, init_msg);
		};

		Node node(new NodeInfo);
		if (UpdateRegInfo(node) && PrepareProcInit(node)) {
			reply |= (node->addrs_[ssn] << 4);
			nodes_[ssn] = node;
			LOG_INFO() << "new node ssn (" << ssn << ") init";
		} else {
			ShmSocket::Remove(shm, ssn);
		}
		return reply;
	}
	void RecordMsg(const MsgI &msg)
	{
		msg.reset_managed(true);
		msgs_.RecordMsg(msg);
	}

	bool SendAllocReply(ShmSocket &socket, const MQInfo &dest, const int64_t reply, const MsgI &msg)
	{
		RecordMsg(msg);
		auto onExpireFree = [this, msg](const SendQ::Data &) { msgs_.FreeMsg(msg.id()); };
		return socket.Send(dest, reply, onExpireFree);
	}
	bool SendAllocMsg(ShmSocket &socket, const MQInfo &dest, const MsgI &msg)
	{
		RecordMsg(msg);
		return socket.Send(dest, msg);
	}

	void OnAlloc(ShmSocket &socket, const int64_t val)
	{
		// LOG_FUNCTION;
		// 8bit size, 4bit socket index, 16bit proc index, 28bit id, ,4bit cmd+flag
		int64_t msg_id = (val >> 4) & MaskBits(28);
		int proc_index = (val >> 32) & MaskBits(16);
		int socket_index = ((val) >> 48) & MaskBits(4);
		auto proc_rec(procs_.Get(proc_index));
		if (proc_rec.proc_.empty()) {
			return;
		}

		MQInfo dest = {proc_rec.ssn_ + socket_index, 0};
		auto FindMq = [&]() {
			auto pos = nodes_.find(proc_rec.ssn_);
			if (pos != nodes_.end()) {
				for (auto &&mq : pos->second->addrs_) {
					if (mq.first == dest.id_) {
						dest.offset_ = mq.second;
						return true;
					}
				}
			}
			return false;
		};
		if (!FindMq()) { return; }

		auto size = GetAllocSize((val >> 52) & MaskBits(8));
		MsgI new_msg;
		if (new_msg.Make(size)) {
			// 31bit proc index, 28bit id, ,4bit cmd+flag
			int64_t reply = (new_msg.Offset() << 32) | (msg_id << 4) | EncodeCmd(eCmdAllocReply0);
			SendAllocReply(socket, dest, reply, new_msg);
		} else {
			int64_t reply = (msg_id << 4) | EncodeCmd(eCmdAllocReply0); // send empty, ack failure.
			socket.Send(dest, reply);
		}
	}

	void OnFree(ShmSocket &socket, const int64_t val)
	{
		int64_t msg_id = (val >> 4) & MaskBits(31);
		msgs_.FreeMsg(msg_id);
	}

	bool OnCommand(ShmSocket &socket, const int64_t val)
	{
		assert(IsCmd(val));
		int cmd = DecodeCmd(val);
		switch (cmd) {
		case eCmdAllocRequest0: OnAlloc(socket, val); break;
		case eCmdFree: OnFree(socket, val); break;
		default: return false;
		}
		return true;
	}

	MsgProcInitReply ProcInit(const BHMsgHead &head, MsgProcInit &msg)
	{
		LOG_DEBUG() << "center got proc init.";
		auto pos = nodes_.find(head.ssn_id());
		if (pos == nodes_.end()) {
			return MakeReply<MsgProcInitReply>(eNotFound, "Node Not Initialised");
		}
		auto index = procs_.Put(head.proc_id(), head.ssn_id());
		auto reply(MakeReply<MsgProcInitReply>(eSuccess));
		reply.set_proc_index(index);

		auto &node = pos->second;
		try {
			for (int i = 0; i < msg.extra_mq_num(); ++i) {
				ShmSocket tmp(BHomeShm(), true, head.ssn_id() + i + 1, 16);
				node->addrs_.emplace(tmp.id(), tmp.AbsAddr());
				auto addr = reply.add_extra_mqs();
				addr->set_mq_id(tmp.id());
				addr->set_abs_addr(tmp.AbsAddr());
			}
			return reply;
		} catch (...) {
			LOG_ERROR() << "proc init create mq error";
			return MakeReply<MsgProcInitReply>(eError, "Create mq failed.");
		}
	}

	MsgCommonReply Register(const BHMsgHead &head, MsgRegister &msg)
	{
		if (msg.proc().proc_id() != head.proc_id()) {
			return MakeReply(eInvalidInput, "invalid proc id.");
		}

		try {
			MQId ssn = head.ssn_id();
			// when node restart, ssn will change,
			// and old node will be removed after timeout.
			auto UpdateRegInfo = [&](Node &node) {
				node->proc_.Swap(msg.mutable_proc());
				node->state_.timestamp_ = head.timestamp();
				node->state_.UpdateState(NowSec(), offline_time_, kill_time_);
			};

			auto pos = nodes_.find(ssn);
			if (pos == nodes_.end()) {
				return MakeReply(eInvalidInput, "invalid session.");
			}

			// update proc info
			Node &node = pos->second;
			UpdateRegInfo(node);
			LOG_DEBUG() << "node (" << head.proc_id() << ") ssn (" << ssn << ")";

			auto old = online_node_addr_map_.find(head.proc_id());
			if (old != online_node_addr_map_.end()) { // old session
				auto &old_ssn = old->second;
				if (old_ssn != ssn) {
					nodes_[old_ssn]->state_.PutOffline(offline_time_);
					LOG_DEBUG() << "put node (" << nodes_[old_ssn]->proc_.proc_id() << ") ssn (" << old->second << ") offline";
					old_ssn = ssn;
				}
			} else {
				online_node_addr_map_.emplace(head.proc_id(), ssn);
			}
			return MakeReply(eSuccess);
		} catch (...) {
			return MakeReply(eError, "register node error.");
		}
	}

	template <class Reply, class Func>
	Reply HandleMsg(const BHMsgHead &head, Func const &op)
	{
		try {
			auto pos = nodes_.find(head.ssn_id());
			if (pos == nodes_.end()) {
				return MakeReply<Reply>(eNotRegistered, "Node is not registered.");
			} else {
				auto &node = pos->second;
				if (!MatchAddr(node->addrs_, SrcAddr(head))) {
					return MakeReply<Reply>(eAddressNotMatch, "Node address error.");
				} else if (head.type() == kMsgTypeHeartbeat && CanHeartbeat(*node)) {
					return op(node);
				} else if (!Valid(*node)) {
					return MakeReply<Reply>(eNoRespond, "Node is not alive.");
				} else {
					return op(node);
				}
			}
		} catch (...) {
			//TODO error log
			return MakeReply<Reply>(eError, "internal error.");
		}
	}
	template <class Func>
	inline MsgCommonReply HandleMsg(const BHMsgHead &head, Func const &op)
	{
		return HandleMsg<MsgCommonReply, Func>(head, op);
	}

	MsgCommonReply Unregister(const BHMsgHead &head, MsgUnregister &msg)
	{
		return HandleMsg(
		    head, [&](Node node) -> MsgCommonReply {
			    NodeInfo &ni = *node;
			    ni.state_.PutOffline(offline_time_);
			    return MakeReply(eSuccess);
		    });
	}

	MsgCommonReply RegisterRPC(const BHMsgHead &head, MsgRegisterRPC &msg)
	{
		return HandleMsg(
		    head, [&](Node node) -> MsgCommonReply {
			    auto src = SrcAddr(head);
			    auto &topics = msg.topics().topic_list();
			    node->services_[src].insert(topics.begin(), topics.end());
			    TopicDest dest = {src, SrcAbsAddr(head), node};
			    for (auto &topic : topics) {
				    service_map_[topic].insert(dest);
			    }
			    LOG_DEBUG() << "node " << node->proc_.proc_id() << " ssn " << node->addrs_.begin()->first << " serve " << topics.size() << " topics:\n";
			    for (auto &topic : topics) {
				    LOG_DEBUG() << "\t" << topic;
			    }
			    return MakeReply(eSuccess);
		    });
	}

	MsgCommonReply Heartbeat(const BHMsgHead &head, const MsgHeartbeat &msg)
	{
		return HandleMsg(head, [&](Node node) {
			NodeInfo &ni = *node;
			ni.state_.timestamp_ = head.timestamp();
			ni.state_.UpdateState(NowSec(), offline_time_, kill_time_);

			auto &info = msg.proc();
			if (!info.public_info().empty()) {
				ni.proc_.set_public_info(info.public_info());
			}
			if (!info.private_info().empty()) {
				ni.proc_.set_private_info(info.private_info());
			}
			return MakeReply(eSuccess);
		});
	}
	MsgQueryProcReply QueryProc(const BHMsgHead &head, const MsgQueryProc &req)
	{
		typedef MsgQueryProcReply Reply;
		auto query = [&](Node self) -> Reply {
			auto Add1 = [](Reply &reply, Node node) {
				auto info = reply.add_proc_list();
				*info->mutable_proc() = node->proc_;
				info->set_online(node->state_.flag_ == kStateNormal);
				for (auto &addr_topics : node->services_) {
					for (auto &topic : addr_topics.second) {
						info->mutable_topics()->add_topic_list(topic);
					}
				}
			};

			if (!req.proc_id().empty()) {
				auto pos = online_node_addr_map_.find(req.proc_id());
				if (pos == online_node_addr_map_.end()) {
					return MakeReply<Reply>(eNotFound, "proc not found.");
				} else {
					auto node_pos = nodes_.find(pos->second);
					if (node_pos == nodes_.end()) {
						return MakeReply<Reply>(eNotFound, "proc node not found.");
					} else {
						auto reply = MakeReply<Reply>(eSuccess);
						Add1(reply, node_pos->second);
						return reply;
					}
				}
			} else {
				Reply reply(MakeReply<Reply>(eSuccess));
				for (auto &kv : nodes_) {
					Add1(reply, kv.second);
				}
				return reply;
			}
		};

		return HandleMsg<Reply>(head, query);
	}

	MsgQueryTopicReply QueryTopic(const BHMsgHead &head, const MsgQueryTopic &req)
	{
		typedef MsgQueryTopicReply Reply;

		auto query = [&](Node self) -> Reply {
			auto pos = service_map_.find(req.topic());
			if (pos != service_map_.end() && !pos->second.empty()) {
				auto &clients = pos->second;
				Reply reply = MakeReply<Reply>(eSuccess);
				for (auto &dest : clients) {
					Node dest_node(dest.weak_node_.lock());
					if (dest_node && Valid(*dest_node)) {
						auto node_addr = reply.add_node_address();
						node_addr->set_proc_id(dest_node->proc_.proc_id());
						node_addr->mutable_addr()->set_mq_id(dest.mq_id_);
						node_addr->mutable_addr()->set_abs_addr(dest.mq_abs_addr_);
					}
				}
				return reply;
			} else {
				return MakeReply<Reply>(eNotFound, "topic server not found.");
			}
		};

		return HandleMsg<Reply>(head, query);
	}

	MsgCommonReply Subscribe(const BHMsgHead &head, const MsgSubscribe &msg)
	{
		return HandleMsg(head, [&](Node node) {
			auto src = SrcAddr(head);
			auto &topics = msg.topics().topic_list();
			node->subscriptions_[src].insert(topics.begin(), topics.end());
			TopicDest dest = {src, SrcAbsAddr(head), node};
			for (auto &topic : topics) {
				subscribe_map_[topic].insert(dest);
			}
			return MakeReply(eSuccess);
		});
	}
	MsgCommonReply Unsubscribe(const BHMsgHead &head, const MsgUnsubscribe &msg)
	{
		return HandleMsg(head, [&](Node node) {
			auto src = SrcAddr(head);
			auto pos = node->subscriptions_.find(src);

			auto RemoveSubTopicDestRecord = [this](const Topic &topic, const TopicDest &dest) {
				auto pos = subscribe_map_.find(topic);
				if (pos != subscribe_map_.end() &&
				    pos->second.erase(dest) != 0 &&
				    pos->second.empty()) {
					subscribe_map_.erase(pos);
				}
			};

			if (pos != node->subscriptions_.end()) {
				const TopicDest &dest = {src, SrcAbsAddr(head), node};
				auto &topics = msg.topics().topic_list();
				// clear node sub records;
				for (auto &topic : topics) {
					pos->second.erase(topic);
					RemoveSubTopicDestRecord(topic, dest);
				}
				if (pos->second.empty()) {
					node->subscriptions_.erase(pos);
				}
			}
			return MakeReply(eSuccess);
		});
	}

	Clients DoFindClients(const std::string &topic)
	{
		Clients dests;
		auto Find1 = [&](const std::string &t) {
			auto pos = subscribe_map_.find(topic);
			if (pos != subscribe_map_.end()) {
				auto &clients = pos->second;
				for (auto &cli : clients) {
					if (Valid(cli.weak_node_)) {
						dests.insert(cli);
					}
				}
			}
		};
		Find1(topic);

		size_t pos = 0;
		while (true) {
			pos = topic.find(kTopicSep, pos);
			if (pos == topic.npos || ++pos == topic.size()) {
				// Find1(std::string()); // sub all.
				break;
			} else {
				Find1(topic.substr(0, pos));
			}
		}
		return dests;
	}
	bool FindClients(const BHMsgHead &head, const MsgPublish &msg, Clients &out, MsgCommonReply &reply)
	{
		bool ret = false;
		HandleMsg(head, [&](Node node) {
			DoFindClients(msg.topic()).swap(out);
			ret = true;
			return MakeReply(eSuccess);
		}).Swap(&reply);
		return ret;
	}

	void OnTimer()
	{
		CheckNodes();
		msgs_.AutoRemove();
	}

private:
	void CheckNodes()
	{
		auto now = NowSec();
		if (now <= last_check_time_) { return; }
		last_check_time_ = now;

		auto it = nodes_.begin();
		while (it != nodes_.end()) {
			auto &cli = *it->second;
			cli.state_.UpdateState(now, offline_time_, kill_time_);
			if (cli.state_.flag_ == kStateKillme) {
				RemoveNode(it->second);
				it = nodes_.erase(it);
			} else {
				++it;
			}
		}
		msgs_.DebugPrint();
	}
	bool CanHeartbeat(const NodeInfo &node)
	{
		return Valid(node) || node.state_.flag_ == kStateOffline;
	}
	bool Valid(const NodeInfo &node)
	{
		return node.state_.flag_ == kStateNormal;
	}
	bool Valid(const WeakNode &weak)
	{
		auto node = weak.lock();
		return node && Valid(*node);
	}
	void RemoveNode(Node &node)
	{
		auto EraseMapRec = [&node](auto &rec_map, auto &node_rec) {
			for (auto &addr_topics : node_rec) {
				TopicDest dest{addr_topics.first, 0, node}; // abs_addr is not used.
				for (auto &topic : addr_topics.second) {
					auto pos = rec_map.find(topic);
					if (pos != rec_map.end()) {
						pos->second.erase(dest);
						if (pos->second.empty()) {
							rec_map.erase(pos);
						}
					}
				}
			}
		};
		EraseMapRec(service_map_, node->services_);
		EraseMapRec(subscribe_map_, node->subscriptions_);

		// remove online record.
		auto pos = online_node_addr_map_.find(node->proc_.proc_id());
		if (pos != online_node_addr_map_.end()) {
			if (node->addrs_.find(pos->second) != node->addrs_.end()) {
				online_node_addr_map_.erase(pos);
			}
		}

		for (auto &addr : node->addrs_) {
			cleaner_(addr.first);
		}

		node->addrs_.clear();
	}
	std::string id_; // center proc id;

	std::unordered_map<Topic, Clients> service_map_;
	std::unordered_map<Topic, Clients> subscribe_map_;
	std::unordered_map<Address, Node> nodes_;
	std::unordered_map<ProcId, Address> online_node_addr_map_;
	ProcRecords procs_; // To get a short index for msg alloc.
	MsgRecords msgs_;   // record all msgs alloced.

	Cleaner cleaner_; // remove mqs.
	int64_t offline_time_;
	int64_t kill_time_;
	int64_t last_check_time_;
};

template <class Body, class OnMsg, class Replyer>
inline void Dispatch(MsgI &msg, BHMsgHead &head, OnMsg const &onmsg, Replyer const &replyer)
{
	if (head.route_size() != 1) { return; }
	Body body;
	if (msg.ParseBody(body)) {
		replyer(onmsg(body));
	}
}

Handler Combine(const Handler &h1, const Handler &h2)
{
	return [h1, h2](ShmSocket &socket, bhome_msg::MsgI &msg, bhome_msg::BHMsgHead &head) {
		return h1(socket, msg, head) || h2(socket, msg, head);
	};
}
template <class... H>
Handler Combine(const Handler &h0, const Handler &h1, const Handler &h2, const H &...rest)
{
	return Combine(Combine(h0, h1), h2, rest...);
}

#define CASE_ON_MSG_TYPE(MsgTag)                                                         \
	case kMsgType##MsgTag:                                                               \
		Dispatch<Msg##MsgTag>(                                                           \
		    msg, head, [&](auto &body) { return center->MsgTag(head, body); }, replyer); \
		return true;

auto MakeReplyer(ShmSocket &socket, BHMsgHead &head, Synced<NodeCenter> &center)
{
	return [&](auto &&rep_body) {
		auto reply_head(InitMsgHead(GetType(rep_body), center->id(), head.ssn_id(), head.msg_id()));
		MQInfo remote = {head.route(0).mq_id(), head.route(0).abs_addr()};
		MsgI msg;
		if (msg.Make(reply_head, rep_body)) {
			DEFER1(msg.Release(););
			center->SendAllocMsg(socket, remote, msg);
		}
	};
}

bool AddCenter(std::shared_ptr<Synced<NodeCenter>> center_ptr)
{
	// command
	auto OnCommand = [center_ptr](ShmSocket &socket, ShmMsgQueue::RawData &cmd) -> bool {
		auto &center = *center_ptr;
		return IsCmd(cmd) && center->OnCommand(socket, cmd);
	};

	// now we can talk.
	auto OnCenterIdle = [center_ptr](ShmSocket &socket) {
		auto &center = *center_ptr;
		auto onInit = [&](const int64_t request) {
			return center->OnNodeInit(socket, request);
		};
		BHCenterHandleInit(onInit);
		center->OnTimer();
	};

	auto OnCenter = [=](ShmSocket &socket, MsgI &msg, BHMsgHead &head) -> bool {
		auto &center = *center_ptr;
		auto replyer = MakeReplyer(socket, head, center);
		switch (head.type()) {
			CASE_ON_MSG_TYPE(ProcInit);
			CASE_ON_MSG_TYPE(Register);
			CASE_ON_MSG_TYPE(Heartbeat);
			CASE_ON_MSG_TYPE(Unregister);

			CASE_ON_MSG_TYPE(RegisterRPC);
			CASE_ON_MSG_TYPE(QueryTopic);
			CASE_ON_MSG_TYPE(QueryProc);
		default: return false;
		}
	};
	BHCenter::Install("#center.main", OnCenter, OnCommand, OnCenterIdle, BHTopicCenterAddress(), 1000);

	auto OnBusIdle = [=](ShmSocket &socket) {};
	auto OnBusCmd = [=](ShmSocket &socket, ShmMsgQueue::RawData &val) { return false; };
	auto OnPubSub = [=](ShmSocket &socket, MsgI &msg, BHMsgHead &head) -> bool {
		auto &center = *center_ptr;
		auto replyer = MakeReplyer(socket, head, center);
		auto OnPublish = [&]() {
			MsgPublish pub;
			NodeCenter::Clients clients;
			MsgCommonReply reply;
			if (head.route_size() != 1 || !msg.ParseBody(pub)) {
				return;
			} else if (!center->FindClients(head, pub, clients, reply)) {
				replyer(reply);
			} else {
				replyer(MakeReply(eSuccess));
				if (clients.empty()) { return; }

				auto it = clients.begin();
				do {
					auto &cli = *it;
					auto node = cli.weak_node_.lock();
					if (node) {
						// should also make sure that mq is not killed before msg expires.
						// it would be ok if (kill_time - offline_time) is longer than expire time.
						socket.Send({cli.mq_id_, cli.mq_abs_addr_}, msg);
						++it;
					} else {
						it = clients.erase(it);
					}
				} while (it != clients.end());
			}
		};
		switch (head.type()) {
			CASE_ON_MSG_TYPE(Subscribe);
			CASE_ON_MSG_TYPE(Unsubscribe);
		case kMsgTypePublish: OnPublish(); return true;
		default: return false;
		}
	};

	BHCenter::Install("#center.bus", OnPubSub, OnBusCmd, OnBusIdle, BHTopicBusAddress(), 1000);

	return true;
}

#undef CASE_ON_MSG_TYPE

} // namespace

BHCenter::CenterRecords &BHCenter::Centers()
{
	static CenterRecords rec;
	return rec;
}

bool BHCenter::Install(const std::string &name, MsgHandler handler, RawHandler raw_handler, IdleHandler idle, const MQInfo &mq, const int mq_len)
{
	Centers()[name] = CenterInfo{name, handler, raw_handler, idle, mq, mq_len};
	return true;
}

BHCenter::BHCenter(Socket::Shm &shm)
{
	auto gc = [&](const MQId id) {
		auto r = ShmSocket::Remove(shm, id);
		if (r) {
			LOG_DEBUG() << "remove mq " << id << " ok\n";
		}
	};

	auto nsec = seconds(NodeTimeoutSec());
	auto center_ptr = std::make_shared<Synced<NodeCenter>>("#bhome_center", gc, nsec, nsec * 3); // *3 to allow other clients to finish sending msgs.
	AddCenter(center_ptr);

	for (auto &kv : Centers()) {
		auto &info = kv.second;
		sockets_[info.name_] = std::make_shared<ShmSocket>(info.mq_.offset_, shm, info.mq_.id_);
	}
}

bool BHCenter::Start()
{
	for (auto &kv : Centers()) {
		auto &info = kv.second;
		sockets_[info.name_]->Start(1, info.handler_, info.raw_handler_, info.idle_);
	}

	return true;
}

bool BHCenter::Stop()
{
	for (auto &kv : sockets_) {
		kv.second->Stop();
	}
	return true;
}