/*
 * =====================================================================================
 *
 *       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 "shm.h"
#include <set>

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

namespace
{
auto Now = []() { time_t t; return time(&t); };

//TODO check proc_id
class NodeCenter
{
public:
	typedef std::string ProcId;
	typedef std::string Address;
	typedef bhome::msg::ProcInfo ProcInfo;

private:
	enum {
		kStateInvalid = 0,
		kStateNormal = 1,
		kStateNoRespond = 2,
		kStateOffline = 3,
	};

	struct ProcState {
		time_t timestamp_ = 0;
		uint32_t flag_ = 0; // reserved
	};
	typedef std::unordered_map<Address, std::set<Topic>> AddressTopics;

	struct NodeInfo {
		ProcState state_;             // state
		Address addr_;                // registered_mqid.
		ProcInfo proc_;               //
		AddressTopics services_;      // address: topics
		AddressTopics subscriptions_; // address: topics
	};
	typedef std::shared_ptr<NodeInfo> Node;
	typedef std::weak_ptr<NodeInfo> WeakNode;

	struct TopicDest {
		Address mq_;
		WeakNode weak_node_;
		bool operator<(const TopicDest &a) const { return mq_ < a.mq_; }
	};
	const std::string &SrcAddr(const BHMsgHead &head) { return head.route(0).mq_id(); }

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

	NodeCenter(const std::string &id = "#Center") :
	    id_(id) {}
	const std::string &id() const { return id_; } // no need to lock.

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

		try {
			Node node(new NodeInfo);
			node->addr_ = SrcAddr(head);
			node->proc_.Swap(msg.mutable_proc());
			node->state_.timestamp_ = Now();
			node->state_.flag_ = kStateNormal;
			nodes_[node->proc_.proc_id()] = node;
			return MakeReply(eSuccess);
		} catch (...) {
			return MakeReply(eError, "register node error.");
		}
	}
	template <class OnSuccess, class OnError>
	auto HandleMsg(const BHMsgHead &head, OnSuccess onOk, OnError onErr)
	{
		auto pos = nodes_.find(head.proc_id());
		if (pos == nodes_.end()) {
			return onErr(eNotRegistered, "Node is not registered.");
		} else {
			auto node = pos->second;
			if (head.type() == kMsgTypeHeartbeat && node->addr_ != SrcAddr(head)) {
				return onErr(eAddressNotMatch, "Node address error.");
			} else if (!Valid(*node)) {
				return onErr(eNoRespond, "Node is not alive.");
			} else {
				return onOk(node);
			}
		}
	}

	template <class Reply, class Func>
	Reply HandleMsg(const BHMsgHead &head, Func const &op)
	{
		try {
			auto onErr = [](const ErrorCode ec, const std::string &str) { return MakeReply<Reply>(ec, str); };
			return HandleMsg(head, op, onErr);

			auto pos = nodes_.find(head.proc_id());
			if (pos == nodes_.end()) {
				return MakeReply<Reply>(eNotRegistered, "Node is not registered.");
			} else {
				auto node = pos->second;
				if (node->addr_ != SrcAddr(head)) {
					return MakeReply<Reply>(eAddressNotMatch, "Node address error.");
				} 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 RegisterRPC(const BHMsgHead &head, MsgRegisterRPC &msg)
	{
		return HandleMsg(
		    head, [&](Node node) -> MsgCommonReply {
			    auto &src = SrcAddr(head);
			    node->services_[src].insert(msg.topics().begin(), msg.topics().end());
			    TopicDest dest = {src, node};
			    for (auto &topic : msg.topics()) {
				    service_map_[topic].insert(dest);
			    }
			    return MakeReply(eSuccess);
		    });
	}

	MsgCommonReply Heartbeat(const BHMsgHead &head, const MsgHeartbeat &msg)
	{
		return HandleMsg(head, [&](Node node) {
			NodeInfo &ni = *node;
			ni.state_.timestamp_ = Now();
			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);
		});
	}

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

		auto query = [&](Node self) -> MsgQueryTopicReply {
			auto pos = service_map_.find(req.topic());
			if (pos != service_map_.end() && !pos->second.empty()) {
				// now just find first one.
				const TopicDest &dest = *(pos->second.begin());
				Node dest_node(dest.weak_node_.lock());
				if (!dest_node) {
					service_map_.erase(pos);
					return MakeReply<Reply>(eOffline, "topic server offline.");
				} else if (!Valid(*dest_node)) {
					return MakeReply<Reply>(eNoRespond, "topic server not responding.");
				} else {
					MsgQueryTopicReply reply = MakeReply<Reply>(eSuccess);
					reply.mutable_address()->set_mq_id(dest.mq_);
					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);
			node->subscriptions_[src].insert(msg.topics().begin(), msg.topics().end());
			TopicDest dest = {src, node};
			for (auto &topic : msg.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, node};
				// clear node sub records;
				for (auto &topic : msg.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;
	}

private:
	bool Valid(const NodeInfo &node)
	{
		return node.state_.flag_ == kStateNormal;
	}
	bool Valid(const WeakNode &weak)
	{
		auto node = weak.lock();
		return node && Valid(*node);
	}
	void CheckAllNodes(); //TODO, call it in timer.
	std::string id_;      // center proc id;

	std::unordered_map<Topic, Clients> service_map_;
	std::unordered_map<Topic, Clients> subscribe_map_;
	std::unordered_map<ProcId, Node> nodes_;
};

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;

bool InstallCenter()
{
	auto center_ptr = std::make_shared<Synced<NodeCenter>>();
	auto MakeReplyer = [](ShmSocket &socket, BHMsgHead &head, const std::string &proc_id) {
		return [&](auto &&rep_body) {
			auto reply_head(InitMsgHead(GetType(rep_body), proc_id, head.msg_id()));
			bool r = socket.Send(head.route(0).mq_id().data(), reply_head, rep_body, 10);
			if (!r) {
				printf("send reply failed.\n");
			}
			//TODO resend failed.
		};
	};

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

			CASE_ON_MSG_TYPE(RegisterRPC);
			CASE_ON_MSG_TYPE(QueryTopic);
		default: return false;
		}
	};

	auto OnPubSub = [=](ShmSocket &socket, MsgI &msg, BHMsgHead &head) -> bool {
		auto &center = *center_ptr;
		auto replyer = MakeReplyer(socket, head, center->id());
		auto OnPublish = [&]() {
			MsgPublish pub;
			NodeCenter::Clients clients;
			MsgCommonReply reply;
			MsgI pubmsg;
			if (head.route_size() != 1 || !msg.ParseBody(pub)) {
				return;
			} else if (!center->FindClients(head, pub, clients, reply)) {
				// send error reply.
				MakeReplyer(socket, head, center->id())(reply);
			} else if (pubmsg.MakeRC(socket.shm(), msg)) {
				DEFER1(pubmsg.Release(socket.shm()));
				for (auto &cli : clients) {
					auto node = cli.weak_node_.lock();
					if (node) {
						socket.Send(cli.mq_.data(), pubmsg, 10);
					}
				}
			}
		};
		switch (head.type()) {
			CASE_ON_MSG_TYPE(Subscribe);
			CASE_ON_MSG_TYPE(Unsubscribe);
		case kMsgTypePublish: OnPublish(); return true;
		default: return false;
		}
	};

	BHCenter::Install("#center.reg", OnCenter, BHTopicCenterAddress(), 1000);
	BHCenter::Install("#center.bus", OnPubSub, BHTopicBusAddress(), 1000);

	return true;
}

#undef CASE_ON_MSG_TYPE

} // namespace

SharedMemory &BHomeShm()
{
	static SharedMemory shm("bhome_default_shm_v0", 1024 * 1024 * 64);
	return shm;
}

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

bool BHCenter::Install(const std::string &name, MsgHandler handler, const std::string &mqid, const int mq_len)
{
	Centers()[name] = CenterInfo{name, handler, mqid, mq_len};
	return true;
}
bool BHCenter::Install(const std::string &name, MsgHandler handler, const MQId &mqid, const int mq_len)
{
	return Install(name, handler, std::string((const char *) &mqid, sizeof(mqid)), mq_len);
}

BHCenter::BHCenter(Socket::Shm &shm)
{
	InstallCenter();

	for (auto &kv : Centers()) {
		auto &info = kv.second;
		sockets_[info.name_] = std::make_shared<ShmSocket>(shm, *(MQId *) info.mqid_.data(), info.mq_len_);
	}
}

BHCenter::BHCenter() :
    BHCenter(BHomeShm()) {}

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

	return true;
}

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