/*
 * =====================================================================================
 *
 *       Filename:  pubsub_center.cpp
 *
 *    Description:  pub/sub center/manager
 *
 *        Version:  1.0
 *        Created:  2021年04月01日 09时29分04秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Li Chao (), 
 *   Organization:  
 *
 * =====================================================================================
 */
#include "pubsub_center.h"
#include "bh_util.h"
using namespace bhome_shm;
namespace
{
class BusCenter
{
	typedef std::set<MQId> Clients;
	std::unordered_map<Topic, Clients> records_;
	// todo cache data if send fail.

public:
	template <class Iter>
	void SubScribe(const MQId &client, Iter topic_begin, Iter topic_end)
	{
		for (auto it = topic_begin; it != topic_end; ++it) {
			records_[*it].insert(client);
		}
	}
	template <class Iter>
	void UnsubScribe(const MQId &client, Iter topic_begin, Iter topic_end)
	{
		for (auto it = topic_begin; it != topic_end; ++it) {
			auto pos = records_.find(*it);
			if (pos != records_.end()) {
				if (pos->second.erase(client) && pos->second.empty()) {
					records_.erase(pos);
				}
			}
		}
	};
	Clients FindClients(const std::string &topic)
	{
		Clients dests;
		auto Find1 = [&](const std::string &t) {
			auto pos = records_.find(topic);
			if (pos != records_.end() && !pos->second.empty()) {
				auto &clients = pos->second;
				for (auto &cli : clients) {
					dests.insert(cli);
				}
			}
		};
		Find1(topic);

		//TODO check and adjust topic on client side sub/pub.
		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;
	}
};

} // namespace

BHCenter::MsgHandler MakeBusCenter()
{
	auto bus_ptr = std::make_shared<Synced<BusCenter>>();

	return [bus_ptr](ShmSocket &socket, MsgI &imsg, BHMsg &msg) {
#ifndef NDEBUG
		static std::atomic<time_t> last(0);
		time_t now = 0;
		time(&now);
		if (last.exchange(now) < now) {
			printf("bus queue size: %ld\n", socket.Pending());
		}
#endif
		auto &bus = *bus_ptr;
		auto &shm = socket.shm();

		auto OnSubChange = [&](auto &&update) {
			MsgSub sub;
			if (!msg.route().empty() && sub.ParseFromString(msg.body()) && !sub.topics().empty()) {
				assert(sizeof(MQId) == msg.route(0).mq_id().size());
				MQId client;
				memcpy(&client, msg.route(0).mq_id().data(), sizeof(client));
				update(client, sub.topics());
			}
		};
		auto Sub = [&](const MQId &id, auto &topics) { bus->SubScribe(id, topics.begin(), topics.end()); };
		auto Unsub = [&](const MQId &id, auto &topics) { bus->UnsubScribe(id, topics.begin(), topics.end()); };

		auto OnPublish = [&]() {
			MsgPub pub;
			if (!pub.ParseFromString(msg.body())) {
				return;
			}
			auto Dispatch = [&](auto &&send1) {
				const auto &clients(bus->FindClients(pub.topic()));
				for (auto &cli : clients) {
					send1(cli);
				}
			};

			if (imsg.IsCounted()) {
				Dispatch([&](const MQId &cli) { ShmMsgQueue::Send(shm, cli, imsg, 10); });
			} else {
				MsgI pubmsg;
				if (!pubmsg.MakeRC(shm, msg)) { return; }
				DEFER1(pubmsg.Release(shm));

				Dispatch([&](const MQId &cli) { ShmMsgQueue::Send(shm, cli, pubmsg, 10); });
			}
		};

		switch (msg.type()) {
		case kMsgTypeSubscribe: OnSubChange(Sub); return true;
		case kMsgTypeUnsubscribe: OnSubChange(Unsub); return true;
		case kMsgTypePublish: OnPublish(); return true;
		default: return false;
		}
	};
}

bool PubSubCenter::Start(const int nworker)
{
	auto handler = MakeBusCenter();
	printf("sizeof(pub/sub handler) = %ld\n", sizeof(handler));

	const int kMaxWorker = 16;
	return socket_.Start(handler, std::min((nworker > 0 ? nworker : 2), kMaxWorker));
}