/*
 * libdatachannel client example
 * Copyright (c) 2019-2020 Paul-Louis Ageneau
 * Copyright (c) 2019 Murat Dogan
 * Copyright (c) 2020 Will Munn
 * Copyright (c) 2020 Nico Chatzi
 * Copyright (c) 2020 Lara Mackey
 * Copyright (c) 2020 Erik Cota-Robles
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; If not, see <http://www.gnu.org/licenses/>.
 */

#include "rtc/rtc.hpp"

#include "parse_cl.h"

#include <nlohmann/json.hpp>

#include <algorithm>
#include <chrono>
#include <future>
#include <iostream>
#include <memory>
#include <random>
#include <stdexcept>
#include <thread>
#include <unordered_map>

using namespace std::chrono_literals;
using std::shared_ptr;
using std::weak_ptr;
template <class T> weak_ptr<T> make_weak_ptr(shared_ptr<T> ptr) { return ptr; }

using nlohmann::json;

std::string localId;
std::unordered_map<std::string, shared_ptr<rtc::PeerConnection>> peerConnectionMap;
std::unordered_map<std::string, shared_ptr<rtc::DataChannel>> dataChannelMap;

shared_ptr<rtc::PeerConnection> createPeerConnection(const rtc::Configuration &config,
                                                     weak_ptr<rtc::WebSocket> wws, std::string id);
std::string randomId(size_t length);

int main(int argc, char **argv) try {
	Cmdline params(argc, argv);

	rtc::InitLogger(rtc::LogLevel::Info);

	rtc::Configuration config;
	std::string stunServer = "";
	if (params.noStun()) {
		std::cout
		    << "No STUN server is configured. Only local hosts and public IP addresses supported."
		    << std::endl;
	} else {
		if (params.stunServer().substr(0, 5).compare("stun:") != 0) {
			stunServer = "stun:";
		}
		stunServer += params.stunServer() + ":" + std::to_string(params.stunPort());
		std::cout << "STUN server is " << stunServer << std::endl;
		config.iceServers.emplace_back(stunServer);
	}

	if (params.udpMux()) {
		std::cout << "ICE UDP mux enabled" << std::endl;
		config.enableIceUdpMux = true;
	}

	localId = randomId(4);
	std::cout << "The local ID is " << localId << std::endl;

	auto ws = std::make_shared<rtc::WebSocket>();

	std::promise<void> wsPromise;
	auto wsFuture = wsPromise.get_future();

	ws->onOpen([&wsPromise]() {
		std::cout << "WebSocket connected, signaling ready" << std::endl;
		wsPromise.set_value();
	});

	ws->onError([&wsPromise](std::string s) {
		std::cout << "WebSocket error" << std::endl;
		wsPromise.set_exception(std::make_exception_ptr(std::runtime_error(s)));
	});

	ws->onClosed([]() { std::cout << "WebSocket closed" << std::endl; });

	ws->onMessage([&config, wws = make_weak_ptr(ws)](auto data) {
		// data holds either std::string or rtc::binary
		if (!std::holds_alternative<std::string>(data))
			return;

		json message = json::parse(std::get<std::string>(data));

		auto it = message.find("id");
		if (it == message.end())
			return;

		auto id = it->get<std::string>();

		it = message.find("type");
		if (it == message.end())
			return;

		auto type = it->get<std::string>();

		shared_ptr<rtc::PeerConnection> pc;
		if (auto jt = peerConnectionMap.find(id); jt != peerConnectionMap.end()) {
			pc = jt->second;
		} else if (type == "offer") {
			std::cout << "Answering to " + id << std::endl;
			pc = createPeerConnection(config, wws, id);
		} else {
			return;
		}

		if (type == "offer" || type == "answer") {
			auto sdp = message["description"].get<std::string>();
			pc->setRemoteDescription(rtc::Description(sdp, type));
		} else if (type == "candidate") {
			auto sdp = message["candidate"].get<std::string>();
			auto mid = message["mid"].get<std::string>();
			pc->addRemoteCandidate(rtc::Candidate(sdp, mid));
		}
	});

	const std::string wsPrefix =
	    params.webSocketServer().find("://") == std::string::npos ? "ws://" : "";
	const std::string url = wsPrefix + params.webSocketServer() + ":" +
	                        std::to_string(params.webSocketPort()) + "/" + localId;

	std::cout << "WebSocket URL is " << url << std::endl;
	ws->open(url);

	std::cout << "Waiting for signaling to be connected..." << std::endl;
	wsFuture.get();

	while (true) {
		std::string id;
		std::cout << "Enter a remote ID to send an offer:" << std::endl;
		std::cin >> id;
		std::cin.ignore();

		if (id.empty())
			break;

		if (id == localId) {
			std::cout << "Invalid remote ID (This is the local ID)" << std::endl;
			continue;
		}

		std::cout << "Offering to " + id << std::endl;
		auto pc = createPeerConnection(config, ws, id);

		// We are the offerer, so create a data channel to initiate the process
		const std::string label = "test";
		std::cout << "Creating DataChannel with label \"" << label << "\"" << std::endl;
		auto dc = pc->createDataChannel(label);

		dc->onOpen([id, wdc = make_weak_ptr(dc)]() {
			std::cout << "DataChannel from " << id << " open" << std::endl;
			if (auto dc = wdc.lock())
				dc->send("Hello from " + localId);
		});

		dc->onClosed([id]() { std::cout << "DataChannel from " << id << " closed" << std::endl; });

		dc->onMessage([id, wdc = make_weak_ptr(dc)](auto data) {
			// data holds either std::string or rtc::binary
			if (std::holds_alternative<std::string>(data))
				std::cout << "Message from " << id << " received: " << std::get<std::string>(data)
				          << std::endl;
			else
				std::cout << "Binary message from " << id
				          << " received, size=" << std::get<rtc::binary>(data).size() << std::endl;
		});

		dataChannelMap.emplace(id, dc);
	}

	std::cout << "Cleaning up..." << std::endl;

	dataChannelMap.clear();
	peerConnectionMap.clear();
	return 0;

} catch (const std::exception &e) {
	std::cout << "Error: " << e.what() << std::endl;
	dataChannelMap.clear();
	peerConnectionMap.clear();
	return -1;
}

// Create and setup a PeerConnection
shared_ptr<rtc::PeerConnection> createPeerConnection(const rtc::Configuration &config,
                                                     weak_ptr<rtc::WebSocket> wws, std::string id) {
	auto pc = std::make_shared<rtc::PeerConnection>(config);

	pc->onStateChange(
	    [](rtc::PeerConnection::State state) { std::cout << "State: " << state << std::endl; });

	pc->onGatheringStateChange([](rtc::PeerConnection::GatheringState state) {
		std::cout << "Gathering State: " << state << std::endl;
	});

	pc->onLocalDescription([wws, id](rtc::Description description) {
		json message = {{"id", id},
		                {"type", description.typeString()},
		                {"description", std::string(description)}};

		if (auto ws = wws.lock())
			ws->send(message.dump());
	});

	pc->onLocalCandidate([wws, id](rtc::Candidate candidate) {
		json message = {{"id", id},
		                {"type", "candidate"},
		                {"candidate", std::string(candidate)},
		                {"mid", candidate.mid()}};

		if (auto ws = wws.lock())
			ws->send(message.dump());
	});

	pc->onDataChannel([id](shared_ptr<rtc::DataChannel> dc) {
		std::cout << "DataChannel from " << id << " received with label \"" << dc->label() << "\""
		          << std::endl;

		dc->onOpen([wdc = make_weak_ptr(dc)]() {
			if (auto dc = wdc.lock())
				dc->send("Hello from " + localId);
		});

		dc->onClosed([id]() { std::cout << "DataChannel from " << id << " closed" << std::endl; });

		dc->onMessage([id](auto data) {
			// data holds either std::string or rtc::binary
			if (std::holds_alternative<std::string>(data))
				std::cout << "Message from " << id << " received: " << std::get<std::string>(data)
				          << std::endl;
			else
				std::cout << "Binary message from " << id
				          << " received, size=" << std::get<rtc::binary>(data).size() << std::endl;
		});

		dataChannelMap.emplace(id, dc);
	});

	peerConnectionMap.emplace(id, pc);
	return pc;
};

// Helper function to generate a random ID
std::string randomId(size_t length) {
	using std::chrono::system_clock;
	static thread_local std::mt19937 rng(
	    static_cast<unsigned int>(system_clock::now().time_since_epoch().count()));
	static const std::string characters(
	    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
	std::string id(length, '0');
	std::uniform_int_distribution<int> uniform(0, int(characters.size() - 1));
	std::generate(id.begin(), id.end(), [&]() { return characters.at(uniform(rng)); });
	return id;
}