duckticker/src/main.cpp

/* Copyright 2022, Michele Santullo
 * This file is part of duckticker.
 *
 * Wrenpp 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 3 of the License, or
 * (at your option) any later version.
 *
 * Wrenpp 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 duckticker.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "bitcoinity_reader.hpp"
#include <wrenpp/vm_fun.hpp>
#include <wrenpp/def_configuration.hpp>
#include <wrenpp/callback_manager.hpp>
#include <utility>

namespace {
constexpr char g_script[] =
R"script(
foreign class TickerPrice {
	construct new() { }

	foreign price
	foreign currency
	foreign exchange
	foreign is_valid
}

class Bitcoinity {
	foreign static ticker(currency, exchange)
}

class App {
	construct new(currency, exchange) {
		_currency = currency
		_exchange = exchange
	}

	start() {
		var price = Bitcoinity.ticker(_currency, _exchange)
		System.print("Ticker: %(price.price) %(price.currency) on %(price.exchange)")
	}
}

var the_app = App.new("USD", "kraken")
)script";

class TickerPrice {
public:
	TickerPrice() = default;
	TickerPrice (double price, std::string&& currency, std::string&& exchange) :
		m_price(price),
		m_currency(std::move(currency)),
		m_exchange(std::move(exchange))
	{}

	void set_price (double price) { m_price = price; }
	void set_currency (std::string&& currency) { m_currency = std::move(currency); }
	void set_exchange (std::string&& exchange) { m_exchange = std::move(exchange); }
	double price() const noexcept { return m_price; }
	const char* currency() const noexcept { return m_currency.c_str(); }
	const char* exchange() const noexcept { return m_exchange.c_str(); }
	bool is_valid() const noexcept { return not m_exchange.empty(); }

private:
	double m_price{};
	std::string m_currency;
	std::string m_exchange;
};

TickerPrice ticker_price_bitoinity (std::string_view currency, std::string_view exchange) {
	static const TickerPrice error_price {0.0, "", ""};

	duck::BitcoinityReader bitcoinity{
		std::string{duck::WebsocketReader::BeastVersionString} + " websocket-client-coro",
		exchange,
		currency
	};

	do {
		//possible values I observed:
		//  {"event":"new_msg","payload":{"data":{"currency":"EUR","exchange_name":"paymium","last":28363.44}},"ref":null,"topic":"webs:markets"}
		//  {"event":"new_msg","payload":{"data":{"currency":"USD","depth":{"price":30071,"type":1,"volume":-1.4123},"exchange_name":"bitfinex"}},"ref":null,"topic":"webs:markets_bitfinex_USD"}
		//  {"event":"new_msg","payload":{"data":{"currency":"USD","exchange_name":"bitfinex","trade":{"amount":0.0486,"date":1652471682,"exchange_name":"bitfinex","price":30072}}},"ref":null,"topic":"webs:markets_bitfinex_USD"}

		double price_out;
		std::optional<double> price;
		auto msg = bitcoinity.read();

		if (msg.payload.has_key("data", "depth_shot"))
			continue;

		if ((price = msg.payload.get_double("data", "last")))
			price_out = *price;
		else if ((price = msg.payload.get_double("data", "depth", "price")))
			price_out = *price;
		else if ((price = msg.payload.get_double("data", "trade", "price")))
			price_out = *price;
		else
			continue; //keep trying, sometimes I get a message like:
					  //{"event":"new_msg","payload":{"data":{"connected_count":1355}},"ref":null,"topic":"webs:markets"}

		std::string_view currency_out = msg.payload.get_string_or_empty("data", "currency");
		std::string_view exchange_out = msg.payload.get_string_or_empty("data", "exchange_name");
		return {price_out, std::string(currency_out), std::string(exchange_out)};
	} while (true);
}

void ticker_price_bitcoinity_wren (wren::VM& vm) {
	TickerPrice* const tp = wren::make_foreign_object<TickerPrice>(vm, "main");
	*tp = ticker_price_bitoinity(wren::get<const char*>(vm, 1), wren::get<const char*>(vm, 2));
}

class MyWrenConfiguration : public wren::DefConfiguration {
public:
	wren::foreign_class_t foreign_class_fn(
		wren::VM* vm,
		std::string_view module,
		std::string_view class_name
	) {
		if (module == "main" and class_name == "TickerPrice")
			return wren::make_foreign_class<TickerPrice>();
		else
			return {nullptr, nullptr};
	}
};
} //unnamed namespace

int main() {
	MyWrenConfiguration config;
	wren::VM vm(&config, nullptr);
	vm.callback_manager()
		.add_callback(true, "main", "Bitcoinity", "ticker(_,_)", &ticker_price_bitcoinity_wren)
		.add_callback(false, "main", "TickerPrice", "price", wren::make_method_bindable<&TickerPrice::price>())
		.add_callback(false, "main", "TickerPrice", "currency", wren::make_method_bindable<&TickerPrice::currency>())
		.add_callback(false, "main", "TickerPrice", "is_valid", wren::make_method_bindable<&TickerPrice::is_valid>())
		.add_callback(false, "main", "TickerPrice", "exchange", wren::make_method_bindable<&TickerPrice::exchange>());

	vm.interpret("main", g_script);
	wren::call<void>(vm, {"main", "the_app"}, "start");

	return 0;
}