feat(Core/Common): add Asio network threading (#6063)

src/common/Asio/Resolver.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2016+ AzerothCore <www.azerothcore.org>, released under GNU AGPL v3 license: https://github.com/azerothcore/azerothcore-wotlk/blob/master/LICENSE-AGPL3
+ * Copyright (C) 2021+ WarheadCore <https://github.com/WarheadCore>
+ */
+
+#ifndef Resolver_h__
+#define Resolver_h__
+
+#include "IoContext.h"
+#include "Optional.h"
+#include <boost/asio/ip/tcp.hpp>
+#include <string>
+
+namespace acore::Asio
+{
+    /**
+     Hack to make it possible to forward declare resolver (one of its template arguments is a typedef to something super long and using nested classes)
+    */
+    class Resolver
+    {
+    public:
+        explicit Resolver(IoContext& ioContext) : _impl(ioContext) { }
+
+        Optional<boost::asio::ip::tcp::endpoint> Resolve(boost::asio::ip::tcp const& protocol, std::string const& host, std::string const& service)
+        {
+            boost::system::error_code ec;
+#if BOOST_VERSION >= 106600
+            boost::asio::ip::resolver_base::flags flagsResolver = boost::asio::ip::resolver_base::all_matching;
+            boost::asio::ip::tcp::resolver::results_type results = _impl.resolve(protocol, host, service, flagsResolver, ec);
+            if (results.begin() == results.end() || ec)
+                return {};
+
+            return results.begin()->endpoint();
+#else
+            boost::asio::ip::resolver_query_base::flags flagsQuery = boost::asio::ip::tcp::resolver::query::all_matching;
+            boost::asio::ip::tcp::resolver::query query(std::move(protocol), std::move(host), std::move(service), flagsQuery);
+            boost::asio::ip::tcp::resolver::iterator itr = _impl.resolve(query, ec);
+            boost::asio::ip::tcp::resolver::iterator end;
+            if (itr == end || ec)
+                return {};
+
+            return itr->endpoint();
+#endif
+        }
+
+    private:
+        boost::asio::ip::tcp::resolver _impl;
+    };
+}
+
+#endif // Resolver_h__