Core/DBLayer: Add nicer api for SQLQueryHolders

(cherry picked from commit 9b806c6b5d)

src/server/database/Database/DatabaseEnvFwd.h

@@ -86,6 +86,8 @@ using HotfixDatabaseQueryHolder = SQLQueryHolder<HotfixDatabaseConnection>;
 using LoginDatabaseQueryHolder = SQLQueryHolder<LoginDatabaseConnection>;
 using WorldDatabaseQueryHolder = SQLQueryHolder<WorldDatabaseConnection>;
 
+class SQLQueryHolderCallback;
+
 // mysql
 struct MySQLHandle;
 struct MySQLResult;

src/server/database/Database/DatabaseWorkerPool.cpp

@@ -227,7 +227,7 @@ QueryCallback DatabaseWorkerPool<T>::AsyncQuery(PreparedStatement<T>* stmt)
 }
 
 template <class T>
-QueryResultHolderFuture DatabaseWorkerPool<T>::DelayQueryHolder(SQLQueryHolder<T>* holder)
+SQLQueryHolderCallback DatabaseWorkerPool<T>::DelayQueryHolder(SQLQueryHolder<T>* holder)
 {
     SQLQueryHolderTask* task = new SQLQueryHolderTask(holder);
     // Store future result before enqueueing - task might get already processed and deleted before returning from this method

src/server/database/Database/DatabaseWorkerPool.h

@@ -160,7 +160,7 @@ class DatabaseWorkerPool
         //! return object as soon as the query is executed.
         //! The return value is then processed in ProcessQueryCallback methods.
         //! Any prepared statements added to this holder need to be prepared with the CONNECTION_ASYNC flag.
-        QueryResultHolderFuture DelayQueryHolder(SQLQueryHolder<T>* holder);
+        SQLQueryHolderCallback DelayQueryHolder(SQLQueryHolder<T>* holder);
 
         /**
             Transaction context methods.

src/server/database/Database/QueryHolder.cpp

@@ -92,3 +92,14 @@ bool SQLQueryHolderTask::Execute()
     m_result.set_value(m_holder);
     return true;
 }
+
+bool SQLQueryHolderCallback::InvokeIfReady()
+{
+    if (m_future.valid() && m_future.wait_for(std::chrono::seconds(0)) == std::future_status::ready)
+    {
+        m_callback(m_future.get());
+        return true;
+    }
+
+    return false;
+}

src/server/database/Database/QueryHolder.h

@@ -63,4 +63,23 @@ class TC_DATABASE_API SQLQueryHolderTask : public SQLOperation
         QueryResultHolderFuture GetFuture() { return m_result.get_future(); }
 };
 
+class TC_DATABASE_API SQLQueryHolderCallback
+{
+public:
+    SQLQueryHolderCallback(QueryResultHolderFuture&& future) : m_future(std::move(future)) { }
+    SQLQueryHolderCallback(SQLQueryHolderCallback&&) = default;
+
+    SQLQueryHolderCallback& operator=(SQLQueryHolderCallback&&) = default;
+
+    void AfterComplete(std::function<void(SQLQueryHolderBase*)> callback) &
+    {
+        m_callback = std::move(callback);
+    }
+
+    bool InvokeIfReady();
+
+    QueryResultHolderFuture m_future;
+    std::function<void(SQLQueryHolderBase*)> m_callback;
+};
+
 #endif