Move factory implementation out of header

src/backend_factory.cpp

@@ -0,0 +1,40 @@
+#include <stdexcept>
+#include <memory>
+
+#ifdef USE_CUDA
+#include "backend/cuda/cuda.cuh"
+#endif
+
+#include "backend.hpp"
+
+namespace CUDANet {    
+    
+std::unique_ptr<Backend> BackendFactory::create(BackendType backend_type, const BackendConfig& config) {
+    switch (backend_type)
+    {
+    case BackendType::CUDA_BACKEND:
+        #ifdef USE_CUDA
+
+        if (!CUDANet::Backends::CUDA::is_cuda_available()) {
+            throw std::runtime_error("No CUDA devices found")
+        }
+
+        auto cuda = std::make_unique<CUDANet::Backends::CUDA>(config);
+        cuda.initialize();
+
+        return cuda;
+
+        #else
+        throw std::runtime_error("Library was compiled without CUDA support.");
+        #endif
+
+        break;
+    
+    default:
+        break;
+    }
+
+    return nullptr;
+}
+
+} // namespace CUDANet