[Feat] (MG_Impl/Program): use helper functions to simplify the code

MobileGL/MG_Impl/GLImpl/Program/GL_Program.cpp

@@ -4,6 +4,58 @@
 
 namespace MobileGL {
     namespace MG_Impl::GLImpl {
+        static bool CheckShaderNameValidity(Uint shader) {
+            if (!MG_State::pGLContext->ValidateShaderName(shader)) {
+                MG_State::pGLContext->RecordError(
+                    ErrorCode::InvalidValue,
+                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                 "`shader` is not a value generated by OpenGL."));
+                return false;
+            }
+            return true;
+        }
+
+        static SharedPtr<MG_State::GLState::ShaderObject> TryToGetShaderObject(Uint shader) {
+            if (!CheckShaderNameValidity(shader))
+                return nullptr;
+
+            auto shaderObject = MG_State::pGLContext->GetShaderObject(shader);
+            if (!shaderObject) {
+                MG_State::pGLContext->RecordError(
+                    ErrorCode::InvalidOperation,
+                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                 "`shader` is not a shader object."));
+                return nullptr;
+            }
+            return shaderObject;
+        }
+
+        static bool CheckProgramNameValidity(GLuint program) {
+            if (!MG_State::pGLContext->ValidateProgramName(program)) {
+                MG_State::pGLContext->RecordError(
+                    ErrorCode::InvalidValue,
+                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                 "`program` is not a value generated by OpenGL"));
+                return false;
+            }
+            return true;
+        }
+
+        static SharedPtr<MG_State::GLState::ProgramObject> TryToGetProgramObject(GLuint program) {
+            if (!CheckProgramNameValidity(program))
+                return nullptr;
+
+            auto programObject = MG_State::pGLContext->GetProgramObject(program);
+            if (!programObject) {
+                MG_State::pGLContext->RecordError(
+                    ErrorCode::InvalidOperation,
+                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
+                                                 "`program` is not a program object."));
+                return nullptr;
+            }
+            return programObject;
+        }
+
         void AttachShader_State(GLuint program, GLuint shader) {
             THROW_UNIMPL_EXCEPTION;
         }
@@ -13,22 +65,9 @@ namespace MobileGL {
         }
 
         void CompileShader_State(GLuint shader) {
-            if (!MG_State::pGLContext->ValidateShaderName(shader)) {
+            auto shaderObject = TryToGetShaderObject(shader);
-                MG_State::pGLContext->RecordError(
+            if (!shaderObject)
-                    ErrorCode::InvalidValue,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`shader` is not a value generated by OpenGL."));
                 return;
-            }
-
-            auto shaderObject = MG_State::pGLContext->GetShaderObject(shader);
-            if (!shaderObject) {
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidOperation,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`shader` is not a shader object."));
-                return;
-            }
             shaderObject->Compile();
         }
 
@@ -49,54 +88,24 @@ namespace MobileGL {
         }
 
         void DeleteProgram_State(GLuint program) {
-            if (!MG_State::pGLContext->ValidateProgramName(program)) {
+            if (!CheckProgramNameValidity(program))
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidValue,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`program` is not a value generated by OpenGL"));
                 return;
-            }
             MG_State::pGLContext->MarkProgramForDeletion(program);
         }
 
         void DeleteShader_State(GLuint shader) {
-            if (!MG_State::pGLContext->ValidateShaderName(shader)) {
+            if (!CheckProgramNameValidity(shader))
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidValue,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`shader` is not a value generated by OpenGL"));
                 return;
-            }
             MG_State::pGLContext->MarkShaderForDeletion(shader);
         }
 
         void DetachShader_State(GLuint program, GLuint shader) {
-            if (!MG_State::pGLContext->ValidateProgramName(program) ||
+            auto shaderObject = TryToGetShaderObject(shader);
-                !MG_State::pGLContext->ValidateShaderName(shader)) {
+            if (!shaderObject)
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidValue,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "Either `program` or `shader` is a value that was not generated by OpenGL"));
                 return;
-            }
+            auto programObject = TryToGetProgramObject(program);
-
+            if (!programObject)
-            auto programObject = MG_State::pGLContext->GetProgramObject(program);
-            if (!programObject) {
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidOperation,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`program` is not a program object."));
                 return;
-            }
-
-            auto shaderObject = MG_State::pGLContext->GetShaderObject(shader);
-            if (!shaderObject) {
-                MG_State::pGLContext->RecordError(
-                    ErrorCode::InvalidOperation,
-                    MakeShared<GenericErrorInfo>("MG_Impl/GLImpl", __func__,
-                                                 "`shader` is not a shader object."));
-                return;
-            }
 
             auto count = programObject->DetachShader(shaderObject);
             if (count <= 0) {
@@ -163,7 +172,7 @@ namespace MobileGL {
              * A program object marked for deletion with glDeleteProgram but still in use as part of current
              * rendering state is still considered a program object and glIsProgram will return GL_TRUE.
             */
-            return MG_State::pGLContext->ValidateProgramName(program);
+            return CheckProgramNameValidity(program);
         }
 
         GLboolean IsShader_State(GLuint shader) {
@@ -171,11 +180,14 @@ namespace MobileGL {
              * A shader object marked for deletion with glDeleteShader but still attached to a program object is still
              * considered a shader object and glIsShader will return GL_TRUE.
             */
-            return MG_State::pGLContext->ValidateShaderName(shader);
+            return CheckShaderNameValidity(shader);
         }
 
         void LinkProgram_State(GLuint program) {
-            THROW_UNIMPL_EXCEPTION;
+            auto programObject = TryToGetProgramObject(program);
+            if (!programObject)
+                return;
+            programObject->Link();
         }
 
         void ShaderSource_State(GLuint shader, GLsizei count, const GLchar* const* string, const GLint* length) {