Core: Workflow to generate RPC headers

CMakeLists.txt

@@ -81,6 +81,33 @@ endif()
 add_library(project_options INTERFACE)
 target_compile_features(project_options INTERFACE cxx_std_17)
 
+# Find Python (defines ${Python_EXECUTABLE})
+find_package(Python REQUIRED)
+message(STATUS "Python_EXECUTABLE: ${Python_EXECUTABLE}")
+message(STATUS "Python_VERSION: ${Python_VERSION}")
+if(NOT ${Python_VERSION_MAJOR} EQUAL 3)
+    message(FATAL_ERROR "Python 3 is required")
+endif()
+
+# Generate RPC calls from IDL
+set_property(
+    DIRECTORY
+    APPEND
+    PROPERTY CMAKE_CONFIGURE_DEPENDS ${CMAKE_SOURCE_DIR}/tools/generate_rpc_stubs.py
+)
+message(STATUS "Generating RPC stubs")
+message(STATUS "Calling: ${Python_EXECUTABLE} ${CMAKE_SOURCE_DIR}/tools/generate_rpc_stubs.py ${CMAKE_BINARY_DIR}")
+execute_process(
+    COMMAND ${Python_EXECUTABLE} ${CMAKE_SOURCE_DIR}/tools/generate_rpc_stubs.py ${CMAKE_BINARY_DIR}
+    WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
+    RESULT_VARIABLE RPC_EXIT_CODE
+)
+if (NOT RPC_EXIT_CODE EQUAL 0)
+    message(FATAL_ERROR "Failed to generate RPC stubs")
+endif()
+
+include_directories(${CMAKE_BINARY_DIR}/generated) # Globally include the build/generated directory
+
 # Link this 'library' to use the warnings specified in CompilerWarnings.cmake
 add_library(project_warnings INTERFACE)
 set_project_warnings(project_warnings)

src/world/world_server.cpp

@@ -95,3 +95,12 @@ void WorldServer::Tick()
 {
     Application::Tick();
 }
+
+auto WorldServer::playersOnline_REQ_RECV(TestStruct) -> std::size_t
+{
+    return 0;
+}
+
+void WorldServer::playersOnline_RES_SEND(std::size_t)
+{
+}

src/world/world_server.h

@@ -30,15 +30,20 @@
 #include "conquest_system.h"
 #include "http_server.h"
 #include "message_server.h"
+#include "rpc_world_service.h"
 
-class WorldServer final : public Application
+class WorldServer final : public Application, public IRPCWorldService
 {
 public:
     WorldServer(int argc, char** argv);
     ~WorldServer() override;
 
     void Tick() override;
 
+    // IRPCWorldService
+    auto playersOnline_REQ_RECV(TestStruct) -> std::size_t override;
+    void playersOnline_RES_SEND(std::size_t) override;
+
     std::unique_ptr<HTTPServer>               httpServer;
     std::unique_ptr<message_server_wrapper_t> messageServer;
 

tools/generate_rpc_stubs.py

@@ -0,0 +1,123 @@
+# Assumed to be run by CMake from the root of the repository.
+# Generated files are placed in /build/generated/
+# Usage: python tools/generate_rpc_stubs.py "${CMAKE_BINARY_DIR}"
+
+import os
+import sys
+
+# ========================
+# Define RPC transport structs here
+#
+# Don't use dynamic arrays or pointers in these structs.
+# ========================
+
+rpc_structs = [
+    ("TestStruct", "int x", "int y", "float z"),
+    ("TestStruct2", "int x", "int y", "float z"),
+]
+
+# ========================
+# Define RPC calls here
+#
+# Each of these generates up to 4 functions:
+# 1. Send function in origin service (SEND)
+# 2. Receive function in destination service (RECV)
+# 3. Send function in destination service (SEND)
+# 4. Receive function in origin service (RECV)
+#
+# So each service will end up with up to 2 function calls per RPC call.
+#
+# Format:
+# (
+#     (Origin Service, Destination Service),
+#     Request Name,
+#     Response Arg (string of C++ type),
+#     Request Args (List of strings of C++ types, can be an empty list),
+# )
+#
+# C++ types can be numerics, structs, enums, etc. (anything that can be serialized).
+# ========================
+
+rpc_calls = [
+    # Map to World
+    (("map", "world"), "playersOnline", "std::size_t", ["TestStruct"]),
+]
+
+# ========================
+
+# Get CMAKE_BINARY_DIR from args
+if len(sys.argv) < 2:
+    print('Usage: python tools/generate_rpc_stubs.py "${CMAKE_BINARY_DIR}"')
+    sys.exit(1)
+
+CMAKE_BINARY_DIR = sys.argv[1]
+GENERATED_PATH = f"{CMAKE_BINARY_DIR}/generated"
+
+print(f"Generating RPC stubs in {GENERATED_PATH}")
+
+# Ensure the generated directory exists
+if not os.path.exists(f"{CMAKE_BINARY_DIR}/generated"):
+    os.makedirs(f"{CMAKE_BINARY_DIR}/generated")
+
+AUTO_GENERATED_WARNING = """// THIS FILE IS AUTO-GENERATED BY `tools/generate_rpc_stubs.py`
+// ANY CHANGES MADE HERE WILL BE OVERWRITTEN BY THE GENERATOR\n"""
+
+map_rpc_funcs = []
+world_rpc_funcs = []
+
+for rpc_call in rpc_calls:
+    origin = rpc_call[0][0]
+    dest = rpc_call[0][1]
+    func_name = rpc_call[1]
+    response_arg = rpc_call[2]
+    request_args = rpc_call[3]
+
+    if origin == "map":
+        # 1. Send function in origin service (SEND)
+        map_rpc_funcs.append(
+            f"    virtual void {func_name}_REQ_SEND({', '.join(request_args)}) = 0;"
+        )
+        # 4. Receive function in origin service (RECV)
+        map_rpc_funcs.append(
+            f"    virtual auto {func_name}_RES_RECV() -> {response_arg} = 0;"
+        )
+
+    if dest == "world":
+        # 2. Receive function in destination service (RECV)
+        world_rpc_funcs.append(
+            f"    virtual auto {func_name}_REQ_RECV({', '.join(request_args)}) -> {response_arg} = 0;"
+        )
+        # 3. Send function in destination service (SEND)
+        world_rpc_funcs.append(
+            f"    virtual void {func_name}_RES_SEND({response_arg}) = 0;"
+        )
+
+with open(f"{CMAKE_BINARY_DIR}/generated/rpc_structs.h", "w") as f:
+    f.write(AUTO_GENERATED_WARNING)
+    f.write("#pragma once\n\n")
+    f.write("#include <cstddef>\n")
+    for struct in rpc_structs:
+        f.write(f"\nstruct {struct[0]}\n{{\n")
+        for member in struct[1:]:
+            f.write(f"    {member};\n")
+        f.write("};\n")
+
+with open(f"{CMAKE_BINARY_DIR}/generated/rpc_map_service.h", "w") as f:
+    f.write(AUTO_GENERATED_WARNING)
+    f.write("#pragma once\n\n")
+    f.write('#include "rpc_structs.h"\n\n')
+    f.write("#include <cstddef>\n\n")
+    f.write("class IRPCMapService\n{\npublic:\n")
+    f.write("    virtual ~IRPCMapService() = default;\n\n")
+    f.write("\n".join(map_rpc_funcs))
+    f.write("\n};\n")
+
+with open(f"{CMAKE_BINARY_DIR}/generated/rpc_world_service.h", "w") as f:
+    f.write(AUTO_GENERATED_WARNING)
+    f.write("#pragma once\n\n")
+    f.write('#include "rpc_structs.h"\n\n')
+    f.write("#include <cstddef>\n\n")
+    f.write("class IRPCWorldService\n{\npublic:\n")
+    f.write("    virtual ~IRPCWorldService() = default;\n\n")
+    f.write("\n".join(world_rpc_funcs))
+    f.write("\n};\n")