Starting point

.gitignore

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+# Build directories
+build/
+cmake-build-*/
+out/
+
+# IDE files
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# Compiled files
+*.o
+*.a
+*.so
+*.dylib
+
+# CMake generated files
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
+compile_commands.json
+CTestTestfile.cmake
+Testing/
+
+# OS files
+.DS_Store
+Thumbs.db

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(factory_hole_core
+    VERSION 0.1.0
+    DESCRIPTION "High-performance ECS-based factory game engine core"
+    LANGUAGES CXX
+)
+
+# C++17 standard
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+# Options
+option(FACTORY_CORE_BUILD_TESTS "Build tests" ON)
+option(FACTORY_CORE_BUILD_EXAMPLES "Build examples" ON)
+
+# Export compile commands for IDE support
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+# Include dependency management
+include(cmake/FetchDependencies.cmake)
+
+# Add subdirectories
+add_subdirectory(src)
+
+if(FACTORY_CORE_BUILD_TESTS)
+    enable_testing()
+    add_subdirectory(tests)
+endif()
+
+if(FACTORY_CORE_BUILD_EXAMPLES)
+    add_subdirectory(examples)
+endif()

cmake/FetchDependencies.cmake

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+include(FetchContent)
+
+# Fetch flecs - high-performance ECS library
+FetchContent_Declare(
+    flecs
+    GIT_REPOSITORY https://github.com/SanderMertens/flecs.git
+    GIT_TAG v4.0.4
+    GIT_SHALLOW TRUE
+)
+
+# Fetch doctest - testing framework (same as Godot uses)
+FetchContent_Declare(
+    doctest
+    GIT_REPOSITORY https://github.com/doctest/doctest.git
+    GIT_TAG v2.4.11
+    GIT_SHALLOW TRUE
+)
+
+# Make dependencies available
+FetchContent_MakeAvailable(flecs doctest)

src/CMakeLists.txt

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+add_subdirectory(core)

src/core/CMakeLists.txt

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+# Factory Core library
+add_library(factory_core STATIC
+    factory_core.cpp
+)
+
+# Add alias for consistent usage
+add_library(factory::core ALIAS factory_core)
+
+target_include_directories(factory_core
+    PUBLIC
+        $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
+        $<INSTALL_INTERFACE:include>
+)
+
+target_link_libraries(factory_core
+    PUBLIC
+        flecs::flecs_static
+)
+
+# Set compile features
+target_compile_features(factory_core PUBLIC cxx_std_17)

src/core/factory_core.cpp

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+#include "factory_core.hpp"
+
+// Implementation file for factory_core
+// Currently empty as Core is header-only, but needed for static library target
+// Future implementations will go here

src/core/factory_core.hpp

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+#pragma once
+
+#include <flecs.h>
+
+namespace factory {
+
+// Core engine class wrapping flecs world
+class Core {
+public:
+    Core() : world_() {}
+
+    // Access the underlying flecs world
+    flecs::world& world() { return world_; }
+    const flecs::world& world() const { return world_; }
+
+    // Progress the simulation by one tick
+    bool progress(float delta_time = 0.0f) {
+        return world_.progress(delta_time);
+    }
+
+private:
+    flecs::world world_;
+};
+
+} // namespace factory

tests/CMakeLists.txt

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+# Test executable
+add_executable(factory_core_tests
+    test_main.cpp
+    test_example.cpp
+)
+
+target_link_libraries(factory_core_tests
+    PRIVATE
+        factory_core
+        doctest::doctest
+)
+
+# Register with CTest
+include(${doctest_SOURCE_DIR}/scripts/cmake/doctest.cmake)
+doctest_discover_tests(factory_core_tests)

tests/test_example.cpp

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+#include <doctest/doctest.h>
+#include "factory_core.hpp"
+
+TEST_CASE("Core initialization") {
+    factory::Core core;
+
+    SUBCASE("World is valid after construction") {
+        CHECK(core.world().id() != 0);
+    }
+
+    SUBCASE("Progress returns true") {
+        CHECK(core.progress() == true);
+    }
+}
+
+TEST_CASE("Basic ECS operations") {
+    factory::Core core;
+    auto& world = core.world();
+
+    SUBCASE("Can create entity") {
+        auto entity = world.entity();
+        CHECK(entity.is_valid());
+    }
+
+    SUBCASE("Can create entity with name") {
+        auto entity = world.entity("test_entity");
+        CHECK(entity.is_valid());
+        CHECK(entity.name() == std::string("test_entity"));
+    }
+}

tests/test_main.cpp

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+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+#include <doctest/doctest.h>