# AGENTS.md

## Project Overview

`cuber` is an OpenGL 3D renderer with multiple scenes.

## Build System

- **Generator:** Ninja
- **CMake minimum:** 3.21
- **C++ standard:** C++23

### Commands

```sh
cmake -S . -B build -GNinja
ninja -C build
./build/cuber
```

### Dependencies

Dependencies are managed via custom `Find*.cmake` scripts in `deps/`.
These scripts use `FetchContent` under the hood to download and build
libraries automatically.

To add a new dependency:

1. Add the corresponding `Find<name>.cmake` to `deps/`
2. Add `find_package(<name> REQUIRED)` to `CMakeLists.txt`
3. Link with `<name>::<name>` in `target_link_libraries()`

### Static Libraries

The project is split into static libraries:

- **`cbt_opengl`** — OpenGL abstraction and window management (window,
  context, buffer, texture, vao, shader, descriptor)
- **`cbt_scene`** — Base scene class
- **`scenes_cube`** — Spinning cube scene implementation
- **`scenes_sphere`** — Cube-to-sphere mapped mesh with diffuse lighting

### CMake Module Path

`deps/` is added to `CMAKE_MODULE_PATH` so `find_package()` resolves
to the custom scripts instead of system-installed packages.

## Coding Conventions

- **Language:** C++23
- **Trailing return type** for function signatures (e.g. `auto fn() -> void`)
- **4-space indentation**
- **No semicolons after closing braces** for namespaces/classes
- `auto` for obvious types (e.g. `auto main(...) -> int`)
- **East const** (e.g. `char const*` not `const char*`)
- **Trailing return type** for all function definitions, including
  operators (e.g. `auto operator=(T&&) noexcept -> T&`)
- **Public members first** in class declarations, private members at the
  bottom
- `<>` includes only for system headers (std, OS, etc.)
- `""` includes for third-party dependencies (e.g. `fmt`,
  `nlohmann/json`)
- **Naming:** `snake_case` for variables, functions, and classes
- **Naming:** `SCREAMING_SNAKE_CASE` only for macros and constants
- Include order:
  1. C++ standard library headers (`<chrono>`, `<vector>`, etc.)
  2. *(blank line)*
  3. C standard library headers (`<stdlib.h>`, `<string.h>`, etc.)
  4. *(blank line)*
  5. OS-specific headers (Windows API, POSIX, etc.)
  6. *(blank line)*
  7. Third-party dependencies (`"fmt/core.h"`, etc.)
  8. *(blank line)*
  9. Local/project headers

## Shell Scripts

- Always use `#!/bin/sh` shebang for shell scripts
- Scripts must be POSIX compliant (no bashisms)
- When providing commands to users:
  - Windows/PowerShell: use `` ` `` for line continuation
  - Unix/Linux/macOS: use `\` for line continuation

## Commit Messages

- Follow the 50/72 rule:
  - Subject line: max 50 characters
  - Body lines: wrapped at 72 characters
- Use conventional commit prefixes (`feat:`, `fix:`, `docs:`, `chore:`,
  etc.)
- Separate subject from body with a blank line

Example:

```
feat: add stopwatch timer

Replace Hello World with a live stopwatch that prints elapsed time
in HH:MM:SS.mmm format, updating every 10ms with color output.
```

## Documentation (Markdown)

- Wrap normal text and lists at **max 80 columns** (for readability in
  terminals and editors).
- **Exceptions**: Tables and code blocks (```` ``` ````) can exceed 80
  columns when formatting requires it (e.g. trees, alignment).
- Use standard Markdown: `**bold**`, `` `inline code` ``, `##` headings,
  `-` or numbered lists, fenced code blocks with language hints
  (```` ```cpp ````, ```` ```sh ````).
- Keep examples concise, up-to-date, and self-documenting.
- This file (`AGENTS.md`) follows its own rules.

## Source Layout

```text
cuber/
  CMakeLists.txt      # Build configuration
  cuber.cpp           # Entry point
  cbt/                # Project namespace (utilities)
    scene.hpp         # Base scene class
    scene.cpp         # Scene implementation
    window.hpp        # GLFW window RAII wrapper
    window.cpp        # Window implementation
    opengl/           # OpenGL abstraction layer
      context.hpp     # OpenGL context RAII wrapper (GLAD setup)
      context.cpp     # Context implementation
      buffer.hpp      # Buffer resource (VBO, EBO, UBO, SSBO)
      buffer.cpp      # Buffer implementation
      texture.hpp     # Texture resource
      texture.cpp     # Texture implementation
      descriptor.hpp  # Descriptor set (Vulkan-style binding)
      descriptor.cpp  # Descriptor implementation
      shader.hpp      # Shader program
      shader.cpp      # Shader implementation
      vao.hpp         # Vertex array object
      vao.cpp         # VAO implementation
  scenes/             # Application scenes
    cube.hpp          # Spinning cube scene
    cube.cpp          # Cube scene implementation
    sphere.hpp        # Cube-to-sphere mapped mesh
    sphere.cpp        # Sphere scene implementation
  deps/               # Custom Find*.cmake scripts
    Findfmt.cmake     # fmt library
```

## Platform Support

The project supports Windows, Linux, Emscripten, and Android via
`Platform.cmake` and `Flags.cmake` in `deps/`.