# GitHub Copilot Instructions for OpenMB

This document provides context and instructions for GitHub Copilot and other AI coding assistants when working on the OpenMB project.

## Project Overview

OpenMB is a C++20 game engine project that follows strict coding standards and conventions. When generating code or suggestions, always adhere to the guidelines outlined in this document.

## Core Principles

1. **Consistency over personal preference** - Follow existing patterns in the codebase
2. **Modern C++20** - Use modern C++ features appropriately
3. **Cross-platform compatibility** - Code must work on Windows, Linux, and macOS
4. **Clear documentation** - All public APIs should have Doxygen comments
5. **Memory safety** - Prefer RAII and smart pointers over manual memory management

## Code Style Requirements

### Formatting

**CRITICAL: All code must follow these formatting rules:**

```cpp
// Braces - ALWAYS on their own line (Allman/BSD style)
void myFunction()
{
    if (condition)
    {
        doSomething();
    }
    else
    {
        doSomethingElse();
    }
}

// NOT this:
void myFunction() {
    if (condition) {
        doSomething();
    } else {
        doSomethingElse();
    }
}
```

- **Indentation**: 4 spaces (NEVER tabs)
- **Line length**: Maximum 120 columns
- **Pointer alignment**: Left-aligned with type (`Ptr* ptr`, not `Ptr *ptr`)
- **Spacing**: Space after control keywords (`if (`, `for (`, `while (`), no space after function names

### Naming Conventions

**CRITICAL: Follow these naming rules exactly:**

```cpp
// Classes and Structs - PascalCase
class PlayerManager { };
struct GameState { };

// Functions and Methods - camelCase
void processInput();
bool isGameRunning() const;

// Member Variables - 'm' prefix + PascalCase
class MyClass
{
private:
    int mHealthPoints;
    std::string mPlayerName;
    bool mIsActive;
};

// Local Variables and Parameters - camelBack
void updatePlayer(const Ptr& playerPtr, int deltaTime)
{
    int currentHealth = getHealth(playerPtr);
    float movementSpeed = calculateSpeed();
}

// Namespaces - PascalCase with MB prefix for project namespaces
namespace MBWorld { }
namespace MBMechanics { }
namespace MBBase { }

// Constants and Enums - PascalCase
enum class GameState
{
    Loading,
    Running,
    Paused
};

constexpr int MaxPlayers = 64;
```

### Include Guards

**ALWAYS use this format for include guards:**

```cpp
#ifndef OPENMB_<PATH_TO_FILE>_H
#define OPENMB_<PATH_TO_FILE>_H

// Header content

#endif
```

Example: For file `apps/openmb/mbworld/player.hpp`
```cpp
#ifndef OPENMB_APPS_OPENMB_MBWORLD_PLAYER_H
#define OPENMB_APPS_OPENMB_MBWORLD_PLAYER_H
```

### Include Order

**ALWAYS organize includes in this order:**

```cpp
#include "relatedheader.hpp"  // Related header first (for .cpp files)

#include <cstdint>            // C system headers
#include <cmath>

#include <string>             // C++ standard library
#include <vector>
#include <memory>

#include <osg/Vec3f>          // External libraries
#include <MyGUI_Widget.h>

#include <components/esm/refid.hpp>  // Project headers
#include "../mbbase/environment.hpp"
```

### Namespace Structure

```cpp
namespace MBWorld
{
    // All namespace content indented
    class MyClass
    {
    public:  // Access modifiers outdented by 4 spaces
        MyClass();
        
    private:
        int mData;
    };
    
    void freeFunction();
}
```

## Code Generation Guidelines

### When Creating New Classes

**ALWAYS generate headers like this:**

```cpp
#ifndef OPENMB_APPS_OPENMB_MBWORLD_MYCLASS_H
#define OPENMB_APPS_OPENMB_MBWORLD_MYCLASS_H

#include <string>
#include <vector>

namespace MBWorld
{
    /// Brief description of what this class does
    class MyClass
    {
    public:
        MyClass();
        ~MyClass() = default;

        /// Brief description of method
        /// \param input Description of parameter
        /// \return Description of return value
        bool processData(int input);

        /// Get the current value
        int getValue() const;

    private:
        int mValue;
        std::string mName;
        std::vector<int> mData;
    };
}

#endif
```

**And implementations like this:**

```cpp
#include "myclass.hpp"

#include <algorithm>
#include <stdexcept>

namespace MBWorld
{
    MyClass::MyClass()
        : mValue(0)
        , mName()
        , mData()
    {
    }

    bool MyClass::processData(int input)
    {
        if (input < 0)
        {
            throw std::runtime_error("Invalid input");
        }

        mValue = input;
        return true;
    }

    int MyClass::getValue() const
    {
        return mValue;
    }
}
```

### Modern C++ Patterns to Use

```cpp
// Smart pointers instead of raw pointers
std::unique_ptr<Dialog> mDialog;
std::shared_ptr<Resource> mResource;

// Range-based for loops
for (const auto& item : container)
{
    process(item);
}

// Auto for complex types
auto iterator = myMap.find(key);
auto result = complexFunction();

// nullptr instead of NULL
Ptr* ptr = nullptr;

// override keyword for virtual functions
void myMethod() override;

// constexpr for compile-time constants
constexpr int BufferSize = 1024;

// Const correctness
void processData(const std::string& input) const;

// Structured bindings (C++17)
for (const auto& [key, value] : myMap)
{
    // ...
}
```

### Patterns to AVOID

```cpp
// DON'T use manual memory management
MyClass* obj = new MyClass();  // BAD
delete obj;                     // BAD

// DO use smart pointers or stack allocation
auto obj = std::make_unique<MyClass>();  // GOOD
MyClass obj;                              // GOOD (when appropriate)

// DON'T omit braces for single-line blocks
if (condition)
    doSomething();  // BAD

// DO always use braces
if (condition)
{
    doSomething();  // GOOD
}

// DON'T use raw pointers for ownership
void takeOwnership(MyClass* ptr);  // BAD

// DO use smart pointers
void takeOwnership(std::unique_ptr<MyClass> ptr);  // GOOD

// DON'T ignore const correctness
void getData(Ptr& ptr);  // BAD if not modifying

// DO use const when appropriate
void getData(const Ptr& ptr) const;  // GOOD
```

### Virtual Functions and Inheritance

```cpp
class Base
{
public:
    virtual ~Base() = default;
    
    /// Pure virtual function
    virtual void mustImplement() = 0;
    
    /// Virtual function with default implementation
    virtual void canOverride();
};

class Derived : public Base
{
public:
    // Always use override keyword
    void mustImplement() override;
    void canOverride() override;
    
    // Use final to prevent further overriding
    void finalMethod() final;
};
```

### Exception Handling

```cpp
// Throw exceptions for error conditions
void MyClass::validate()
{
    if (!isValid())
    {
        throw std::runtime_error("Invalid state detected");
    }
    
    if (mData.empty())
    {
        throw std::logic_error("Data cannot be empty");
    }
}

// Use specific exception types
void processFile(const std::string& filename)
{
    if (!fileExists(filename))
    {
        throw std::invalid_argument("File does not exist: " + filename);
    }
}
```

### Documentation Comments

**ALWAYS add Doxygen comments for:**
- All public classes
- All public methods
- All public member variables
- Complex private methods

```cpp
/// Manages the game's resource loading and caching
///
/// This class handles asynchronous loading of game resources
/// and maintains a cache to avoid redundant disk access.
class ResourceManager
{
public:
    /// Load a resource by its identifier
    ///
    /// \param resourceId The unique identifier of the resource
    /// \param async If true, load asynchronously
    /// \return Pointer to the loaded resource, or nullptr if failed
    /// \throws std::runtime_error if resource format is invalid
    Resource* loadResource(const ESM::RefId& resourceId, bool async = false);
    
    int mCacheSize; ///< Maximum number of cached resources
};
```

## Common OpenMB Patterns

### Using Project Types

```cpp
// ESM::RefId for game object identifiers
ESM::RefId mItemId;
ESM::RefId mSpellId;

// Ptr and ConstPtr for game object references
void processObject(const MBWorld::ConstPtr& ptr);
void modifyObject(MBWorld::Ptr& ptr);

// Common project classes
MBWorld::CellStore* cell;
MBBase::Environment& env = MBBase::Environment::get();
```

### Initialization Lists

**ALWAYS use initialization lists for constructors:**

```cpp
MyClass::MyClass(int value, const std::string& name)
    : mValue(value)
    , mName(name)
    , mCounter(0)
    , mIsActive(false)
{
    // Constructor body for additional logic only
}
```

### Const Correctness

```cpp
class DataManager
{
public:
    // Non-const methods for modification
    void addData(int value);
    void clearData();
    
    // Const methods for reading only
    int getDataCount() const;
    bool hasData() const;
    const std::vector<int>& getData() const;
    
    // Return const reference when not modifying
    const std::string& getName() const { return mName; }
    
private:
    std::vector<int> mData;
    std::string mName;
};
```

### Error Handling in Base Classes

```cpp
// Use exceptions for unsupported operations in base classes
class GameObjectBase
{
public:
    virtual InventoryStore& getInventoryStore(const Ptr& ptr) const
    {
        throw std::runtime_error("This object type does not have an inventory");
    }
    
    virtual float getWeight(const Ptr& ptr) const
    {
        throw std::runtime_error("This object type does not have weight");
    }
};
```

## File Organization

### Header File Template

```cpp
#ifndef OPENMB_<PATH>_H
#define OPENMB_<PATH>_H

// Includes in proper order
#include <standard/library>

#include <external/library>

#include <components/project/header.hpp>

// Forward declarations
namespace MBWorld
{
    class Ptr;
}

namespace <YourNamespace>
{
    /// Class documentation
    class ClassName
    {
    public:
        // Public interface
        
    protected:
        // Protected members
        
    private:
        // Private members
        // All member variables with 'm' prefix
    };
}

#endif
```

### Implementation File Template

```cpp
#include "classname.hpp"

#include <algorithm>
#include <stdexcept>

#include "../other/project/headers.hpp"

namespace <YourNamespace>
{
    ClassName::ClassName()
        : mMember1()
        , mMember2(0)
    {
    }
    
    void ClassName::method()
    {
        // Implementation
    }
}
```

## Platform Considerations

```cpp
// Avoid platform-specific code when possible
// If necessary, use clear preprocessor guards

#ifdef _WIN32
    // Windows-specific code
#elif defined(__linux__)
    // Linux-specific code
#elif defined(__APPLE__)
    // macOS-specific code
#else
    #error "Unsupported platform"
#endif

// Prefer cross-platform solutions
#include <filesystem>  // C++17 cross-platform filesystem
namespace fs = std::filesystem;
```

## Testing and Validation

When generating code, consider:

1. **Is the code cross-platform compatible?**
2. **Are all member variables initialized?**
3. **Is const correctness maintained?**
4. **Are there proper Doxygen comments?**
5. **Does it follow the naming conventions?**
6. **Is memory managed safely (RAII/smart pointers)?**
7. **Are exceptions used appropriately?**
8. **Does it follow the brace style (Allman)?**

## Quick Reference Checklist

Before generating code, verify:

- [ ] Braces on their own line (Allman style)
- [ ] 4 space indentation (no tabs)
- [ ] Member variables have 'm' prefix
- [ ] Functions use camelCase
- [ ] Classes use PascalCase
- [ ] Include guards follow OPENMB_<PATH>_H format
- [ ] Includes are in correct order
- [ ] Const correctness is maintained
- [ ] Smart pointers used instead of raw pointers for ownership
- [ ] Override keyword used for virtual functions
- [ ] Doxygen comments on public APIs
- [ ] Initialization lists used in constructors
- [ ] Namespaces properly indented
- [ ] Line length under 120 columns
- [ ] Exception handling for error conditions

## Example: Complete Class Generation

When asked to create a new class, generate both header and implementation following this pattern:

**Header (playermanager.hpp):**
```cpp
#ifndef OPENMB_APPS_OPENMB_MBWORLD_PLAYERMANAGER_H
#define OPENMB_APPS_OPENMB_MBWORLD_PLAYERMANAGER_H

#include <memory>
#include <string>
#include <vector>

#include <components/esm/refid.hpp>

namespace MBWorld
{
    class Ptr;
    class CellStore;

    /// Manages player state and interactions
    ///
    /// This class handles player initialization, state updates,
    /// and interactions with the game world.
    class PlayerManager
    {
    public:
        PlayerManager();
        ~PlayerManager() = default;

        /// Initialize the player in the game world
        /// \param playerId The unique identifier for the player
        /// \param startCell The starting cell for the player
        /// \return True if initialization succeeded
        bool initialize(const ESM::RefId& playerId, CellStore* startCell);

        /// Update player state
        /// \param deltaTime Time elapsed since last update in seconds
        void update(float deltaTime);

        /// Get the current player pointer
        /// \return Const reference to the player pointer
        const Ptr& getPlayer() const;

        /// Check if player is initialized
        bool isInitialized() const;

    private:
        /// Load player data from save
        void loadPlayerData(const ESM::RefId& playerId);

        /// Validate player state
        bool validateState() const;

        Ptr mPlayer;
        ESM::RefId mPlayerId;
        bool mIsInitialized;
        float mTimeSinceLastUpdate;
    };
}

#endif
```

**Implementation (playermanager.cpp):**
```cpp
#include "playermanager.hpp"

#include <stdexcept>

#include "../mbbase/environment.hpp"
#include "cellstore.hpp"
#include "ptr.hpp"

namespace MBWorld
{
    PlayerManager::PlayerManager()
        : mPlayer()
        , mPlayerId()
        , mIsInitialized(false)
        , mTimeSinceLastUpdate(0.0f)
    {
    }

    bool PlayerManager::initialize(const ESM::RefId& playerId, CellStore* startCell)
    {
        if (!startCell)
        {
            throw std::invalid_argument("Start cell cannot be null");
        }

        if (playerId.empty())
        {
            throw std::invalid_argument("Player ID cannot be empty");
        }

        mPlayerId = playerId;
        loadPlayerData(playerId);

        // Additional initialization logic here

        mIsInitialized = validateState();
        return mIsInitialized;
    }

    void PlayerManager::update(float deltaTime)
    {
        if (!mIsInitialized)
        {
            throw std::runtime_error("Cannot update uninitialized player");
        }

        mTimeSinceLastUpdate += deltaTime;

        // Update logic here
    }

    const Ptr& PlayerManager::getPlayer() const
    {
        if (!mIsInitialized)
        {
            throw std::runtime_error("Player not initialized");
        }

        return mPlayer;
    }

    bool PlayerManager::isInitialized() const
    {
        return mIsInitialized;
    }

    void PlayerManager::loadPlayerData(const ESM::RefId& playerId)
    {
        // Load implementation
    }

    bool PlayerManager::validateState() const
    {
        // Validation implementation
        return true;
    }
}
```

## Summary

When generating code for OpenMB:
1. Follow Allman brace style (braces on own lines)
2. Use proper naming (mMemberVars, camelCaseFunctions, PascalCaseClasses)
3. Include Doxygen documentation
4. Use modern C++20 features
5. Maintain const correctness
6. Use smart pointers and RAII
7. Follow include order and guards
8. Keep code cross-platform

**Remember: Consistency with existing code is paramount. When in doubt, follow the patterns already established in the codebase.**