# Addon

**Path**: [`src/modbus/Addon.h`](../src/modbus/Addon.h)

**Revision History**: Initial documentation

Addon is a base class that extends the Component class, providing a foundation for creating modular extensions within the modbus system. It serves as a backward compatibility layer while ensuring consistent behavior across different types of add-ons.

## REQUIREMENTS

- ESP-32 microcontroller
- Platform.io development environment

## PROVIDES

- `Addon` class: Base class for creating modular components
- `Addons` type: A Vector container for storing Addon pointers
- `AddonFnPtr` type: Function pointer type for addon methods
- `byId()` utility function: Find an addon by its ID in a collection

## FEATURES

- Inheritance from Component class for consistent behavior
- Default run flags for standard execution modes
- Support for identifying addons through unique IDs
- Vector-based storage and retrieval of addons

## DEPENDENCIES

- [Component.h](../src/modbus/Component.h)
- [enums.h](../src/modbus/enums.h)
- [error_codes.h](../src/modbus/error_codes.h)
- [macros.h](../src/modbus/macros.h)
- [WString.h](https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/WString.h)
- [Vector.h](https://github.com/janelia-arduino/Vector)
- [Arduino.h](https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/Arduino.h)

```mermaid
graph TD
    Addon --> Component
    Addon --> enums
    Addon --> error_codes
    Addon --> macros
    Addon --> WString
    Addon --> Vector
```

## BEHAVIOUR

The Addon class extends Component, inheriting its lifecycle methods and adding specific functionality for modular components.

```mermaid
graph TD
    Start[Initialize Addon] --> Construct[Constructor sets name, id, flags]
    Construct --> Setup[Setup phase]
    Setup --> Loop[Loop function execution]
    Loop --> Info[Info reporting]
    Info --> Loop
```

## TODOS

### PERFORMANCE

- Consider optimizing the `byId()` function for large collections using more efficient data structures or search algorithms
- Evaluate memory usage when multiple addons are instantiated

### SECURITY

- Add validation for addon IDs to prevent duplication
- Consider implementing access control mechanisms for sensitive addons

### COMPLIANCE

- Ensure compatibility with industrial Modbus-485 specifications
- Maintain backward compatibility with existing addon implementations

### RECOMMENDATIONS

- Use meaningful, unique IDs for each addon to simplify management
- Consider implementing a registration system to avoid manual management of addon collections
- Document specific addon implementations with clear usage examples