# Lifecycle

### Overview

A lifecycle defines the operational boundaries of a mode, from its activation to its completion or transition to another mode. It is responsible for initializing, managing, and safely terminating a mode's operation, ensuring predictable transitions, consistent state handling, and controlled execution of mode-specific logic.

A mode represents a functional state of the robot, such as Guard, SLAM, or Navigation, and each mode runs within a lifecycle that determines how and when it starts, executes, and ends.

![](/files/LGNPWiW14bAedV3FH7KM)

### Conceptual Model

| Concept       | Description                                                                          |
| ------------- | ------------------------------------------------------------------------------------ |
| **Lifecycle** | Defines the start, execution, and end of a mode                                      |
| **Stage**     | Represents a logical phase within the lifecycle (e.g., startup, entry, active, exit) |
| **Hook**      | A programmable event point that executes specific actions at key stages              |
| **Mode**      | The operational context governed by the lifecycle                                    |

> **In short:** Lifecycle controls the flow → Stages define phases → Hooks perform actions → Mode defines behavior.

### Stages and Hooks

Each lifecycle is composed of several stages. Hooks are executed at specific points in these stages to perform initialization, cleanup, or handling tasks.

| Stage        | Hook          | Description                                                                                   |
| ------------ | ------------- | --------------------------------------------------------------------------------------------- |
| **Startup**  | `ON_STARTUP`  | Executes system-level initialization before any mode begins                                   |
| **Entry**    | `ON_ENTRY`    | Runs when entering a mode; prepares mode-specific resources and context                       |
| **Active**   | —             | Main operational phase; mode logic runs continuously (no fixed hook)                          |
| **Exit**     | `ON_EXIT`     | Executes cleanup, saves state, and prepares for the next transition                           |
| **Timeout**  | `ON_TIMEOUT`  | Handles cases where a mode exceeds its defined duration or fails to complete expected actions |
| **Shutdown** | `ON_SHUTDOWN` | Performs final cleanup and safe termination of the lifecycle management system                |

#### Startup Stage

Triggered by `ON_STARTUP`. Executes system-level initialization before any mode begins.

#### Entry Stage

Triggered by `ON_ENTRY`. Runs when entering a mode; prepares mode-specific resources and context.

#### Active Stage

Represents the main operational phase of the mode. No fixed hook; mode logic runs continuously during this stage.

#### Exit Stage

Triggered by `ON_EXIT`. Executes cleanup, saves state, and prepares for the next transition.

#### Timeout Stage

Triggered by `ON_TIMEOUT`. Handles cases where a mode exceeds its defined duration or fails to complete expected actions.

#### Shutdown Stage

Triggered by `ON_SHUTDOWN`. Performs final cleanup and safe termination of the lifecycle management system.


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