About Hierarchical Final State Machine

HFSM (Hierarchical Finite State Machine) is a simple and flexible library for building state machines in C#. The library provides an easy-to-use API for defining states, transitions, and hierarchical relationships between states.

Feature

- Define states with custom behavior (OnEnter, OnUpdate, OnExit)

- Define transitions based on events and/or guard conditions


- Hierarchical state organization


- State machine builder for easy construction and configuration


- Event-driven state updates

Exemple of usage - Fictionnal

// Define your state and event enums
public enum MyState { Root, Idle, Walk, Run }
public enum MyEvent { FreezePlayer , StartRun}

private HFSM<MyState, MyEvent> m_hfsm;

private void BuildHFSM()
{
// Create a new HFSMBuilder instance
    var builder = new HFSMBuilder<MyState, MyEvent>();

    // Add states to the builder
    builder.AddState(MyState.Movement);
    builder.AddState(MyState.Idle, MyState.Movement);
    builder.AddState(MyState.Walk, MyState.Movement, OnStartWalk, OnUpdateWalk, OnExitWalk);
    builder.AddState(MyState.Run, MyState.Movement);
    builder.AddState(MyState.Freeze, OnEnterFreeze);

    //// Define transitions between states
    // Can use a guard
    builder.AddTransition(MyState.Idle, MyState.Walk, () => IsMoving); 

    // An event
    builder.AddTransition(MyState.Movement, MyState.Freeze, MyEvent.FreezePlayer);

    // Or both
    builder.AddTransition(MyState.Walk, MyState.Run, () => Pawn.Velocity > 15, MyEvent.StartRun);

    // Build the state machine
    var hfsm = builder.Build();

}

protected override void OnActivate()
{
    BuildHFSM();
    base.OnActivate();
}

[GameEvent.Tick]
private void OnUpdate()
{
   // Update the state machine
   m_hfsm.Update();
}

private void OnStartWalk() 
{
    Log.Info("I'm walking!")
}

private void OnUpdateWalk() 
{
    // Do stuff
}

private void OnExitWalk()
{
    // Do stuff
}

private void OnEnterFreeze()
{
    Log.Info("It's getting cold in there!")
}

protected override void OnDeactivate()
{
    // Stop the state machine
    m_hfsm.Stop();
}

Another exemple - Movement controller

public partial class MovementsController : EntityComponent<Pawn>
{
    private void BuildHFSM()
    {
        HFSMBuilder<States, TransitionEvents> builder = new HFSMBuilder<States, TransitionEvents>();
        builder.AddState( States.OnGroundState , OnEnterGroundState, OnUpdateGroundState, OnExitGroundState);
        {
            builder.AddState( States.JogState ,States.OnGroundState, OnEnterJogState);
            {
                builder.AddTransition( States.JogState, States.RunState , () => Input.Down( "run" ));
                builder.AddTransition( States.JogState, States.WalkState , () => Input.Down( "walk" ));
                builder.AddTransition( States.JogState, States.DuckState , () => Input.Down( "duck" ));
            }
            builder.AddState( States.RunState ,States.OnGroundState, OnEnterSprintState);
            {
                builder.AddTransition( States.RunState, States.JogState , () => !Input.Down( "run" ));
                builder.AddTransition( States.RunState, States.WalkState , () => Input.Down( "walk" ));
                builder.AddTransition( States.RunState, States.DuckState , () => Input.Down( "duck" ));
            }
            builder.AddState( States.WalkState ,States.OnGroundState, OnEnterWalkState);
            {
                builder.AddTransition( States.WalkState, States.JogState , () => !Input.Down( "walk" ));
                builder.AddTransition( States.WalkState, States.DuckState , () => Input.Down( "duck" ));
            }
            builder.AddState( States.DuckState, States.OnGroundState, OnEnterDuckState, null , OnExitDuckState);
            {
                builder.AddTransition( States.DuckState, States.JogState , () => !Input.Down( "duck" ) && CanUnduck());
            }
            builder.AddTransition( States.OnGroundState, States.InAirState , () => !Grounded);
        }
        builder.AddState( States.InAirState , OnEnterAirState, OnUpdateAirState, OnExitAirState);
        {
            builder.AddTransition( States.InAirState, States.DuckState , () => Input.Down( "duck" ) && Grounded ); 
            builder.AddTransition( States.InAirState, States.OnGroundState , () => Grounded );
        }
        m_hfsm = builder.Build();
    }
}
}