===== AI ved Finite State Machine (FSM)=====

StateMachine er baseret på denne video, se video og forsøg at implementere statemachine.
 
  * [[https://www.youtube.com/watch?v=Kcg1SEgDqyk|StateMachine C# Godot]]


==== Opgaver ====

  - Opret en Tilstandsmaskine(FSM) og Tilstande (States) ud fra ovenstående tutorials. (Det er ikke nødvendigt at se disse videoer i deres fulde længde) Hav fokus på FSM delen, og mindre fokus på det grafiske, animationer m.m.
  - Lav en konkret tilstandsmaskine **EnemyFSM** ud fra "Make a basic finite state machine".
  - Implementer tilstandene **Patrol**, **Chase** og **Attack**.




==== State ====

<code csharp State.cs>
using Godot;
using System;

public partial class State : Node
{
	public StateMachine fsm;
	public virtual void Ready() { }

	// ENTER state
	public virtual void Enter() { }
	// UPDATE state (Process)
	public virtual void Update(float delta) { }
	// EXIT state
	public virtual void Exit() { }

	public virtual void PhysicsUpdate(float delta) {}
	public virtual void HandleInput(InputEvent @event) { }
}

</code>

----

==== StateMachine ====
<code csharp StateMachine.cs>
using Godot;
using System;
using System.Collections.Generic;

public abstract partial class StateMachine : Node
{
	[Export] public CharacterBody2D npc;
	[Export] public NodePath initialState; // Start tilstand skal angives...

	private Dictionary<string, State> _states;  // alle tilstande i denne datastruktur
	private State _currentState;    // nuværende tilstand

	public override void _Ready()
	{

		if (npc == null) {
			GD.Print("You forgot to set NPC..export");
		}

		if (initialState == null)
		{
			GD.Print("You forgot to set initialState..export");
		}

		_states = new Dictionary<string, State>();

		foreach (Node node in this.GetChildren()) {
			if (node is State s) {
				_states[node.Name] = s;
				s.fsm = this;
				s.Ready();
				s.Exit();
			}
		}

		_currentState = GetNode<State>(initialState);
		_currentState.Enter();

		GD.Print("StateMachine is ready.");
	}

	// Der der skiftes tilstand

	public void TransitionTo(string stateName){
		// sikkerheds tjeck at tilstand eksisterer, eller at den allerede er valgt
		if (!_states.ContainsKey(stateName) || _currentState == _states[stateName])
		{
			return;
		}

		// Der skiftes tilstand
		_currentState.Exit(); // vi rydder op efter os !
		_currentState = _states[stateName]; // Vi skifter til den nye tilstands
		_currentState.Enter(); // initialisering..
	}

	public override void _Process(double delta)
	{
		_currentState.Update((float) delta);
	}

	public override void _PhysicsProcess(double delta)
	{
		_currentState.PhysicsUpdate((float)delta);
	}

	// Sender ikke håndterede events videre til nuværende tilstand (State)
	public override void _UnhandledInput(InputEvent @event) {
		_currentState.HandleInput(@event);
	}
}

</code>

----

==== Patrolstate ====

<code csharp Patrol.cs>
using Godot;
using System;

public partial class PatrolState : State
{
	[Export] public float Speed = 40f;
	[Export] public float visibilityRange = 50f;

	[Export] public Node2D[] waypoints; // Waypoints som der patruljeres imellem.
	[Export] public CharacterBody2D player;

	public int currentWaypointIndex = 0; // Det nuværende waypoint
	public Vector2 targetPosition;

	public override void Ready()
	{
		targetPosition = waypoints[currentWaypointIndex].GlobalPosition;
		GD.Print("PatrolState ready.");
	}

	public override void Update(float delta)
	{
		fsm.npc.Velocity = fsm.npc.GlobalPosition.DirectionTo(targetPosition) * Speed;

		// Er vi nået til vores nuværende Waypoint?
		if( fsm.npc.GlobalPosition.DistanceTo( targetPosition ) < 1.5f ){
			currentWaypointIndex++;

			if (currentWaypointIndex > waypoints.Length - 1) {
				currentWaypointIndex = 0;
			}
			targetPosition = waypoints[currentWaypointIndex].GlobalPosition;
		}

		// Er vi inde for visibility range af Player?
		if (fsm.npc.GlobalPosition.DistanceTo(player.GlobalPosition) < this.visibilityRange) {
			GD.Print("Skift til ChaseState");
			fsm.TransitionTo("ChaseState");
		}

		fsm.npc.MoveAndSlide();
	}
}

</code>

----

==== ChaseState ====

<code csharp ChaseState.cs>
using Godot;
using System;

public partial class ChaseState : State
{
	[Export] public float Speed = 40f;
	[Export] public Node2D player;

	public CharacterBody2D skeleton;

	public override void Ready()
	{
		if (player == null) {
			GD.Print("Du har glemt at lave en reference til Player.");
		}
		GD.Print("ChaseState ready.");
	}

	public override void PhysicsUpdate(float delta)
	{
		fsm.npc.Velocity = fsm.npc.GlobalPosition.DirectionTo(player.GlobalPosition) * this.Speed;

		if ( fsm.npc.GlobalPosition.DistanceTo( player.GlobalPosition ) > 50f )
		{
			GD.Print("Skift til PatrolState");
			fsm.TransitionTo("PatrolState");
		}
		if (fsm.npc.GlobalPosition.DistanceTo(player.GlobalPosition) < 10f)
		{
			GD.Print("Skift til AttackState");
			fsm.TransitionTo("AttackState");
		}

		fsm.npc.MoveAndSlide();
	}
}

</code>

----