Godot Ability System

# ability.gd
class_name Ability
extends Resource

@export var ability_name: String
@export var cost: float = 0.0
@export var cooldown: float = 1.0
@export var cast_time: float = 0.0

# Override in subclasses or compose via exported effect resources.
func can_activate(caster: Node) -> bool:
    return true

func activate(caster: Node) -> void:
    pass

# ability_component.gd
class_name AbilityComponent
extends Node

signal ability_activated(ability: Ability)
signal ability_failed(ability: Ability, reason: String)
signal cooldown_started(ability: Ability, duration: float)
signal cooldown_finished(ability: Ability)

@export var resource_pool: float = 100.0

var _granted: Dictionary = {}        # ability_name -> Ability
var _cooldowns: Dictionary = {}      # ability_name -> seconds remaining

func grant(ability: Ability) -> void:
    _granted[ability.ability_name] = ability

func _process(delta: float) -> void:
    for name in _cooldowns.keys():
        _cooldowns[name] -= delta
        if _cooldowns[name] <= 0.0:
            _cooldowns.erase(name)
            if _granted.has(name):
                cooldown_finished.emit(_granted[name])

func try_activate(ability_name: String) -> bool:
    var ability: Ability = _granted.get(ability_name)
    if ability == null:
        return false
    if _cooldowns.has(ability_name):
        ability_failed.emit(ability, "on_cooldown")
        return false
    if resource_pool < ability.cost:
        ability_failed.emit(ability, "insufficient_resource")
        return false
    if not ability.can_activate(get_parent()):
        ability_failed.emit(ability, "conditions_unmet")
        return false
    resource_pool -= ability.cost
    ability.activate(get_parent())
    _cooldowns[ability_name] = ability.cooldown
    cooldown_started.emit(ability, ability.cooldown)
    ability_activated.emit(ability)
    return true

// Ability.cs
using Godot;

[GlobalClass]
public partial class Ability : Resource
{
    [Export] public string AbilityName { get; set; } = "";
    [Export] public float Cost { get; set; } = 0.0f;
    [Export] public float Cooldown { get; set; } = 1.0f;
    [Export] public float CastTime { get; set; } = 0.0f;

    public virtual bool CanActivate(Node caster) => true;
    public virtual void Activate(Node caster) { }
}

// AbilityComponent.cs
using Godot;
using System.Collections.Generic;

public partial class AbilityComponent : Node
{
    [Signal] public delegate void AbilityActivatedEventHandler(Ability ability);
    [Signal] public delegate void AbilityFailedEventHandler(Ability ability, string reason);
    [Signal] public delegate void CooldownStartedEventHandler(Ability ability, float duration);
    [Signal] public delegate void CooldownFinishedEventHandler(Ability ability);

    [Export] public float ResourcePool { get; set; } = 100.0f;

    private readonly Dictionary<string, Ability> _granted = new();
    private readonly Dictionary<string, float> _cooldowns = new();

    public void Grant(Ability ability) => _granted[ability.AbilityName] = ability;

    public override void _Process(double delta)
    {
        foreach (var name in new List<string>(_cooldowns.Keys))
        {
            _cooldowns[name] -= (float)delta;
            if (_cooldowns[name] <= 0.0f)
            {
                _cooldowns.Remove(name);
                if (_granted.TryGetValue(name, out var finished))
                    EmitSignal(SignalName.CooldownFinished, finished);
            }
        }
    }

    public bool TryActivate(string abilityName)
    {
        if (!_granted.TryGetValue(abilityName, out var ability)) return false;
        if (_cooldowns.ContainsKey(abilityName))
        {
            EmitSignal(SignalName.AbilityFailed, ability, "on_cooldown");
            return false;
        }
        if (ResourcePool < ability.Cost)
        {
            EmitSignal(SignalName.AbilityFailed, ability, "insufficient_resource");
            return false;
        }
        if (!ability.CanActivate(GetParent()))
        {
            EmitSignal(SignalName.AbilityFailed, ability, "conditions_unmet");
            return false;
        }
        ResourcePool -= ability.Cost;
        ability.Activate(GetParent());
        _cooldowns[abilityName] = ability.Cooldown;
        EmitSignal(SignalName.CooldownStarted, ability, ability.Cooldown);
        EmitSignal(SignalName.AbilityActivated, ability);
        return true;
    }
}

# effect.gd
class_name Effect
extends Resource

@export var effect_name: String
@export var duration: float = 5.0       # seconds; <= 0 means instant
@export var tick_interval: float = 0.0  # 0 = no periodic tick

func on_apply(target: Node) -> void: pass
func on_tick(target: Node) -> void: pass
func on_expire(target: Node) -> void: pass

# effect_holder.gd
class_name EffectHolder
extends Node

signal effect_applied(effect: Effect)
signal effect_expired(effect: Effect)

# effect -> [elapsed, tick_accum]
var _active: Dictionary = {}

func apply_effect(effect: Effect) -> void:
    effect.on_apply(get_parent())
    effect_applied.emit(effect)
    if effect.duration <= 0.0:
        effect.on_expire(get_parent())
        effect_expired.emit(effect)
        return
    _active[effect] = [0.0, 0.0]

func _process(delta: float) -> void:
    var to_remove: Array = []
    for effect in _active:
        _active[effect][0] += delta
        if effect.tick_interval > 0.0:
            _active[effect][1] += delta
            if _active[effect][1] >= effect.tick_interval:
                _active[effect][1] -= effect.tick_interval
                effect.on_tick(get_parent())
        if effect.duration > 0.0 and _active[effect][0] >= effect.duration:
            to_remove.append(effect)
    for effect in to_remove:
        _active.erase(effect)
        effect.on_expire(get_parent())
        effect_expired.emit(effect)

// Effect.cs
using Godot;

[GlobalClass]
public partial class Effect : Resource
{
    [Export] public string EffectName { get; set; } = "";
    [Export] public float Duration { get; set; } = 5.0f;     // <= 0 = instant
    [Export] public float TickInterval { get; set; } = 0.0f; // 0 = no tick

    public virtual void OnApply(Node target) { }
    public virtual void OnTick(Node target) { }
    public virtual void OnExpire(Node target) { }
}

// EffectHolder.cs
using Godot;
using System.Collections.Generic;

public partial class EffectHolder : Node
{
    [Signal] public delegate void EffectAppliedEventHandler(Effect effect);
    [Signal] public delegate void EffectExpiredEventHandler(Effect effect);

    private readonly Dictionary<Effect, (float Elapsed, float TickAccum)> _active = new();

    public void ApplyEffect(Effect effect)
    {
        effect.OnApply(GetParent());
        EmitSignal(SignalName.EffectApplied, effect);
        if (effect.Duration <= 0f)
        {
            effect.OnExpire(GetParent());
            EmitSignal(SignalName.EffectExpired, effect);
            return;
        }
        _active[effect] = (0f, 0f);
    }

    public override void _Process(double delta)
    {
        var toRemove = new List<Effect>();
        foreach (var effect in new List<Effect>(_active.Keys))
        {
            var (elapsed, tickAccum) = _active[effect];
            elapsed += (float)delta;
            if (effect.TickInterval > 0f)
            {
                tickAccum += (float)delta;
                if (tickAccum >= effect.TickInterval)
                {
                    tickAccum -= effect.TickInterval;
                    effect.OnTick(GetParent());
                }
            }
            if (effect.Duration > 0f && elapsed >= effect.Duration)
                toRemove.Add(effect);
            else
                _active[effect] = (elapsed, tickAccum); // still active — write back updated elapsed and tick accumulator
        }
        foreach (var effect in toRemove)
        {
            _active.Remove(effect);
            effect.OnExpire(GetParent());
            EmitSignal(SignalName.EffectExpired, effect);
        }
    }
}