godot-host-test/Game/Target/TargetSpawner.cs

using System.Collections.Generic;
using Godot;
using GodotHostTest.Helpers;
using GodotHostTest.Interfaces;
using OwofGames.AetherBind;
using R3;

namespace GodotHostTest.Game.Target;

public partial class TargetSpawner : Node2D, ITargetCollector, ITargetSpawner
{
    private readonly List<ITarget> _availableTargets = [];
    private readonly Subject<ITarget> _targetSpawned = new();

    [Export] public required Timer Timer;

    [Inject] private ILevel _level = null!;
    [Inject] private ITargetEventBus _targetEventBus = null!;

    /// <inheritdoc />
    public void NewTarget(ITarget target)
    {
        // record the target as available
        _availableTargets.Add(target);

        // whenever the target gets disabled, mark it as available again
        target.Hit.Merge(target.TimedOut)
            .Select(_ => target)
            .Subscribe(_availableTargets.Add)
            .AddTo(this);
    }

    public Observable<ITarget> TargetSpawned => _targetSpawned.AsObservable();

    public override void _Ready()
    {
        // inform the target event bus that there's a new target spawner
        _targetEventBus.NewTargetSpawner(this);

        // spawn every total seconds (and immediately spawn something at ready)
        Timer.Start(_level.TimeBetweenSpawns.TotalSeconds);
        Spawn();
    }

    private void OnTimer()
    {
        Spawn();
    }

    private void Spawn()
    {
        // pick a random target
        var randomIndex = GD.RandRange(0, _availableTargets.Count - 1);
        var target = _availableTargets[randomIndex];
        _availableTargets.RemoveAt(randomIndex);

        // enable it
        target.Enable();

        // notify that a target has been spawned
        _targetSpawned.OnNext(target);
    }

    protected override void Dispose(bool disposing)
    {
        base.Dispose(disposing);
        _targetSpawned.Dispose();
    }
}