namespace OECS.PlayTest;

/// <summary>
/// A pool of agents selected by weight. Higher weight = more likely to be picked.
/// </summary>
public class WeightedAgentPool<TDecision>
{
    private readonly List<(IAgent<TDecision> Agent, int Weight)> _agents = new();
    private int _totalWeight;
    private static readonly Random _rng = new();

    public void Add(IAgent<TDecision> agent, int weight)
    {
        _agents.Add((agent, weight));
        _totalWeight += weight;
    }

    public IAgent<TDecision> Pick()
    {
        if (_agents.Count == 0)
            throw new InvalidOperationException("WeightedAgentPool is empty");

        int roll = _rng.Next(_totalWeight);
        int cumulative = 0;
        foreach (var (agent, weight) in _agents)
        {
            cumulative += weight;
            if (roll < cumulative)
                return agent;
        }
        return _agents[^1].Agent;
    }
}