using System.Collections.Concurrent;

namespace NeonSprawl.Server.Game.Npc;

/// <summary>Thread-safe in-memory aggro holders for prototype NPC instances (NEO-92).</summary>
public sealed class InMemoryThreatStateStore : IThreatStateStore
{
    private readonly ConcurrentDictionary<string, string?> holderByNpcId = new(StringComparer.Ordinal);

    private readonly ConcurrentDictionary<string, object> idLocks = new(StringComparer.Ordinal);

    /// <inheritdoc />
    public bool TryGet(string? npcInstanceId, out ThreatStateSnapshot snapshot)
    {
        var key = NormalizeNpcInstanceId(npcInstanceId);
        if (key.Length == 0 || !PrototypeNpcRegistry.TryGet(key, out _))
        {
            snapshot = default;
            return false;
        }

        lock (idLocks.GetOrAdd(key, _ => new object()))
        {
            if (!holderByNpcId.TryGetValue(key, out var holder))
            {
                holder = null;
                holderByNpcId[key] = holder;
            }

            snapshot = new ThreatStateSnapshot(key, holder);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TrySetHolder(string? npcInstanceId, string? playerIdLowercaseOrNull)
    {
        var key = NormalizeNpcInstanceId(npcInstanceId);
        if (key.Length == 0 || !PrototypeNpcRegistry.TryGet(key, out _))
        {
            return false;
        }

        var normalizedHolder = NormalizePlayerId(playerIdLowercaseOrNull);

        lock (idLocks.GetOrAdd(key, _ => new object()))
        {
            holderByNpcId[key] = normalizedHolder;
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryClearHolder(string? npcInstanceId) => TrySetHolder(npcInstanceId, null);

    private static string NormalizeNpcInstanceId(string? npcInstanceId) =>
        npcInstanceId?.Trim().ToLowerInvariant() ?? string.Empty;

    private static string? NormalizePlayerId(string? playerId)
    {
        if (string.IsNullOrWhiteSpace(playerId))
        {
            return null;
        }

        return playerId.Trim().ToLowerInvariant();
    }
}