using System.Collections.Concurrent;

namespace NeonSprawl.Server.Game.Combat;

/// <summary>Thread-safe in-memory session player combat HP; empty at startup — lazy rows only (NEO-95).</summary>
public sealed class InMemoryPlayerCombatHealthStore : IPlayerCombatHealthStore
{
    private readonly ConcurrentDictionary<string, int> currentHpById = new(StringComparer.Ordinal);

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

    /// <inheritdoc />
    public bool TryGet(string? playerId, out PlayerCombatHealthSnapshot snapshot)
    {
        var key = NormalizePlayerId(playerId);
        if (key.Length == 0)
        {
            snapshot = default;
            return false;
        }

        lock (idLocks.GetOrAdd(key, _ => new object()))
        {
            EnsureRowInitialized(key);
            snapshot = CreateSnapshot(key, currentHpById[key]);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryApplyDamage(string? playerId, int damage, out PlayerCombatHealthSnapshot snapshot)
    {
        snapshot = default;
        if (damage < 0)
        {
            return false;
        }

        var key = NormalizePlayerId(playerId);
        if (key.Length == 0)
        {
            return false;
        }

        lock (idLocks.GetOrAdd(key, _ => new object()))
        {
            EnsureRowInitialized(key);
            var current = currentHpById[key];
            var next = Math.Max(0, current - damage);
            currentHpById[key] = next;
            snapshot = CreateSnapshot(key, next);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryResetToFull(string? playerId, out PlayerCombatHealthSnapshot snapshot)
    {
        var key = NormalizePlayerId(playerId);
        if (key.Length == 0)
        {
            snapshot = default;
            return false;
        }

        lock (idLocks.GetOrAdd(key, _ => new object()))
        {
            currentHpById[key] = PlayerCombatHealthDefaults.MaxHp;
            snapshot = CreateSnapshot(key, PlayerCombatHealthDefaults.MaxHp);
            return true;
        }
    }

    private void EnsureRowInitialized(string normalizedId)
    {
        if (!currentHpById.ContainsKey(normalizedId))
        {
            currentHpById[normalizedId] = PlayerCombatHealthDefaults.MaxHp;
        }
    }

    private static PlayerCombatHealthSnapshot CreateSnapshot(string playerId, int currentHp) =>
        new(
            playerId,
            PlayerCombatHealthDefaults.MaxHp,
            currentHp,
            currentHp <= 0);

    private static string NormalizePlayerId(string? playerId) =>
        playerId?.Trim().ToLowerInvariant() ?? string.Empty;
}