using System.Collections.Concurrent;

namespace NeonSprawl.Server.Game.Encounters;

/// <summary>Thread-safe in-memory encounter progress; empty at startup (NEO-104).</summary>
public sealed class InMemoryEncounterProgressStore : IEncounterProgressStore
{
    private sealed class ProgressRow(bool started, HashSet<string> defeatedNpcInstanceIds)
    {
        public bool Started { get; } = started;

        public HashSet<string> DefeatedNpcInstanceIds { get; } = defeatedNpcInstanceIds;
    }

    private readonly ConcurrentDictionary<string, ProgressRow> byKey = new(StringComparer.Ordinal);

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

    /// <inheritdoc />
    public bool TryGetProgress(string playerId, string encounterId, out EncounterProgressSnapshot snapshot)
    {
        snapshot = default!;
        var key = EncounterProgressIds.MakeProgressKey(playerId, encounterId);
        if (key.Length == 0)
        {
            return false;
        }

        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            if (!byKey.TryGetValue(key, out var row))
            {
                return false;
            }

            snapshot = new EncounterProgressSnapshot(
                EncounterProgressIds.NormalizePlayerId(playerId),
                EncounterProgressIds.NormalizeEncounterId(encounterId),
                row.Started,
                new HashSet<string>(row.DefeatedNpcInstanceIds, StringComparer.Ordinal));
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryActivate(string playerId, string encounterId)
    {
        var key = EncounterProgressIds.MakeProgressKey(playerId, encounterId);
        if (key.Length == 0)
        {
            return false;
        }

        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            if (byKey.TryGetValue(key, out var existing) && existing.Started)
            {
                return false;
            }

            byKey[key] = new ProgressRow(
                started: true,
                defeatedNpcInstanceIds: new HashSet<string>(StringComparer.Ordinal));
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryAddDefeatedTarget(string playerId, string encounterId, string npcInstanceId)
    {
        var key = EncounterProgressIds.MakeProgressKey(playerId, encounterId);
        var npcKey = EncounterProgressIds.NormalizeNpcInstanceId(npcInstanceId);
        if (key.Length == 0 || npcKey.Length == 0)
        {
            return false;
        }

        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            if (!byKey.TryGetValue(key, out var row) || !row.Started)
            {
                return false;
            }

            return row.DefeatedNpcInstanceIds.Add(npcKey);
        }
    }
}