using System.Collections.Concurrent;
using Microsoft.Extensions.Options;
using NeonSprawl.Server.Game.PositionState;

namespace NeonSprawl.Server.Game.Quests;

/// <summary>Thread-safe in-memory quest progress; seeds the configured dev player (NEO-116).</summary>
public sealed class InMemoryPlayerQuestStateStore(IOptions<GamePositionOptions> options) : IPlayerQuestStateStore
{
    private sealed class ProgressRow(
        QuestProgressStatus status,
        int currentStepIndex,
        Dictionary<string, int> objectiveCounters,
        DateTimeOffset? completedAt)
    {
        public QuestProgressStatus Status { get; private set; } = status;

        public int CurrentStepIndex { get; private set; } = currentStepIndex;

        public Dictionary<string, int> ObjectiveCounters { get; } = objectiveCounters;

        public DateTimeOffset? CompletedAt { get; private set; } = completedAt;

        public QuestStepState ToSnapshot(string playerId, string questId) =>
            new(
                playerId,
                questId,
                Status,
                CurrentStepIndex,
                new Dictionary<string, int>(ObjectiveCounters, StringComparer.Ordinal),
                CompletedAt);

        public void SetStepIndex(int newStepIndex)
        {
            CurrentStepIndex = newStepIndex;
            ObjectiveCounters.Clear();
        }

        public void SetObjectiveCounter(string objectiveId, int newCount) =>
            ObjectiveCounters[objectiveId] = newCount;

        public void MarkCompleted(DateTimeOffset completedAt)
        {
            Status = QuestProgressStatus.Completed;
            CompletedAt = completedAt;
        }

        public static ProgressRow CreateActive() =>
            new(QuestProgressStatus.Active, 0, new Dictionary<string, int>(StringComparer.Ordinal), null);
    }

    private readonly HashSet<string> knownPlayers = CreateKnownPlayers(options.Value);

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

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

    private static HashSet<string> CreateKnownPlayers(GamePositionOptions o)
    {
        var id = QuestProgressIds.NormalizePlayerId(o.DevPlayerId);
        if (id.Length == 0)
        {
            throw new InvalidOperationException("Game:DevPlayerId must be non-empty.");
        }

        return new HashSet<string>(StringComparer.OrdinalIgnoreCase) { id };
    }

    /// <inheritdoc />
    public bool CanWritePlayer(string playerId)
    {
        var player = QuestProgressIds.NormalizePlayerId(playerId);
        return player.Length > 0 && knownPlayers.Contains(player);
    }

    /// <inheritdoc />
    public bool TryGetProgress(string playerId, string questId, out QuestStepState snapshot)
    {
        snapshot = null!;
        var player = QuestProgressIds.NormalizePlayerId(playerId);
        var quest = QuestProgressIds.NormalizeQuestId(questId);
        var key = QuestProgressIds.MakeProgressKey(player, quest);
        if (key.Length == 0 || !knownPlayers.Contains(player))
        {
            return false;
        }

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

            snapshot = row.ToSnapshot(player, quest);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryActivate(string playerId, string questId, out QuestStepState snapshot)
    {
        snapshot = null!;
        var player = QuestProgressIds.NormalizePlayerId(playerId);
        var quest = QuestProgressIds.NormalizeQuestId(questId);
        var key = QuestProgressIds.MakeProgressKey(player, quest);
        if (key.Length == 0 || !knownPlayers.Contains(player))
        {
            return false;
        }

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

            var row = ProgressRow.CreateActive();
            byKey[key] = row;
            snapshot = row.ToSnapshot(player, quest);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryAdvanceStep(string playerId, string questId, int newStepIndex, out QuestStepState snapshot)
    {
        snapshot = null!;
        if (newStepIndex < 0)
        {
            return false;
        }

        var player = QuestProgressIds.NormalizePlayerId(playerId);
        var quest = QuestProgressIds.NormalizeQuestId(questId);
        var key = QuestProgressIds.MakeProgressKey(player, quest);
        if (key.Length == 0 || !knownPlayers.Contains(player))
        {
            return false;
        }

        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            if (!byKey.TryGetValue(key, out var row) ||
                row.Status != QuestProgressStatus.Active ||
                newStepIndex <= row.CurrentStepIndex)
            {
                if (byKey.TryGetValue(key, out var existing))
                {
                    snapshot = existing.ToSnapshot(player, quest);
                }

                return false;
            }

            row.SetStepIndex(newStepIndex);
            snapshot = row.ToSnapshot(player, quest);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryUpdateObjectiveCounter(
        string playerId,
        string questId,
        string objectiveId,
        int newCount,
        out QuestStepState snapshot)
    {
        snapshot = null!;
        if (newCount < 0)
        {
            return false;
        }

        var player = QuestProgressIds.NormalizePlayerId(playerId);
        var quest = QuestProgressIds.NormalizeQuestId(questId);
        var objective = QuestProgressIds.NormalizeObjectiveId(objectiveId);
        var key = QuestProgressIds.MakeProgressKey(player, quest);
        if (key.Length == 0 || objective.Length == 0 || !knownPlayers.Contains(player))
        {
            return false;
        }

        lock (keyLocks.GetOrAdd(key, _ => new object()))
        {
            if (!byKey.TryGetValue(key, out var row) || row.Status != QuestProgressStatus.Active)
            {
                if (byKey.TryGetValue(key, out var existing))
                {
                    snapshot = existing.ToSnapshot(player, quest);
                }

                return false;
            }

            row.SetObjectiveCounter(objective, newCount);
            snapshot = row.ToSnapshot(player, quest);
            return true;
        }
    }

    /// <inheritdoc />
    public bool TryMarkComplete(string playerId, string questId, DateTimeOffset completedAt, out QuestStepState snapshot)
    {
        snapshot = null!;
        var player = QuestProgressIds.NormalizePlayerId(playerId);
        var quest = QuestProgressIds.NormalizeQuestId(questId);
        var key = QuestProgressIds.MakeProgressKey(player, quest);
        if (key.Length == 0 || !knownPlayers.Contains(player))
        {
            return false;
        }

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

            if (row.Status == QuestProgressStatus.Completed)
            {
                snapshot = row.ToSnapshot(player, quest);
                return false;
            }

            row.MarkCompleted(completedAt);
            snapshot = row.ToSnapshot(player, quest);
            return true;
        }
    }
}