using System;
using System.Collections.Generic;
using System.Linq;
using log4net;
using Plugin.DeviceDebug.Entity;
using Aging.Infrastructure.Contracts;

namespace Plugin.DeviceDebug.Model
{
    /// <summary>
    /// 调试会话管理器 - 负责状态机转换和权限校验
    /// </summary>
    public class DebugSessionManager
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(DebugSessionManager));
        private readonly DeviceDebugModel _model;
        private readonly IResourceManager? _resourceManager;

        // 内存中的活跃会话缓存
        private readonly Dictionary<string, DebugSession> _activeSessions = new();

        /// <summary>
        /// 维护租约心跳：与 LayeredResourceManager.DefaultTtlSeconds(300s) 对齐，
        /// 每 120s 续期一次，防止长时间维护会话的 arb.db 租约过期进入 RecoveryRequired 后禁止 I/O。
        /// </summary>
        private System.Threading.Timer _renewTimer;
        private const int MaintenanceTtlSeconds = 300;
        private const int RenewIntervalMs = 120_000;

        /// <summary>
        /// 会话→资源令牌缓存：LayeredResourceManager 的租约按 TokenId 索引，
        /// 而 ResourceOwnerToken.TokenId 每次 new 都是新 GUID，必须复用同一实例才能释放到租约
        /// </summary>
        private readonly Dictionary<string, ResourceOwnerToken> _sessionOwnerTokens = new();

        public DebugSessionManager(DeviceDebugModel model, IResourceManager? resourceManager = null)
        {
            _model = model;
            _resourceManager = resourceManager;
        }

        /// <summary>
        /// 打开会话（ReadOnly模式）
        /// </summary>
        public DebugSession OpenSession(string deviceId, string operatorId, string operatorName, string effectiveVersion)
        {
            try
            {
                // 检查是否已有活跃会话
                var existingSession = GetActiveSessionByDevice(deviceId);
                if (existingSession != null)
                {
                    // 进程内存中存在 = 本会话真活跃，直接复用
                    if (_activeSessions.ContainsKey(existingSession.SessionId))
                    {
                        log.Warn($"设备 {deviceId} 已有活跃会话: {existingSession.SessionId}");
                        return existingSession;
                    }

                    // 仅存在于数据库且不在本进程内存 = 旧进程退出前的残留会话：
                    // 其内存上下文/维护租约（arb.db 侧靠 TTL 过期+回收）已随进程消亡，
                    // 必须回收为 Closed 再新建，否则 RequestMaintenance 永远“会话不存在”拒绝
                    _activeSessions[existingSession.SessionId] = existingSession;
                    existingSession.State = DebugSessionState.Closed;
                    existingSession.ClosedAt = DateTime.Now;
                    _model.UpdateSession(existingSession);
                    _activeSessions.Remove(existingSession.SessionId);
                    log.Warn($"已回收设备 {deviceId} 的残留会话 {existingSession.SessionId}（进程重启导致死会话），新建会话替代");
                }

                var session = new DebugSession
                {
                    DeviceId = deviceId,
                    OperatorId = operatorId,
                    OperatorName = operatorName,
                    EffectiveVersion = effectiveVersion,
                    State = DebugSessionState.ReadOnly
                };

                // 持久化到数据库
                _model.CreateSession(session);

                // 更新内存缓存
                _activeSessions[session.SessionId] = session;

                log.Info($"打开会话: {session.SessionId}, 设备: {deviceId}, 操作员: {operatorName}");
                return session;
            }
            catch (Exception ex)
            {
                log.Error($"打开会话失败: {ex.Message}", ex);
                throw;
            }
        }

        /// <summary>
        /// 请求进入维护模式（ReadOnly → AcquiringMaintenance）
        /// 检查：设备是否有生产Reserved
        /// </summary>
        public bool RequestMaintenance(string sessionId)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    // 兜底：会话可能在数据库（如 UI 持有的 sessionID 属于重启前残留）→ 恢复进缓存后继续
                    session = _model.GetSession(sessionId);
                    if (session == null || session.State == DebugSessionState.Closed)
                    {
                        log.Warn($"会话不存在: {sessionId}");
                        return false;
                    }
                    _activeSessions[sessionId] = session;
                    log.Warn($"会话 {sessionId} 从数据库恢复进内存缓存后继续维护请求");
                }

                // 验证状态转换
                if (session.State != DebugSessionState.ReadOnly)
                {
                    log.Warn($"会话 {sessionId} 当前状态为 {session.State}，无法请求维护模式");
                    return false;
                }

                // 检查设备是否有生产Reserved（与资源预约系统集成）
                if (_resourceManager != null)
                {
                    var resourceKey = new ResourceKey(session.DeviceId, "Generic");
                    // 复用已缓存令牌（残留会话从 DB 恢复后首次进入时同样新建并存入）
                    if (!_sessionOwnerTokens.TryGetValue(sessionId, out var ownerToken))
                    {
                        ownerToken = new ResourceOwnerToken(OwnerType.Maintenance, session.SessionId);
                        _sessionOwnerTokens[sessionId] = ownerToken;
                    }

                    try
                    {
                        var reservation = _resourceManager.ReserveAsync(
                            ownerToken, resourceKey, CancellationToken.None).GetAwaiter().GetResult();
                        session.ReservationRef = reservation.ReservationId;
                    }
                    catch (ResourceConflictException)
                    {
                        _sessionOwnerTokens.Remove(sessionId);
                        log.Warn($"设备 {session.DeviceId} 已被生产预约占用，拒绝维护请求");
                        return false;
                    }
                }
                else
                {
                    // 降级模式：无 ResourceManager 时允许所有请求（向后兼容）
                    log.Warn("ResourceManager 未初始化，跳过资源预约检查");
                }

                // 状态转换
                session.State = DebugSessionState.AcquiringMaintenance;

                // 持久化
                _model.UpdateSession(session);

                log.Info($"会话 {sessionId} 请求维护模式");
                return true;
            }
            catch (Exception ex)
            {
                log.Error($"请求维护模式失败: {ex.Message}", ex);
                return false;
            }
        }

        /// <summary>
        /// 激活维护模式（AcquiringMaintenance → MaintenanceActive）
        /// </summary>
        public void ActivateMaintenance(string sessionId)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    log.Warn($"会话不存在: {sessionId}");
                    throw new InvalidOperationException($"会话不存在: {sessionId}");
                }

                // 验证状态转换
                if (session.State != DebugSessionState.AcquiringMaintenance)
                {
                    log.Warn($"会话 {sessionId} 当前状态为 {session.State}，无法激活维护模式");
                    throw new InvalidOperationException($"会话 {sessionId} 当前状态为 {session.State}，无法激活维护模式");
                }

                // 状态转换
                session.State = DebugSessionState.MaintenanceActive;

                // 持久化
                _model.UpdateSession(session);

                // 启动维护租约心跳续期（防止 TTL 过期）
                EnsureRenewHeartbeat();

                log.Info($"会话 {sessionId} 激活维护模式");
            }
            catch (Exception ex)
            {
                log.Error($"激活维护模式失败: {ex.Message}", ex);
                throw;
            }
        }

        /// <summary>首次进入维护时启动周期续期定时器（幂等）。</summary>
        private void EnsureRenewHeartbeat()
        {
            if (_renewTimer != null) return;
            _renewTimer = new System.Threading.Timer(_ => RenewActiveMaintenance(),
                null, RenewIntervalMs, RenewIntervalMs);
            log.Info("维护租约心跳已启动");
        }

        /// <summary>周期回调：对所有 MaintenanceActive 会话续期其 arb.db 租约。</summary>
        private void RenewActiveMaintenance()
        {
            var lrm = _resourceManager as Aging.Infrastructure.Core.LayeredResourceManager;
            if (lrm == null) return; // 非分层实现（无 Coordinator）时降级不续期
            try
            {
                foreach (var kv in _activeSessions.ToArray())
                {
                    var s = kv.Value;
                    if (s.State != DebugSessionState.MaintenanceActive) continue;
                    if (!_sessionOwnerTokens.TryGetValue(s.SessionId, out var token)) continue;
                    if (!lrm.TryGetGrants(token.TokenId, out var grants) || grants == null) continue;
                    foreach (var g in grants)
                    {
                        try { lrm.Coordinator.Renew(g, MaintenanceTtlSeconds); }
                        catch (Exception ex) { log.Warn($"续期设备 {s.DeviceId} 租约失败: {ex.Message}"); }
                    }
                }
            }
            catch (Exception ex) { log.Error($"维护租约心跳异常: {ex.Message}", ex); }
        }

        /// <summary>无维护中会话时停止心跳，避免空转。</summary>
        private void StopRenewHeartbeatIfIdle()
        {
            if (_renewTimer == null) return;
            if (_activeSessions.Values.Any(s => s.State == DebugSessionState.MaintenanceActive)) return;
            try { _renewTimer.Dispose(); } catch { }
            _renewTimer = null;
            log.Info("无维护中会话，维护租约心跳已停止");
        }

        /// <summary>
        /// 关闭会话（MaintenanceActive → Closing → Closed）
        /// 执行安全状态检查
        /// </summary>
        public void CloseSession(string sessionId)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    log.Warn($"会话不存在: {sessionId}");
                    throw new InvalidOperationException($"会话不存在: {sessionId}");
                }

                // 验证状态转换（只有 MaintenanceActive 可以关闭）
                if (session.State != DebugSessionState.MaintenanceActive)
                {
                    log.Warn($"会话 {sessionId} 当前状态为 {session.State}，无法关闭");
                    throw new InvalidOperationException($"会话 {sessionId} 当前状态为 {session.State}，无法关闭");
                }

                // 状态转换: MaintenanceActive → Closing
                session.State = DebugSessionState.Closing;
                _model.UpdateSession(session);
                log.Debug($"会话 {sessionId} 进入关闭中状态");

                // 执行安全状态检查：释放资源预约
                if (_resourceManager != null && !string.IsNullOrEmpty(session.ReservationRef))
                {
                    try
                    {
                        var resourceKey = new ResourceKey(session.DeviceId, "Generic");
                        // 必须复用进入维护时的同一令牌实例：LayeredResourceManager 按 TokenId(GUID) 索引租约，
                        // 重新 new 会导致 FindGrant 落空、租约永不释放→过期后 RecoveryRequired 永久阻塞后续维护
                        if (!_sessionOwnerTokens.TryGetValue(sessionId, out var ownerToken))
                        {
                            ownerToken = new ResourceOwnerToken(OwnerType.Maintenance, session.SessionId);
                        }

                        _resourceManager.ReleaseReservationAsync(
                            ownerToken, resourceKey, CancellationToken.None).GetAwaiter().GetResult();

                        // 注意：不删除 _sessionOwnerTokens[sessionId]！
                        // 令牌必须保持稳定（TokenId 不变），否则下次进入维护时 new 出的新 Token
                        // 无法在 LayeredResourceManager._grantsByToken 中找到旧租约 → 释放落空 → 租约永久泄漏
                        log.Info($"已释放设备 {session.DeviceId} 的资源预约（令牌保留供复用）");
                    }
                    catch (Exception ex)
                    {
                        log.Error($"释放资源预约失败: {ex.Message}", ex);
                        // 不阻止关闭流程，但记录警告
                    }
                }

                // 状态转换: Closing → Closed
                session.State = DebugSessionState.Closed;
                session.ClosedAt = DateTime.Now;
                _model.UpdateSession(session);

                // 从缓存中移除
                _activeSessions.Remove(sessionId);

                // 若无维护中会话则停止心跳
                StopRenewHeartbeatIfIdle();

                log.Info($"会话 {sessionId} 已关闭");
            }
            catch (Exception ex)
            {
                log.Error($"关闭会话失败: {ex.Message}", ex);
                throw;
            }
        }

        /// <summary>
        /// 故障处理（任意 → Faulted）
        /// </summary>
        public void FaultSession(string sessionId, string errorMessage)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    log.Warn($"会话不存在: {sessionId}");
                    return;
                }

                // 记录当前状态
                var previousState = session.State;

                // 状态转换
                session.State = DebugSessionState.Faulted;

                // 持久化
                _model.UpdateSession(session);

                log.Error($"会话 {sessionId} 发生故障，从 {previousState} 转为 Faulted: {errorMessage}");
            }
            catch (Exception ex)
            {
                log.Error($"标记故障状态失败: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 标记需要恢复（任意 → RecoveryRequired）
        /// </summary>
        public void MarkRecoveryRequired(string sessionId)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    log.Warn($"会话不存在: {sessionId}");
                    return;
                }

                // 记录当前状态
                var previousState = session.State;

                // 状态转换
                session.State = DebugSessionState.RecoveryRequired;

                // 持久化
                _model.UpdateSession(session);

                log.Warn($"会话 {sessionId} 标记为需要恢复，从 {previousState} 转为 RecoveryRequired");
            }
            catch (Exception ex)
            {
                log.Error($"标记恢复状态失败: {ex.Message}", ex);
            }
        }

        /// <summary>
        /// 验证命令是否允许执行（只有 MaintenanceActive 状态允许写操作）
        /// </summary>
        public bool ValidateCommand(string sessionId, DebugCommand command)
        {
            try
            {
                if (!_activeSessions.TryGetValue(sessionId, out var session))
                {
                    log.Warn($"会话不存在: {sessionId}");
                    return false;
                }

                // 只有 MaintenanceActive 状态允许写操作
                bool allowed = session.State == DebugSessionState.MaintenanceActive;

                if (!allowed)
                {
                    log.Warn($"会话 {sessionId} 状态为 {session.State}，拒绝执行命令: {command.CommandType}");
                }

                // 增加资源预约验证
                if (allowed && _resourceManager != null)
                {
                    var resourceKey = new ResourceKey(session.DeviceId, "Generic");
                    allowed = _resourceManager.ValidateOwner(
                        new ResourceOwnerToken(OwnerType.Maintenance, session.SessionId),
                        resourceKey);
                    if (!allowed)
                    {
                        log.Warn($"会话 {sessionId} 资源预约验证失败，拒绝执行命令: {command.CommandType}");
                    }
                }

                return allowed;
            }
            catch (Exception ex)
            {
                log.Error($"验证命令失败: {ex.Message}", ex);
                return false;
            }
        }

        /// <summary>
        /// 获取会话状态
        /// </summary>
        public DebugSessionState? GetSessionState(string sessionId)
        {
            try
            {
                if (_activeSessions.TryGetValue(sessionId, out var session))
                {
                    return session.State;
                }

                // 从数据库查询
                var dbSession = _model.GetSession(sessionId);
                return dbSession?.State;
            }
            catch (Exception ex)
            {
                log.Error($"获取会话状态失败: {ex.Message}", ex);
                return null;
            }
        }

        /// <summary>
        /// 获取设备当前会话（如果有）
        /// </summary>
        public DebugSession? GetActiveSessionByDevice(string deviceId)
        {
            try
            {
                // 先从内存缓存查找
                var cachedSession = _activeSessions.Values
                    .FirstOrDefault(s => s.DeviceId == deviceId && s.State != DebugSessionState.Closed);

                if (cachedSession != null)
                {
                    return cachedSession;
                }

                // 从数据库查询
                var activeSessions = _model.GetActiveSessionsByDevice(deviceId);
                return activeSessions.FirstOrDefault();
            }
            catch (Exception ex)
            {
                log.Error($"获取设备活跃会话失败: {ex.Message}", ex);
                return null;
            }
        }
    }
}