using System.Text.Json;
using Admin.NET.Core.Service;

namespace Admin.NET.Plugin.ApprovalFlow.Service;

/// <summary>
/// 流程推进引擎 — 核心状态机
/// 不暴露为 API，由其他 Service 内部调用
/// </summary>
public class FlowEngineService : ITransient
{
    private readonly SqlSugarRepository<ApprovalFlow> _flowRep;
    private readonly SqlSugarRepository<ApprovalFlowInstance> _instanceRep;
    private readonly SqlSugarRepository<ApprovalFlowTask> _taskRep;
    private readonly SqlSugarRepository<ApprovalFlowLog> _logRep;
    private readonly SqlSugarRepository<SysUserRole> _userRoleRep;
    private readonly SqlSugarRepository<SysUser> _userRep;
    private readonly SqlSugarRepository<SysOrg> _orgRep;
    private readonly SqlSugarRepository<ApprovalFlowDelegate> _delegateRep;
    private readonly SqlSugarRepository<ApprovalFlowCompletedNode> _completedNodeRep;
    private readonly UserManager _userManager;
    private readonly SysOrgService _sysOrgService;
    private readonly FlowNotifyService _notifyService;

    public FlowEngineService(
        SqlSugarRepository<ApprovalFlow> flowRep,
        SqlSugarRepository<ApprovalFlowInstance> instanceRep,
        SqlSugarRepository<ApprovalFlowTask> taskRep,
        SqlSugarRepository<ApprovalFlowLog> logRep,
        SqlSugarRepository<SysUserRole> userRoleRep,
        SqlSugarRepository<SysUser> userRep,
        SqlSugarRepository<SysOrg> orgRep,
        SqlSugarRepository<ApprovalFlowDelegate> delegateRep,
        SqlSugarRepository<ApprovalFlowCompletedNode> completedNodeRep,
        UserManager userManager,
        SysOrgService sysOrgService,
        FlowNotifyService notifyService)
    {
        _flowRep = flowRep;
        _instanceRep = instanceRep;
        _taskRep = taskRep;
        _logRep = logRep;
        _userRoleRep = userRoleRep;
        _userRep = userRep;
        _orgRep = orgRep;
        _delegateRep = delegateRep;
        _completedNodeRep = completedNodeRep;
        _userManager = userManager;
        _sysOrgService = sysOrgService;
        _notifyService = notifyService;
    }

    /// <summary>
    /// 机构数据权限依赖实体的 OrgId；插入时必须与当前用户机构一致，否则非超管在「我发起的/待办」中查不到（OrgId=0 会被过滤）。
    /// </summary>
    private async Task<long> ResolveOrgIdForNewFlowEntityAsync()
    {
        var oid = _userManager.OrgId;
        if (oid > 0) return oid;
        var list = await _sysOrgService.GetUserOrgIdList();
        return list is { Count: > 0 } ? list[0] : 0;
    }

    // ═══════════════════════════════════════════
    //  核心生命周期
    // ═══════════════════════════════════════════

    /// <summary>
    /// 发起流程
    /// </summary>
    public async Task<long> StartFlow(StartFlowInput input)
    {
        var flow = await _flowRep.AsQueryable()
            .Where(u => u.BizType == input.BizType && u.IsPublished && !u.IsDelete)
            .OrderByDescending(u => u.Version)
            .FirstAsync() ?? throw Oops.Oh($"未找到业务类型 [{input.BizType}] 的已发布流程定义");

        if (string.IsNullOrWhiteSpace(flow.FlowJson))
            throw Oops.Oh("流程定义的 FlowJson 为空，请先设计流程图");

        var flowData = JsonSerializer.Deserialize<ApprovalFlowItem>(flow.FlowJson)
            ?? throw Oops.Oh("FlowJson 反序列化失败");

        var orgId = await ResolveOrgIdForNewFlowEntityAsync();
        var instance = new ApprovalFlowInstance
        {
            FlowId = flow.Id,
            FlowVersion = flow.Version,
            BizType = input.BizType,
            BizId = input.BizId,
            BizNo = input.BizNo,
            Title = input.Title ?? $"{flow.Name}-{input.BizNo}",
            InitiatorId = _userManager.UserId,
            InitiatorName = _userManager.RealName,
            Status = FlowInstanceStatusEnum.Running,
            FlowJsonSnapshot = flow.FlowJson,
            StartTime = DateTime.Now,
            OrgId = orgId,
        };

        var startNode = flowData.Nodes.FirstOrDefault(n =>
            n.Type is "bpmn:startEvent" or "start-node")
            ?? throw Oops.Oh("流程图中未找到开始节点");

        await _instanceRep.InsertAsync(instance);

        await WriteLog(instance.Id, null, startNode.Id, FlowLogActionEnum.Submit, input.Comment);

        // 开始节点登记为已完成，随后沿出边推进（兼容首节点即为并行网关 Fork 的拓扑）
        await MarkNodeCompleted(instance.Id, startNode);
        var firstOutgoing = flowData.Edges.Where(e => e.SourceNodeId == startNode.Id).Select(e => e.TargetNodeId).ToList();
        if (firstOutgoing.Count == 0)
            throw Oops.Oh("流程图开始节点未连接任何后继节点");
        foreach (var target in firstOutgoing)
        {
            await ProcessNextNode(instance, flowData, target);
        }

        await InvokeHandler(input.BizType, h => h.OnFlowStarted(input.BizId, instance.Id));

        return instance.Id;
    }

    /// <summary>
    /// 同意
    /// </summary>
    public async Task Approve(long taskId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        task.Status = FlowTaskStatusEnum.Approved;
        task.Comment = comment;
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        // P1-6 审批代理：同步取消配对的本人/代理任务
        await CancelPairedDelegateTask(task);

        await WriteLog(task.InstanceId, taskId, task.NodeId, FlowLogActionEnum.Approve, comment);

        var instance = await _instanceRep.GetByIdAsync(task.InstanceId)
            ?? throw Oops.Oh("流程实例不存在");

        if (await IsNodeCompleted(instance, task.NodeId))
        {
            await InvokeHandler(instance.BizType,
                h => h.OnNodeCompleted(instance.BizId, instance.Id, task.NodeId, task.NodeName ?? "", task.AssigneeId));

            var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);
            await AdvanceToNext(instance, flowData, task.NodeId);
        }
    }

    /// <summary>
    /// 拒绝
    /// </summary>
    public async Task Reject(long taskId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        task.Status = FlowTaskStatusEnum.Rejected;
        task.Comment = comment;
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        // Reject 导致流程终止：取消整个实例所有剩余 Pending 任务（含并行分支、配对代理任务等）
        await CancelAllPendingTasks(task.InstanceId, task.Id);

        var instance = await _instanceRep.GetByIdAsync(task.InstanceId)
            ?? throw Oops.Oh("流程实例不存在");
        instance.Status = FlowInstanceStatusEnum.Rejected;
        instance.EndTime = DateTime.Now;
        await _instanceRep.AsUpdateable(instance).ExecuteCommandAsync();

        await WriteLog(instance.Id, taskId, task.NodeId, FlowLogActionEnum.Reject, comment);
        // P4-17: 驳回人 = 当前被指派的审批人
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, instance.Id, FlowInstanceStatusEnum.Rejected, task.AssigneeId));
        await _notifyService.NotifyFlowCompleted(instance.InitiatorId, instance.Id, instance.Title, FlowInstanceStatusEnum.Rejected, instance.BizType);
    }

    // ═══════════════════════════════════════════
    //  扩展操作
    // ═══════════════════════════════════════════

    /// <summary>
    /// 转办
    /// </summary>
    public async Task Transfer(long taskId, long targetUserId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        task.Status = FlowTaskStatusEnum.Transferred;
        task.Comment = comment;
        task.ActionTime = DateTime.Now;
        task.TransferToId = targetUserId;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        var targetUser = await _userRep.GetByIdAsync(targetUserId);
        var instForOrg = await _instanceRep.GetByIdAsync(task.InstanceId);
        var newTask = new ApprovalFlowTask
        {
            InstanceId = task.InstanceId,
            NodeId = task.NodeId,
            NodeName = task.NodeName,
            AssigneeId = targetUserId,
            AssigneeName = targetUser?.RealName,
            Status = FlowTaskStatusEnum.Pending,
            OrgId = instForOrg?.OrgId ?? 0,
        };
        await _taskRep.InsertAsync(newTask);

        await WriteLog(task.InstanceId, taskId, task.NodeId, FlowLogActionEnum.Transfer,
            $"{comment} → 转办给 {targetUser?.RealName}");

        var instance = await _instanceRep.GetByIdAsync(task.InstanceId);
        await _notifyService.NotifyTransferred(targetUserId, task.InstanceId, instance?.Title ?? "", _userManager.RealName, instance?.BizType ?? "");
    }

    /// <summary>
    /// 撤回（发起人撤回）
    /// </summary>
    public async Task Withdraw(long instanceId)
    {
        var instance = await _instanceRep.GetByIdAsync(instanceId)
            ?? throw Oops.Oh("流程实例不存在");
        if (instance.InitiatorId != _userManager.UserId)
            throw Oops.Oh("只有发起人可以撤回");
        if (instance.Status != FlowInstanceStatusEnum.Running)
            throw Oops.Oh("当前流程状态不允许撤回");

        var pendingTasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instanceId && t.Status == FlowTaskStatusEnum.Pending)
            .ToListAsync();
        var doneTasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instanceId &&
                        t.Status != FlowTaskStatusEnum.Pending &&
                        t.Status != FlowTaskStatusEnum.Cancelled)
            .CountAsync();
        if (doneTasks > 0)
            throw Oops.Oh("已有人审批过，不可撤回");

        var cancelledUserIds = pendingTasks.Select(t => t.AssigneeId).Distinct().ToList();

        foreach (var t in pendingTasks)
        {
            t.Status = FlowTaskStatusEnum.Cancelled;
            t.ActionTime = DateTime.Now;
        }
        await _taskRep.AsUpdateable(pendingTasks).ExecuteCommandAsync();

        instance.Status = FlowInstanceStatusEnum.Cancelled;
        instance.EndTime = DateTime.Now;
        await _instanceRep.AsUpdateable(instance).ExecuteCommandAsync();

        await WriteLog(instanceId, null, instance.CurrentNodeId, FlowLogActionEnum.Withdraw, null);
        // P4-17: 撤回场景无"审批人"，lastApproverId = null
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, instanceId, FlowInstanceStatusEnum.Cancelled, null));

        await _notifyService.NotifyWithdrawn(cancelledUserIds, instanceId, instance.Title, instance.InitiatorName, instance.BizType);
    }

    /// <summary>
    /// 退回上一步
    /// </summary>
    public async Task ReturnToPrev(long taskId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        var instance = await _instanceRep.GetByIdAsync(task.InstanceId)
            ?? throw Oops.Oh("流程实例不存在");

        var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);

        var prevNodeId = FindPrevUserTaskNodeId(flowData, task.NodeId);
        if (prevNodeId == null)
            throw Oops.Oh("已是第一个审批节点，无法退回");

        await CancelPendingTasks(task.InstanceId, task.NodeId);
        task.Status = FlowTaskStatusEnum.Returned;
        task.Comment = comment;
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        instance.CurrentNodeId = prevNodeId;
        await _instanceRep.AsUpdateable(instance).ExecuteCommandAsync();

        await CreateTasksForNode(instance, flowData, prevNodeId);
        await WriteLog(instance.Id, taskId, task.NodeId, FlowLogActionEnum.Return, comment);

        var returnedTasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instance.Id && t.NodeId == prevNodeId && t.Status == FlowTaskStatusEnum.Pending)
            .ToListAsync();
        var returnedUserIds = returnedTasks.Select(t => t.AssigneeId).Distinct().ToList();
        await _notifyService.NotifyReturned(returnedUserIds, instance.Id, instance.Title, _userManager.RealName, instance.BizType);
    }

    /// <summary>
    /// 加签
    /// </summary>
    public async Task AddSign(long taskId, long targetUserId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        var targetUser = await _userRep.GetByIdAsync(targetUserId);

        var instForAddSign = await _instanceRep.GetByIdAsync(task.InstanceId);
        var newTask = new ApprovalFlowTask
        {
            InstanceId = task.InstanceId,
            NodeId = task.NodeId,
            NodeName = task.NodeName,
            AssigneeId = targetUserId,
            AssigneeName = targetUser?.RealName,
            Status = FlowTaskStatusEnum.Pending,
            IsAddSign = true,
            AddSignById = _userManager.UserId,
            OrgId = instForAddSign?.OrgId ?? 0,
        };
        await _taskRep.InsertAsync(newTask);

        await WriteLog(task.InstanceId, taskId, task.NodeId, FlowLogActionEnum.AddSign,
            $"{comment} → 加签给 {targetUser?.RealName}");

        var instance = await _instanceRep.GetByIdAsync(task.InstanceId);
        await _notifyService.NotifyAddSign(targetUserId, task.InstanceId, instance?.Title ?? "", _userManager.RealName, instance?.BizType ?? "");
    }

    /// <summary>
    /// 手动升级 — 当前审批人主动将任务升级到更高层级
    /// </summary>
    public async Task Escalate(long taskId, string? comment)
    {
        var task = await GetPendingTask(taskId);
        var instance = await _instanceRep.GetByIdAsync(task.InstanceId)
            ?? throw Oops.Oh("流程实例不存在");

        var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);
        var node = flowData.Nodes.FirstOrDefault(n => n.Id == task.NodeId)
            ?? throw Oops.Oh("节点不存在");

        var props = node.Properties;
        if (props?.EnableManualEscalation != true
            || string.IsNullOrWhiteSpace(props.EscalationApproverType)
            || string.IsNullOrWhiteSpace(props.EscalationApproverIds))
            throw Oops.Oh("该节点未配置升级目标，无法升级");

        task.Status = FlowTaskStatusEnum.Escalated;
        task.Comment = comment;
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        await CancelPendingTasks(task.InstanceId, task.NodeId, task.Id);

        var escalationApprovers = await ResolveApprovers(
            new FlowProperties
            {
                ApproverType = props.EscalationApproverType,
                ApproverIds = props.EscalationApproverIds,
                ApproverNames = props.EscalationApproverNames,
            },
            instance.InitiatorId);

        if (escalationApprovers.Count == 0)
            throw Oops.Oh("升级目标审批人列表为空");

        var newTasks = escalationApprovers.Select(a => new ApprovalFlowTask
        {
            InstanceId = instance.Id,
            NodeId = task.NodeId,
            NodeName = task.NodeName,
            AssigneeId = a.userId,
            AssigneeName = a.userName,
            Status = FlowTaskStatusEnum.Pending,
            OrgId = instance.OrgId,
        }).ToList();
        await _taskRep.AsInsertable(newTasks).ExecuteCommandAsync();

        var targetNames = string.Join(", ", escalationApprovers.Select(a => a.userName));
        await WriteLog(instance.Id, taskId, task.NodeId, FlowLogActionEnum.Escalate,
            $"{comment} → 升级给 {targetNames}");

        var targetUserIds = escalationApprovers.Select(a => a.userId).Distinct().ToList();
        await _notifyService.NotifyEscalated(targetUserIds, instance.Id, instance.Title,
            _userManager.RealName, task.NodeName, instance.BizType);
    }

    /// <summary>
    /// 催办
    /// </summary>
    public async Task Urge(long instanceId)
    {
        var instance = await _instanceRep.GetByIdAsync(instanceId)
            ?? throw Oops.Oh("流程实例不存在");
        if (instance.Status != FlowInstanceStatusEnum.Running)
            throw Oops.Oh("当前流程不在审批中");

        await WriteLog(instanceId, null, instance.CurrentNodeId, FlowLogActionEnum.Urge, "催办");

        var pendingTasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instanceId && t.Status == FlowTaskStatusEnum.Pending)
            .ToListAsync();
        var userIds = pendingTasks.Select(t => t.AssigneeId).Distinct().ToList();
        await _notifyService.NotifyUrge(userIds, instanceId, instance.Title, instance.BizType);
    }

    // ═══════════════════════════════════════════
    //  超时自动处理（由 FlowTimeoutJob 调用，无 UserManager 上下文）
    // ═══════════════════════════════════════════

    /// <summary>
    /// 扫描所有 Pending 且已超过 timeoutHours 的任务，按节点 timeoutAction 执行对应动作。
    /// 与 FlowTimeoutJob 扫描等价，抽出公共方法以便管理员接口立即触发（运维/E2E 测试用）。
    /// 返回本次处理的任务条数。
    /// </summary>
    public async Task<int> ScanTimeoutTasks(CancellationToken stoppingToken = default)
    {
        var pendingTasks = await _taskRep.Context.Queryable<ApprovalFlowTask>()
            .InnerJoin<ApprovalFlowInstance>((t, i) => t.InstanceId == i.Id)
            .Where((t, i) => t.Status == FlowTaskStatusEnum.Pending
                          && i.Status == FlowInstanceStatusEnum.Running)
            .Select((t, i) => new
            {
                TaskId = t.Id,
                TaskCreatedAt = t.CreateTime,
                NodeId = t.NodeId,
                FlowJsonSnapshot = i.FlowJsonSnapshot,
            })
            .ToListAsync();

        var now = DateTime.Now;
        var processed = 0;

        foreach (var item in pendingTasks)
        {
            if (stoppingToken.IsCancellationRequested) break;

            if (string.IsNullOrWhiteSpace(item.FlowJsonSnapshot)) continue;

            ApprovalFlowItem? flowData;
            try { flowData = JsonSerializer.Deserialize<ApprovalFlowItem>(item.FlowJsonSnapshot); }
            catch { continue; }

            var node = flowData?.Nodes?.FirstOrDefault(n => n.Id == item.NodeId);
            var props = node?.Properties;
            if (props?.TimeoutHours == null || props.TimeoutHours <= 0) continue;
            if (string.IsNullOrWhiteSpace(props.TimeoutAction)) continue;

            var deadline = item.TaskCreatedAt.AddHours(props.TimeoutHours.Value);
            if (now < deadline) continue;

            // Notify 动作幂等：已记录过 AutoTimeout 日志的跳过，避免每轮重复催办
            if (props.TimeoutAction == "Notify")
            {
                var alreadyNotified = await _logRep.AsQueryable()
                    .AnyAsync(log => log.TaskId == item.TaskId
                                  && log.Action == FlowLogActionEnum.AutoTimeout);
                if (alreadyNotified) continue;
            }

            try
            {
                await HandleTimeoutTask(item.TaskId);
                processed++;
            }
            catch
            {
                // 单任务异常隔离：吞掉继续下一个，由 Job/Admin API 层统一记日志
            }
        }

        return processed;
    }

    /// <summary>
    /// 处理单个超时任务（由定时任务调用）
    /// </summary>
    public async Task HandleTimeoutTask(long taskId)
    {
        var task = await _taskRep.GetByIdAsync(taskId);
        if (task == null || task.Status != FlowTaskStatusEnum.Pending) return;

        var instance = await _instanceRep.GetByIdAsync(task.InstanceId);
        if (instance == null || instance.Status != FlowInstanceStatusEnum.Running) return;

        var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);
        var node = flowData.Nodes.FirstOrDefault(n => n.Id == task.NodeId);
        var props = node?.Properties;
        if (props == null) return;

        switch (props.TimeoutAction)
        {
            case "Notify":
                await _notifyService.NotifyTimeout(
                    new List<long> { task.AssigneeId }, instance.Id, instance.Title, instance.BizType);
                await WriteSystemLog(instance.Id, task.Id, task.NodeId,
                    FlowLogActionEnum.AutoTimeout, "审批超时，已发送提醒通知");
                break;
            case "AutoApprove":
                await AutoApproveTask(task, instance);
                break;
            case "AutoReject":
                await AutoRejectTask(task, instance);
                break;
            case "AutoEscalate":
                await AutoEscalateTask(task, props, instance);
                break;
        }
    }

    private async Task AutoApproveTask(ApprovalFlowTask task, ApprovalFlowInstance instance)
    {
        task.Status = FlowTaskStatusEnum.Approved;
        task.Comment = "系统自动通过（超时）";
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        await WriteSystemLog(instance.Id, task.Id, task.NodeId,
            FlowLogActionEnum.AutoTimeout, "审批超时，系统自动通过");

        if (await IsNodeCompleted(instance, task.NodeId))
        {
            // P4-17: 系统自动通过，无人工审批人，approverUserId = null
            await InvokeHandler(instance.BizType,
                h => h.OnNodeCompleted(instance.BizId, instance.Id, task.NodeId, task.NodeName ?? "", null));
            var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);
            await AdvanceToNext(instance, flowData, task.NodeId);
        }
    }

    private async Task AutoRejectTask(ApprovalFlowTask task, ApprovalFlowInstance instance)
    {
        task.Status = FlowTaskStatusEnum.Rejected;
        task.Comment = "系统自动拒绝（超时）";
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        await CancelPendingTasks(task.InstanceId, task.NodeId, task.Id);

        instance.Status = FlowInstanceStatusEnum.Rejected;
        instance.EndTime = DateTime.Now;
        await _instanceRep.AsUpdateable(instance).ExecuteCommandAsync();

        await WriteSystemLog(instance.Id, task.Id, task.NodeId,
            FlowLogActionEnum.AutoTimeout, "审批超时，系统自动拒绝");

        // P4-17: 系统自动拒绝，无人工审批人，lastApproverId = null
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, instance.Id, FlowInstanceStatusEnum.Rejected, null));
        await _notifyService.NotifyFlowCompleted(instance.InitiatorId, instance.Id,
            instance.Title, FlowInstanceStatusEnum.Rejected, instance.BizType);
    }

    private async Task AutoEscalateTask(ApprovalFlowTask task, FlowProperties nodeProps, ApprovalFlowInstance instance)
    {
        if (string.IsNullOrWhiteSpace(nodeProps.EscalationApproverType)
            || string.IsNullOrWhiteSpace(nodeProps.EscalationApproverIds))
            return;

        task.Status = FlowTaskStatusEnum.Escalated;
        task.Comment = "系统自动升级（超时）";
        task.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(task).ExecuteCommandAsync();

        await CancelPendingTasks(task.InstanceId, task.NodeId, task.Id);

        var approvers = await ResolveApprovers(
            new FlowProperties
            {
                ApproverType = nodeProps.EscalationApproverType,
                ApproverIds = nodeProps.EscalationApproverIds,
            },
            instance.InitiatorId);

        if (approvers.Count == 0) return;

        var newTasks = approvers.Select(a => new ApprovalFlowTask
        {
            InstanceId = instance.Id,
            NodeId = task.NodeId,
            NodeName = task.NodeName,
            AssigneeId = a.userId,
            AssigneeName = a.userName,
            Status = FlowTaskStatusEnum.Pending,
            OrgId = instance.OrgId,
        }).ToList();
        await _taskRep.AsInsertable(newTasks).ExecuteCommandAsync();

        var targetNames = string.Join(", ", approvers.Select(a => a.userName));
        await WriteSystemLog(instance.Id, task.Id, task.NodeId,
            FlowLogActionEnum.AutoTimeout, $"审批超时，自动升级给 {targetNames}");

        var targetUserIds = approvers.Select(a => a.userId).Distinct().ToList();
        await _notifyService.NotifyEscalated(targetUserIds, instance.Id, instance.Title,
            "系统", task.NodeName, instance.BizType);
    }

    private async Task WriteSystemLog(long instanceId, long? taskId, string? nodeId,
        FlowLogActionEnum action, string? comment)
    {
        await _logRep.InsertAsync(new ApprovalFlowLog
        {
            InstanceId = instanceId,
            TaskId = taskId,
            NodeId = nodeId,
            Action = action,
            OperatorId = 0,
            OperatorName = "系统",
            Comment = comment,
        });
    }

    // ═══════════════════════════════════════════
    //  内部引擎方法
    // ═══════════════════════════════════════════

    /// <summary>
    /// 推进到下一节点。支持并行网关（Fork / Join）。
    /// 行为约定：
    /// - 进入本方法前，调用方（如 <see cref="Approve"/>）应已将 <paramref name="currentNodeId"/>（userTask）标记为完成节点；
    ///   本方法会将途经的网关节点也写入 <see cref="ApprovalFlowCompletedNode"/>。
    /// - 并行网关 Fork（出边&gt;=2）：沿每条出边递归推进；
    ///   并行网关 Join（入边&gt;=2）：校验所有前驱节点是否都在"已完成"集合中，
    ///   任一尚未完成则**静默等待**（不报错、不推进），由后续分支完成后再次触发 Join 校验。
    /// </summary>
    private async Task AdvanceToNext(ApprovalFlowInstance instance, ApprovalFlowItem flowData, string currentNodeId)
    {
        // 当前节点可能是 userTask（完成记录由 Approve 写入）或网关（入口处已写入）；此处统一确保幂等入库
        var currentNode = flowData.Nodes.FirstOrDefault(n => n.Id == currentNodeId);
        await MarkNodeCompleted(instance.Id, currentNode);

        var outgoingEdges = flowData.Edges.Where(e => e.SourceNodeId == currentNodeId).ToList();
        if (outgoingEdges.Count == 0)
        {
            await CompleteInstance(instance, FlowInstanceStatusEnum.Approved);
            return;
        }

        // 非并行网关场景：当前节点一般只有 1 条出边
        foreach (var edge in outgoingEdges)
        {
            await ProcessNextNode(instance, flowData, edge.TargetNodeId);
        }
    }

    /// <summary>
    /// 处理某个"下一节点"。根据节点类型分发：
    /// - endEvent：所有分支任务都结束时触发实例完成
    /// - exclusiveGateway：按条件选择分支
    /// - parallelGateway：Fork 并行分发；Join 等待所有前驱完成
    /// - userTask / 其他：创建任务
    /// </summary>
    private async Task ProcessNextNode(ApprovalFlowInstance instance, ApprovalFlowItem flowData, string nextNodeId)
    {
        var nextNode = flowData.Nodes.FirstOrDefault(n => n.Id == nextNodeId);
        if (nextNode == null)
        {
            await CompleteInstance(instance, FlowInstanceStatusEnum.Approved);
            return;
        }

        if (nextNode.Type is "bpmn:endEvent" or "end-node")
        {
            // 所有并行分支都已结束（无其它 Pending 任务）才真正完成实例
            var hasOtherPending = await _taskRep.AsQueryable()
                .AnyAsync(t => t.InstanceId == instance.Id && t.Status == FlowTaskStatusEnum.Pending);
            if (hasOtherPending) return;

            await CompleteInstance(instance, FlowInstanceStatusEnum.Approved);
            return;
        }

        if (nextNode.Type is "bpmn:exclusiveGateway")
        {
            await MarkNodeCompleted(instance.Id, nextNode);
            var bizData = await GetBizData(instance.BizType, instance.BizId);
            var targetNodeId = EvaluateGateway(nextNode.Properties?.Conditions, flowData, nextNode.Id, bizData);
            instance.CurrentNodeId = targetNodeId;
            await _instanceRep.AsUpdateable(instance).UpdateColumns(i => new { i.CurrentNodeId }).ExecuteCommandAsync();
            await ProcessNextNode(instance, flowData, targetNodeId);
            return;
        }

        if (nextNode.Type is "bpmn:parallelGateway")
        {
            var incoming = flowData.Edges.Where(e => e.TargetNodeId == nextNode.Id).Select(e => e.SourceNodeId).ToList();
            var outgoing = flowData.Edges.Where(e => e.SourceNodeId == nextNode.Id).Select(e => e.TargetNodeId).ToList();

            // Join 语义：入边 >= 2，需等所有前驱都已完成
            if (incoming.Count >= 2)
            {
                var completedSet = await GetCompletedNodeIdSet(instance.Id);
                if (!incoming.All(p => completedSet.Contains(p)))
                {
                    // 未汇合，静默等待后续分支抵达
                    return;
                }
            }

            // Fork 或 Join 通过：标记网关完成，沿所有出边推进
            await MarkNodeCompleted(instance.Id, nextNode);
            foreach (var target in outgoing)
            {
                await ProcessNextNode(instance, flowData, target);
            }
            return;
        }

        // userTask 或其他：创建任务
        instance.CurrentNodeId = nextNodeId;
        await _instanceRep.AsUpdateable(instance).UpdateColumns(i => new { i.CurrentNodeId }).ExecuteCommandAsync();
        await CreateTasksForNode(instance, flowData, nextNodeId);
    }

    /// <summary>
    /// 标记节点已完成（幂等：重复写入被唯一索引拦截后忽略）
    /// </summary>
    private async Task MarkNodeCompleted(long instanceId, ApprovalFlowNodeItem? node)
    {
        if (node == null) return;
        try
        {
            await _completedNodeRep.InsertAsync(new ApprovalFlowCompletedNode
            {
                InstanceId = instanceId,
                NodeId = node.Id,
                NodeName = node.Properties?.NodeName ?? node.Text?.Value,
                NodeType = node.Type,
                CompletedTime = DateTime.Now,
            });
        }
        catch
        {
            // 并发场景下可能触发唯一索引冲突，忽略（已存在即可）
        }
    }

    /// <summary>
    /// 查询实例已完成节点 Id 集合
    /// </summary>
    private async Task<HashSet<string>> GetCompletedNodeIdSet(long instanceId)
    {
        var ids = await _completedNodeRep.AsQueryable()
            .Where(c => c.InstanceId == instanceId)
            .Select(c => c.NodeId)
            .ToListAsync();
        return new HashSet<string>(ids);
    }

    private async Task CompleteInstance(ApprovalFlowInstance instance, FlowInstanceStatusEnum status)
    {
        // 幂等：并行分支同时到达 end 时避免重复完成
        var latest = await _instanceRep.GetByIdAsync(instance.Id);
        if (latest == null || latest.Status != FlowInstanceStatusEnum.Running) return;

        instance.Status = status;
        instance.EndTime = DateTime.Now;
        await _instanceRep.AsUpdateable(instance)
            .UpdateColumns(i => new { i.Status, i.EndTime })
            .ExecuteCommandAsync();

        // P4-17: 正常完成路径的 lastApproverId = 最后一条人工 Approve 日志的操作人（系统自动通过不算）
        var lastApproverId = status == FlowInstanceStatusEnum.Approved
            ? await GetLastHumanApproverIdAsync(instance.Id)
            : null;
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, instance.Id, status, lastApproverId));
        await _notifyService.NotifyFlowCompleted(instance.InitiatorId, instance.Id, instance.Title, status, instance.BizType);
    }

    /// <summary>
    /// P4-17: 查询该实例最后一条人工 Approve 日志的操作人 UserId
    /// （系统超时自动通过写入的是 AutoTimeout，不会被此查询命中）
    /// </summary>
    private async Task<long?> GetLastHumanApproverIdAsync(long instanceId)
    {
        var lastLog = await _logRep.AsQueryable()
            .Where(l => l.InstanceId == instanceId && l.Action == FlowLogActionEnum.Approve)
            .OrderByDescending(l => l.CreateTime)
            .FirstAsync();
        return lastLog?.OperatorId > 0 ? lastLog.OperatorId : null;
    }

    private async Task CreateTasksForNode(ApprovalFlowInstance instance, ApprovalFlowItem flowData, string nodeId)
    {
        var node = flowData.Nodes.FirstOrDefault(n => n.Id == nodeId)
            ?? throw Oops.Oh($"FlowJson 中未找到节点 [{nodeId}]");

        var approvers = await ResolveApprovers(node.Properties, instance.InitiatorId);
        if (approvers.Count == 0)
            throw Oops.Oh($"节点 [{node.Properties?.NodeName ?? nodeId}] 未配置审批人或审批人列表为空");

        var nodeName = node.Properties?.NodeName ?? node.Text?.Value;
        var tasks = approvers.Select(a => new ApprovalFlowTask
        {
            InstanceId = instance.Id,
            NodeId = nodeId,
            NodeName = nodeName,
            AssigneeId = a.userId,
            AssigneeName = a.userName,
            Status = FlowTaskStatusEnum.Pending,
            OrgId = instance.OrgId,
        }).ToList();

        // P1-6 审批代理：为每个原审批人检查是否存在有效代理，是则并行创建一条代理任务
        var delegateTasks = new List<ApprovalFlowTask>();
        foreach (var a in approvers)
        {
            var del = await FindEffectiveDelegate(a.userId, instance.BizType);
            if (del == null) continue;
            // 代理人和原审批人不能重复，代理人也不能是原审批人列表中其他人（避免同一人两条任务）
            if (approvers.Any(x => x.userId == del.DelegateUserId)) continue;

            delegateTasks.Add(new ApprovalFlowTask
            {
                InstanceId = instance.Id,
                NodeId = nodeId,
                NodeName = nodeName,
                AssigneeId = del.DelegateUserId,
                AssigneeName = del.DelegateUserName,
                Status = FlowTaskStatusEnum.Pending,
                OrgId = instance.OrgId,
                IsDelegate = true,
                DelegateForUserId = a.userId,
                DelegateForUserName = a.userName,
            });
        }

        var allTasks = tasks.Concat(delegateTasks).ToList();
        await _taskRep.AsInsertable(allTasks).ExecuteCommandAsync();

        var assigneeIds = allTasks.Select(t => t.AssigneeId).Distinct().ToList();
        await _notifyService.NotifyNewTask(assigneeIds, instance.Id, instance.Title, nodeName, instance.BizType);
    }

    /// <summary>
    /// 查找指定用户当前生效的审批代理（时间窗口内 + 已启用 + BizType 匹配或全局）
    /// </summary>
    private async Task<ApprovalFlowDelegate?> FindEffectiveDelegate(long userId, string? bizType)
    {
        var now = DateTime.Now;
        return await _delegateRep.AsQueryable()
            .Where(d => d.UserId == userId
                     && d.IsEnabled
                     && d.StartTime <= now
                     && d.EndTime >= now
                     && (string.IsNullOrEmpty(d.BizType) || d.BizType == bizType))
            .OrderBy(d => d.BizType == null ? 1 : 0) // 优先匹配指定 BizType 的代理
            .OrderByDescending(d => d.CreateTime)
            .FirstAsync();
    }

    /// <summary>
    /// 取消与已完成任务配对的代理任务（P1-6）
    /// - 本人任务完成：取消对应的代理任务
    /// - 代理任务完成：取消对应的本人任务
    /// </summary>
    private async Task CancelPairedDelegateTask(ApprovalFlowTask completedTask)
    {
        ApprovalFlowTask? paired;
        if (completedTask.IsDelegate)
        {
            var originalUserId = completedTask.DelegateForUserId ?? 0;
            if (originalUserId == 0) return;
            paired = await _taskRep.AsQueryable()
                .Where(t => t.InstanceId == completedTask.InstanceId
                         && t.NodeId == completedTask.NodeId
                         && t.Status == FlowTaskStatusEnum.Pending
                         && t.AssigneeId == originalUserId
                         && !t.IsDelegate)
                .FirstAsync();
        }
        else
        {
            paired = await _taskRep.AsQueryable()
                .Where(t => t.InstanceId == completedTask.InstanceId
                         && t.NodeId == completedTask.NodeId
                         && t.Status == FlowTaskStatusEnum.Pending
                         && t.IsDelegate
                         && t.DelegateForUserId == completedTask.AssigneeId)
                .FirstAsync();
        }

        if (paired == null) return;
        paired.Status = FlowTaskStatusEnum.Cancelled;
        paired.ActionTime = DateTime.Now;
        await _taskRep.AsUpdateable(paired).ExecuteCommandAsync();
    }

    private async Task<List<(long userId, string userName)>> ResolveApprovers(FlowProperties? props, long initiatorId)
    {
        if (props == null || string.IsNullOrWhiteSpace(props.ApproverType))
            return new List<(long, string)>();

        var approverType = props.ApproverType;

        if (approverType == nameof(ApproverTypeEnum.Initiator))
        {
            var initiator = await _userRep.GetByIdAsync(initiatorId);
            return initiator != null
                ? new List<(long, string)> { (initiator.Id, initiator.RealName ?? "") }
                : new List<(long, string)>();
        }

        if (string.IsNullOrWhiteSpace(props.ApproverIds))
            return new List<(long, string)>();

        var ids = props.ApproverIds.Split(',', StringSplitOptions.RemoveEmptyEntries)
            .Select(s => long.TryParse(s.Trim(), out var v) ? v : 0).Where(id => id > 0).ToList();

        if (approverType == nameof(ApproverTypeEnum.SpecificUser))
        {
            var users = await _userRep.AsQueryable()
                .Where(u => ids.Contains(u.Id)).ToListAsync();
            return users.Select(u => (u.Id, u.RealName ?? "")).ToList();
        }

        if (approverType == nameof(ApproverTypeEnum.Role))
        {
            var userIds = await _userRoleRep.AsQueryable()
                .Where(ur => ids.Contains(ur.RoleId))
                .Select(ur => ur.UserId)
                .ToListAsync();
            var users = await _userRep.AsQueryable()
                .Where(u => userIds.Contains(u.Id)).ToListAsync();
            return users.Select(u => (u.Id, u.RealName ?? "")).ToList();
        }

        if (approverType == nameof(ApproverTypeEnum.Department))
        {
            var users = await _userRep.AsQueryable()
                .Where(u => ids.Contains(u.OrgId)).ToListAsync();
            return users.Select(u => (u.Id, u.RealName ?? "")).ToList();
        }

        if (approverType == nameof(ApproverTypeEnum.DepartmentLeader))
        {
            var initiator = await _userRep.GetByIdAsync(initiatorId);
            if (initiator == null || initiator.OrgId <= 0)
                return new List<(long, string)>();

            var org = await _orgRep.GetByIdAsync(initiator.OrgId);
            if (org?.DirectorId != null && org.DirectorId > 0)
            {
                var director = await _userRep.GetByIdAsync(org.DirectorId.Value);
                if (director != null)
                    return new List<(long, string)> { (director.Id, director.RealName ?? "") };
            }

            if (initiator.ManagerUserId != null && initiator.ManagerUserId > 0)
            {
                var manager = await _userRep.GetByIdAsync(initiator.ManagerUserId.Value);
                if (manager != null)
                    return new List<(long, string)> { (manager.Id, manager.RealName ?? "") };
            }

            return new List<(long, string)>();
        }

        return new List<(long, string)>();
    }

    /// <summary>
    /// 评估排他网关 — 依次尝试各非默认分支的条件表达式，首个匹配的获胜；
    /// 全不匹配则走默认分支；无默认则走第一条出边
    /// 支持简单比较表达式：variable op value（op: ==,!=,>,>=,&lt;,&lt;=）
    /// </summary>
    private string EvaluateGateway(List<GatewayCondition>? conditions, ApprovalFlowItem flowData, string gatewayNodeId, Dictionary<string, object>? bizData)
    {
        if (conditions != null && conditions.Count > 0 && bizData != null && bizData.Count > 0)
        {
            foreach (var cond in conditions.Where(c => !c.IsDefault))
            {
                if (!string.IsNullOrWhiteSpace(cond.Expression) && EvalSimpleExpression(cond.Expression, bizData))
                    return cond.TargetNodeId;
            }

            var defaultBranch = conditions.FirstOrDefault(c => c.IsDefault);
            if (defaultBranch != null)
                return defaultBranch.TargetNodeId;
        }
        else if (conditions != null && conditions.Count > 0)
        {
            var defaultBranch = conditions.FirstOrDefault(c => c.IsDefault);
            if (defaultBranch != null) return defaultBranch.TargetNodeId;
            return conditions.First().TargetNodeId;
        }

        var edge = flowData.Edges.FirstOrDefault(e => e.SourceNodeId == gatewayNodeId);
        return edge?.TargetNodeId ?? throw Oops.Oh("排他网关没有出边");
    }

    /// <summary>
    /// 简单表达式求值：支持 "field op value" 格式（如 "urgent == 1", "customLevel >= 3", "amount > 10000"）
    /// 多条件用 &amp;&amp; 连接
    /// </summary>
    private static bool EvalSimpleExpression(string expression, Dictionary<string, object> bizData)
    {
        var parts = expression.Split("&&", StringSplitOptions.TrimEntries);
        foreach (var part in parts)
        {
            if (!EvalSingleComparison(part.Trim(), bizData))
                return false;
        }
        return true;
    }

    private static bool EvalSingleComparison(string expr, Dictionary<string, object> bizData)
    {
        string[] ops = { ">=", "<=", "!=", "==", ">", "<" };
        foreach (var op in ops)
        {
            var idx = expr.IndexOf(op, StringComparison.Ordinal);
            if (idx < 0) continue;

            var fieldName = expr[..idx].Trim();
            var valueStr = expr[(idx + op.Length)..].Trim().Trim('"', '\'');

            if (!bizData.TryGetValue(fieldName, out var fieldValue))
                return false;

            if (decimal.TryParse(fieldValue?.ToString(), out var numLeft) && decimal.TryParse(valueStr, out var numRight))
            {
                return op switch
                {
                    "==" => numLeft == numRight,
                    "!=" => numLeft != numRight,
                    ">" => numLeft > numRight,
                    ">=" => numLeft >= numRight,
                    "<" => numLeft < numRight,
                    "<=" => numLeft <= numRight,
                    _ => false,
                };
            }

            var strLeft = fieldValue?.ToString() ?? "";
            return op switch
            {
                "==" => strLeft.Equals(valueStr, StringComparison.OrdinalIgnoreCase),
                "!=" => !strLeft.Equals(valueStr, StringComparison.OrdinalIgnoreCase),
                _ => false,
            };
        }
        return false;
    }

    private async Task<Dictionary<string, object>?> GetBizData(string bizType, long bizId)
    {
        var handlers = App.GetServices<IFlowBizHandler>();
        var handler = handlers?.FirstOrDefault(h => h.BizType == bizType);
        if (handler == null) return null;
        return await handler.GetBizData(bizId);
    }

    private string? FindNextNodeId(ApprovalFlowItem flowData, string currentNodeId)
    {
        var edge = flowData.Edges.FirstOrDefault(e => e.SourceNodeId == currentNodeId);
        return edge?.TargetNodeId;
    }

    private string? FindPrevUserTaskNodeId(ApprovalFlowItem flowData, string currentNodeId)
    {
        var inEdge = flowData.Edges.FirstOrDefault(e => e.TargetNodeId == currentNodeId);
        if (inEdge == null) return null;

        var prevNode = flowData.Nodes.FirstOrDefault(n => n.Id == inEdge.SourceNodeId);
        if (prevNode == null) return null;

        if (prevNode.Type is "bpmn:userTask" or "user-node" or "task-node")
            return prevNode.Id;

        // 递归跳过网关等非用户任务节点
        return FindPrevUserTaskNodeId(flowData, prevNode.Id);
    }

    private async Task<bool> IsNodeCompleted(ApprovalFlowInstance instance, string nodeId)
    {
        var flowData = DeserializeFlowJson(instance.FlowJsonSnapshot);
        var node = flowData.Nodes.FirstOrDefault(n => n.Id == nodeId);
        var mode = node?.Properties?.MultiApproveMode;

        if (mode == nameof(MultiApproveModeEnum.All))
        {
            var pendingCount = await _taskRep.AsQueryable()
                .Where(t => t.InstanceId == instance.Id && t.NodeId == nodeId && t.Status == FlowTaskStatusEnum.Pending)
                .CountAsync();
            return pendingCount == 0;
        }

        // 默认或签（Any）：一人通过即完成，取消其他 Pending
        await CancelPendingTasks(instance.Id, nodeId);
        return true;
    }

    private async Task CancelPendingTasks(long instanceId, string nodeId, long? excludeTaskId = null)
    {
        var tasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instanceId && t.NodeId == nodeId && t.Status == FlowTaskStatusEnum.Pending)
            .WhereIF(excludeTaskId.HasValue, t => t.Id != excludeTaskId!.Value)
            .ToListAsync();
        foreach (var t in tasks)
        {
            t.Status = FlowTaskStatusEnum.Cancelled;
            t.ActionTime = DateTime.Now;
        }
        if (tasks.Count > 0)
            await _taskRep.AsUpdateable(tasks).ExecuteCommandAsync();
    }

    /// <summary>
    /// 取消整个实例下所有剩余 Pending 任务（Reject 时跨并行分支使用）
    /// </summary>
    private async Task CancelAllPendingTasks(long instanceId, long? excludeTaskId = null)
    {
        var tasks = await _taskRep.AsQueryable()
            .Where(t => t.InstanceId == instanceId && t.Status == FlowTaskStatusEnum.Pending)
            .WhereIF(excludeTaskId.HasValue, t => t.Id != excludeTaskId!.Value)
            .ToListAsync();
        foreach (var t in tasks)
        {
            t.Status = FlowTaskStatusEnum.Cancelled;
            t.ActionTime = DateTime.Now;
        }
        if (tasks.Count > 0)
            await _taskRep.AsUpdateable(tasks).ExecuteCommandAsync();
    }

    private async Task<ApprovalFlowTask> GetPendingTask(long taskId)
    {
        var task = await _taskRep.GetByIdAsync(taskId)
            ?? throw Oops.Oh("审批任务不存在");
        if (task.Status != FlowTaskStatusEnum.Pending)
            throw Oops.Oh("该任务已处理");
        if (task.AssigneeId != _userManager.UserId)
            throw Oops.Oh("当前用户不是该任务的审批人");
        return task;
    }

    private async Task WriteLog(long instanceId, long? taskId, string? nodeId, FlowLogActionEnum action, string? comment)
    {
        await _logRep.InsertAsync(new ApprovalFlowLog
        {
            InstanceId = instanceId,
            TaskId = taskId,
            NodeId = nodeId,
            Action = action,
            OperatorId = _userManager.UserId,
            OperatorName = _userManager.RealName,
            Comment = comment,
        });
    }

    private static ApprovalFlowItem DeserializeFlowJson(string? json)
    {
        if (string.IsNullOrWhiteSpace(json))
            throw Oops.Oh("FlowJson 快照为空");
        return JsonSerializer.Deserialize<ApprovalFlowItem>(json)
            ?? throw Oops.Oh("FlowJson 反序列化失败");
    }

    private async Task InvokeHandler(string bizType, Func<IFlowBizHandler, Task> action)
    {
        var handlers = App.GetServices<IFlowBizHandler>();
        var handler = handlers?.FirstOrDefault(h => h.BizType == bizType);
        if (handler != null)
            await action(handler);
    }
}