AiDOPWarehouse/server/Plugins/Admin.NET.Plugin.ApprovalFlow/Service/FlowEngine/FlowEngineService.cs

using System.Text.Json;

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 UserManager _userManager;
    private readonly FlowNotifyService _notifyService;

    public FlowEngineService(
        SqlSugarRepository<ApprovalFlow> flowRep,
        SqlSugarRepository<ApprovalFlowInstance> instanceRep,
        SqlSugarRepository<ApprovalFlowTask> taskRep,
        SqlSugarRepository<ApprovalFlowLog> logRep,
        SqlSugarRepository<SysUserRole> userRoleRep,
        SqlSugarRepository<SysUser> userRep,
        UserManager userManager,
        FlowNotifyService notifyService)
    {
        _flowRep = flowRep;
        _instanceRep = instanceRep;
        _taskRep = taskRep;
        _logRep = logRep;
        _userRoleRep = userRoleRep;
        _userRep = userRep;
        _userManager = userManager;
        _notifyService = notifyService;
    }

    // ═══════════════════════════════════════════
    //  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 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,
        };

        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");

        var firstTaskNodeId = FindNextNodeId(flowData, startNode.Id);
        instance.CurrentNodeId = firstTaskNodeId;

        await _instanceRep.InsertAsync(instance);

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

        await CreateTasksForNode(instance, flowData, firstTaskNodeId);

        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();

        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, task.NodeId, task.NodeName ?? ""));

            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();

        await CancelPendingTasks(task.InstanceId, task.NodeId, 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);
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, FlowInstanceStatusEnum.Rejected));
        await _notifyService.NotifyFlowCompleted(instance.InitiatorId, instance.Id, instance.Title, FlowInstanceStatusEnum.Rejected);
    }

    // ═══════════════════════════════════════════
    //  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 newTask = new ApprovalFlowTask
        {
            InstanceId = task.InstanceId,
            NodeId = task.NodeId,
            NodeName = task.NodeName,
            AssigneeId = targetUserId,
            AssigneeName = targetUser?.RealName,
            Status = FlowTaskStatusEnum.Pending,
        };
        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);
    }

    /// <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);
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, FlowInstanceStatusEnum.Cancelled));

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

    /// <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);
    }

    /// <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 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,
        };
        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);
    }

    /// <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);
    }

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

    private async Task AdvanceToNext(ApprovalFlowInstance instance, ApprovalFlowItem flowData, string currentNodeId)
    {
        var nextNodeId = FindNextNodeId(flowData, currentNodeId);
        if (nextNodeId == null)
        {
            await CompleteInstance(instance, FlowInstanceStatusEnum.Approved);
            return;
        }

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

        if (nextNode.Type is "bpmn:exclusiveGateway")
        {
            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 AdvanceToNext(instance, flowData, nextNode.Id);
            return;
        }

        instance.CurrentNodeId = nextNodeId;
        await _instanceRep.AsUpdateable(instance).UpdateColumns(i => new { i.CurrentNodeId }).ExecuteCommandAsync();
        await CreateTasksForNode(instance, flowData, nextNodeId);
    }

    private async Task CompleteInstance(ApprovalFlowInstance instance, FlowInstanceStatusEnum status)
    {
        instance.Status = status;
        instance.EndTime = DateTime.Now;
        await _instanceRep.AsUpdateable(instance)
            .UpdateColumns(i => new { i.Status, i.EndTime })
            .ExecuteCommandAsync();
        await InvokeHandler(instance.BizType,
            h => h.OnFlowCompleted(instance.BizId, status));
        await _notifyService.NotifyFlowCompleted(instance.InitiatorId, instance.Id, instance.Title, status);
    }

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

        await _taskRep.AsInsertable(tasks).ExecuteCommandAsync();

        var assigneeIds = tasks.Select(t => t.AssigneeId).Distinct().ToList();
        await _notifyService.NotifyNewTask(assigneeIds, instance.Id, instance.Title, node.Properties?.NodeName ?? node.Text?.Value);
    }

    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();
        }

        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();
    }

    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);
    }
}