您将如何重构此特定代码？

Question

我想问一下您如何重构此代码：

public static EmailSetup GetEmailSetup(ApprovalContainer approval, PivotalApprovalInformation info, ApprovalStep step, ReportTrigger trigger)
    {
        EmailSetup setup = new EmailSetup() { EmailAdresses = new List<string>(), ReportTypes = new List<ReportType>() };
        List<string> emailRecipients = new List<string>();

        if (trigger == ReportTrigger.Closed)
        {
            emailRecipients = approval.ApprovalTeam.Select(ap => ap.Employee.Email).ToList();
            setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
            setup.ReportTypes.Add(ReportType.CommonReport);
            return setup;
        }

        else if (step.ApprovalType == ApprovalType.CustomerSpecial)
        {
            if (step.ApproverType == ApproverType.RDev1)
            {
                emailRecipients = new List<string>() { approval.Initiator.Employee.Email, step.EmployeeApprover.Employee.Email };
                setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
                setup.ReportTypes.Add(ReportType.CustomerSpecialReport);
            }
            if (step.ApproverType == ApproverType.RDev2)
            {
                if (trigger == ReportTrigger.Created)
                {
                    emailRecipients = new List<string>() { approval.Initiator.Employee.Email, step.EmployeeApprover.Employee.Email };
                    setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
                    setup.ReportTypes.Add(ReportType.CustomerSpecialReport);
                }
                else
                {
                    string rD1Email = approval.ApprovalSteps.Where(appStep => appStep.ApproverType == ApproverType.RDev1).FirstOrDefault().EmployeeApprover.Employee.Email;
                    emailRecipients = new List<string>() { approval.Initiator.Employee.Email, step.EmployeeApprover.Employee.Email, rD1Email };
                    setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
                    setup.ReportTypes.Add(ReportType.CustomerSpecialReport);
                }
            }
        }
        else if (step.ApprovalType == ApprovalType.ExtraCosts)
        {
            if (trigger == ReportTrigger.Created)
            {
                string projectManagerEmail = approval.ApprovalTeam.Where(em => em.Role == ApprovalRole.ProjectManager).FirstOrDefault().Employee.Email;
                string projectLeaderEmail = approval.ApprovalTeam.Where(em => em.Role == ApprovalRole.ProjectLeader).FirstOrDefault().Employee.Email;
                emailRecipients = new List<string> { projectManagerEmail, projectLeaderEmail };
                setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
                setup.ReportTypes.Add(ReportType.CommonReport);
            }
            else
            {
                //List<IConfigurationBase> deniedParts = approval.AllValidIconfigurationBases.Where(ap => ap.ApprovalStatus == BaseApprovalStatus.Rejected).ToList();
                setup.EmailAdresses.Add(approval.Initiator.Employee.Email);
            }
        }
        else if (step.ApprovalType == ApprovalType.ApproveChanges)
        {
            setup.EmailAdresses.Add(approval.Initiator.Employee.Email);
            setup.ReportTypes.Add(ReportType.CommonReport);
        }
        else if (step.ApprovalType == ApprovalType.UpdateMissingCostandPrice)
        {
            if (trigger == ReportTrigger.Created)
            {
                string csasEmail = step.EmployeeApprover.Employee.Email;
                emailRecipients = new List<string> { csasEmail, approval.Initiator.Employee.Email };
                setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
                setup.ReportTypes.Add(ReportType.CommonReport);
            }
            else
            {
                setup.EmailAdresses.Add(approval.Initiator.Employee.Email);
                setup.ReportTypes.Add(ReportType.CommonReport);
            }
        }
        else if (step.ApprovalType == ApprovalType.CustomerApproval)
        {
            string projectManagerEmail = approval.ApprovalTeam.Where(ea => ea.Role == ApprovalRole.ProjectManager).FirstOrDefault().Employee.Email;
            string accountManagerEmail = approval.AccountManager == null ? null : approval.AccountManager.Employee.Email;
            emailRecipients = new List<string> { projectManagerEmail, accountManagerEmail };
            setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
        }
        else if (step.ApprovalType == ApprovalType.ApproveCosts)
        {
            //string regionalSalesDirectorEmail = approval.ApprovalSteps.Where(appStep => appStep.ApproverType == ApproverType.COstSD).FirstOrDefault().EmployeeApprover.Employee.Email;
            //string vicePresidentEmail = approval.ApprovalSteps.Where(appStep => appStep.ApproverType == ApproverType.CostVP).FirstOrDefault().EmployeeApprover.Employee.Email;
            //string presidentEmail = approval.ApprovalSteps.Where(appStep => appStep.ApproverType == ApproverType.CostPre).FirstOrDefault().EmployeeApprover.Employee.Email;
            string responsibleApprover = step.EmployeeApprover.Employee.Email;
            emailRecipients = new List<string> { responsibleApprover, approval.Initiator.Employee.Email };
            setup.EmailAdresses.AddRange(emailRecipients.Where(er => !string.IsNullOrEmpty(er)));
            setup.ReportTypes.Add(ReportType.CommonReport);
        }
        return setup;
    }

我意识到这很容易理解，但是该方法基于Approvalcontainer，Reporttrigger枚举和Approvalstep中包含的信息创建了一个不同的EmailSetup对象。

在我看来，此代码长度似乎是多余的，但我想不出更短的编写方法。可能使用元组或字典，但我对它们并不熟悉。