[Feature] 정산 상세 내역 화면 구현 및 정산 계산 로직 고도화

Domain/Sources/UseCase/Settlement/CalculateSettlementUseCaseProtocol.swift → Domain/Sources/Entity/Settlement/SettlementCalculation.swift

@@ -1,5 +1,5 @@
 //
-//  CalculateSettlementUseCaseProtocol.swift
+//  SettlementCalculation.swift
 //  Domain
 //
 //  Created by 홍석현 on 12/10/25.
@@ -14,28 +14,28 @@ public struct SettlementCalculation: Equatable {
     public let totalPersonCount: Int // 인원수
     public let averagePerPerson: Double // 1인 평균 지출
     public let myNetBalance: Double // 내 순 차액 (Pay - Owe)
-    public let memberBalances: [String: Double] // 각 멤버의 순 차액
     public let paymentsToMake: [PaymentInfo] // 지급 예정 금액
     public let paymentsToReceive: [PaymentInfo] // 수령 예정 금액
+    public let memberDetails: [MemberSettlementDetail] // 멤버별 정산 상세
 
     public init(
         totalExpenseAmount: Double,
         myShareAmount: Double,
         totalPersonCount: Int,
         averagePerPerson: Double,
         myNetBalance: Double,
-        memberBalances: [String: Double],
         paymentsToMake: [PaymentInfo],
-        paymentsToReceive: [PaymentInfo]
+        paymentsToReceive: [PaymentInfo],
+        memberDetails: [MemberSettlementDetail]
     ) {
         self.totalExpenseAmount = totalExpenseAmount
         self.myShareAmount = myShareAmount
         self.totalPersonCount = totalPersonCount
         self.averagePerPerson = averagePerPerson
         self.myNetBalance = myNetBalance
-        self.memberBalances = memberBalances
         self.paymentsToMake = paymentsToMake
         self.paymentsToReceive = paymentsToReceive
+        self.memberDetails = memberDetails
     }
 }
 
@@ -58,11 +58,3 @@ public struct PaymentInfo: Equatable, Identifiable {
         self.amount = amount
     }
 }
-
-public protocol CalculateSettlementUseCaseProtocol {
-    func execute(
-        expenses: [Expense],
-        members: [TravelMember],
-        currentUserId: String?
-    ) -> SettlementCalculation
-}

Domain/Sources/Entity/Settlement/SettlementDetail.swift

@@ -0,0 +1,66 @@
+//
+//  SettlementDetail.swift
+//  Domain
+//
+//  Created by SseuDam on 2025.
+//
+
+import Foundation
+
+// MARK: - Member Settlement Detail
+public struct MemberSettlementDetail: Equatable, Identifiable {
+    public let id: String
+    public let memberId: String
+    public let memberName: String
+    public let netBalance: Double
+    public let totalPaid: Double
+    public let totalOwe: Double
+    public let paidExpenses: [ExpenseDetail]
+    public let sharedExpenses: [ExpenseDetail]
+
+    public init(
+        id: String,
+        memberId: String,
+        memberName: String,
+        netBalance: Double,
+        totalPaid: Double,
+        totalOwe: Double,
+        paidExpenses: [ExpenseDetail],
+        sharedExpenses: [ExpenseDetail]
+    ) {
+        self.id = id
+        self.memberId = memberId
+        self.memberName = memberName
+        self.netBalance = netBalance
+        self.totalPaid = totalPaid
+        self.totalOwe = totalOwe
+        self.paidExpenses = paidExpenses
+        self.sharedExpenses = sharedExpenses
+    }
+}
+
+// MARK: - Expense Detail
+public struct ExpenseDetail: Equatable, Identifiable {
+    public let id: String
+    public let title: String
+    public let amount: Double
+    public let shareAmount: Double
+    public let participantCount: Int
+    public let expenseDate: Date
+
+    public init(
+        id: String,
+        title: String,
+        amount: Double,
+        shareAmount: Double,
+        participantCount: Int,
+        expenseDate: Date
+    ) {
+        self.id = id
+        self.title = title
+        self.amount = amount
+        self.shareAmount = shareAmount
+        self.participantCount = participantCount
+        self.expenseDate = expenseDate
+    }
+}

Domain/Sources/UseCase/Settlement/CalculateSettlementUseCase.swift

@@ -8,19 +8,27 @@
 import Foundation
 import ComposableArchitecture
 
-public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
+public protocol CalculateSettlementUseCaseProtocol {
+    func execute(
+        expenses: [Expense],
+        members: [TravelMember],
+        currentUserId: String?
+    ) -> SettlementCalculation
+}
 
+public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
+
     public init() {}
-
+    
     public func execute(
         expenses: [Expense],
         members: [TravelMember],
         currentUserId: String?
     ) -> SettlementCalculation {
-
+        
         // 1. 총 지출 금액
         let totalExpenseAmount = expenses.reduce(0) { $0 + $1.convertedAmount }
-
+        
         // 2. 내가 부담해야 할 금액 (내가 참여한 지출들의 분담금 합계)
         let myShareAmount: Double
         if let userId = currentUserId {
@@ -36,70 +44,77 @@ public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
         } else {
             myShareAmount = 0
         }
-
+        
         // 3. 인원수
         let totalPersonCount = members.count
-
+        
         // 4. 1인 평균 지출
         let averagePerPerson = totalPersonCount > 0 ? totalExpenseAmount / Double(totalPersonCount) : 0
-
+        
         // 5. 각 멤버의 순 차액 계산 (Net Balance = Pay - Owe)
         var memberBalances: [String: Double] = [:]
-
+        
         // 모든 멤버 초기화
         for member in members {
             memberBalances[member.id] = 0.0
         }
-
+        
         // 각 지출에 대해 계산
         for expense in expenses {
             let participantCount = Double(expense.participants.count)
             guard participantCount > 0 else { continue }
-
+            
             let amountPerPerson = expense.convertedAmount / participantCount
-
+            
             // 결제자는 전체 금액을 지불한 것으로 (+)
             memberBalances[expense.payerId, default: 0] += expense.convertedAmount
-
+            
             // 참여자들은 각자 분담금을 빚진 것으로 (-)
             for participant in expense.participants {
                 memberBalances[participant.id, default: 0] -= amountPerPerson
             }
         }
-
+        
         // 6. 내 순 차액
         let myNetBalance = currentUserId.flatMap { memberBalances[$0] } ?? 0
-
+        
         // 7. 지급 예정 금액 계산
         let paymentsToMake = calculatePaymentsToMake(
             myBalance: myNetBalance,
             memberBalances: memberBalances,
             members: members,
             currentUserId: currentUserId
         )
-
+        
         // 8. 수령 예정 금액 계산
         let paymentsToReceive = calculatePaymentsToReceive(
             myBalance: myNetBalance,
             memberBalances: memberBalances,
             members: members,
             currentUserId: currentUserId
         )
-
+
+        // 9. 멤버별 정산 상세 계산
+        let memberDetails = calculateMemberDetails(
+            expenses: expenses,
+            members: members,
+            memberBalances: memberBalances
+        )
+
         return SettlementCalculation(
             totalExpenseAmount: totalExpenseAmount,
             myShareAmount: myShareAmount,
             totalPersonCount: totalPersonCount,
             averagePerPerson: averagePerPerson,
             myNetBalance: myNetBalance,
-            memberBalances: memberBalances,
             paymentsToMake: paymentsToMake,
-            paymentsToReceive: paymentsToReceive
+            paymentsToReceive: paymentsToReceive,
+            memberDetails: memberDetails
         )
     }
-
+    
     // MARK: - Private Helper Methods
-
+    
     // 지급 예정 금액 (내가 빚진 사람들에게 갚아야 할 돈)
     private func calculatePaymentsToMake(
         myBalance: Double,
@@ -109,20 +124,20 @@ public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
     ) -> [PaymentInfo] {
         guard currentUserId != nil else { return [] }
         guard myBalance < 0 else { return [] } // 내가 받을 돈이 있으면 지급할 것이 없음
-
+        
         // 양수 잔액을 가진 멤버들 (받을 돈이 있는 사람들)
         let creditors = memberBalances
             .filter { $0.value > 0 }
             .sorted { $0.value > $1.value } // 많이 받을 사람부터
-
+        
         var payments: [PaymentInfo] = []
         var remainingDebt = abs(myBalance)
-
+        
         for (memberId, creditAmount) in creditors {
             guard remainingDebt > 0.01 else { break } // 소수점 오차 고려
-
+            
             let paymentAmount = min(remainingDebt, creditAmount)
-
+            
             if let member = members.first(where: { $0.id == memberId }) {
                 payments.append(PaymentInfo(
                     id: UUID().uuidString,
@@ -133,10 +148,10 @@ public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
                 remainingDebt -= paymentAmount
             }
         }
-
+        
         return payments
     }
-
+    
     // 수령 예정 금액 (나에게 빚진 사람들로부터 받을 돈)
     private func calculatePaymentsToReceive(
         myBalance: Double,
@@ -146,20 +161,20 @@ public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
     ) -> [PaymentInfo] {
         guard currentUserId != nil else { return [] }
         guard myBalance > 0 else { return [] } // 내가 빚진 돈이 있으면 받을 것이 없음
-
+        
         // 음수 잔액을 가진 멤버들 (빚진 사람들)
         let debtors = memberBalances
             .filter { $0.value < 0 }
             .sorted { $0.value < $1.value } // 많이 빚진 사람부터
-
+        
         var receipts: [PaymentInfo] = []
         var remainingCredit = myBalance
-
+        
         for (memberId, debtAmount) in debtors {
             guard remainingCredit > 0.01 else { break } // 소수점 오차 고려
-
+            
             let receiptAmount = min(remainingCredit, abs(debtAmount))
-
+            
             if let member = members.first(where: { $0.id == memberId }) {
                 receipts.append(PaymentInfo(
                     id: UUID().uuidString,
@@ -170,17 +185,74 @@ public struct CalculateSettlementUseCase: CalculateSettlementUseCaseProtocol {
                 remainingCredit -= receiptAmount
             }
         }
-
+        
         return receipts
     }
+
+    // 멤버별 정산 상세 계산
+    // 시간 복잡도: O(E * P + M) - E: 지출 수, P: 평균 참여자 수, M: 멤버 수
+    private func calculateMemberDetails(
+        expenses: [Expense],
+        members: [TravelMember],
+        memberBalances: [String: Double]
+    ) -> [MemberSettlementDetail] {
+        // 1. 멤버별로 결제한 지출과 참여한 지출을 그룹화
+        // O(E * P) - 지출을 한 번만 순회
+        var memberPaidExpenses: [String: [ExpenseDetail]] = [:]
+        var memberSharedExpenses: [String: [ExpenseDetail]] = [:]
+
+        for expense in expenses {
+            let participantCount = expense.participants.count
+            let shareAmount = participantCount > 0 ? expense.convertedAmount / Double(participantCount) : 0
+
+            let expenseDetail = ExpenseDetail(
+                id: expense.id,
+                title: expense.title,
+                amount: expense.convertedAmount,
+                shareAmount: shareAmount,
+                participantCount: participantCount,
+                expenseDate: expense.expenseDate
+            )
+
+            // 결제자에게 추가
+            memberPaidExpenses[expense.payerId, default: []].append(expenseDetail)
+
+            // 참여자들에게 추가
+            for participant in expense.participants {
+                memberSharedExpenses[participant.id, default: []].append(expenseDetail)
+            }
+        }
+
+        // 2. 각 멤버의 정산 상세 생성
+        // O(M)
+        return members.map { member in
+            let paidExpenses = memberPaidExpenses[member.id] ?? []
+            let sharedExpenses = memberSharedExpenses[member.id] ?? []
+
+            let totalPaid = paidExpenses.reduce(0) { $0 + $1.amount }
+            let totalOwe = sharedExpenses.reduce(0) { $0 + $1.shareAmount }
+            let netBalance = memberBalances[member.id] ?? 0
+
+            return MemberSettlementDetail(
+                id: member.id,
+                memberId: member.id,
+                memberName: member.name,
+                netBalance: netBalance,
+                totalPaid: totalPaid,
+                totalOwe: totalOwe,
+                paidExpenses: paidExpenses,
+                sharedExpenses: sharedExpenses
+            )
+        }
+    }
 }
 
 // MARK: - DependencyKey
 public enum CalculateSettlementUseCaseDependencyKey: DependencyKey {
     public static var liveValue: any CalculateSettlementUseCaseProtocol = CalculateSettlementUseCase()
-
+    
     public static var testValue: any CalculateSettlementUseCaseProtocol = CalculateSettlementUseCase()
-
+    
     public static var previewValue: any CalculateSettlementUseCaseProtocol = CalculateSettlementUseCase()
 }