[Feature] AsyncStream 및 로컬 캐싱 적용을 통한 지출 내역 로딩 개선

Data/Sources/DTO/Expense/Local/ExpenseCache.swift

@@ -0,0 +1,30 @@
+//
+//  ExpenseCache.swift
+//  Data
+//
+//  Created by 홍석현 on 12/9/25.
+//
+
+import Foundation
+
+public struct ExpenseCache: Codable {
+    let travelId: String
+    let expenses: [TravelExpenseResponseDTO.ExpenseDTO]
+    let cachedAt: Date
+    let expiredAt: Date
+
+    var isExpired: Bool {
+        Date() > expiredAt
+    }
+
+    init(
+        travelId: String,
+        expenses: [TravelExpenseResponseDTO.ExpenseDTO],
+    ) {
+        self.travelId = travelId
+        self.expenses = expenses
+        self.cachedAt = .now
+        self.expiredAt = .now.addingTimeInterval(3600)
+    }
+}
+

Data/Sources/DTO/Expense/Request/CreateExpenseRequestDTO.swift

@@ -19,10 +19,14 @@ public struct CreateExpenseRequestDTO: Encodable {
 
 extension Expense {
     func toCreateRequestDTO() -> CreateExpenseRequestDTO {
-        let dateFormatter = ISO8601DateFormatter()
-        dateFormatter.formatOptions = [.withFullDate]
+        // yyyy-MM-dd 형식으로 날짜 변환 (사용자가 선택한 날짜 그대로 전송)
+        let dateFormatter = DateFormatter()
+        dateFormatter.dateFormat = "yyyy-MM-dd"
+        dateFormatter.calendar = Calendar(identifier: .gregorian)
+        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+        // Plain date는 timezone 변환하지 않음 (기본값 = TimeZone.current)
         let dateString = dateFormatter.string(from: expenseDate)
-        
+
         return CreateExpenseRequestDTO(
             title: title,
             amount: amount,

Data/Sources/DTO/Expense/Request/UpdateExpenseRequestDTO.swift

@@ -19,8 +19,12 @@ public struct UpdateExpenseRequestDTO: Encodable {
 
 extension Expense {
     func toUpdateRequestDTO() -> UpdateExpenseRequestDTO {
-        let dateFormatter = ISO8601DateFormatter()
-        dateFormatter.formatOptions = [.withFullDate]
+        // yyyy-MM-dd 형식으로 날짜 변환 (사용자가 선택한 날짜 그대로 전송)
+        let dateFormatter = DateFormatter()
+        dateFormatter.dateFormat = "yyyy-MM-dd"
+        dateFormatter.calendar = Calendar(identifier: .gregorian)
+        dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+        // Plain date는 timezone 변환하지 않음 (기본값 = TimeZone.current)
         let dateString = dateFormatter.string(from: expenseDate)
 
         return UpdateExpenseRequestDTO(

Data/Sources/DTO/Expense/Response/TravelExpenseResponseDTO.swift

@@ -14,7 +14,7 @@ public struct TravelExpenseResponseDTO: Decodable {
     let limit: Int
     let items: [ExpenseDTO]
 
-    struct ExpenseDTO: Decodable {
+    struct ExpenseDTO: Codable {
         let id: String
         let title: String
         let amount: Double
@@ -27,7 +27,7 @@ public struct TravelExpenseResponseDTO: Decodable {
         let authorId: String
         let participants: [ParticipantDTO]
 
-        struct ParticipantDTO: Decodable {
+        struct ParticipantDTO: Codable {
             let memberId: String
             let name: String
 
@@ -41,12 +41,12 @@ public struct TravelExpenseResponseDTO: Decodable {
         }
 
         func toDomain() -> Expense? {
-            // yyyy-MM-dd 날짜 파싱
+            // yyyy-MM-dd 날짜 파싱 (서버에서 받은 날짜 그대로 사용)
             let dateFormatter = DateFormatter()
             dateFormatter.dateFormat = "yyyy-MM-dd"
             dateFormatter.calendar = Calendar(identifier: .gregorian)
-            dateFormatter.locale = Locale(identifier: "ko_KR")
-            dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
+            dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+            // Plain date는 timezone 변환하지 않음 (기본값 = TimeZone.current)
 
             guard let date = dateFormatter.date(from: expenseDate) else {
                 return nil

Data/Sources/DataSource/Local/ExpenseLocalDataSource.swift

@@ -0,0 +1,104 @@
+//
+//  ExpenseLocalDataSource.swift
+//  Data
+//
+//  Created by 홍석현 on 12/9/25.
+//
+
+import Foundation
+import Domain
+
+public enum ExpenseCacheError: Error {
+    case cacheDirectoryUnavailable
+    case fileNotFound
+    case dataCorrupted
+}
+
+public protocol ExpenseLocalDataSourceProtocol {
+    func loadCachedExpenses(_ travelId: String) async throws -> ExpenseCache
+    func saveCachedExpenses(_ cache: ExpenseCache) async throws
+}
+
+public actor ExpenseLocalDataSource: ExpenseLocalDataSourceProtocol {
+    private let fileManager = FileManager.default
+    private lazy var cacheDirectory: URL? = {
+        guard var cachesURL = fileManager.urls(
+            for: .cachesDirectory,
+            in: .userDomainMask
+        ).first else {
+            return nil
+        }
+        cachesURL.append(
+            path: "expenses",
+            directoryHint: .isDirectory
+        )
+        try? fileManager.createDirectory(
+            at: cachesURL,
+            withIntermediateDirectories: true
+        )
+        return cachesURL
+    }()
+    private let encoder: JSONEncoder = {
+        let encoder = JSONEncoder()
+        encoder.dateEncodingStrategy = .iso8601
+        return encoder
+    }()
+
+    private let decoder: JSONDecoder = {
+        let decoder = JSONDecoder()
+        decoder.dateDecodingStrategy = .iso8601
+        return decoder
+    }()
+
+
+    public init() {}
+
+    private func cacheURL(for travelId: String) throws -> URL {
+        guard var directory = cacheDirectory else {
+            throw ExpenseCacheError.cacheDirectoryUnavailable
+        }
+
+        directory.append(path: "travel_\(travelId).json", directoryHint: .notDirectory)
+        return directory
+    }
+
+    public func loadCachedExpenses(_ travelId: String) async throws -> ExpenseCache {
+        let url = try cacheURL(for: travelId)
+
+        guard fileManager.fileExists(atPath: url.path()) else {
+            throw ExpenseCacheError.cacheDirectoryUnavailable
+        }
+
+        do {
+            let data = try Data(contentsOf: url)
+            let cache = try decoder.decode(ExpenseCache.self, from: data)
+
+            if cache.isExpired {
+                clearCache(travelId)
+                throw ExpenseCacheError.dataCorrupted
+            }
+            return cache
+        } catch {
+            try? fileManager.removeItem(at: url)
+            throw ExpenseCacheError.dataCorrupted
+        }
+    }
+
+    public func saveCachedExpenses(_ cache: ExpenseCache) async throws {
+        let url = try cacheURL(for: cache.travelId)
+        let data = try encoder.encode(cache)
+
+        try data.write(to: url, options: [.atomic])
+    }
+
+    private func clearCache(_ travelId: String) {
+        guard let directory = cacheDirectory else { return }
+        try? fileManager.removeItem(at: directory)
+
+        // 디렉토리 재생성
+        try? fileManager.createDirectory(
+            at: directory,
+            withIntermediateDirectories: true
+        )
+    }
+}

Data/Sources/DataSource/Remote/ExpenseRemoteDataSource.swift

@@ -21,7 +21,7 @@ public struct ExpenseRemoteDataSource: ExpenseRemoteDataSourceProtocol {
 
     private let provider: MoyaProvider<ExpenseAPI>
 
-    public init(provider: MoyaProvider<ExpenseAPI> = MoyaProvider<ExpenseAPI>()) {
+    public init(provider: MoyaProvider<ExpenseAPI> = .default) {
         self.provider = provider
     }
 
@@ -75,7 +75,7 @@ extension ExpenseAPI: BaseTargetType {
             return "/\(travelId)/expenses"
         case .createExpense(let travelId, _):
             return "/\(travelId)/expenses"
-        case .updateExpense(let travelId, let expenseId, let _):
+        case .updateExpense(let travelId, let expenseId, _):
             return "/\(travelId)/expenses/\(expenseId)"
         case .deleteExpense(let travelId, let expenseId):
             return "/\(travelId)/expenses/\(expenseId)"

Data/Sources/Repository/Expense/ExpenseRepository.swift

@@ -0,0 +1,76 @@
+//
+//  ExpenseRepository.swift
+//  Data
+//
+//  Created by 홍석현 on 11/28/25.
+//
+
+import Foundation
+import Domain
+
+public final class ExpenseRepository: ExpenseRepositoryProtocol {
+
+    private let remote: ExpenseRemoteDataSourceProtocol
+    private let local: ExpenseLocalDataSourceProtocol
+
+    public init(
+        remote: ExpenseRemoteDataSourceProtocol,
+        local: ExpenseLocalDataSourceProtocol
+    ) {
+        self.remote = remote
+        self.local = local
+    }
+
+    public func fetchTravelExpenses(
+        travelId: String,
+        page: Int,
+        limit: Int
+    ) -> AsyncStream<Result<[Expense], Error>> {
+        AsyncStream { continuation in
+            Task {
+                // 1. 캐시 데이터
+                if let cached = try? await local.loadCachedExpenses(travelId) {
+                    let expense = cached.expenses.compactMap { $0.toDomain() }
+                    continuation.yield(.success(expense))
+                }
+
+                // 2. 네트워크
+                do {
+                    let responseDTO = try await remote.fetchTravelExpenses(
+                        travelId: travelId,
+                        page: page,
+                        limit: limit
+                    )
+                    let expenses = responseDTO.items.compactMap { $0.toDomain() }
+
+                    Task.detached { [weak self] in
+                        let cache = ExpenseCache(
+                            travelId: travelId,
+                            expenses: responseDTO.items
+                        )
+
+                        try? await self?.local.saveCachedExpenses(cache)
+                    }
+                    continuation.yield(.success(expenses))
+                } catch {
+                    continuation.yield(.failure(error))
+                }
+                continuation.finish()
+            }
+        }
+    }
+
+    public func save(travelId: String, expense: Expense) async throws {
+        let requestDTO = expense.toCreateRequestDTO()
+        try await remote.createExpense(travelId: travelId, body: requestDTO)
+    }
+
+    public func update(travelId: String, expense: Expense) async throws {
+        let requestDTO = expense.toUpdateRequestDTO()
+        try await remote.updateExpense(travelId: travelId, expenseId: expense.id, body: requestDTO)
+    }
+
+    public func delete(travelId: String, expenseId: String) async throws {
+        try await remote.deleteExpense(travelId: travelId, expenseId: expenseId)
+    }
+}

Domain/Sources/Repository/ExpenseRepositoryProtocol.swift

@@ -10,7 +10,7 @@ import Dependencies
 
 public protocol ExpenseRepositoryProtocol {
     // 여행의 지출 내역 조회
-    func fetchTravelExpenses(travelId: String, page: Int, limit: Int) async throws -> [Expense]
+    func fetchTravelExpenses(travelId: String, page: Int, limit: Int) -> AsyncStream<Result<[Expense], Error>>
 
     // 지출 내역 저장
     func save(travelId: String, expense: Expense) async throws

Domain/Sources/Repository/Mock/MockExpenseRepository.swift

@@ -8,6 +8,7 @@
 import Foundation
 
 final public actor MockExpenseRepository: ExpenseRepositoryProtocol {
+
     private var storage: [String: Expense] = [:]
     private var shouldFailSave = false
     private var shouldFailUpdate = false
@@ -34,12 +35,17 @@ final public actor MockExpenseRepository: ExpenseRepositoryProtocol {
         saveErrorReason = nil
     }
 
-    public func fetchTravelExpenses(
+    nonisolated public func fetchTravelExpenses(
         travelId: String,
         page: Int,
         limit: Int
-    ) async throws -> [Expense] {
-        return Expense.mockList
+    ) -> AsyncStream<Result<[Expense], any Error>> {
+        AsyncStream { continuation in
+            Task {
+                continuation.yield(.success(Expense.mockList))
+                continuation.finish()
+            }
+        }
     }
 
     public func save(