Map ImageComments into ImageCommentsViewModels

EssentialFeed/Image Comments Presentation/ImageCommentsPresenter.swift

@@ -7,11 +7,39 @@
 
 import Foundation
 
+public struct ImageCommentsViewModel {
+    public let comments: [ImageCommentViewModel]
+}
+
+public struct ImageCommentViewModel: Equatable {
+    public let message: String
+    public let date: String
+    public let username: String
+
+    public init(message: String, date: String, username: String) {
+        self.message = message
+        self.date = date
+        self.username = username
+    }
+}
+
 public final class ImageCommentsPresenter {
     public static var title: String {
         NSLocalizedString("IMAGE_COMMENTS_VIEW_TITLE",
                           tableName: "ImageComments",
                           bundle: Bundle(for: Self.self),
                           comment: "Title for the image comments view")
     }
+
+    public static func map(_ comments: [ImageComment]) -> ImageCommentsViewModel {
+        let formatter = RelativeDateTimeFormatter()
+
+        return ImageCommentsViewModel(comments: comments.map { comment in
+            ImageCommentViewModel(
+                message: comment.message,
+                date: formatter.localizedString(for: comment.createdAt, relativeTo: Date()),
+                username: comment.username
+            )
+        })
+    }
 }

EssentialFeedTests/Feed Cache/Helpers/FeedCacheTestHelpers.swift

@@ -26,14 +26,4 @@ extension Date {
     private var feedCacheMaxAgeInDays: Int {
         7
     }
-
-    private func adding(days: Int) -> Date {
-        Calendar(identifier: .gregorian).date(byAdding: .day, value: days, to: self)!
-    }
-}
-
-extension Date {
-    func adding(seconds: TimeInterval) -> Date {
-        self + seconds
-    }
 }

EssentialFeedTests/Helpers/SharedTestHelpers.swift

@@ -31,3 +31,17 @@ extension HTTPURLResponse {
         self.init(url: anyURL(), statusCode: statusCode, httpVersion: nil, headerFields: nil)!
     }
 }
+
+extension Date {
+    func adding(seconds: TimeInterval) -> Date {
+        return self + seconds
+    }
+
+    func adding(minutes: Int) -> Date {
+        return Calendar(identifier: .gregorian).date(byAdding: .minute, value: minutes, to: self)!
+    }
+
+    func adding(days: Int) -> Date {
+        return Calendar(identifier: .gregorian).date(byAdding: .day, value: days, to: self)!
+    }
+}

EssentialFeedTests/Image Comments Presentation/ImageCommentsPresenterTests.swift

@@ -13,6 +13,40 @@ class ImageCommentsPresenterTests: XCTestCase {
         XCTAssertEqual(ImageCommentsPresenter.title, localized("IMAGE_COMMENTS_VIEW_TITLE"))
     }
 
+    func test_map_createsViewModels() {
+        let now = Date()
+
+        let comments = [
+            ImageComment(
+                id: UUID(),
+                message: "a message",
+                createdAt: now.adding(minutes: -5),
+                username: "a username"
+            ),
+            ImageComment(
+                id: UUID(),
+                message: "another message",
+                createdAt: now.adding(days: -1),
+                username: "another username"
+            ),
+        ]
+
+        let viewModel = ImageCommentsPresenter.map(comments)
+
+        XCTAssertEqual(viewModel.comments, [
+            ImageCommentViewModel(
+                message: "a message",
+                date: "5 minutes ago",
+                username: "a username"
+            ),
+            ImageCommentViewModel(
+                message: "another message",
+                date: "1 day ago",
+                username: "another username"
+            ),
+        ])
+    }
+
     // MARK: - Helpers
 
     private func localized(_ key: String, file: StaticString = #file, line: UInt = #line) -> String {