Refactoring and tidy up.

Make the preview manager a singleton (passing in the MXSession to functions). Fix tests.

PreviewManager → URLPreviewManager
URLPreviewViewData → URLPreviewData
URLPreviewCache → URLPreviewStore

RiotTests/URLPreviewStoreTests.swift

@@ -0,0 +1,152 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import XCTest
+@testable import Riot
+
+class URLPreviewStoreTests: XCTestCase {
+    var store: URLPreviewStore!
+    
+    /// Creates mock URL preview data for matrix.org
+    func matrixPreview() -> URLPreviewData {
+        let preview = URLPreviewData(url: URL(string: "https://www.matrix.org/")!,
+                                     eventID: "",
+                                     roomID: "",
+                                     siteName: "Matrix",
+                                     title: "Home",
+                                     text: "An open network for secure, decentralized communication")
+        preview.image = Asset.Images.appSymbol.image
+        
+        return preview
+    }
+    
+    /// Creates mock URL preview data for element.io
+    func elementPreview() -> URLPreviewData {
+        URLPreviewData(url: URL(string: "https://element.io/")!,
+                       eventID: "",
+                       roomID: "",
+                       siteName: "Element",
+                       title: "Home",
+                       text: "Secure and independent communication, connected via Matrix")
+    }
+    
+    
+    /// Creates a fake `MXEvent` object to be passed to the store as needed.
+    func fakeEvent() -> MXEvent {
+        let event = MXEvent()
+        event.eventId = ""
+        event.roomId = ""
+        return event
+    }
+    
+    override func setUpWithError() throws {
+        // Create a fresh in-memory cache for each test.
+        store = URLPreviewStore(inMemory: true)
+    }
+    
+    func testStoreAndRetrieve() {
+        // Given a URL preview
+        let preview = matrixPreview()
+        
+        // When storing and retrieving that preview.
+        store.store(preview)
+        
+        guard let cachedPreview = store.preview(for: preview.url, and: fakeEvent()) else {
+            XCTFail("The cache should return a preview after storing one with the same URL.")
+            return
+        }
+        
+        // Then the content in the retrieved preview should match the original preview.
+        XCTAssertEqual(cachedPreview.url, preview.url, "The url should match.")
+        XCTAssertEqual(cachedPreview.siteName, preview.siteName, "The site name should match.")
+        XCTAssertEqual(cachedPreview.title, preview.title, "The title should match.")
+        XCTAssertEqual(cachedPreview.text, preview.text, "The text should match.")
+        XCTAssertEqual(cachedPreview.image == nil, preview.image == nil, "The cached preview should have an image if the original did.")
+    }
+    
+    func testUpdating() {
+        // Given a preview stored in the cache.
+        let preview = matrixPreview()
+        store.store(preview)
+        
+        guard let cachedPreview = store.preview(for: preview.url, and: fakeEvent()) else {
+            XCTFail("The cache should return a preview after storing one with the same URL.")
+            return
+        }
+        XCTAssertEqual(cachedPreview.text, preview.text, "The text should match the original preview's text.")
+        XCTAssertEqual(store.cacheCount(), 1, "There should be 1 item in the cache.")
+        
+        // When storing an updated version of that preview.
+        let updatedPreview = URLPreviewData(url: preview.url,
+                                            eventID: "",
+                                            roomID: "",
+                                            siteName: "Matrix",
+                                            title: "Home",
+                                            text: "We updated our website.")
+        store.store(updatedPreview)
+        
+        // Then the store should update the original preview.
+        guard let updatedCachedPreview = store.preview(for: preview.url, and: fakeEvent()) else {
+            XCTFail("The cache should return a preview after storing one with the same URL.")
+            return
+        }
+        XCTAssertEqual(updatedCachedPreview.text, updatedPreview.text, "The text should match the updated preview's text.")
+        XCTAssertEqual(store.cacheCount(), 1, "There should still only be 1 item in the cache.")
+    }
+    
+    func testPreviewExpiry() {
+        // Given a preview generated 30 days ago.
+        let preview = matrixPreview()
+        store.store(preview, generatedOn: Date().addingTimeInterval(-60 * 60 * 24 * 30))
+        
+        // When retrieving that today.
+        let cachedPreview = store.preview(for: preview.url, and: fakeEvent())
+        
+        // Then no preview should be returned.
+        XCTAssertNil(cachedPreview, "The expired preview should not be returned.")
+    }
+    
+    func testRemovingExpiredItems() {
+        // Given a cache with 2 items, one of which has expired.
+        testPreviewExpiry()
+        let preview = elementPreview()
+        store.store(preview)
+        XCTAssertEqual(store.cacheCount(), 2, "There should be 2 items in the cache.")
+        
+        // When removing expired items.
+        store.removeExpiredItems()
+        
+        // Then only the expired item should have been removed.
+        XCTAssertEqual(store.cacheCount(), 1, "Only 1 item should have been removed from the cache.")
+        if store.preview(for: preview.url, and: fakeEvent()) == nil {
+            XCTFail("The valid preview should still be in the cache.")
+        }
+    }
+    
+    func testClearingTheCache() {
+        // Given a cache with 2 items.
+        testStoreAndRetrieve()
+        let preview = elementPreview()
+        store.store(preview)
+        XCTAssertEqual(store.cacheCount(), 2, "There should be 2 items in the cache.")
+        
+        // When clearing the cache.
+        store.deleteAll()
+        
+        // Then no items should be left in the cache
+        XCTAssertEqual(store.cacheCount(), 0, "The cache should be empty.")
+    }
+}