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Add MediaImageService unit tests
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@kean
kean committed Sep 20, 2023
1 parent 9d57153 commit 5567de8
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Showing 2 changed files with 124 additions and 57 deletions.
125 changes: 68 additions & 57 deletions WordPress/Classes/Services/MediaImageService.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -10,9 +10,10 @@ final class MediaImageService: NSObject {
private let mediaFileManager: MediaFileManager
private let ioQueue = DispatchQueue(label: "org.automattic.MediaImageService")

init(coreDataStack: CoreDataStackSwift = ContextManager.shared) {
init(coreDataStack: CoreDataStackSwift = ContextManager.shared,
mediaFileManager: MediaFileManager = MediaFileManager(directory: .cache)) {
self.coreDataStack = coreDataStack
self.mediaFileManager = MediaFileManager(directory: .cache)
self.mediaFileManager = mediaFileManager

let configuration = URLSessionConfiguration.default
// `MediaImageService` has its own disk cache, so it's important to
Expand All @@ -30,76 +31,79 @@ final class MediaImageService: NSObject {
/// (bitmapped) and are ready to be displayed.
@MainActor
func thumbnail(for media: Media) async throws -> UIImage {
let size = ThumbnailSize.small
guard media.remoteStatus != .stub else {
let media = try await fetchStubMedia(for: media)
// This should never happen, but adding it just in case to avoid recusion
guard media.remoteStatus != .stub else {
assertionFailure("The fetched media still has a .stub status")
throw MediaThumbnailExporter.ThumbnailExportError.failedToGenerateThumbnailFileURL
}
return try await _thumbnail(for: media)
return try await _thumbnail(for: media, size: size)
}

return try await _thumbnail(for: media)
return try await _thumbnail(for: media, size: size)
}

@MainActor
private func _thumbnail(for media: Media) async throws -> UIImage {
if let image = await cachedThumbnail(for: media) {
private func _thumbnail(for media: Media, size: ThumbnailSize) async throws -> UIImage {
if let image = await cachedThumbnail(for: media, size: size) {
return image
}
let targetSize = MediaImageService.preferredThumbnailSize
if let image = await localThumbnail(for: media, targetSize: targetSize) {
if let image = await localThumbnail(for: media, size: size) {
return image
}
return try await remoteThumbnail(for: media, targetSize: targetSize)
return try await remoteThumbnail(for: media, size: size)
}

// MARK: - Cached Thumbnail

/// Returns a local thumbnail for the given media object (if available).
@MainActor
private func cachedThumbnail(for media: Media) async -> UIImage? {
private func cachedThumbnail(for media: Media, size: ThumbnailSize) async -> UIImage? {
let objectID = media.objectID
return try? await Task.detached(priority: .userInitiated) {
let imageURL = try self.getCachedThumbnailURL(for: objectID)
return try? await Task.detached {
let imageURL = try self.getCachedThumbnailURL(for: objectID, size: size)
let data = try Data(contentsOf: imageURL)
return try decompressedImage(from: data)
}.value
}

private func getCachedThumbnailURL(for objectID: NSManagedObjectID) throws -> URL {
private func getCachedThumbnailURL(for objectID: NSManagedObjectID, size: ThumbnailSize) throws -> URL {
let objectID = objectID.uriRepresentation().lastPathComponent
return try mediaFileManager.makeLocalMediaURL(
withFilename: "\(objectID)-small-thumbnail",
fileExtension: nil // It can be different between local and remove thumbnails
withFilename: "\(objectID)-\(size.rawValue)-thumbnail",
fileExtension: nil, // It can be different between local and remove thumbnails
incremented: false
)
}

// The save is performed asynchronously to eliminate any delays. It's
// exceedingly unlikely it'll result in any duplicated work thanks to the
// memore caches.
@MainActor
private func saveThumbnail(for media: Media, _ closure: @escaping (URL) throws -> Void) {
private func saveThumbnail(for media: Media, size: ThumbnailSize, _ closure: @escaping (URL) throws -> Void) {
let objectID = media.objectID
ioQueue.async {
guard let targetURL = try? self.getCachedThumbnailURL(for: objectID) else { return }
guard let targetURL = try? self.getCachedThumbnailURL(for: objectID, size: size) else { return }
try? closure(targetURL)
}
}

/// Flushes all pending I/O changes to disk.
///
/// - warning: For testing purposes only.
func flush() {
ioQueue.sync {}
}

// MARK: - Local Thumbnail

/// Generates a thumbnail from a local asset.
///
/// - Parameters:
/// - media: The Media object.
/// - targetSize: An ideal size of the thumbnail in pixels.
/// Generates a thumbnail from a local asset and saves it in cache.
@MainActor
private func localThumbnail(for media: Media, targetSize: CGSize) async -> UIImage? {
private func localThumbnail(for media: Media, size: ThumbnailSize) async -> UIImage? {
let exporter = MediaThumbnailExporter()
exporter.mediaDirectoryType = .cache
exporter.options.preferredSize = MediaImageService.targetSize(for: media, targetSize: targetSize)
exporter.options.preferredSize = MediaImageService.getThumbnailSize(for: media, size: size)
exporter.options.scale = 1 // In pixels

guard let sourceURL = media.absoluteLocalURL,
Expand All @@ -111,13 +115,13 @@ final class MediaImageService: NSObject {
return nil
}

let image = try? await Task.detached(priority: .userInitiated) {
let image = try? await Task.detached {
let data = try Data(contentsOf: export.url)
return try decompressedImage(from: data)
}.value

// The order is important to ensure `export.url` still exists when creating an image
saveThumbnail(for: media) { targetURL in
saveThumbnail(for: media, size: size) { targetURL in
try FileManager.default.moveItem(at: export.url, to: targetURL)
}

Expand All @@ -126,14 +130,10 @@ final class MediaImageService: NSObject {

// MARK: - Remote Thumbnail

/// Downloads thumbnail for the given media object and saves it locally. Returns
/// a file URL for the downloaded thumbnail.
///
/// - Parameters:
/// - media: The Media object.
/// - targetSize: An ideal size of the thumbnail in pixels.
/// Downloads a remote thumbnail and saves it in cache.
@MainActor
private func remoteThumbnail(for media: Media, targetSize: CGSize) async throws -> UIImage {
private func remoteThumbnail(for media: Media, size: ThumbnailSize) async throws -> UIImage {
let targetSize = MediaImageService.getThumbnailSize(for: media, size: size)
guard let imageURL = remoteThumbnailURL(for: media, targetSize: targetSize) else {
throw URLError(.badURL)
}
Expand All @@ -146,11 +146,11 @@ final class MediaImageService: NSObject {
}
let (data, _) = try await session.data(for: request)

saveThumbnail(for: media) { targetURL in
saveThumbnail(for: media, size: size) { targetURL in
try data.write(to: targetURL)
}

return try await Task.detached(priority: .userInitiated) {
return try await Task.detached {
try decompressedImage(from: data)
}.value
}
Expand Down Expand Up @@ -188,35 +188,46 @@ final class MediaImageService: NSObject {

// MARK: - Target Size

/// Returns a preferred thumbnail size (in pixels) optimized for the device.
enum ThumbnailSize: String {
case small
}

/// Returns an optiomal target size in pixels for a thumbnail of the given
/// size for the given media asset.
///
/// - important: It makes sure the app uses the same thumbnails across
/// different screens and presentation modes to avoid fetching and caching
/// more than one version of the same image.
private static let preferredThumbnailSize: CGSize = {
let screenSide = min(UIScreen.main.bounds.width, UIScreen.main.bounds.height)
let itemPerRow = UIDevice.current.userInterfaceIdiom == .pad ? 5 : 4
let availableWidth = screenSide - MediaViewController.spacing * CGFloat(itemPerRow - 1)
let targetSide = (availableWidth / CGFloat(itemPerRow)).rounded(.down)
let targetSize = CGSize(width: targetSide, height: targetSide)
return targetSize.scaled(by: UIScreen.main.scale)
}()

// Both Photon (Site Optimizer) and MediaThumbnailExporter doesn't support
// "aspect-fill" resizing mode, which is want we want for the thumbnails.
//
// This method converts the target size to support aspect fill mode.
//
// Example: if media size is 2000x3000 px and targetSize is 200x200 px, the
// returned value will be 200x300 px.
private static func targetSize(for media: Media, targetSize: CGSize) -> CGSize {
/// The size is calculated to fill a collection view cell, assuming the app
/// displays a few cells in a row. The cell size can vary depending on whether the
/// device is in landscape or portrait mode, but the thumbnail size is
/// guaranteed to always be the same across app launches.
///
/// Example: if media size is 2000x3000 px and targetSize is 200x200 px, the
/// returned value will be 200x300 px.
static func getThumbnailSize(for media: Media, size: ThumbnailSize) -> CGSize {
let mediaSize = CGSize(
width: CGFloat(media.width?.floatValue ?? 0),
height: CGFloat(media.height?.floatValue ?? 0)
)
let targetSize = MediaImageService.getPreferredThumbnailSize(for: size)
return MediaImageService.targetSize(forMediaSize: mediaSize, targetSize: targetSize)
}

/// Returns a preferred thumbnail size (in pixels) optimized for the device.
///
/// - important: It makes sure the app uses the same thumbnails across
/// different screens and presentation modes to avoid fetching and caching
/// more than one version of the same image.
private static func getPreferredThumbnailSize(for thumbnail: ThumbnailSize) -> CGSize {
switch thumbnail {
case .small:
let screenSide = min(UIScreen.main.bounds.width, UIScreen.main.bounds.height)
let itemPerRow = UIDevice.current.userInterfaceIdiom == .pad ? 5 : 4
let availableWidth = screenSide - MediaViewController.spacing * CGFloat(itemPerRow - 1)
let targetSide = (availableWidth / CGFloat(itemPerRow)).rounded(.down)
let targetSize = CGSize(width: targetSide, height: targetSide)
return targetSize.scaled(by: UIScreen.main.scale)
}
}

static func targetSize(forMediaSize mediaSize: CGSize, targetSize originalTargetSize: CGSize) -> CGSize {
guard mediaSize.width > 0 && mediaSize.height > 0 else {
return originalTargetSize
Expand Down
56 changes: 56 additions & 0 deletions WordPress/WordPressTest/MediaImageServiceTests.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,62 @@ import XCTest
@testable import WordPress

class MediaImageServiceTests: CoreDataTestCase {
var mediaFileManager: MediaFileManager!
var sut: MediaImageService!

override func setUp() {
super.setUp()

mediaFileManager = MediaFileManager(directory: .temporary(id: UUID()))
sut = MediaImageService(
coreDataStack: contextManager,
mediaFileManager: mediaFileManager
)
}

override func tearDown() {
super.tearDown()

if let directoryURL = try? mediaFileManager.directoryURL() {
try? FileManager.default.removeItem(at: directoryURL)
}
}

// MARK: - Thumbnail for Local Resource

func testThatSmallThumbnailForLocalAssetIsGenerated() async throws {
// GIVEN
let media = Media(context: mainContext)
media.width = 1024
media.height = 680
let localURL = try makeLocalURL(forResource: "test-image", withExtension: "jpg")
media.absoluteLocalURL = localURL
try mainContext.obtainPermanentIDs(for: [media])

// WHEN
let thumbnail = try await sut.thumbnail(for: media)

// THEN a small thumbnail is created
XCTAssertEqual(thumbnail.size, MediaImageService.getThumbnailSize(for: media, size: .small))

// GIVEN local asset is deleted
try FileManager.default.removeItem(at: localURL)
sut.flush()

// WHEN
let cachedThumbnail = try await sut.thumbnail(for: media)

// THEN cached thumbnail is still available
XCTAssertEqual(cachedThumbnail.size, MediaImageService.getThumbnailSize(for: media, size: .small))
}

/// `Media` is hardcoded to work with a specific direcoty URL managed by `MediaFileManager`
func makeLocalURL(forResource name: String, withExtension ext: String) throws -> URL {
let sourceURL = try XCTUnwrap(Bundle.test.url(forResource: "test-image", withExtension: "jpg"))
let mediaURL = try MediaFileManager.default.makeLocalMediaURL(withFilename: name, fileExtension: ext)
try FileManager.default.copyItem(at: sourceURL, to: mediaURL)
return mediaURL
}

// MARK: - Target Size

Expand Down

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