84 lines
2.1 KiB
Swift
84 lines
2.1 KiB
Swift
//
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// AuthorAvatarDownloader.swift
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// Evergreen
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//
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// Created by Brent Simmons on 11/26/17.
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// Copyright © 2017 Ranchero Software. All rights reserved.
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//
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import AppKit
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import Articles
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extension Notification.Name {
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static let AvatarDidBecomeAvailable = Notification.Name("AvatarDidBecomeAvailableNotification") // UserInfoKey.imageURL (which is an avatarURL)
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}
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final class AuthorAvatarDownloader {
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private let imageDownloader: ImageDownloader
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private var cache = [String: NSImage]() // avatarURL: NSImage
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private var waitingForAvatarURLs = Set<String>()
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init(imageDownloader: ImageDownloader) {
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self.imageDownloader = imageDownloader
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NotificationCenter.default.addObserver(self, selector: #selector(imageDidBecomeAvailable(_:)), name: .ImageDidBecomeAvailable, object: imageDownloader)
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}
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func image(for author: Author) -> NSImage? {
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guard let avatarURL = author.avatarURL else {
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return nil
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}
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if let cachedImage = cache[avatarURL] {
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return cachedImage
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}
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if let image = imageDownloader.image(for: avatarURL) {
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handleImageDidBecomeAvailable(avatarURL, image)
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return image
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}
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else {
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waitingForAvatarURLs.insert(avatarURL)
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}
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return nil
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}
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@objc func imageDidBecomeAvailable(_ note: Notification) {
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guard let avatarURL = note.userInfo?[UserInfoKey.url] as? String else {
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return
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}
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guard waitingForAvatarURLs.contains(avatarURL) else {
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return
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}
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guard let image = imageDownloader.image(for: avatarURL) else {
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return
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}
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handleImageDidBecomeAvailable(avatarURL, image)
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}
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}
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private extension AuthorAvatarDownloader {
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func handleImageDidBecomeAvailable(_ avatarURL: String, _ image: NSImage) {
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if cache[avatarURL] == nil {
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cache[avatarURL] = image
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}
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if waitingForAvatarURLs.contains(avatarURL) {
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waitingForAvatarURLs.remove(avatarURL)
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postAvatarDidBecomeAvailableNotification(avatarURL)
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}
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}
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func postAvatarDidBecomeAvailableNotification(_ avatarURL: String) {
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DispatchQueue.main.async {
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NotificationCenter.default.post(name: .AvatarDidBecomeAvailable, object: self, userInfo: [UserInfoKey.url: avatarURL])
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}
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}
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}
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