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141 lines
3.0 KiB
Swift
141 lines
3.0 KiB
Swift
//
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// ImageDownloader.swift
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// NetNewsWire
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//
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// Created by Brent Simmons on 11/25/17.
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// Copyright © 2017 Ranchero Software. All rights reserved.
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//
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import Foundation
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import RSCore
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import RSWeb
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extension Notification.Name {
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static let ImageDidBecomeAvailable = Notification.Name("ImageDidBecomeAvailableNotification") // UserInfoKey.url
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}
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final class ImageDownloader {
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private let folder: String
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private var diskCache: BinaryDiskCache
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private let queue: DispatchQueue
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private var imageCache = [String: Data]() // url: image
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private var urlsInProgress = Set<String>()
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private var badURLs = Set<String>() // That return a 404 or whatever. Just skip them in the future.
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init(folder: String) {
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self.folder = folder
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self.diskCache = BinaryDiskCache(folder: folder)
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self.queue = DispatchQueue(label: "ImageDownloader serial queue - \(folder)")
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}
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@discardableResult
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func image(for url: String) -> Data? {
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if let data = imageCache[url] {
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return data
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}
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findImage(url)
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return nil
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}
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}
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private extension ImageDownloader {
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func cacheImage(_ url: String, _ image: Data) {
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imageCache[url] = image
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postImageDidBecomeAvailableNotification(url)
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}
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func findImage(_ url: String) {
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guard !urlsInProgress.contains(url) && !badURLs.contains(url) else {
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return
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}
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urlsInProgress.insert(url)
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readFromDisk(url) { (image) in
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if let image = image {
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self.cacheImage(url, image)
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self.urlsInProgress.remove(url)
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return
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}
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self.downloadImage(url) { (image) in
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if let image = image {
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self.cacheImage(url, image)
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}
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self.urlsInProgress.remove(url)
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}
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}
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}
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func readFromDisk(_ url: String, _ completion: @escaping (Data?) -> Void) {
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queue.async {
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if let data = self.diskCache[self.diskKey(url)], !data.isEmpty {
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DispatchQueue.main.async {
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completion(data)
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}
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return
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}
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DispatchQueue.main.async {
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completion(nil)
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}
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}
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}
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func downloadImage(_ url: String, _ completion: @escaping (Data?) -> Void) {
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guard let imageURL = URL(string: url) else {
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completion(nil)
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return
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}
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downloadUsingCache(imageURL) { (data, response, error) in
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if let data = data, !data.isEmpty, let response = response, response.statusIsOK, error == nil {
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self.saveToDisk(url, data)
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completion(data)
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return
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}
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if let response = response as? HTTPURLResponse, response.statusCode >= HTTPResponseCode.badRequest && response.statusCode <= HTTPResponseCode.notAcceptable {
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self.badURLs.insert(url)
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}
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if let error = error {
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appDelegate.logMessage("Error downloading image at \(url): \(error)", type: .warning)
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}
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completion(nil)
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}
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}
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func saveToDisk(_ url: String, _ data: Data) {
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queue.async {
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self.diskCache[self.diskKey(url)] = data
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}
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}
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func diskKey(_ url: String) -> String {
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return (url as NSString).rs_md5Hash()
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}
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func postImageDidBecomeAvailableNotification(_ url: String) {
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DispatchQueue.main.async {
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NotificationCenter.default.post(name: .ImageDidBecomeAvailable, object: self, userInfo: [UserInfoKey.url: url])
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}
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}
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}
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