mirror of
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100 lines
2.3 KiB
Swift
100 lines
2.3 KiB
Swift
//
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// FeaturedImageDownloader.swift
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// NetNewsWire
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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 Foundation
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import Articles
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import RSParser
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final class FeaturedImageDownloader {
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private let imageDownloader: ImageDownloader
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private var articleURLToFeaturedImageURLCache = [String: String]()
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private var articleURLsWithNoFeaturedImage = Set<String>()
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private var urlsInProgress = Set<String>()
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init(imageDownloader: ImageDownloader) {
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self.imageDownloader = imageDownloader
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}
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func image(for article: Article) -> RSImage? {
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if let imageLink = article.imageLink {
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return image(forFeaturedImageURL: imageLink)
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}
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if let link = article.link {
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return image(forArticleURL: link)
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}
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return nil
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}
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func image(forArticleURL articleURL: String) -> RSImage? {
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if articleURLsWithNoFeaturedImage.contains(articleURL) {
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return nil
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}
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if let featuredImageURL = cachedURL(for: articleURL) {
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return image(forFeaturedImageURL: featuredImageURL)
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}
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findFeaturedImageURL(for: articleURL)
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return nil
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}
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func image(forFeaturedImageURL featuredImageURL: String) -> RSImage? {
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if let data = imageDownloader.image(for: featuredImageURL) {
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return RSImage(data: data)
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}
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return nil
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}
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}
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private extension FeaturedImageDownloader {
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func cachedURL(for articleURL: String) -> String? {
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return articleURLToFeaturedImageURLCache[articleURL]
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}
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func cacheURL(for articleURL: String, _ featuredImageURL: String) {
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articleURLsWithNoFeaturedImage.remove(articleURL)
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articleURLToFeaturedImageURLCache[articleURL] = featuredImageURL
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}
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func findFeaturedImageURL(for articleURL: String) {
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guard !urlsInProgress.contains(articleURL) else {
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return
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}
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urlsInProgress.insert(articleURL)
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HTMLMetadataDownloader.downloadMetadata(for: articleURL) { (metadata) in
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self.urlsInProgress.remove(articleURL)
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guard let metadata = metadata else {
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return
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}
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self.pullFeaturedImageURL(from: metadata, articleURL: articleURL)
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}
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}
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func pullFeaturedImageURL(from metadata: RSHTMLMetadata, articleURL: String) {
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if let url = metadata.bestFeaturedImageURL() {
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cacheURL(for: articleURL, url)
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let _ = image(forFeaturedImageURL: url)
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return
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}
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articleURLsWithNoFeaturedImage.insert(articleURL)
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}
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}
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