Revision control
Copy as Markdown
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
import Foundation
import Fuzi
/// Scrapes the HTML at a given site for images
protocol FaviconURLFetcher {
/// Scrapes the HTML at the given url for a favicon image
/// - Parameter siteURL: The web address we want to retrieve the favicon for
/// - Parameter completion: Returns a result type of either a URL on success or a SiteImageError on failure
func fetchFaviconURL(siteURL: URL) async throws -> URL
}
struct DefaultFaviconURLFetcher: FaviconURLFetcher {
private let network: HTMLDataRequest
init(network: HTMLDataRequest = DefaultHTMLDataRequest()) {
self.network = network
}
func fetchFaviconURL(siteURL: URL) async throws -> URL {
do {
let data = try await network.fetchDataForURL(siteURL)
let url = try await self.processHTMLDocument(siteURL: siteURL,
data: data)
return url
} catch {
throw error
}
}
private func processHTMLDocument(siteURL: URL, data: Data) async throws -> URL {
guard let root = try? HTMLDocument(data: data) else {
throw SiteImageError.invalidHTML
}
var reloadURL: URL?
// Check if we need to redirect
for meta in root.xpath("//head/meta") {
if let refresh = meta["http-equiv"], refresh == "Refresh",
let content = meta["content"],
let index = content.range(of: "URL="),
let url = URL(string: String(content[index.upperBound...]), invalidCharacters: false) {
reloadURL = url
}
}
// Redirect if needed
if let reloadURL = reloadURL {
return try await fetchFaviconURL(siteURL: reloadURL)
}
// Search for the first reference to an icon
for link in root.xpath("//head//link[contains(@rel, 'icon')]") {
guard let href = link["href"] else { continue }
if let faviconURL = URL(string: href, relativeTo: siteURL) {
return faviconURL
}
}
// Fallback to the favicon at the root of the domain
// This is a fallback because it's generally low res
if let faviconURL = siteURL.faviconUrl() {
return faviconURL
}
throw SiteImageError.noFaviconFound
}
}