import SwiftUI
import WebKit
/// An item's show notes.
///
/// They are feed-supplied HTML, sanitized server-side with ammonia before they are sent. There
/// is no good native renderer for that: NSAttributedString(html:) is slow, single-threaded and
/// ugly, and writing a real one is a project. So this is a web view carrying only the notes,
/// dressed to match, and that is a deliberate choice rather than a thing left undone.
struct ShowNotesView: UIViewRepresentable {
let html: String
let baseURL: URL?
/// The notes size themselves; the pane scrolls as one, so the view grows to fit.
@Binding var height: CGFloat
func makeCoordinator() -> Coordinator { Coordinator(self) }
func makeUIView(context: Context) -> WKWebView {
let cfg = WKWebViewConfiguration()
// Cookies, so a picture behind the same sign-in loads.
cfg.websiteDataStore = .default()
let web = WKWebView(frame: .zero, configuration: cfg)
web.navigationDelegate = context.coordinator
web.scrollView.isScrollEnabled = false
web.isOpaque = false
web.backgroundColor = .clear
web.scrollView.backgroundColor = .clear
return web
}
func updateUIView(_ web: WKWebView, context: Context) {
guard context.coordinator.shown != html else { return }
context.coordinator.shown = html
web.loadHTMLString(page(for: context.environment.colorScheme), baseURL: baseURL)
}
/// The notes wrapped in just enough stylesheet to belong to the app: the system font at the
/// body size, the label colours, and links in the accent. Nothing else is imposed -- the
/// markup is the publisher's and should read as they wrote it.
private func page(for scheme: ColorScheme) -> String {
let dark = scheme == .dark
let fg = dark ? "#f5f5f7" : "#1d1d1f"
let dim = dark ? "#aeaeb2" : "#515154"
let link = dark ? "#409cff" : "#0055aa"
let rule = dark ? "rgba(255,255,255,.14)" : "rgba(0,0,0,.12)"
return """
\(html)
"""
}
final class Coordinator: NSObject, WKNavigationDelegate {
private let parent: ShowNotesView
var shown: String?
init(_ parent: ShowNotesView) { self.parent = parent }
func webView(_ web: WKWebView, didFinish navigation: WKNavigation!) {
// Measure once it has laid out, so the pane can give it the room it asked for.
web.evaluateJavaScript("document.body.scrollHeight") { value, _ in
if let h = value as? CGFloat { self.parent.height = max(h, 1) }
}
}
/// A link in the notes opens in Safari. Following one inside this view would replace the
/// notes with somebody's website and leave no way back.
func webView(_ web: WKWebView,
decidePolicyFor action: WKNavigationAction,
decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
guard action.navigationType == .linkActivated, let url = action.request.url else {
return decisionHandler(.allow)
}
UIApplication.shared.open(url)
decisionHandler(.cancel)
}
}
}