app_for_reddit/App AI for Reddit/Utilities/RedditShareBridgeStyle.swift

import Foundation

enum RedditShareBridgeStyle {
    static let messageHandlerName = "reddoraShare"

    /// WKWebView does not implement navigator.share. Reddit's share button relies on it
    /// in Safari, so we bridge to the native macOS share sheet.
    static let injectionScript = """
    (function() {
      if (window.__reddoraShareBridgeInstalled) return;
      window.__reddoraShareBridgeInstalled = true;

      function hasBridge() {
        return !!(
          window.webkit &&
          window.webkit.messageHandlers &&
          window.webkit.messageHandlers.reddoraShare
        );
      }

      window.__reddoraShareCallback = function(success) {
        const resolve = window.__reddoraShareResolve;
        const reject = window.__reddoraShareReject;
        window.__reddoraShareResolve = null;
        window.__reddoraShareReject = null;

        if (success && resolve) {
          resolve();
        } else if (!success && reject) {
          reject(new DOMException('Share canceled', 'AbortError'));
        }
      };

      function nativeShare(data) {
        return new Promise(function(resolve, reject) {
          if (!hasBridge()) {
            reject(new DOMException('Share unavailable', 'NotSupportedError'));
            return;
          }

          window.__reddoraShareResolve = resolve;
          window.__reddoraShareReject = reject;
          window.webkit.messageHandlers.reddoraShare.postMessage({
            title: data && data.title ? String(data.title) : '',
            text: data && data.text ? String(data.text) : '',
            url: data && data.url ? String(data.url) : ''
          });
        });
      }

      function canShare(data) {
        if (!hasBridge()) return false;
        if (!data) return true;
        if (data.files && data.files.length) return false;
        return !!(data.url || data.text || data.title);
      }

      try {
        Object.defineProperty(navigator, 'share', {
          value: nativeShare,
          configurable: true,
          writable: true
        });
        Object.defineProperty(navigator, 'canShare', {
          value: canShare,
          configurable: true,
          writable: true
        });
      } catch (error) {
        navigator.share = nativeShare;
        navigator.canShare = canShare;
      }
    })();
    """
}