using System;
using Foundation;
using ObjCRuntime;
using WebKit;
 
namespace Microsoft.Maui.Platform
{
	// Use interface instead of base class here
	// https://developer.apple.com/documentation/webkit/wknavigationdelegate/1455641-webview?language=objc#discussion
	// The newer policy method is implemented in the base class
	// and the doc remarks state the older policy method is not called
	// if the newer one is implemented, but the new one is v13+
	// so we'd like to stick with the older one for now
	public class MauiWebViewNavigationDelegate : NSObject, IWKNavigationDelegate
	{
		readonly WeakReference<IWebViewHandler> _handler;
		WebNavigationEvent _lastEvent;
 
		public MauiWebViewNavigationDelegate(IWebViewHandler handler)
		{
			_ = handler ?? throw new ArgumentNullException(nameof(handler));
			_handler = new WeakReference<IWebViewHandler>(handler);
		}
 
		[Export("webView:didFinishNavigation:")]
		public void DidFinishNavigation(WKWebView webView, WKNavigation navigation)
		{
			var handler = Handler;
 
			if (handler is null || !handler.IsConnected())
				return;
 
			var platformView = handler?.PlatformView;
			var virtualView = handler?.VirtualView;
 
			if (platformView is null || virtualView is null)
				return;
 
			platformView.UpdateCanGoBackForward(virtualView);
 
			if (webView.IsLoading)
				return;
 
			var url = GetCurrentUrl();
 
			if (url == $"file://{NSBundle.MainBundle.BundlePath}/")
				return;
 
			virtualView.Navigated(_lastEvent, url, WebNavigationResult.Success);
 
			// ProcessNavigatedAsync calls UpdateCanGoBackForward
			if (handler is WebViewHandler webViewHandler)
				webViewHandler.ProcessNavigatedAsync(url).FireAndForget();
			else
				platformView.UpdateCanGoBackForward(virtualView);
		}
 
		[Export("webView:didFailNavigation:withError:")]
		public void DidFailNavigation(WKWebView webView, WKNavigation navigation, NSError error)
		{
			var handler = Handler;
 
			if (handler is null || !handler.IsConnected())
				return;
 
			var platformView = handler?.PlatformView;
			var virtualView = handler?.VirtualView;
 
			if (platformView is null || virtualView is null)
				return;
 
			var url = GetCurrentUrl();
 
			virtualView.Navigated(_lastEvent, url, WebNavigationResult.Failure);
 
			platformView.UpdateCanGoBackForward(virtualView);
		}
 
		[Export("webView:didFailProvisionalNavigation:withError:")]
		public void DidFailProvisionalNavigation(WKWebView webView, WKNavigation navigation, NSError error)
		{
			var handler = Handler;
 
			if (handler is null || !handler.IsConnected())
				return;
 
			var platformView = handler?.PlatformView;
			var virtualView = handler?.VirtualView;
 
			if (platformView is null || virtualView is null)
				return;
 
			var url = GetCurrentUrl();
 
			virtualView.Navigated(_lastEvent, url, WebNavigationResult.Failure);
 
			platformView.UpdateCanGoBackForward(virtualView);
		}
 
		// https://stackoverflow.com/questions/37509990/migrating-from-uiwebview-to-wkwebview
		[Export("webView:decidePolicyForNavigationAction:decisionHandler:")]
		public void DecidePolicy(WKWebView webView, WKNavigationAction navigationAction, Action<WKNavigationActionPolicy> decisionHandler)
		{
			var handler = Handler;
 
			if (handler is null || !handler.IsConnected())
			{
				decisionHandler.Invoke(WKNavigationActionPolicy.Cancel);
				return;
			}
 
			var platformView = handler?.PlatformView;
			var virtualView = handler?.VirtualView;
 
			if (platformView is null || virtualView is null)
			{
				decisionHandler.Invoke(WKNavigationActionPolicy.Cancel);
				return;
			}
 
			var navEvent = WebNavigationEvent.NewPage;
			var navigationType = navigationAction.NavigationType;
 
			switch (navigationType)
			{
				case WKNavigationType.LinkActivated:
					navEvent = WebNavigationEvent.NewPage;
 
					if (navigationAction.TargetFrame == null)
						webView?.LoadRequest(navigationAction.Request);
 
					break;
				case WKNavigationType.FormSubmitted:
					navEvent = WebNavigationEvent.NewPage;
					break;
				case WKNavigationType.BackForward:
					navEvent = CurrentNavigationEvent;
					break;
				case WKNavigationType.Reload:
					navEvent = WebNavigationEvent.Refresh;
					break;
				case WKNavigationType.FormResubmitted:
					navEvent = WebNavigationEvent.NewPage;
					break;
				case WKNavigationType.Other:
					navEvent = WebNavigationEvent.NewPage;
					break;
			}
 
			_lastEvent = navEvent;
 
			var request = navigationAction.Request;
			var lastUrl = request.Url.ToString();
 
			bool cancel = virtualView.Navigating(navEvent, lastUrl);
			platformView.UpdateCanGoBackForward(virtualView);
			decisionHandler(cancel ? WKNavigationActionPolicy.Cancel : WKNavigationActionPolicy.Allow);
		}
 
		string GetCurrentUrl()
		{
			return Handler?.PlatformView?.Url?.AbsoluteUrl?.ToString() ?? string.Empty;
		}
 
		internal WebNavigationEvent CurrentNavigationEvent
		{
			get;
			set;
		}
 
		IWebViewHandler? Handler
		{
			get
			{
				if (_handler.TryGetTarget(out var handler))
				{
					return handler;
				}
 
				return null;
			}
		}
	}
}