/*
 * Copyright (c) 2019 ETH Zürich, Educational Development and Technology (LET)
 * 
 * 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
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

using System;
using System.Collections.Specialized;
using CefSharp;
using SafeExamBrowser.Configuration.Contracts;

namespace SafeExamBrowser.Browser.Handlers
{
	internal class ResourceRequestHandler : CefSharp.Handler.ResourceRequestHandler
	{
		private AppConfig appConfig;

		internal ResourceRequestHandler(AppConfig appConfig)
		{
			this.appConfig = appConfig;
		}

		protected override CefReturnValue OnBeforeResourceLoad(IWebBrowser browserControl, IBrowser browser, IFrame frame, IRequest request, IRequestCallback callback)
		{
			// TODO: CEF does not yet support intercepting requests from service workers, thus the user agent must be statically set at browser
			//       startup for now. Once CEF has full support of service workers, the static user agent should be removed and the method below
			//       reactivated. See https://bitbucket.org/chromiumembedded/cef/issues/2622 for the current status of development.
			// AppendCustomUserAgent(request);

			if (IsMailtoUrl(request.Url))
			{
				return CefReturnValue.Cancel;
			}

			ReplaceCustomScheme(request);

			return base.OnBeforeResourceLoad(browserControl, browser, frame, request, callback);
		}

		private void AppendCustomUserAgent(IRequest request)
		{
			var headers = new NameValueCollection(request.Headers);
			var userAgent = request.Headers["User-Agent"];

			headers["User-Agent"] = $"{userAgent} SEB/{appConfig.ProgramInformationalVersion}";
			request.Headers = headers;
		}

		private bool IsMailtoUrl(string url)
		{
			return url.StartsWith(Uri.UriSchemeMailto);
		}

		private void ReplaceCustomScheme(IRequest request)
		{
			if (Uri.IsWellFormedUriString(request.Url, UriKind.RelativeOrAbsolute))
			{
				var uri = new Uri(request.Url);

				if (uri.Scheme == appConfig.SebUriScheme)
				{
					request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttp }.Uri.AbsoluteUri;
				}
				else if (uri.Scheme == appConfig.SebUriSchemeSecure)
				{
					request.Url = new UriBuilder(uri) { Scheme = Uri.UriSchemeHttps }.Uri.AbsoluteUri;
				}
			}
		}
	}
}