using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web.Mvc;
using Umbraco.Core;
using Umbraco.Core.IO;

namespace Umbraco.Web.Mvc
{
	/// <summary>
	/// A view engine to look into the template location specified in the config for the front-end/Rendering part of the cms,
	/// this includes paths to render partial macros and media item templates.
	/// </summary>
	public class RenderViewEngine : RazorViewEngine
	{

		private readonly IEnumerable<string> _supplementedViewLocations = new[] { "/{0}.cshtml" };
		private readonly IEnumerable<string> _supplementedPartialViewLocations = new[] { "/{0}.cshtml", "/Partials/{0}.cshtml", "/MacroPartials/{0}.cshtml" };

		/// <summary>
		/// Constructor
		/// </summary>
		public RenderViewEngine()
		{
			const string templateFolder = Constants.ViewLocation;

			var replaceWithUmbracoFolder = _supplementedViewLocations.ForEach(location => templateFolder + location);
			var replacePartialWithUmbracoFolder = _supplementedPartialViewLocations.ForEach(location => templateFolder + location);

			//The Render view engine doesn't support Area's so make those blank
			ViewLocationFormats = replaceWithUmbracoFolder.ToArray();
			PartialViewLocationFormats = replacePartialWithUmbracoFolder.ToArray();

			AreaPartialViewLocationFormats = new string[] { };
			AreaViewLocationFormats = new string[] { };

			EnsureFolderAndWebConfig();
		}

		/// <summary>
		/// Ensures that the correct web.config for razor exists in the /Views folder.
		/// </summary>
		private void EnsureFolderAndWebConfig()
		{
			var viewFolder = IOHelper.MapPath(Constants.ViewLocation);
			//ensure the web.config file is in the ~/Views folder
			Directory.CreateDirectory(viewFolder);
			if (!File.Exists(Path.Combine(viewFolder, "web.config")))
			{
				using (var writer = File.CreateText(Path.Combine(viewFolder, "web.config")))
				{
					writer.Write(Strings.web_config);
				}
			}
		}

		public override ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
		{
			if (!ShouldFindView(controllerContext, false))
			{
				return new ViewEngineResult(new string[] { });
			}

			return base.FindView(controllerContext, viewName, masterName, useCache);
		}

		public override ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache)
		{
			if (!ShouldFindView(controllerContext, true))
			{
				return new ViewEngineResult(new string[] { });
			}

			return base.FindPartialView(controllerContext, partialViewName, useCache);
		}

		/// <summary>
		/// Determines if the view should be found, this is used for view lookup performance and also to ensure 
		/// less overlap with other user's view engines. This will return true if the Umbraco back office is rendering
		/// and its a partial view or if the umbraco front-end is rendering but nothing else.
		/// </summary>
		/// <param name="controllerContext"></param>
		/// <param name="isPartial"></param>
		/// <returns></returns>
		private bool ShouldFindView(ControllerContext controllerContext, bool isPartial)
		{
			//first check if we're rendering a partial view for the back office, or surface controller, etc...
			//anything that is not IUmbracoRenderModel as this should only pertain to Umbraco views.
			if (isPartial
			    && controllerContext.RouteData.DataTokens.ContainsKey("umbraco")
			    && !(controllerContext.RouteData.DataTokens["umbraco"] is RenderModel))
			{
				return true;
			}

			//only find views if we're rendering the umbraco front end
			if (controllerContext.RouteData.DataTokens.ContainsKey("umbraco")
			    && controllerContext.RouteData.DataTokens["umbraco"] != null
			    && controllerContext.RouteData.DataTokens["umbraco"] is RenderModel)
			{
				return true;
			}

			return false;
		}

	}
}