using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Reflection;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc.Infrastructure;
using Microsoft.AspNetCore.Routing;
using Microsoft.Extensions.Primitives;
using Umbraco.Core;
using Umbraco.Core.Services;
using Umbraco.Extensions;
using Umbraco.Web.BackOffice.Controllers;
using Umbraco.Web.Common.Attributes;
using Umbraco.Web.Common.Exceptions;
using Umbraco.Web.Common.Filters;
using Umbraco.Web.Common.ModelBinders;
using Umbraco.Web.Models.Trees;
using Umbraco.Web.Services;
using Umbraco.Web.Trees;
using Constants = Umbraco.Core.Constants;

namespace Umbraco.Web.BackOffice.Trees
{
    /// <summary>
    /// Used to return tree root nodes
    /// </summary>
    [AngularJsonOnlyConfiguration]
    [PluginController(Constants.Web.Mvc.BackOfficeTreeArea)]
    public class ApplicationTreeController : UmbracoAuthorizedApiController
    {
        private readonly ITreeService _treeService;
        private readonly ISectionService _sectionService;
        private readonly ILocalizedTextService _localizedTextService;
        private readonly IControllerFactory _controllerFactory;
        private readonly IActionDescriptorCollectionProvider _actionDescriptorCollectionProvider;


        public ApplicationTreeController(
            ITreeService treeService,
            ISectionService sectionService,
            ILocalizedTextService localizedTextService,
            IControllerFactory controllerFactory,
            IActionDescriptorCollectionProvider actionDescriptorCollectionProvider
            )
        {
            _treeService = treeService;
            _sectionService = sectionService;
            _localizedTextService = localizedTextService;
            _controllerFactory = controllerFactory;
            _actionDescriptorCollectionProvider = actionDescriptorCollectionProvider;
        }

        /// <summary>
        /// Returns the tree nodes for an application
        /// </summary>
        /// <param name="application">The application to load tree for</param>
        /// <param name="tree">An optional single tree alias, if specified will only load the single tree for the request app</param>
        /// <param name="queryStrings"></param>
        /// <param name="use">Tree use.</param>
        /// <returns></returns>
        public async Task<TreeRootNode> GetApplicationTrees(string application, string tree, [ModelBinder(typeof(HttpQueryStringModelBinder))] FormCollection queryStrings, TreeUse use = TreeUse.Main)
        {
            application = application.CleanForXss();

            if (string.IsNullOrEmpty(application))
                throw new HttpResponseException(HttpStatusCode.NotFound);

            var section = _sectionService.GetByAlias(application);
            if (section == null)
                throw new HttpResponseException(HttpStatusCode.NotFound);

            //find all tree definitions that have the current application alias
            var groupedTrees = _treeService.GetBySectionGrouped(application, use);
            var allTrees = groupedTrees.Values.SelectMany(x => x).ToList();

            if (allTrees.Count == 0)
            {
                //if there are no trees defined for this section but the section is defined then we can have a simple
                //full screen section without trees
                var name = _localizedTextService.Localize("sections/" + application);
                return TreeRootNode.CreateSingleTreeRoot(Constants.System.RootString, null, null, name, TreeNodeCollection.Empty, true);
            }

            // handle request for a specific tree / or when there is only one tree
            if (!tree.IsNullOrWhiteSpace() || allTrees.Count == 1)
            {
                var t = tree.IsNullOrWhiteSpace()
                    ? allTrees[0]
                    : allTrees.FirstOrDefault(x => x.TreeAlias == tree);

                if (t == null)
                    throw new HttpResponseException(HttpStatusCode.NotFound);

                var treeRootNode = await GetTreeRootNode(t, Constants.System.Root, queryStrings);
                if (treeRootNode != null)
                    return treeRootNode;

                throw new HttpResponseException(HttpStatusCode.NotFound);
            }

            // handle requests for all trees
            // for only 1 group
            if (groupedTrees.Count == 1)
            {
                var nodes = new TreeNodeCollection();
                foreach (var t in allTrees)
                {
                    var node = await TryGetRootNode(t, queryStrings);
                    if (node != null)
                        nodes.Add(node);
                }

                var name = _localizedTextService.Localize("sections/" + application);

                if (nodes.Count > 0)
                {
                    var treeRootNode = TreeRootNode.CreateMultiTreeRoot(nodes);
                    treeRootNode.Name = name;
                    return treeRootNode;
                }

                // otherwise it's a section with all empty trees, aka a fullscreen section
                // todo is this true? what if we just failed to TryGetRootNode on all of them? SD: Yes it's true but we should check the result of TryGetRootNode and throw?
                return TreeRootNode.CreateSingleTreeRoot(Constants.System.RootString, null, null, name, TreeNodeCollection.Empty, true);
            }

            // for many groups
            var treeRootNodes = new List<TreeRootNode>();
            foreach (var (groupName, trees) in groupedTrees)
            {
                var nodes = new TreeNodeCollection();
                foreach (var t in trees)
                {
                    var node = await TryGetRootNode(t, queryStrings);
                    if (node != null)
                        nodes.Add(node);
                }

                if (nodes.Count == 0)
                    continue;

                // no name => third party
                // use localization key treeHeaders/thirdPartyGroup
                // todo this is an odd convention
                var name = groupName.IsNullOrWhiteSpace() ? "thirdPartyGroup" : groupName;

                var groupRootNode = TreeRootNode.CreateGroupNode(nodes, application);
                groupRootNode.Name = _localizedTextService.Localize("treeHeaders/" + name);
                treeRootNodes.Add(groupRootNode);
            }

            return TreeRootNode.CreateGroupedMultiTreeRoot(new TreeNodeCollection(treeRootNodes.OrderBy(x => x.Name)));
        }

        /// <summary>
        /// Tries to get the root node of a tree.
        /// </summary>
        /// <remarks>
        /// <para>Returns null if the root node could not be obtained due to an HttpResponseException,
        /// which probably indicates that the user isn't authorized to view that tree.</para>
        /// </remarks>
        private async Task<TreeNode> TryGetRootNode(Tree tree, FormCollection querystring)
        {
            if (tree == null)
                throw new ArgumentNullException(nameof(tree));

            try
            {
                return await GetRootNode(tree, querystring);
            }
            catch (HttpResponseException)
            {
                // if this occurs its because the user isn't authorized to view that tree,
                // in this case since we are loading multiple trees we will just return
                // null so that it's not added to the list.
                return null;
            }
        }

        /// <summary>
        /// Get the tree root node of a tree.
        /// </summary>
        private async Task<TreeRootNode> GetTreeRootNode(Tree tree, int id, FormCollection querystring)
        {
            if (tree == null)
                throw new ArgumentNullException(nameof(tree));

            var children = await GetChildren(tree, id, querystring);
            var rootNode = await GetRootNode(tree, querystring);

            var sectionRoot = TreeRootNode.CreateSingleTreeRoot(
                Constants.System.RootString,
                rootNode.ChildNodesUrl,
                rootNode.MenuUrl,
                rootNode.Name,
                children,
                tree.IsSingleNodeTree);

            // assign the route path based on the root node, this means it will route there when the
            // section is navigated to and no dashboards will be available for this section
            sectionRoot.RoutePath = rootNode.RoutePath;
            sectionRoot.Path = rootNode.Path;

            foreach (var d in rootNode.AdditionalData)
                sectionRoot.AdditionalData[d.Key] = d.Value;

            return sectionRoot;
        }

        /// <summary>
        /// Gets the root node of a tree.
        /// </summary>
        private async Task<TreeNode> GetRootNode(Tree tree, FormCollection querystring)
        {
            if (tree == null)
                throw new ArgumentNullException(nameof(tree));

            var controller = (TreeControllerBase)await GetApiControllerProxy(tree.TreeControllerType, "GetRootNode", querystring);
            var rootNode = controller.GetRootNode(querystring);
            if (rootNode == null)
                throw new InvalidOperationException($"Failed to get root node for tree \"{tree.TreeAlias}\".");
            return rootNode;
        }

        /// <summary>
        /// Get the child nodes of a tree node.
        /// </summary>
        private async Task<TreeNodeCollection> GetChildren(Tree tree, int id, FormCollection querystring)
        {
            if (tree == null)
                throw new ArgumentNullException(nameof(tree));

            // the method we proxy has an 'id' parameter which is *not* in the querystring,
            // we need to add it for the proxy to work (else, it does not find the method,
            // when trying to run auth filters etc).
            var d = querystring?.ToDictionary(x => x.Key, x => x.Value) ?? new Dictionary<string, StringValues>();
            d["id"] = StringValues.Empty;
            var proxyQuerystring = new FormCollection(d);

            var controller = (TreeControllerBase)await GetApiControllerProxy(tree.TreeControllerType, "GetNodes", proxyQuerystring);
            return controller.GetNodes(id.ToInvariantString(), querystring);
        }

        /// <summary>
        /// Gets a proxy to a controller for a specified action.
        /// </summary>
        /// <param name="controllerType">The type of the controller.</param>
        /// <param name="action">The action.</param>
        /// <param name="querystring">The querystring.</param>
        /// <returns>An instance of the controller.</returns>
        /// <remarks>
        /// <para>Creates an instance of the <paramref name="controllerType"/> and initializes it with a route
        /// and context etc. so it can execute the specified <paramref name="action"/>. Runs the authorization
        /// filters for that action, to ensure that the user has permission to execute it.</para>
        /// </remarks>
        private async Task<object> GetApiControllerProxy(Type controllerType, string action, FormCollection querystring)
        {
            // note: this is all required in order to execute the auth-filters for the sub request, we
            // need to "trick" mvc into thinking that it is actually executing the proxied controller.

            var controllerName = controllerType.Name.Substring(0, controllerType.Name.Length - 10); // remove controller part of name;
            // create proxy route data specifying the action & controller to execute
            var routeData = new RouteData(new RouteValueDictionary()
            {
                ["action"] = action,
                ["controller"] = controllerName
            });
            if (!(querystring is null))
            {
                foreach (var (key, value) in querystring)
                {
                    routeData.Values[key] = value;
                }
            }

            var actionDescriptor = _actionDescriptorCollectionProvider.ActionDescriptors.Items
                .Cast<ControllerActionDescriptor>()
                .First(x =>
                    x.ControllerName.Equals(controllerName) &&
                    x.ActionName == action);

            var actionContext = new ActionContext(HttpContext, routeData, actionDescriptor);
            var proxyControllerContext = new ControllerContext(actionContext);
            var controller = (TreeController)_controllerFactory.CreateController(proxyControllerContext);

            var isAllowed = await controller.ControllerContext.InvokeAuthorizationFiltersForRequest(actionContext);
            if (!isAllowed)
                throw new HttpResponseException(HttpStatusCode.Forbidden);

            return controller;
        }


    }
}