using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Media;
using Tango.Core;
using Tango.Core.Commands;
using Tango.PPC.Common;
using Tango.PPC.Common.Modules;
using Tango.PPC.Common.Navigation;
using Tango.PPC.Common.Threading;
using Tango.PPC.UI.Views;
using Tango.SharedUI.Controls;

namespace Tango.PPC.UI.Navigation
{
    /// <summary>
    /// Represents the default PPC navigation manager.
    /// </summary>
    /// <seealso cref="Tango.PPC.Common.Navigation.INavigationManager" />
    public class DefaultNavigationManager : ExtendedObject, INavigationManager
    {
        private event Action<Object, Object> NavigationCycleCompleted;

        private IDispatcherProvider _dispatcherProvider;
        private IPPCModuleLoader _moduleLoader;
        private Object _currentVM;
        private String _lastFullPath;
        private bool _preventHistory;
        private bool _navigating_back;

        private Stack<String> _navigationHistory;

        /// <summary>
        /// Gets the current view model.
        /// </summary>
        public PPCViewModel CurrentVM
        {
            get { return _currentVM as PPCViewModel; }
        }

        private IPPCModule _currentModule;
        /// <summary>
        /// Gets or sets the current module.
        /// </summary>
        public IPPCModule CurrentModule
        {
            get { return _currentModule; }
            private set { _currentModule = value; RaisePropertyChangedAuto(); }
        }

        /// <summary>
        /// Navigates to the previous view.
        /// </summary>
        public RelayCommand NavigateBackCommand { get; private set; }

        /// <summary>
        /// Navigates to the specified full path in command parameter.
        /// </summary>
        public RelayCommand<String> NavigateToCommand { get; private set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="DefaultNavigationManager"/> class.
        /// </summary>
        /// <param name="moduleLoader">The module loader.</param>
        public DefaultNavigationManager(IPPCModuleLoader moduleLoader, IDispatcherProvider dispatcherProvider)
        {
            _navigationHistory = new Stack<String>();
            _moduleLoader = moduleLoader;

            NavigateToCommand = new RelayCommand<string>(async (x) => await NavigateTo(x));
            NavigateBackCommand = new RelayCommand(async () => await NavigateBack());

            _dispatcherProvider = dispatcherProvider;
        }

        /// <summary>
        /// Navigates to the specified PPC view.
        /// </summary>
        /// <param name="view">The view.</param>
        public Task<bool> NavigateTo(NavigationView view, bool pushToHistory = true)
        {
            if (view == NavigationView.HomeModule)
            {
                _navigationHistory.Clear();
                _lastFullPath = null;

                var firstModule = _moduleLoader.UserModules.FirstOrDefault();
                var moduleAtt = firstModule.GetType().GetCustomAttribute<PPCModuleAttribute>();

                if (moduleAtt != null)
                {
                    return NavigateTo(firstModule.GetType(), pushToHistory, moduleAtt.HomeViewName);
                }
                else
                {
                    return NavigateTo(firstModule.GetType(), pushToHistory);
                }
            }
            else
            {
                MainView.Instance.NavigationControl.NavigateTo(view.ToString());
                return Task.FromResult(true);
            }
        }

        /// <summary>
        /// Navigates to the specified PPC view with the specified receive object.
        /// </summary>
        /// <param name="view">The view.</param>
        /// <param name="obj"></param>
        /// <param name="pushToHistory"></param>
        /// <returns></returns>
        public Task<bool> NavigateWithObject<TPass>(NavigationView view, TPass obj, bool pushToHistory = true)
        {
            MainView.Instance.NavigationControl.NavigateTo(view.ToString());
            INavigationObjectReceiver<TPass> receiver =  MainView.Instance.NavigationControl.Elements.FirstOrDefault(x => (x.GetType().Name == view.ToString() || NavigationControl.GetNavigationName(x) == view.ToString()) && x.DataContext is INavigationObjectReceiver<TPass>).DataContext as INavigationObjectReceiver<TPass>;

            if (receiver != null)
            {
                receiver.OnNavigatedToWithObject(obj);
            }

            return Task.FromResult(true);
        }

        /// <summary>
        /// Navigates to the specified module.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        public Task<bool> NavigateTo<T>(bool pushToHistory = true) where T : IPPCModule
        {
            return NavigateTo(typeof(T));
        }

        /// <summary>
        /// Navigates to the specified module using the view path (e.g MainView.JobsView).
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="viewPath">The view path.</param>
        public Task<bool> NavigateTo<T>(string viewPath, bool pushToHistory = true) where T : IPPCModule
        {
            return NavigateTo<T>(pushToHistory, viewPath.Split('.'));
        }

        /// <summary>
        /// Navigates to the specified module using the view path (e.g MainView,JobsView).
        /// This method makes it easy to do stuff like NavigateTo(nameof(MainView),nameof(JobsView));
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="viewPath">The view path.</param>
        public Task<bool> NavigateTo<T>(bool pushToHistory = true, params String[] viewPath) where T : IPPCModule
        {
            return NavigateTo(typeof(T), pushToHistory, viewPath);
        }

        /// <summary>
        /// Navigates to the specified module and view by full path (e.g Jobs.JobsView).
        /// </summary>
        /// <param name="fullPath">The full path.</param>
        public async Task<bool> NavigateTo(String fullPath, bool pushToHistory = true)
        {
            String[] path = fullPath.Split('.');
            var module = _moduleLoader.UserModules.SingleOrDefault(x => x.GetType().Name == path[0] || x.Name == path[0]);

            if (path.Length == 1 && path[0] == CurrentModule.Name) return true;

            var fromVM = _currentVM;

            if (_currentVM != null && _currentVM is INavigationBlocker)
            {
                if (_navigating_back)
                {
                    if (!await (_currentVM as INavigationBlocker).OnNavigateBackRequest())
                    {
                        return false;
                    }
                }
                else
                {
                    if (!await (_currentVM as INavigationBlocker).OnNavigateOutRequest())
                    {
                        return false;
                    }
                }
            }

            if (pushToHistory && _lastFullPath != null && !_preventHistory)
            {
                _navigationHistory.Push(_lastFullPath);
                RaisePropertyChanged(nameof(CanNavigateBack));
            }

            _lastFullPath = fullPath;

            MainView.Instance.NavigationControl.NavigateTo(NavigationView.LayoutView.ToString());
            var navigationControl = LayoutView.Instance.NavigationControl;
            CurrentModule = module;
            var moduleView = navigationControl.NavigateTo(module.Name);

            _currentVM = moduleView.DataContext;

            if (path.Length > 1)
            {
                var moduleNavigation = moduleView.FindChildOffline<NavigationControl>();

                moduleNavigation.RegisterForLoadedOrNow(async (x, e) =>
                {
                    foreach (var view in path.Skip(1))
                    {
                        await Task.Delay(100);
                        var v = moduleNavigation.NavigateTo(view);

                        if (v != null)
                        {
                            _currentVM = v.DataContext;

                            if (view != path.Last())
                            {
                                moduleNavigation = v.FindChildOffline<NavigationControl>();
                            }
                        }
                        else
                        {
                            throw new ArgumentNullException("Could not navigate to " + fullPath);
                        }
                    }

                    NavigationCycleCompleted?.Invoke(fromVM, _currentVM);
                });
            }

            return true;
        }

        /// <summary>
        /// Navigates for result.
        /// </summary>
        /// <typeparam name="TModule">The type of the module.</typeparam>
        /// <typeparam name="TView">The type of the view.</typeparam>
        /// <typeparam name="TResult">The type of the result.</typeparam>
        /// <typeparam name="TObject">The type of the object.</typeparam>
        /// <param name="obj">The object.</param>
        /// <param name="pushToHistory">if set to <c>true</c> [push to history].</param>
        /// <returns></returns>
        public Task<TResult> NavigateForResult<TModule, TView, TResult, TObject>(TObject obj, bool pushToHistory = true)
               where TModule : IPPCModule
        {
            TaskCompletionSource<TResult> source = new TaskCompletionSource<TResult>();

            var fromVM = _currentVM;
            Object toVM = null;


            Action<Object, Object> handler = null;

            handler = (from, to) =>
            {
                if (toVM == null)
                {
                    toVM = to;
                    if (toVM is INavigationResultProvider<TResult, TObject>)
                    {
                        (toVM as INavigationResultProvider<TResult, TObject>).OnNavigationObjectReceived(obj);
                    }
                }
                else
                {
                    if (to == fromVM && from == toVM)
                    {
                        if (from is INavigationResultProvider<TResult, TObject>)
                        {
                            source.SetResult((from as INavigationResultProvider<TResult, TObject>).GetNavigationResult());
                        }
                    }

                    NavigationCycleCompleted -= handler;
                }
            };

            NavigationCycleCompleted += handler;

            NavigateTo<TModule>(typeof(TView).Name, pushToHistory);

            return source.Task;
        }

        /// <summary>
        /// Navigates to the specified module and view with the specified object.
        /// </summary>
        /// <typeparam name="TModule">The type of the module.</typeparam>
        /// <typeparam name="TView">The type of the view.</typeparam>
        /// <typeparam name="TPass">The type of the pass.</typeparam>
        /// <param name="obj">The object.</param>
        /// <param name="pushToHistory">if set to <c>true</c> [push to history].</param>
        /// <returns></returns>
        public Task<bool> NavigateWithObject<TModule, TView, TPass>(TPass obj, bool pushToHistory = true) where TModule : IPPCModule
        {
            TaskCompletionSource<bool> source = new TaskCompletionSource<bool>();

            Action<Object, Object> handler = null;

            handler = (from, to) =>
            {
                if (to is INavigationObjectReceiver<TPass>)
                {
                    (to as INavigationObjectReceiver<TPass>).OnNavigatedToWithObject(obj);
                }

                NavigationCycleCompleted -= handler;
            };

            NavigationCycleCompleted += handler;

            NavigateTo<TModule>(typeof(TView).Name, pushToHistory);

            return source.Task;
        }

        private Task<bool> NavigateTo(Type moduleType, bool pushToHistory = true, params String[] viewPath)
        {
            if (viewPath != null && viewPath.Length > 0)
            {
                return NavigateTo(moduleType.Name + "." + String.Join(".", viewPath), pushToHistory);
            }
            else
            {
                return NavigateTo(moduleType.Name, pushToHistory);
            }
        }

        /// <summary>
        /// Gets a value indicating whether the navigation system is able to navigate to the previous view.
        /// </summary>
        public bool CanNavigateBack
        {
            get { return _navigationHistory.Count > 0; }
        }

        /// <summary>
        /// Navigates to the previous view if <see cref="P:Tango.PPC.Common.Navigation.INavigationManager.CanNavigateBack" /> is true.
        /// </summary>
        public async Task<bool> NavigateBack()
        {
            _navigating_back = true;

            String first = _navigationHistory.Pop();
            _preventHistory = true;


            if (await NavigateTo(first))
            {
                RaisePropertyChanged(nameof(CanNavigateBack));
                _preventHistory = false;
                _navigating_back = false;
                return true;
            }
            else
            {
                _navigationHistory.Push(first);
                _preventHistory = false;
                _navigating_back = false;
                RaisePropertyChanged(nameof(CanNavigateBack));
                return false;
            }
        }

        /// <summary>
        /// Clears the navigation back history.
        /// </summary>
        public void ClearHistory()
        {
            _navigationHistory.Clear();
            RaisePropertyChanged(nameof(CanNavigateBack));
        }

        public void ClearHistoryExcept<T>()
        {
            var history_list = _navigationHistory.ToList();
            history_list = history_list.Where(x => x.Contains(typeof(T).Name)).Distinct().ToList();
            _navigationHistory.Clear();

            foreach (var item in history_list)
            {
                _navigationHistory.Push(item);
            }

            RaisePropertyChanged(nameof(CanNavigateBack));
        }
    }
}