using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using TINK.Services.CopriApi.ServerUris;
using TINK.View;
using TINK.View.Account;
using TINK.View.Contact;
using TINK.View.Info;
using TINK.View.Login;
using TINK.View.Map;
using TINK.View.FindBike;
using TINK.View.MyBikes;
using TINK.View.Root;
using TINK.View.Settings;
using Xamarin.Forms;
using TINK.ViewModel.MasterDetail;
#if USEFLYOUT
using TINK.View.MasterDetail;
#endif
using TINK.Services;
using TINK.View.Themes;

namespace TINK.ViewModel.Root
{
    /// <summary>
    /// View model for flyout menu entries. Respositility
    /// - populates entries depending on app state on showing menu
    /// - updates menu denpending on app state change, i.e. user logs in/ out. 
    /// </summary>
    public class RootPageFlyoutViewModel : INotifyPropertyChanged
    {
        /// <summary>
        /// Dictionary to manage collection of menu items.
        /// </summary>
        private Dictionary<Type, int> m_oEntryDictionary;

        public event PropertyChangedEventHandler PropertyChanged;

        /// <summary> Updates menu entries depending on state. </summary>
        private void UpdateMenuEntries()
        {
            for (int l_iIndex = MenuItems.Count - 1; l_iIndex >= 0; l_iIndex--)
            {
                MenuItems.Clear();
                m_oEntryDictionary.Clear();
            }

            CheckAddItem(typeof(MapPage));

            if (App.ModelRoot.ActiveUser.IsLoggedIn)
            {
                CheckAddItem(typeof(MyBikesPage));
                CheckAddItem(typeof(FindBikePage));
                CheckAddItem(typeof(AccountPage));
            }
            else
            {
                CheckAddItem(typeof(LoginPage));
            }

            if (App.ModelRoot.Uris.ActiveUri.Host.GetIsCopri()
                || App.ModelRoot.ActiveUser.IsLoggedIn)
            {
                CheckAddItem(typeof(SettingsPage));
            }

            CheckAddItem(typeof(FeesAndBikesPage)); // Fees and bikes

            CheckAddItem(typeof(ContactPage)); // Feedback and contact

            CheckAddItem(typeof(InfoPage)); // About sharee.bike
        }

        /// <summary>Adds a menu item to master detail menu.</summary>
        /// <param name="p_oType">Type decribing entry to be added.</param>
        private void CheckAddItem(Type p_oType)
        {
            if (m_oEntryDictionary.ContainsKey(p_oType))
            {
                // Nothing to do because has already been added.
                return;
            }

            m_oEntryDictionary.Add(
                p_oType,
                m_oEntryDictionary.Count);

            MenuItems.Add(new RootPageFlyoutMenuItem {
                TargetType = p_oType,
                GlyphCode = Helper.GetGlyphCode(p_oType),
                Title = Helper.GetCaption(p_oType),
                Id = m_oEntryDictionary[p_oType] }) ;
        }

        /// <summary> Removes a page from menu.</summary>
        /// <param name="p_oType"></param>
        private void RemoveItem(Type p_oType)
        {
            if (!m_oEntryDictionary.ContainsKey(p_oType))
            {
                // Nothing to do because item was never added/ already removed.
                return;
            }

            MenuItems.Remove(MenuItems[m_oEntryDictionary[p_oType]]);
            m_oEntryDictionary.Remove(p_oType);
        }

        public RootPageFlyoutViewModel()
        {
            MenuItems = new ObservableCollection<RootPageFlyoutMenuItem>();
            m_oEntryDictionary = new Dictionary<Type, int>();

            // Update menu entries on login/ logout actions.
            App.ModelRoot.ActiveUser.StateChanged += (sender, eventargs) => OnUpdateRequired();

            // Update flyout view model whenever theme is switched.
            App.ModelRoot.Themes.PropertyChanged += (sender, eventargs) =>
            {
                if (!(sender is ServicesContainerMutable<object> themes))
                    return;

                MasterDetailMenuTitlte = GetMasterDetailMenuTitle(themes.Active);

                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MasterDetailMenuTitlte)));
            };

            MasterDetailMenuTitlte = GetMasterDetailMenuTitle(App.ModelRoot.Themes.Active);

            UpdateMenuEntries();
        }

        /// <summary>
        /// Gets the flyout title from theme name
        /// </summary>
        /// <param name="theme">Name of theme.</param>
        /// <returns>Flyout title.</returns>
        private string GetMasterDetailMenuTitle(object theme)
        {
            if (!(theme is ITheme active))
                return Themes.Konrad.OPERATORINFO;

            return $"{(!string.IsNullOrEmpty(active.OperatorInfo) ? ($"{active.OperatorInfo}") : "sharee.bike")}";
        }

        /// <summary>
        /// Holds the title of the fylout page.
        /// </summary>
        public string MasterDetailMenuTitlte { get; private set; }


        /// <summary>
        /// Provides collection of menu items for master page.
        /// </summary>
        public ObservableCollection<RootPageFlyoutMenuItem> MenuItems
        {
            get; private set;
        }

        /// <summary>
        /// Gets or sets the selected item.
        /// </summary>
        public MainPageMenuItem SelectedMenuItem
        {
            get;
            set;
        }

        /// <summary>
        /// Command object which is invoked from view when an item is selected.
        /// </summary>
        public Command MenuItemSelected
        {
            get
            {
                return new Command(OnUpdateRequired);
            }

        }

        /// <summary> Manges updates required due to selection of a menu or login events.</summary>
        public void OnUpdateRequired()
        {

            UpdateMenuEntries();

            if (SelectedMenuItem == null)
            {
                // Nothing to do if no menu entry is selected.
                return;
            }
        }
    }
}