// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an 
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific 
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.Security;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Esri.ArcGISRuntime;
using Xamarin.Forms;


#if __IOS__
using Xamarin.Forms.Platform.iOS;
using Xamarin.Auth;
using UIKit;
#endif

#if __ANDROID__
using Android.App;
using Application = Xamarin.Forms.Application;
using Xamarin.Auth;
#endif

namespace ArcGISRuntime.Samples.SearchPortalMaps
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
        name: "Search for webmap",
        category: "Map",
        description: "Find webmap portal items by using a search term.",
        instructions: "Enter search terms into the search bar. Once the search is complete, a list is populated with the resultant webmaps. Tap on a webmap to set it to the map view. Scrolling to the bottom of the webmap recycler view will get more results.",
        tags: new[] { "keyword", "query", "search", "webmap" })]
    public partial class SearchPortalMaps : ContentPage, IOAuthAuthorizeHandler
    {
        // Constants for OAuth-related values ...
        // URL of the server to authenticate with (ArcGIS Online)
        private const string ArcGISOnlineUrl = "https://www.arcgis.com/sharing/rest";

        // Client ID for the app registered with the server (Portal Maps)
        public string _appClientId = "2Gh53JRzkPtOENQq";

        // Redirect URL after a successful authorization (configured for the Portal Maps application)
        private string _oAuthRedirectUrl = "https://developers.arcgis.com";

        public SearchPortalMaps()
        {
            InitializeComponent();

            // Display a default map
            DisplayDefaultMap();

            // Show the default OAuth settings in the entry controls
            ClientIDEntry.Text = _appClientId;
            RedirectUrlEntry.Text = _oAuthRedirectUrl;

            // Change the style of the layer list view for Android and UWP
            if (Device.RuntimePlatform == Device.UWP)
            {
                // Semi-transparent background on Windows with a small margin around the control
                MapsListView.BackgroundColor = Color.FromRgba(255, 255, 255, 0.3);
                MapsListView.Margin = new Thickness(50);
                SearchMapsUI.BackgroundColor = Color.FromRgba(255, 255, 255, 0.3);
                SearchMapsUI.Margin = new Thickness(50);
                OAuthSettingsGrid.BackgroundColor = Color.FromRgba(255, 255, 255, 0.3);
                OAuthSettingsGrid.Margin = new Thickness(50);
            }
        }

        private void DisplayDefaultMap()
        {
            // Create a new Map instance
            Map myMap = new Map(Basemap.CreateStreets());

            // Provide Map to the MapView
            MyMapView.Map = myMap;
        }

        private void OAuthSettingsCancel(object sender, EventArgs e)
        {
            OAuthSettingsGrid.IsVisible = false;
        }

        private void SaveOAuthSettings(object sender, EventArgs e)
        {
            var appClientId = ClientIDEntry.Text.Trim();
            var oAuthRedirectUrl = RedirectUrlEntry.Text.Trim();

            if (!String.IsNullOrWhiteSpace(appClientId) && !String.IsNullOrWhiteSpace(oAuthRedirectUrl))
            {
                _appClientId = appClientId;
                _oAuthRedirectUrl = oAuthRedirectUrl;
            }

            OAuthSettingsGrid.IsVisible = false;

            // Call a function to set up the AuthenticationManager
            UpdateAuthenticationManager();
        }

        private async void SearchPublicMaps(string searchText)
        {
            try
            {
                // Get web map portal items from a keyword search
                IEnumerable<PortalItem> mapItems;

                // Connect to the portal (anonymously)
                ArcGISPortal portal = await ArcGISPortal.CreateAsync(new Uri(ArcGISOnlineUrl));

                // Create a query expression that will get public items of type 'web map' with the keyword(s) in the items tags
                string queryExpression = $"tags:\"{searchText}\" access:public type: (\"web map\" NOT \"web mapping application\")";
            
                // Create a query parameters object with the expression and a limit of 10 results
                PortalQueryParameters queryParams = new PortalQueryParameters(queryExpression, 10);

                // Search the portal using the query parameters and await the results
                PortalQueryResultSet<PortalItem> findResult = await portal.FindItemsAsync(queryParams);
            
                // Get the items from the query results
                mapItems = findResult.Results;

                // Hide the search controls
                SearchMapsUI.IsVisible = false;

                // Show the list of web maps
                MapsListView.ItemsSource = mapItems.ToList(); // Explicit ToList() needed to avoid Xamarin.Forms UWP ListView bug.
                MapsListView.IsVisible = true;
            }
            catch (Exception e)
            {
                await Application.Current.MainPage.DisplayAlert("Error", e.ToString(), "OK");
            }
        }

        private void ShowSearchUI(object sender, EventArgs e)
        {
            // Show the map search controls
            SearchMapsUI.IsVisible = true;
        }

        private async void GetMyMaps(object sender, EventArgs e)
        {
            try
            {
                // Call a sub that will force the user to log in to ArcGIS Online (if they haven't already)
                bool loggedIn = await EnsureLoggedInAsync();
                if (!loggedIn) { return; }

                // Connect to the portal (will connect using the provided credentials)
                ArcGISPortal portal = await ArcGISPortal.CreateAsync(new Uri(ArcGISOnlineUrl));

                // Get the user's content (items in the root folder and a collection of sub-folders)
                PortalUserContent myContent = await portal.User.GetContentAsync();

                // Get the web map items in the root folder
                IEnumerable<PortalItem> mapItems = from item in myContent.Items where item.Type == PortalItemType.WebMap select item;

                // Loop through all sub-folders and get web map items, add them to the mapItems collection
                foreach (PortalFolder folder in myContent.Folders)
                {
                    IEnumerable<PortalItem> folderItems = await portal.User.GetContentAsync(folder.FolderId);
                    mapItems = mapItems.Concat(from item in folderItems where item.Type == PortalItemType.WebMap select item);
                }

                // Show the list of web maps
                MapsListView.ItemsSource = mapItems.ToList(); // Explicit ToList() needed to avoid Xamarin.Forms UWP ListView bug.
                MapsListView.IsVisible = true;
            }
            catch (Exception ex)
            {
                await Application.Current.MainPage.DisplayAlert("Error", ex.ToString(), "OK");
            }
        }
        
        private void MapItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            // Get the selected web map item in the list box
            PortalItem selectedMap = MapsListView.SelectedItem as PortalItem;
            if (selectedMap == null) { return; }

            // Create a new map, pass the web map portal item to the constructor
            Map webMap = new Map(selectedMap);

            // Handle change in the load status (to report load errors)
            webMap.LoadStatusChanged += WebMapLoadStatusChanged;

            // Show the web map in the map view
            MyMapView.Map = webMap;

            // Hide the list of maps
            MapsListView.IsVisible = false;
        }

        private void WebMapLoadStatusChanged(object sender, Esri.ArcGISRuntime.LoadStatusEventArgs e)
        {
            // Report errors if map failed to load
            if (e.Status == LoadStatus.FailedToLoad)
            {
                Map map = (Map)sender;
                Exception err = map.LoadError;
                if (err != null)
                {
                    Device.BeginInvokeOnMainThread(() => Application.Current.MainPage.DisplayAlert(err.Message, "Map Load Error", "OK"));
                }
            }
        }

        private async Task<bool> EnsureLoggedInAsync()
        {
            bool loggedIn = false;

            try
            {
                // Create a challenge request for portal credentials (OAuth credential request for arcgis.com)
                CredentialRequestInfo challengeRequest = new CredentialRequestInfo
                {

                    // Use the OAuth implicit grant flow
                    GenerateTokenOptions = new GenerateTokenOptions
                    {
                        TokenAuthenticationType = TokenAuthenticationType.OAuthImplicit
                    },

                    // Indicate the url (portal) to authenticate with (ArcGIS Online)
                    ServiceUri = new Uri(ArcGISOnlineUrl)
                };

                // Call GetCredentialAsync on the AuthenticationManager to invoke the challenge handler
                Credential cred = await AuthenticationManager.Current.GetCredentialAsync(challengeRequest, false);
                loggedIn = cred != null;
            }
            catch (OperationCanceledException)
            {
                // Login was canceled
                // .. ignore, user can still search public maps without logging in
            }
            catch (Exception ex)
            {
                // Login failure
                await Application.Current.MainPage.DisplayAlert("Login Error", ex.Message, "OK");
            }

            return loggedIn;
        }

        private void CancelSearchClicked(object sender, EventArgs e)
        {
            // Hide the search controls if the cancel button is clicked
            SearchMapsUI.IsVisible = false;
        }

        private void SearchMapsClicked(object sender, EventArgs e)
        {
            // Search ArcGIS Online maps with the text entered
            SearchPublicMaps(SearchTextEntry.Text);
        }

        #region OAuth
        private void UpdateAuthenticationManager()
        {
            // Define the server information for ArcGIS Online
            ServerInfo portalServerInfo = new ServerInfo
            {
                // ArcGIS Online URI
                ServerUri = new Uri(ArcGISOnlineUrl),
                // Type of token authentication to use
                TokenAuthenticationType = TokenAuthenticationType.OAuthImplicit
            };

            // Define the OAuth information
            OAuthClientInfo oAuthInfo = new OAuthClientInfo
            {
                ClientId = _appClientId,
                RedirectUri = new Uri(_oAuthRedirectUrl)
            };
            portalServerInfo.OAuthClientInfo = oAuthInfo;

            // Get a reference to the (singleton) AuthenticationManager for the app
            AuthenticationManager thisAuthenticationManager = AuthenticationManager.Current;

            // Register the ArcGIS Online server information with the AuthenticationManager
            thisAuthenticationManager.RegisterServer(portalServerInfo);

            // Create a new ChallengeHandler that uses a method in this class to challenge for credentials
            thisAuthenticationManager.ChallengeHandler = new ChallengeHandler(CreateCredentialAsync);

            // Set the OAuthAuthorizeHandler component (this class) for Android or iOS platforms
#if __ANDROID__ || __IOS__
            thisAuthenticationManager.OAuthAuthorizeHandler = this;
#endif
        }

        // ChallengeHandler function that will be called whenever access to a secured resource is attempted
        public async Task<Credential> CreateCredentialAsync(CredentialRequestInfo info)
        {
            Credential credential = null;

            try
            {
                // IOAuthAuthorizeHandler will challenge the user for OAuth credentials
                credential = await AuthenticationManager.Current.GenerateCredentialAsync(info.ServiceUri);
            }
            catch (TaskCanceledException) { return credential; }
            catch (Exception)
            {
                // Exception will be reported in calling function
                throw;
            }

            return credential;
        }

        #region IOAuthAuthorizationHandler implementation
        // Use a TaskCompletionSource to track the completion of the authorization
        private TaskCompletionSource<IDictionary<string, string>> _taskCompletionSource;

        // IOAuthAuthorizeHandler.AuthorizeAsync implementation
        public Task<IDictionary<string, string>> AuthorizeAsync(Uri serviceUri, Uri authorizeUri, Uri callbackUri)
        {
            // If the TaskCompletionSource is not null, authorization may already be in progress and should be cancelled
            if (_taskCompletionSource != null)
            {
                // Try to cancel any existing authentication task
                _taskCompletionSource.TrySetCanceled();
            }

            // Create a task completion source
            _taskCompletionSource = new TaskCompletionSource<IDictionary<string, string>>();
#if __ANDROID__ || __IOS__

#if __ANDROID__
            // Get the current Android Activity
            Activity activity = (Activity)ArcGISRuntime.Droid.MainActivity.Instance;
#endif
            // Create a new Xamarin.Auth.OAuth2Authenticator using the information passed in
            Xamarin.Auth.OAuth2Authenticator authenticator = new Xamarin.Auth.OAuth2Authenticator(
                clientId: _appClientId,
                scope: "",
                authorizeUrl: authorizeUri,
                redirectUrl: callbackUri)
            {
                ShowErrors = false
            };

            // Allow the user to cancel the OAuth attempt
            authenticator.AllowCancel = true;

            // Define a handler for the OAuth2Authenticator.Completed event
            authenticator.Completed += (sender, authArgs) =>
            {
                try
                {
#if __IOS__
                    // Dismiss the OAuth UI when complete
                    Device.BeginInvokeOnMainThread(() =>
                    {
                        var viewController = UIApplication.SharedApplication.KeyWindow.RootViewController;
                        viewController.DismissViewController(true, null);
                    });
#endif

                    // Check if the user is authenticated
                    if (authArgs.IsAuthenticated)
                    {
                        // If authorization was successful, get the user's account
                        Xamarin.Auth.Account authenticatedAccount = authArgs.Account;

                        // Set the result (Credential) for the TaskCompletionSource
                        _taskCompletionSource.SetResult(authenticatedAccount.Properties);
                    }
                    else
                    {
                        throw new Exception("Unable to authenticate user.");
                    }
                }
                catch (Exception ex)
                {
                    // If authentication failed, set the exception on the TaskCompletionSource
                    _taskCompletionSource.TrySetException(ex);

                    // Cancel authentication
                    authenticator.OnCancelled();
                }
#if __ANDROID__ 
                finally
                {
                    // Dismiss the OAuth login
                    activity.FinishActivity(99);
                }
#endif
            };

            // If an error was encountered when authenticating, set the exception on the TaskCompletionSource
            authenticator.Error += (sndr, errArgs) =>
            {
                // If the user cancels, the Error event is raised but there is no exception ... best to check first
                if (errArgs.Exception != null)
                {
                    _taskCompletionSource.TrySetException(errArgs.Exception);
                }
                else
                {
                    // Login canceled: dismiss the OAuth login
                    if (_taskCompletionSource != null)
                    {
                        _taskCompletionSource.TrySetCanceled();
#if __ANDROID__ 
                        activity.FinishActivity(99);
#endif
                    }
                }

                // Cancel authentication
                authenticator.OnCancelled();
            };

            // Present the OAuth UI so the user can enter user name and password
#if __ANDROID__
            var intent = authenticator.GetUI(activity);
            activity.StartActivityForResult(intent, 99);
#endif
#if __IOS__
            // Present the OAuth UI (on the app's UI thread) so the user can enter user name and password
            Device.BeginInvokeOnMainThread(() =>
            {
                var viewController = UIApplication.SharedApplication.KeyWindow.RootViewController;
                viewController.PresentViewController(authenticator.GetUI(), true, null);
            });
#endif

#endif 
            // Return completion source task so the caller can await completion
            return _taskCompletionSource.Task;
        }
        #endregion

        #endregion
    }
}