namespace DrDobbsApp.Services
{
    using System.Collections.Generic;
    using System.Threading.Tasks;

    //// DrDobbsApp.Entities (Portable Class Library)
    using Entities;

    public interface IGroupService
    {
        Task<IEnumerable<Group>> GetAll();
    }
}

namespace DrDobbsApp.Services.Implementation
{
    using System;
    using System.Collections.Generic;
    using System.Net.Http;
    using System.Net.Http.Headers;
    using System.Threading.Tasks;
    using System.Runtime.Serialization;
    using System.Runtime.Serialization.Json;

    //// DrDobbsApp.Entities (Portable Class Library)
    using Entities;

    public class GroupService : IGroupService
    {
        private const string RestServiceUrl = "http://localhost:46037/api/";

        public async Task<IEnumerable<Group>> GetAll()
        {
            var client = new HttpClient
            {
                BaseAddress = new Uri(RestServiceUrl)
            };
            
            //// I want to add and accept a header for JSON
            client.DefaultRequestHeaders.Accept.Add(new 
MediaTypeWithQualityHeaderValue(
"application/json"));

            //// Retrieve all the groups with their items
            var response = await client.GetAsync("groups");

            //// Throw an exception if something went wrong
            response.EnsureSuccessStatusCode();

            //// In case you need date and time properties
            const string dateTimeFormat = "yyyy-MM-ddTHH:mm:ss.fffffffZ";
            var jsonSerializerSettings = new DataContractJsonSerializerSettings
            {
                DateTimeFormat = new DateTimeFormat(dateTimeFormat)
            };

            var jsonSerializer = new DataContractJsonSerializer(
                typeof(Group[]),
                jsonSerializerSettings);

            var stream = await response.Content.ReadAsStreamAsync();
            return (Group[]) jsonSerializer.ReadObject(stream);
        }
    }
}

var client = new HttpClient
{
    BaseAddress = new Uri(RestServiceUrl)
};

client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

var response = await client.GetAsync("groups");

response.EnsureSuccessStatusCode();

const string dateTimeFormat = "yyyy-MM-ddTHH:mm:ss.fffffffZ";
var jsonSerializerSettings = new DataContractJsonSerializerSettings
{
    DateTimeFormat = new DateTimeFormat(dateTimeFormat)
};

var jsonSerializer = new DataContractJsonSerializer(
    typeof(Group[]),
    jsonSerializerSettings);

var stream = await response.Content.ReadAsStreamAsync();

return (Group[]) jsonSerializer.ReadObject(stream);</p>

public static async Task RefreshDataSource()
{
    var groupService = new GroupService();
    var allGroups = await groupService.GetAll();
    foreach (var group in allGroups)
    {
        var sampleDataGroup = new SampleDataGroup(
            group.Id,
            group.Title,
            group.Subtitle,
            "Assets/LightGray.png",
            group.Description);

        _sampleDataSource.AllGroups.Add(sampleDataGroup);

        if (group.Items != null)
        {
            foreach (var item in group.Items)
            {
                sampleDataGroup.Items.Add(new SampleDataItem(
                    item.Id,
                    item.Title,
                    item.Subtitle,
                    "Assets/LightGray.png",
                    item.Description,
                    item.Content,
                    sampleDataGroup));
            }
        }
    }
}

protected override async void OnLaunched(LaunchActivatedEventArgs args)
{
    Frame rootFrame = Window.Current.Content as Frame;

    // Do not repeat app initialization when the Window already has content,
    // just ensure that the window is active
            
    if (rootFrame == null)
    {
        // Create a Frame to act as the navigation context, and navigate to first page
        rootFrame = new Frame();
        //Associate the frame with a SuspensionManager key                                
        SuspensionManager.RegisterFrame(rootFrame, "AppFrame");

        if (args.PreviousExecutionState == ApplicationExecutionState.Terminated)
        {
            // Restore the saved session state only when appropriate
            try
            {
                await SuspensionManager.RestoreAsync();
            }
            catch (SuspensionManagerException)
            {
                //Something went wrong restoring state.
                //Assume there is no state and continue
            }
        }
        else if (args.PreviousExecutionState == ApplicationExecutionState.NotRunning)
        {
            //// Retrieve all the groups by making a call to the REST service
            try
            {
                await Data.SampleDataSource.RefreshDataSource();
            }
            catch (Exception ex)
            {
                ////Something went wrong refreshing the data source
                ////It is obviously necessary to add more code here :)
            }
        }

        // Place the frame in the current Window
        Window.Current.Content = rootFrame;
    }
    if (rootFrame.Content == null)
    {
        // When the navigation stack isn't restored navigate to the first page,
        // configuring the new page by passing required information as a navigation
        // parameter
        if (!rootFrame.Navigate(typeof(GroupedItemsPage), "AllGroups"))
        {
            throw new Exception("Failed to create initial page");
        }
    }
    // Ensure the current window is active
    Window.Current.Activate();
}